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Building a Microservices application with Spring Boot

Microservices is a very hot topic in these years, you can see it everywhere, there are a lots of books, blog entries, conference sessions, training courses etc. are talking about it.

What is Microservices ?

Microservices is not a standard specification, so there is no official definition. Here I listed some well-known explanation from the communities.

Martin Fowler described it as the following in his article Microservices:

In short, the Microservices architectural style is an approach to developing a single application as a suite of small services, each running in its own process and communicating with lightweight mechanisms, often an HTTP resource API. These services are built around business capabilities and independently deployable by fully automated deployment machinery. There is a bare minimum of centralized management of these services, which may be written in different programming languages and use different data storage technologies.

On the Wikipedia Microservices page, Microservices was defined as:

Microservices is a variant of the service-oriented architecture (SOA) architectural style that structures an application as a collection of loosely coupled services. In a Microservices architecture, services should be fine-grained and the protocols should be lightweight. The benefit of decomposing an application into different smaller services is that it improves modularity and makes the application easier to understand, develop and test. It also parallelizes development by enabling small autonomous teams to develop, deploy and scale their respective services independently.[1] It also allows the architecture of an individual service to emerge through continuous refactoring. Microservices-based architectures enable continuous delivery and deployment.

Chris Richardson, the author of POJOs in Action and the creator of the original CloudFoundry.com, and also an advocator of Microservices , summarized Microservices as the following in the home page of Microservices.io.

Microservices - also known as the Microservices architecture - is an architectural style that structures an application as a collection of loosely coupled services, which implement business capabilities. The Microservices architecture enables the continuous delivery/deployment of large, complex applications. It also enables an organization to evolve its technology stack.

There are some common characteristics can be used to describe a Microservices based application.

  • A Microservices application should be consisted of a collection of small services. One single service is not Microservices . Every service is fine-grained, and target to perform a small functionality. So Microservices was described as fine-grained SOA or SOA done right in some articles. So This is the main difference from traditional monolithic applications.

  • Every service should have its own independent life cycle. Every service can be developed and deployed independently, if you are using a CI/CD automation service, every service should be delivered through a standard DevOps pipeline, but not affect others.

  • Service-to-service communication is based on light-weight protocols, eg. HTTP based REST APIs for synchronous communication, WebSocket for asynchronous messages, MQTT/AMQP protocol for varied messaging from client or devices(eg. IOT applications).

  • The organization or team structures should be changed simultaneously when you are embracing Microservices architecture. In the traditional application development, especially your organization follows the waterfall development prototype, your teams are organized by roles, eg architects, database administrators, developers, testers, operators etc. You have to break your traditional organization tree. In the development stage of a Microservices based application, a small team should be responsible for the whole DevOps lifecycle (design, develop, test, deploy, etc.) of one or more services.

Microservices componentizes your application into small services(componentized applications), and make it more maintainable and scalable. In this demo application, I will show you building a Microservices application via Spring Boot.

Migrating to Microservices architecture

Contrast with Microservices applications, traditional layered enterprise applications were called monolithic applications.

In the past years, I have created some samples to demonstrate different technology stack, such as REST APIs sample with Spring MVC, REST APIs sample with Spring Boot. In these code samples, the backends are monolithic applications and they are based on the same model prototype, a blog application.

  • A user can log in with an existed account, or sign up a new account.
  • An authenticated user can create a new post.
  • An authenticated user can update his/her posts.
  • An authenticated user who has ADMIN role can delete a post directly.
  • All users(who are authenticated or anonymous) can view posts.
  • An authenticated user can add comments to an existed post.
  • ...

No doubt these monolithic backend applications are easy to develop and deploy, but as time goes by, when the application becomes more complex, the backend will be problematic, you maybe face some barriers which block you to the next stages.

  • When applying a change, you have to redeploy the whole backend application even it is just a small fix. The application may be stopped to work for some minutes or some hours.
  • When scaling your applications and deploying multiple copies of the backend applications behinds a load balance server, the transactional consistence will be a new challenge.
  • The database itself will be a huge performance bottleneck when the concurrency of incoming requests are increasing.

Microservices architecture addresses these problems, including:

  1. Smaller services are easier to maintain in a complex application, when you upgrade one service, you do not need to shut down all services in the production environment.
  2. ACID can not satisfy the scenario of those long run workflows which across several services, although it is still a good option in a single service, but for these long run transactions, a stateful Saga or workflow solution fills this field.
  3. A service can has its own database, and only responsible for storing data of this service itself. Traditional complex queries will become a big challenge, in Microservices architecture, it could need to query multi independent database and aggregate the query results. CQRS, Event Store can save these. Perform commands in standalone services, and execute queries in another service which has marshal view of the data and was synced with messaging from events triggered by other services.

Follow the Bounded Context concept of DDD(Domain Driven Design), we break the backend monolithic application into three small services, including:

  • An auth-service is serving the operations of signin, signup and signout.
  • A user-service is responsible for user management.
  • A post-service exposes APIs for a simple CMS, including posts and comments.
  • An API Gateway which is just responsible for routing the incoming requests to downstream services.
  • The databases are also aligned to Microservices architecture, and user-service and post-service have their own databases, a Redis is used for sharing session between services, and to simplify the security.

Microservices

As mentioned, if there is a legacy application planned to migrate to Microservices architecture, you can follow the following steps to extract some domain into a standalone service.

  1. Find the domains which are easiest to separate from the main application, eg, posts and comments in our application.
  2. Use an identifier object in the entity links instead of the hard relations of entities outside of this domain. eg. use a Username which stands for a unique username of a User entity, and erase the direct connection to User entity.
  3. Move the related data to a standalone database, and connect to this new database in your service.

When I start a new project, should I embrace Microservices architecture right now?

Although we are talking about Microservices in this post, I still suggest you start building your application in a monolithic architecture if you know little about the complexity of Microservices , it could be consisted of a RESTful backend and an SPA based frontend UI. In the initial development stage, either monolithic architecture or Microservices , you have to spend lots of time on clarifying the problem domains, defining the bounded context etc. Starting a monolithic application is still valuable when you are ready for migrating to Microservices architecture.

Cooking your first service

This sample application is built on the newest Spring technology stack, including Spring Boot, Spring Data, Spring Security, etc.

  • Every small service is a Spring Boot application. Every service will be packaged as a jar file and use the embedded Tomcat as target runtime to serve the services.
  • Every small service owns its database, eg. we use MySQL as the backing database for auth-service, and PostgreSQL for the post-service.
  • Spring Data is used for simplifying data operations.
  • Spring Session provides a simple strategy to generate and validate header based authentication token via sharing sessions in a backing session repository, in this sample we use Redis as session storage.
  • Spring Security is responsible for protecting RESTful APIs.

Follow the 12 factors application guide, I suggest you use Docker in both development and production environment to make sure the same code base works well in different environments.

In this section, we will build our first service, post-service, which is designated to exposes REST APIs to clients.

Prerequisites

I assume you have some experience of Spring, and know well about the REST convention, especially the CHAPTER 5: Representational State Transfer (REST) from Roy Fielding's dissertation: Architectural Styles and the Design of Network-based Software Architectures.

And you have also installed the following software.

Setup local development environment

Make sure you have installed the latest Docker, Docker Compose and Docker Machine, more info please refer to the installation guide from Docker official website.

NOTE: Under Windows system, you can install Docker Desktop for Windows to simplify the installation.

Docker Compose allows you start up the dependent infrastructural services(such as Database etc) via a single docker-compose command.

docker-compose up

We will use MySQL, PostgreSQL and Redis in this demo, the following is a sample docker-compose.yml file.

version: '3.3' # specify docker-compose version

services:    
  userdb:
    container_name: userdb
    image: mysql
    ports:
      - "3306:3306"
    environment:
      MYSQL_ROOT_PASSWORD: mysecret
      MYSQL_USER: user
      MYSQL_PASSWORD: password
      MYSQL_DATABASE: userdb
    volumes:
      - ./data/userdb:/var/lib/mysql
      
  postdb:
    container_name:  postdb
    image: postgres
    ports:
      - "5432:5432"
    restart: always
    environment:
      POSTGRES_PASSWORD: password
      POSTGRES_DB: postdb
    volumes:
      - ./data/postdb:/var/lib/postgresql     
      

  redis:
    container_name: redis
    image: redis
    ports:
      - "6379:6379"

Docker Toolbox Notes

If you are using the legacy Docker Toolbox, create a new machine for this project.

$ docker-machine create -d virtualbox --engine-registry-mirror https://docker.mirrors.ustc.edu.cn springms

NOTE: The --engine-registry-mirror https://docker.mirrors.ustc.edu.cn will add a docker registry mirror setting in docker-machine specific config.json. For most of Chinese users, using a local mirror will speed up the Docker images downloading.

Then switch to the new created machine springms, and set the environment variables.

eval "$(docker-machine env springms)"

Forward the virtualbox ports to your local system, thus you can access the servers via localhost instead of the docker machine IP address.

 VBoxManage modifyvm "springms" --natpf1 "tcp-port3306,tcp,,3306,,3306"
 VBoxManage modifyvm "springms" --natpf1 "tcp-port5432,tcp,,5432,,5432"
 VBoxManage modifyvm "springms" --natpf1 "tcp-port5672,tcp,,5672,,5672"
 VBoxManage modifyvm "springms" --natpf1 "tcp-port15672,tcp,,15672,,15672"
 VBoxManage modifyvm "springms" --natpf1 "tcp-port6379,tcp,,6379,,6379"
 VBoxManage modifyvm "springms" --natpf1 "tcp-port27017,tcp,,27017,,27017"

Then run the dependent servers via docker-compose command line.

Generate project skeleton

With Spring Initializr, you can get a Spring Boot based project skeleton in seconds.

Open your browser, go to Spring Initializr page, fill the following essential fields for a project.

  1. Choose Java as programming language.
  2. Select the latest version of Spring Boot, 2.0.0.RELEASE is the latest milestone at the moment when I wrote this post.
  3. Search and select the required facilities will be used in your project, such as Web, Data JPA, Data Redis, Security, Session, Lombok etc.
  4. Set project name(maven artifact id) to post-service.

Click Generate Project button or press ALT+ENTER keys to generate the project skeleton for downloading in your browser.

After downloading the generated archive, extract the files into your local disk and import it into your favorite IDE.

REST API Overview

Following the REST convention and HTTP protocol specification, the REST APIs of post-service are designed as the following table.

Uri Http Method Request Response Description
/posts GET 200, [{'id':1, 'title'},{}] Get all posts
/posts POST {'id':1, 'title':'test title','content':'test content'} 201 Create a new post
/posts/{postSlug} GET 200, {'id':1, 'title'} Get a post by postSlug
/posts/{postSlug} PUT {'title':'test title','content':'test content'} 204 Update a post
/posts/{postSlug} DELETE 204 Delete a post by postSlug
/posts/{postSlug}/comments GET 200, [{'id':1, 'content':'comment content'},{}] Get all comments of the certain post
/posts/{postSlug}/comments POST {'content':'test content'} 201 Create a new comment of the certain post

Create a new Entity

A domain entity is a persistent object in DDD concept, JPA @Entity a is a good match.

Create our first entity Post.

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
@Entity
class Post extends AuditableEntity {

    @JsonView(View.Summary.class)
    @NotEmpty
    private String title;
    
    @NotEmpty
    private String postSlug;

    @JsonView(View.Public.class)
    @NotEmpty
    private String content;

    @Enumerated(EnumType.STRING)
    @Builder.Default
    @JsonView(View.Summary.class)
    private Status status = Status.DRAFT;

    static enum Status {
        DRAFT,
        PUBLISHED
    }
      
    @PrePersist
    public void slugify(){
        this.postSlug = new Slugify().slugify(this.title);
    }

}

@Data, @Builder, @NoArgsConstructor and @AllArgsConstructor are from project Lombok, which provides some helper annotations to make your source codes clean. With @Data, you can remove the tedious setters, getters of all fields, and the generic equals, hashCode, toString methods. @Builder will generate an inner builder class. @NoArgsConstructor will create a none-argument constructor, @AllArgsConstructor will take all fields as constructor arguments.

These annotations will be handled by JDK Annotation Processing Tooling, and generate code fragment in class files at compile time.

@Entity indicates Post is a standard JPA Entity.

@PrePersist is a JPA lifecycle hook. The @PrePersist annotated methods will be executed before the entity is persisted. We use post postSlug as the unique identifier of a Post, and we use slugify() method to generate the post postSlug automatically.

AuditableEntity is a helper class to centralize some common fields of a JPA entity in one place.

@Data
@MappedSuperclass
@EntityListeners(value = AuditingEntityListener.class)
public abstract class AuditableEntity extends PersistableEntity {

    public AuditableEntity() {
    }

    @CreatedDate
    @JsonView(View.Summary.class)
    protected LocalDateTime createdDate;

    @Embedded
    @AttributeOverrides(value = {
        @AttributeOverride(name = "username", column = @Column(name = "author"))
    })
    @CreatedBy
    @JsonView(View.Summary.class)
    protected Username author;

}

@CreatedDate and @CreatedBy will fill in the creation date timestamp and the current user if the data auditing feature is enabled.

Use a standalone @Configuration bean to configure Spring Data JPA auditing.

@Configuration
@EnableJpaAuditing(auditorAwareRef = "auditorAware")
@Slf4j
public class DataJpaConfig {

    @Bean
    @Scope(value = ConfigurableBeanFactory.SCOPE_PROTOTYPE)
    public AuditorAware<Username> auditorAware() {

        Authentication authentication = SecurityContextHolder.getContext().getAuthentication();

        log.debug("current authentication:" + authentication);

        if (authentication == null || !authentication.isAuthenticated()) {
            return () -> Optional.<Username>empty();
        }

        return () -> Optional.of(
            Username.builder()
                .username(((UserDetails) authentication.getPrincipal()).getUsername())
                .build()
        );

    }
}

AuditorAware bean is required when you want to set auditor automatically. The population work is done by JPA @EntityListener, note there is a @EntityListeners(value = AuditingEntityListener.class) already added on the AuditableEntity class.

Have a look at the base PersistableEntity, it just defines the identity field of a JPA entity.

@Data
@MappedSuperclass
public abstract class PersistableEntity implements Serializable {
    
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @JsonView(View.Summary.class)
    protected Long id;

    public PersistableEntity() {
    }
    
}

Similarly, create an another entity Comment.

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
@Entity
public class Comment extends AuditableEntity {


    @NotEmpty
    @Size(min = 10)
    private String content;


    @Embedded
    @AttributeOverrides(
        value = {
            @AttributeOverride(name = "postSlug", column = @Column(name = "post_slug"))
        }
    )
    @JsonIgnore
    private Slug post;


}

NOTE: we do not user a JPA @OneToMany or @ManyToOne to connect two entities, but use a simple Post Slug identifier object instead. If one day this service becomes heavy, we could split comments into another standalone service.

Create Repository for Entities

In DDD, a Repository is responsible for retrieving entities from or saving back to a Repository. Spring Data Repository interface and Spring Data JPA specific JpaRepository interface are a good match with Repository concept in DDD.

Create a Repository for the Post Entity.

public interface PostRepository extends JpaRepository<Post, Long>, JpaSpecificationExecutor<Post> {

    Optional<Post> findBySlug(String postSlug);
    
}

Create a Domain Service

@Service
@Transactional
public class PostService {

    @Inject
    private PostRepository postRepository;
    

    public Post createPost(PostForm form) {
        Post _post = Post.builder()
            .title(form.getTitle())
            .content(form.getContent())
            .build();
        
        Post saved = this.postRepository.save(_post);
        
        return saved;
    }

    public Post updatePost(String postSlug, PostForm form) {
        Post _post = this.postRepository.findBySlug(postSlug).orElseThrow(
            ()-> {
                return new PostNotFoundException(postSlug);
            }
        );
        
        _post.setTitle(form.getTitle());
        _post.setContent(form.getContent());
        
       Post saved =  this.postRepository.save(_post);
       
       return saved;
    }

    public void deletePost(String postSlug) {
        this.postRepository.delete(this.postRepository.findBySlug(postSlug).orElseThrow(
            () -> {
                return new PostNotFoundException(postSlug);
            }
        ));
    }

}

In the PostService, the main purpose is treating with exceptions when creating or update a post. In a real world application, you could handle domain events in a domain service, eg. Post is published, etc.

Expose RESTful APIs

Let's expose RESTful APIs for Post via PostController.

@RestController
@RequestMapping("/posts")
@Slf4j
public class PostController {

    private PostService postService;

    private PostRepository postRepository;

    private CommentRepository commentRepository;

    public PostController(PostService postService, PostRepository postRepository, CommentRepository commentRepository) {
        this.postService = postService;
        this.postRepository = postRepository;
        this.commentRepository = commentRepository;
    }

    @GetMapping()
    @JsonView(View.Summary.class)
    public ResponseEntity<Page<Post>> getAllPosts(
        @RequestParam(value = "q", required = false) String keyword, //
        @RequestParam(value = "status", required = false) Post.Status status, //
        @PageableDefault(page = 0, size = 10, sort = "createdDate", direction = Direction.DESC) Pageable page) {

        log.debug("get all posts of q@" + keyword + ", status @" + status + ", page@" + page);

        Page<Post> posts = this.postRepository.findAll(PostSpecifications.filterByKeywordAndStatus(keyword, status), page);

        return ok(posts);
    }

    @GetMapping(value = "/{postSlug}")
    @JsonView(View.Public.class)
    public ResponseEntity<Post> getPost(@PathVariable("postSlug") String postSlug) {

        log.debug("get postsinfo by postSlug @" + postSlug);

        Post post = this.postRepository.findBySlug(postSlug).orElseThrow(
            () -> {
                return new PostNotFoundException(postSlug);
            }
        );

        log.debug("get post @" + post);

        return ok(post);
    }

    @PostMapping()
    public ResponseEntity<Void> createPost(@RequestBody @Valid PostForm post, HttpServletRequest request) {

        log.debug("create a new post@" + post);

        Post saved = this.postService.createPost(post);

        log.debug("saved post id is @" + saved.getId());
        URI createdUri = ServletUriComponentsBuilder
            .fromContextPath(request)
            .path("/posts/{postSlug}")
            .buildAndExpand(saved.getSlug())
            .toUri();

        return created(createdUri).build();
    }

    @PutMapping(value = "/{postSlug}")
    public ResponseEntity<Void> updatePost(@PathVariable("postSlug") String postSlug, @RequestBody @Valid PostForm form) {

        log.debug("update post by id @" + postSlug + ", form content@" + form);

        this.postService.updatePost(postSlug, form);

        return noContent().build();
    }

    @DeleteMapping(value = "/{postSlug}")
    public ResponseEntity<Void> deletePostById(@PathVariable("postSlug") String postSlug) {

        log.debug("delete post by id @" + postSlug);

        this.postService.deletePost(postSlug);

        return noContent().build();
    }

    @GetMapping(value = "/{postSlug}/comments")
    public ResponseEntity<Page<Comment>> getCommentsOfPost(
        @PathVariable("postSlug") String postSlug,
        @PageableDefault(page = 0, size = 10, sort = "createdDate", direction = Direction.DESC) Pageable page) {

        log.debug("get comments of post@" + postSlug + ", page@" + page);

        Page<Comment> commentsOfPost = this.commentRepository.findByPost(new Slug(postSlug), page);

        log.debug("get post comment size @" + commentsOfPost.getTotalElements());

        return ok(commentsOfPost);
    }

    @PostMapping(value = "/{postSlug}/comments")
    public ResponseEntity<Void> createComment(
        @PathVariable("postSlug") @NotNull String postSlug, @RequestBody CommentForm comment, HttpServletRequest request) {

        log.debug("new comment of post@" + postSlug + ", comment" + comment);

        Comment _comment = Comment.builder()
            .post(new Slug(postSlug))
            .content(comment.getContent())
            .build();

        Comment saved = this.commentRepository.save(_comment);

        log.debug("saved comment @" + saved.getId());

        URI location = ServletUriComponentsBuilder
            .fromContextPath(request)
            .path("/posts/{postSlug}/comments/{id}")
            .buildAndExpand(postSlug, saved.getId())
            .toUri();

         return created(location).build();
    }

}

In the above codes,

  • getAllPosts method accepts a q (keyword) and a status (post status) and a Pageable as query parameters, it returns a Page<Post> result.
  • The postRepository.findAll method accepts a Specification object. Specification is a wrapper class of JPA 2.0 criteria APIs, which provides effective type safe query condition building.
public class PostSpecifications {

    private PostSpecifications() {
    }

    public static Specification<Post> filterByKeywordAndStatus(
        final String keyword,//
        final Post.Status status) {
        return (Root<Post> root, CriteriaQuery<?> query, CriteriaBuilder cb) -> {
            List<Predicate> predicates = new ArrayList<>();
            if (StringUtils.hasText(keyword)) {
                predicates.add(
                    cb.or(
                        cb.like(root.get(Post_.title), "%" + keyword + "%"),
                        cb.like(root.get(Post_.content), "%" + keyword + "%")
                    )
                );
            }

            if (status != null) {
                predicates.add(cb.equal(root.get(Post_.status), status));
            }

            return cb.and(predicates.toArray(new Predicate[predicates.size()]));
        };
    }

}

According to the REST convention and HTTP protocol, a HTTP POST Method is used to create a new resource, it can return a 201 HTTP status code with the new created resource URI as HTTP header Location. And for update and delete operations on resource, return a 204 HTTP status. In the above codes, we apply these simple rules.

Exception Handling

As mentioned above, in our PostService, I have added some extra steps to check the existence of a post by id in the updatePost and deletePost methods. If it is not found throw a PostNotFoundException.

public class PostNotFoundException extends RuntimeException {

    private String postSlug;

    public PostNotFoundException(String postSlug) {
        super("post:" + postSlug + " was not found");
        this.postSlug = postSlug;
    }

    public String getSlug() {
        return postSlug;
    }
    
}

And we will handle this exception in a common class annotated with @RestControllerAdvice. When a PostNotFoundException is caught, notFound method will handle it convert the exception to a friendly message body and return a HTTP 404 status code to the client.

@RestControllerAdvice
public class PostExceptionHandler {

    @ExceptionHandler(PostNotFoundException.class)
    public ResponseEntity notFound(PostNotFoundException ex, WebRequest req) {
        Map<String, String> errors = new HashMap<>();
        errors.put("entity", "POST");
        errors.put("id", "" + ex.getSlug());
        errors.put("code", "not_found");
        errors.put("message", ex.getMessage());

        return ResponseEntity.status(HttpStatus.NOT_FOUND).body(errors);
    }

}

Miscellaneous

In a real world application, when you fetch post list, you maybe do not want to show all fields of the post. It is easy to control the representation view sent to client by customizing Jackson JsonView.

public final class View {

    interface Summary {
    }

    interface Public extends Summary {
    }
}

In the Post class, add the following annotations to its fields.

class Post extends AuditableEntity {

    @JsonView(View.Summary.class)
    private String title;
    

    @JsonView(View.Public.class)
    private String content;

    @JsonView(View.Summary.class)
    private Status status = Status.DRAFT;

}

In the PostController, add a @JsonView annotation.

@JsonView(View.Summary.class)
public ResponseEntity<Page<Post>> getAllPosts()

Thus only the Summary labeled fields will be included in the result of getAllPosts.

Another small issue you could have found is the Page object serialized result looks a little tedious, too much unused fields from Pageable are included in the json result.

{
  "content" : [ {
    "title" : "test post 2",
    "postSlug" : "test-post-2",
    "status" : "DRAFT",
    "id" : 2,
    "createdDate" : "2017-05-25T06:53:30",
    "author" : {
      "username" : "user"
    }
  }, {
    "title" : "test post",
    "postSlug" : "test-post",
    "status" : "DRAFT",
    "id" : 1,
    "createdDate" : "2017-05-25T06:52:45",
    "author" : {
      "username" : "user"
    }
  } ],
  "pageable" : {
    "sort" : {
      "sorted" : true,
      "unsorted" : false
    },
    "pageSize" : 10,
    "pageNumber" : 0,
    "offset" : 0,
    "paged" : true,
    "unpaged" : false
  },
  "last" : true,
  "totalElements" : 2,
  "totalPages" : 1,
  "sort" : {
    "sorted" : true,
    "unsorted" : false
  },
  "numberOfElements" : 2,
  "first" : true,
  "size" : 10,
  "number" : 0
}

Create a @JsonComponent bean to customize the serialized json result.

@JsonComponent
public class PageJsonSerializer extends JsonSerializer<PageImpl> {

    @Override
    public void serialize(PageImpl value, JsonGenerator gen, SerializerProvider serializers) throws IOException, JsonProcessingException {
        gen.writeStartObject();
        gen.writeNumberField("number", value.getNumber());
        gen.writeNumberField("numberOfElements", value.getNumberOfElements());
        gen.writeNumberField("totalElements", value.getTotalElements());
        gen.writeNumberField("totalPages", value.getTotalPages());
        gen.writeNumberField("size", value.getSize());
        gen.writeFieldName("content");
        serializers.defaultSerializeValue(value.getContent(), gen);
        gen.writeEndObject();
    }

}

When this bean is activated, the result cloud look like the following:

{
  "content" : [ {
    "title" : "test post 2",
    "postSlug" : "test-post-2",
    "status" : "DRAFT",
    "id" : 2,
    "createdDate" : "2017-05-25T06:53:30",
    "author" : {
      "username" : "user"
    }
  }, {
    "title" : "test post",
    "postSlug" : "test-post",
    "status" : "DRAFT",
    "id" : 1,
    "createdDate" : "2017-05-25T06:52:45",
    "author" : {
      "username" : "user"
    }
  } ],
  "numberOfElements" : 2,
  "totalElements" : 2,
  "totalPages" : 1,
  "size" : 10,
  "number" : 0
}

The details of auth-service and user-service, please check the [source codes](https://github.com/hantsy/spring-Microservices -sample) and explore them yourself.

Secures Microservices

Let's have a look at how a user get authentication in this demo.

  1. A user try to get authentication from auth-service using usename and password.
  2. If it is a valid user and it is authenticated successfully, the response header will include a X-AUTH-TOKEN header.
  3. Extract the value of X-AUTH-TOKEN header, and add X-AUTH-TOKEN header into the new request to get access permission of the protected resource, such as APIs in post-service.

We use Spring Session and Redis to archive this purpose.

In all services, we add the following codes to resolve Session by HTTP header instead of Cookie.

@Configuration
public class RedisSessionConfig {

    @Bean
    public HttpSessionIdResolver httpSessionStrategy() {
        return HeaderHttpSessionIdResolver.xAuthToken();
    }

}

And add the follow configuration in the application.yml to tell Spring to use Redis as session store.

spring:
  session: 
    store-type: redis

In auth-service, use a controller to serve user authentication.

@RequestMapping(value = "/auth")
@RestController
public class AuthenticationController {

	@PostMapping(value = "/signin")
    public AuthenticationResult signin(
        @RequestBody @Valid AuthenticationRequest authenticationRequest,
        HttpServletRequest request) {
        
        if (log.isDebugEnabled()) {
            log.debug("signin form  data@" + authenticationRequest);
        }
        
        return this.handleAuthentication(
            authenticationRequest.getUsername(),
            authenticationRequest.getPassword(),
            request);
    }
    
    private AuthenticationResult handleAuthentication(
        String username,
        String password,
        HttpServletRequest request) {
        
        final UsernamePasswordAuthenticationToken token = new UsernamePasswordAuthenticationToken(
            username,
            password
        );
        
        final Authentication authentication = this.authenticationManager
            .authenticate(token);
        
        SecurityContextHolder.getContext().setAuthentication(authentication);
        
        final HttpSession session = request.getSession(true);
        
        session.setAttribute(
            HttpSessionSecurityContextRepository.SPRING_SECURITY_CONTEXT_KEY,
            SecurityContextHolder.getContext());
        
        return AuthenticationResult.builder()
            .name(authentication.getName())
            .roles(authentication.getAuthorities().stream().map(r -> r.getAuthority()).collect(Collectors.toList()))
            .token(session.getId())
            .build();
    }
	
	...

When you are authenticated, the /auth/signin endpoint will return userinfo and token(session id) in the result.

To protect the resource APIs, just add a SecurityConfig. The following is a configuration for post-service. All GET methods are permitted, and when DELETE a post, you should have a ADMIN role.

@Configuration
@Slf4j
public class SecurityConfig {
    
    @Bean
    public WebSecurityConfigurerAdapter securityConfigBean(){
        
        return new  WebSecurityConfigurerAdapter() {

            @Override
            protected void configure(HttpSecurity http) throws Exception {
                // We need this to prevent the browser from popping up a dialog on a 401
                http
                    .httpBasic()
                    .and()
                        .authorizeRequests()
                        .antMatchers(HttpMethod.GET, "/posts/**").permitAll()
                        .antMatchers(HttpMethod.DELETE, "/posts/**").hasRole("ADMIN")
                        .anyRequest().authenticated()
                    .and()
                        .csrf().disable();
            }
        };   
    }
}

Let's try to run the demo in local system.

Running Microservices application

In your local development environment, it is easy to run the services one by one via Spring Boot maven plugin or build and run them in local Docker container via a predefined docker compose file.

Running application via Maven plugin

Make sure the dependent servers are running by executing docker-compose up.

Enter the root folder of every service, execute the following command to start up them one by one.

mvn spring-boot:run // run in user-service, auth-service, post-service

The following endpoints will be provided.

Service Url Description
auth-service http://localhost:8000/user,http://localhost:8000/auth Authentication APIs(signin, signup, signout), user info
user-service http://localhost:8001/users User management APIs
post-service http://localhost:8002/posts Post and comment APIs

Follow the authentication flow to have a try.

When all service are running successfully, firstly try to get authentication.

curl -v  http://localhost:8000/user -u user:test123
* timeout on name lookup is not supported
*   Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 8000 (#0)
* Server auth using Basic with user 'user'
> GET /user HTTP/1.1
> Host: localhost:8000
> Authorization: Basic dXNlcjp0ZXN0MTIz
> User-Agent: curl/7.54.0
> Accept: */*
>
< HTTP/1.1 200
< X-Content-Type-Options: nosniff
< X-XSS-Protection: 1; mode=block
< Cache-Control: no-cache, no-store, max-age=0, must-revalidate
< Pragma: no-cache
< Expires: 0
< X-Frame-Options: DENY
< X-Auth-Token: 49090ba7-e641-45e3-935b-894a43b85f62
< Content-Type: application/json;charset=UTF-8
< Transfer-Encoding: chunked
< Date: Mon, 15 May 2017 09:29:14 GMT
<
{"name":"user","roles":["USER"]}* Connection #0 to host localhost left intact

You will see a X-Auth-Token header in the response.

Put this header into a new request when you want to access the protected resources in another resource server.

curl -v  http://localhost:8001/user -H "x-auth-token: 49090ba7-e641-45e3-935b-894a43b85f62"

Try to add some posts data:

>curl -v  http://localhost:8002/posts 
-H "x-auth-token:  49090ba7-e641-45e3-935b-894a43b85f62" 
-H "Accept: application/json" 
-H "Content-Type: application/json;charset=UTF-8" 
-X POST 
-d "{\"title\": \"test post\", \"content\":\"test content of post\"}"

You will see the result. It returns 201 status, and set Location header to the new created Post.

Note: Unnecessary use of -X or --request, POST is already inferred.
* timeout on name lookup is not supported
*   Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 8002 (#0)
> POST /posts HTTP/1.1
> Host: localhost:8002
> User-Agent: curl/7.54.0
> x-auth-token:  49090ba7-e641-45e3-935b-894a43b85f62
> Accept: application/json
> Content-Type: application/json;charset=UTF-8
> Content-Length: 56
>
* upload completely sent off: 56 out of 56 bytes
< HTTP/1.1 201
< X-Content-Type-Options: nosniff
< X-XSS-Protection: 1; mode=block
< Cache-Control: no-cache, no-store, max-age=0, must-revalidate
< Pragma: no-cache
< Expires: 0
< X-Frame-Options: DENY
< Location: http://localhost:8002/posts/4
< Content-Length: 0
< Date: Thu, 18 May 2017 06:54:40 GMT

Fetch the new created post.

curl -v  http://localhost:8002/posts/4 -H "Accept: application/json"
* timeout on name lookup is not supported
*   Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 8002 (#0)
> GET /posts/4 HTTP/1.1
> Host: localhost:8002
> User-Agent: curl/7.54.0
> Accept: application/json
>
< HTTP/1.1 200
< X-Content-Type-Options: nosniff
< X-XSS-Protection: 1; mode=block
< Cache-Control: no-cache, no-store, max-age=0, must-revalidate
< Pragma: no-cache
< Expires: 0
< X-Frame-Options: DENY
< Content-Type: application/json;charset=UTF-8
< Transfer-Encoding: chunked
< Date: Thu, 18 May 2017 06:59:42 GMT
<
{"id":4,"title":"test post","content":"test content of post","status":"DRAFT","author":null,"createdDate":null}*

Running application via Docker Compose

Firstly build all services into Docker images.

Prepare a Dockfile for every service. For example, create a Dockerfile in the root folder of post-service project.

FROM frolvlad/alpine-oraclejdk8:slim
VOLUME /tmp
ADD ./target/post-service-0.0.1-SNAPSHOT.jar app.jar
RUN sh -c 'touch /app.jar'
ENV JAVA_OPTS=""
ENTRYPOINT [ "sh", "-c", "java $JAVA_OPTS -Djava.security.egd=file:/dev/./urandom -jar /app.jar" ]

The Dockerfile in auth-service and user-service are similar, just replaced the maven build target jar file.

FROM frolvlad/alpine-oraclejdk8:slim
VOLUME /tmp
ADD ./target/auth-service-0.0.1-SNAPSHOT.jar app.jar
RUN sh -c 'touch /app.jar'
ENV JAVA_OPTS=""
ENTRYPOINT [ "sh", "-c", "java $JAVA_OPTS -Djava.security.egd=file:/dev/./urandom -jar /app.jar" ]

Create a Dockerfile for ngnix. We will use ngnix as a reverse proxy to unite the entry of the application.

# Set nginx base image
FROM nginx 

#RUN mkdir /etc/nginx/ssl  
#COPY ssl /etc/nginx/ssl 

# Copy custom configuration file from the current directory
COPY nginx.conf /etc/nginx/nginx.conf
  
#COPY www /usr/share/nginx/www  
#COPY archive /usr/share/nginx/archive

And the content of ngnix.conf.

worker_processes 1;

events { worker_connections 1024; }

http {
    sendfile on;

	server {
		listen 80;
		server_name localhost;

		proxy_set_header Host $host;
		proxy_set_header X-Forwarded-For $remote_addr;


		location /users {
			proxy_pass http://user-service:8001;
		}
		location /posts {
			proxy_pass http://post-service:8002;
		}
		location / {
			proxy_pass http://auth-service:8000;
		}
	}
}

Create a standalone docker-compose.local.yml file to run all services.

version: '3.1' # specify docker-compose version

services:

  nginx-proxy:
    image: hantsy/nginx-proxy
    container_name: nginx-proxy
    build: 
      context: ./nginx
      dockerfile: Dockerfile
    depends_on:
      - auth-service
      - user-service
      - post-service
    ports:
      - "80:80"
      
  auth-service:
    image: hantsy/auth-service
    container_name: auth-service
    build: 
      context: ./auth-service # specify the directory of the Dockerfile
      dockerfile: Dockerfile
    environment:
      USERDB_URL: jdbc:mysql://userdb:3306/userdb
      REDIS_HOST: redis
    ports:
      - "8000:8000" #specify ports forewarding
    depends_on:
      - userdb
      - redis
      
  user-service: 
    image: hantsy/user-service
    container_name: user-service
    build: 
      context: ./user-service
      dockerfile: Dockerfile
    environment:
      USERDB_URL: jdbc:mysql://userdb:3306/userdb
      REDIS_HOST: redis
    ports:
      - "8001:8001" #specify ports forewarding
    depends_on:
      - userdb
      - redis
  
  post-service: 
    image: hantsy/post-service
    container_name: post-service
    build: 
      context: ./post-service
      dockerfile: Dockerfile
    environment:
      POSTDB_URL: jdbc:mysql://postdb:3306/postdb
      REDIS_HOST: redis
    ports:
      - "8002:8002" #specify ports forewarding
    depends_on:
      - postdb
      - redis

Run all services in your local system or a staging server.

Build the project via mvn command.

mvn clean package -DskipTests

Then run the following command to run all services.

docker-compose -f docker-compose.yml -f docker-compose.local.yml up --build

The --build parameter tells Docker build Docker images for all services firstly, then create containers based on the built images.

We have run a Nginx a reverse proxy, all APIs can be accessed through a single entry.

The following services will be provided.

Service Url Description
auth-service http://localhost/user,http://localhost/auth Authentication APIs(signin, signup, signout), user info
user-service http://localhost/users User management APIs
post-service http://localhost/posts Post and comment APIs

Next, let's try the endpoints by curl command.

Get authentication by sending user/password pair via HTTP BASIC header.

curl -v  http://localhost/user -u user:test123

>
< HTTP/1.1 200
< Server: nginx/1.13.0
< Date: Thu, 25 May 2017 06:49:52 GMT
< Content-Type: application/json;charset=UTF-8
< Transfer-Encoding: chunked
< Connection: keep-alive
< X-Content-Type-Options: nosniff
< X-XSS-Protection: 1; mode=block
< Cache-Control: no-cache, no-store, max-age=0, must-revalidate
< Pragma: no-cache
< Expires: 0
< X-Frame-Options: DENY
< X-Auth-Token: 8b185a90-37db-444a-832b-6cbcd6db6df8
<
{"name":"user","roles":["USER"]}* Connection #0 to host localhost left intact

As you see the response headers includes a X-Auth-Token item.

Then add this header to the request headers when creating a new post, it return a successful CREATED status, and the new created post can be located via Location header in the response.

curl -v  http://localhost/posts -X POST -H "X-Auth-Token: 8b185a90-37db-444a-832b-6cbcd6db6df8" -H "Content-Type:application/json" -d "{\"title\": \"test post\", \"content\":\"test content of post\"}"
Note: Unnecessary use of -X or --request, POST is already inferred.
* timeout on name lookup is not supported
*   Trying ::1...
* TCP_NODELAY set
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 80 (#0)
> POST /posts HTTP/1.1
> Host: localhost
> User-Agent: curl/7.54.0
> Accept: */*
> X-Auth-Token: 8b185a90-37db-444a-832b-6cbcd6db6df8
> Content-Type:application/json
> Content-Length: 56
>
* upload completely sent off: 56 out of 56 bytes
< HTTP/1.1 201
< Server: nginx/1.13.0
< Date: Thu, 25 May 2017 06:52:46 GMT
< Content-Length: 0
< Connection: keep-alive
< X-Content-Type-Options: nosniff
< X-XSS-Protection: 1; mode=block
< Cache-Control: no-cache, no-store, max-age=0, must-revalidate
< Pragma: no-cache
< Expires: 0
< X-Frame-Options: DENY
< Location: http://localhost/posts/1
<
* Connection #0 to host localhost left intact

Create another new post.

curl -v  http://localhost/posts -X POST -H "X-Auth-Token: 8b185a90-37db-444a-832b-6cbcd6db6df8" -H "Content-Type:application/json" -d "{\"title\": \"test post 2\", \"content\":\"test content of post 2\"}"
Note: Unnecessary use of -X or --request, POST is already inferred.
* timeout on name lookup is not supported
*   Trying ::1...
* TCP_NODELAY set
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 80 (#0)
> POST /posts HTTP/1.1
> Host: localhost
> User-Agent: curl/7.54.0
> Accept: */*
> X-Auth-Token: 8b185a90-37db-444a-832b-6cbcd6db6df8
> Content-Type:application/json
> Content-Length: 60
>
* upload completely sent off: 60 out of 60 bytes
< HTTP/1.1 201
< Server: nginx/1.13.0
< Date: Thu, 25 May 2017 06:53:29 GMT
< Content-Length: 0
< Connection: keep-alive
< X-Content-Type-Options: nosniff
< X-XSS-Protection: 1; mode=block
< Cache-Control: no-cache, no-store, max-age=0, must-revalidate
< Pragma: no-cache
< Expires: 0
< X-Frame-Options: DENY
< Location: http://localhost/posts/test-post-2
<
* Connection #0 to host localhost left intact

Get all post, and verify the created posts.

curl -v  http://localhost/posts  -H "Accpet:application/json"
* timeout on name lookup is not supported
*   Trying ::1...
* TCP_NODELAY set
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 80 (#0)
> GET /posts HTTP/1.1
> Host: localhost
> User-Agent: curl/7.54.0
> Accept: */*
> Accpet:application/json
>
< HTTP/1.1 200
< Server: nginx/1.13.0
< Date: Thu, 25 May 2017 06:53:58 GMT
< Content-Type: application/json;charset=UTF-8
< Transfer-Encoding: chunked
< Connection: keep-alive
< X-Content-Type-Options: nosniff
< X-XSS-Protection: 1; mode=block
< Cache-Control: no-cache, no-store, max-age=0, must-revalidate
< Pragma: no-cache
< Expires: 0
< X-Frame-Options: DENY
<
{
  "content" : [ {
    "title" : "test post 2",
    "postSlug" : "test-post-2",
    "status" : "DRAFT",
    "id" : 2,
    "createdDate" : "2017-05-25T06:53:30",
    "author" : {
      "username" : "user"
    }
  }, {
    "title" : "test post",
    "postSlug" : "test-post",
    "status" : "DRAFT",
    "id" : 1,
    "createdDate" : "2017-05-25T06:52:45",
    "author" : {
      "username" : "user"
    }
  } ],
  "pageable" : {
    "sort" : {
      "sorted" : true,
      "unsorted" : false
    },
    "pageSize" : 10,
    "pageNumber" : 0,
    "offset" : 0,
    "paged" : true,
    "unpaged" : false
  },
  "last" : true,
  "totalElements" : 2,
  "totalPages" : 1,
  "sort" : {
    "sorted" : true,
    "unsorted" : false
  },
  "numberOfElements" : 2,
  "first" : true,
  "size" : 10,
  "number" : 0
}* Connection #0 to host localhost left intact

Create a comment for "test post 2". Do not forget to add the X-Auth-Token header to the request headers.

curl -v  http://localhost/posts/test-post-2/comments -X POST -H "X-Auth-Token: 8b185a90-37db-444a-832b-6cbcd6db6df8" -H "Content-Type:application/json" -d "{ \"content\":\"conmment content of post 2\"}"
Note: Unnecessary use of -X or --request, POST is already inferred.
* timeout on name lookup is not supported
*   Trying ::1...
* TCP_NODELAY set
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 80 (#0)
> POST /posts/test-post-2/comments HTTP/1.1
> Host: localhost
> User-Agent: curl/7.54.0
> Accept: */*
> X-Auth-Token: 8b185a90-37db-444a-832b-6cbcd6db6df8
> Content-Type:application/json
> Content-Length: 41
>
* upload completely sent off: 41 out of 41 bytes
< HTTP/1.1 201
< Server: nginx/1.13.0
< Date: Thu, 25 May 2017 06:54:59 GMT
< Content-Length: 0
< Connection: keep-alive
< X-Content-Type-Options: nosniff
< X-XSS-Protection: 1; mode=block
< Cache-Control: no-cache, no-store, max-age=0, must-revalidate
< Pragma: no-cache
< Expires: 0
< X-Frame-Options: DENY
< Location: http://localhost/posts/test-post-2/comments/3
<
* Connection #0 to host localhost left intact

Create another comment.

curl -v  http://localhost/posts/test-post-2/comments -X POST -H "X-Auth-Token: 8b185a90-37db-444a-832b-6cbcd6db6df8" -H "Content-Type:application/json" -d "{ \"content\":\"conmment content of post, another comment\"}"
Note: Unnecessary use of -X or --request, POST is already inferred.
* timeout on name lookup is not supported
*   Trying ::1...
* TCP_NODELAY set
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 80 (#0)
> POST /posts/test-post-2/comments HTTP/1.1
> Host: localhost
> User-Agent: curl/7.54.0
> Accept: */*
> X-Auth-Token: 8b185a90-37db-444a-832b-6cbcd6db6df8
> Content-Type:application/json
> Content-Length: 56
>
* upload completely sent off: 56 out of 56 bytes
< HTTP/1.1 201
< Server: nginx/1.13.0
< Date: Thu, 25 May 2017 06:55:21 GMT
< Content-Length: 0
< Connection: keep-alive
< X-Content-Type-Options: nosniff
< X-XSS-Protection: 1; mode=block
< Cache-Control: no-cache, no-store, max-age=0, must-revalidate
< Pragma: no-cache
< Expires: 0
< X-Frame-Options: DENY
< Location: http://localhost/posts/test-post-2/comments/4
<
* Connection #0 to host localhost left intact

Now get all comments of the post test-post-2 to verify the comments.

curl -v  http://localhost/posts/test-post-2/comments  -H "Accpet:application/json"
* timeout on name lookup is not supported
*   Trying ::1...
* TCP_NODELAY set
* connect to ::1 port 80 failed: Connection refused
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 80 (#0)
> GET /posts/test-post-2/comments HTTP/1.1
> Host: localhost
> User-Agent: curl/7.54.0
> Accept: */*
> Accpet:application/json
>
< HTTP/1.1 200
< Server: nginx/1.13.0
< Date: Thu, 25 May 2017 06:55:35 GMT
< Content-Type: application/json;charset=UTF-8
< Transfer-Encoding: chunked
< Connection: keep-alive
< X-Content-Type-Options: nosniff
< X-XSS-Protection: 1; mode=block
< Cache-Control: no-cache, no-store, max-age=0, must-revalidate
< Pragma: no-cache
< Expires: 0
< X-Frame-Options: DENY
<
{
  "content" : [ {
    "content" : "conmment content of post, another comment",
    "id" : 4,
    "createdDate" : "2017-05-25T06:55:22",
    "author" : {
      "username" : "user"
    }
  }, {
    "content" : "conmment content of post 2",
    "id" : 3,
    "createdDate" : "2017-05-25T06:54:59",
    "author" : {
      "username" : "user"
    }
  } ],
  "pageable" : {
    "sort" : {
      "sorted" : true,
      "unsorted" : false
    },
    "pageSize" : 10,
    "pageNumber" : 0,
    "offset" : 0,
    "paged" : true,
    "unpaged" : false
  },
  "last" : true,
  "totalElements" : 2,
  "totalPages" : 1,
  "sort" : {
    "sorted" : true,
    "unsorted" : false
  },
  "numberOfElements" : 2,
  "first" : true,
  "size" : 10,
  "number" : 0
}* Connection #0 to host localhost left intact

Testing Microservices

As stated in the previous sections, every single service is a small Spring Boot application. To test the whole Microservices application, firstly you should fully test the services/components themselves.

Testing Single Service

Testing a single service is similar to testing a general Spring Boot application, for example, in this application, to test post service, you should test very components in this service.

  • Simple POJOs, such as @Entity classes, DTOs.
  • Database related facilities, such as JPA and Repository classes.
  • Web layer, such as Controller and exception handlers.
  • Additionally, integration tests is a must to ensure the application is working well close to a real world deployment environment.

Testing POJOs

It is very simple, like testing a single POJO classes in a Java application, no dependent object in it. An example of testing the Post entity class.

public class PostTest {

    @Test
    public void testSlug() {
        System.out.println("getSlug");
        Post instance = new Post();
        instance.setTitle("test post 1");
        instance.slugify();
        assertEquals("test-post-1", instance.getSlug());
    }
}

Testing Repository

There are some utilities can be used to test a Spring Data Repository bean.

For Spring Data JPA, there is a @DataJpaTest annotation which will autoconfigure the essential dependencies for testing a Repository bean, that means it does not load all beans from the application context when running the tests. And when adding an embedded RDBMS, such as H2 in the test classpath, it will bypass the real database configuration in the application properties and use the embedded database instead when running the tests.

Additionally, Spring Boot provides a TestEntityManager bean which is similar to the standard EntityManager, but provides more methods for test purpose.

Add H2 to test scope in the pom.xml file.

<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <scope>test</scope>
</dependency>

Create a test calss to test PostRepository.

 @RunWith(SpringRunner.class)
 @DataJpaTest()
 @Slf4j
 public class PostRepositoryTest {
 
     @Autowired
     private TestEntityManager em;
 
     @Autowired
     PostRepository posts;
 
     @Before
     public void setup() {
         assertNotNull("posts is not null", posts);
         posts.deleteAllInBatch();
         em.persist(Post.builder().title("test post 1").content("test content of test post 1").build());
     }
 
     @Test
     public void testGetAllPosts() {
         assertTrue(1 == posts.findAll().size());
         Post post = posts.findAll().get(0);
         assertTrue("test-post-1".equals(post.getSlug()));
     }
 
 }

Testing PostService

The PostService depends on PostRepsoitory bean. To test the internal logic of PostService, we can mock the dependent beans(eg. PostRepository bean) and stub the behavior of PostRepository bean, and verify the logic in PostService works as expected.

@RunWith(SpringRunner.class)
@Slf4j
public class PostServiceTest {

    @MockBean
    private PostRepository posts;

    @Autowired
    private PostService postService;


    @Test
    public void createPost() {
        final String TITLE = "test post title";
        final String CONTENT = "test post content";

        final PostForm input = PostForm.builder().title(TITLE).content(CONTENT).build();
        Post expected = Post.builder().title(TITLE).content(CONTENT).build();
        expected.setId(1L);

        given(posts.save(Post.builder().title(input.getTitle()).content(input.getContent()).build()))
                .willReturn(expected);

        Post returned = postService.createPost(input);

        assertTrue(returned == expected);

        verify(posts, times(1)).save(any(Post.class));
        verifyNoMoreInteractions(posts);
    }

    @TestConfiguration
    @Import(PostService.class)
    static class TestConfig {

    }

}

Testing web facilities

For Spring WebMVC applications, Spring Boot includes a simple @WebMvcTest to prepare the test environment for testing controller classes. When running a test annotated with @WebMvcTest, a MockMvc bean is available in the application context. In the @WebMvcTest, use the controllers to specify the controllers you wan to tests, and there is a secure attribute indicates if enabling Spring Security support in this test.

@RunWith(SpringRunner.class)
@Slf4j
@WebMvcTest(controllers = PostController.class, secure = false)
public class PostControllerTest {

    @MockBean
    PostRepository posts;

    @MockBean
    CommentRepository comments;

    @MockBean
    PostService postService;

    @Autowired
    ObjectMapper objectMapper;

    @Autowired
    MockMvc mockMvc;

    @Test
    public void createPost() throws Exception {
        Post _data = Post.builder().slug("test-my-first-post").title("my first post").content("my content of my post").build();
        given(this.postService.createPost(any(PostForm.class)))
                .willReturn(_data);

        this.mockMvc
                .perform(
                        post("/posts")
                                .content(objectMapper.writeValueAsString(PostForm.builder().title("my first post").content("my content of my post").build()))
                                .contentType(MediaType.APPLICATION_JSON)
                )
                .andExpect(status().isCreated())
                .andExpect(header().exists("Location"));

        verify(this.postService, times(1)).createPost(any(PostForm.class));
        verifyNoMoreInteractions(this.postService);
    }

}

Note: In the latest Spring Boot, the secure attribute of @WebMvcTest is deprecated. If you want to exclude Spring Security configuration, you have to exclude the Spring Security related Configurations, see this example.

For fine grained configure the MockMvc, you can create it through MockMvcBuilders.standaloneSetup or MockMvcBuilders.webAppContextSetup, the former will choose the controllers to tests, and the later will load all controllers from the application context.

The following is an example test using MockMvcBuilders.standaloneSetup to configure a MockMvc object.

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.MOCK)
@RunWith(SpringRunner.class)
@Slf4j
public class ApplicationControllerMockMvcTest {

    @Autowired
    WebApplicationContext wac;

    @MockBean
    PostRepository posts;

    @MockBean
    CommentRepository comments;

    @MockBean
    PostService postService;

    @Autowired
    ObjectMapper objectMapper;

    @Autowired
    FilterChainProxy springSecurityFilterChain;

    MockMvc mockMvc;

    @Before
    public void setup() {
        this.mockMvc = standaloneSetup(new PostController(postService, posts, comments))
                .setCustomArgumentResolvers(
                        new PageableHandlerMethodArgumentResolver()
                )
                .setMessageConverters(
                        new MappingJackson2HttpMessageConverter(objectMapper)
                )
                .alwaysDo(print())
                .apply(springSecurity(springSecurityFilterChain))
                .build();
    }

    @Test
    //@Ignore
    public void testGetAllPosts() throws Exception {
        given(this.posts
                .findAll(any(Specification.class), any(Pageable.class)))
                .willReturn(
                        new PageImpl(
                                Arrays.asList(
                                        Post.builder().title("my first post1").content("my content of my post1").build(),
                                        Post.builder().title("my first post2").content("my content of my post2").build(),
                                        Post.builder().title("my first post3").content("my content of my post3").build()
                                ),
                                PageRequest.of(0, 10),
                                3L
                        )
                );

        MvcResult result = this.mockMvc
                .perform(
                        get("/posts?q=my")
                                .accept(MediaType.APPLICATION_JSON)
                )
                .andExpect(status().isOk())
                .andExpect(jsonPath("$.content[*].title", hasItem("my first post1")))
                .andReturn();

        log.debug("mvc result:::" + result.getResponse().getContentAsString());
        verify(this.posts, times(1)).findAll(any(Specification.class), any(Pageable.class));
        verifyNoMoreInteractions(this.posts);
    }

    @Test
    public void createPostWithoutAuthentication() throws Exception {
        Post _data = Post.builder().title("my first post").content("my content of my post").build();
        given(this.postService.createPost(any(PostForm.class)))
                .willReturn(_data);

        MvcResult result = this.mockMvc
                .perform(
                        post("/posts")
                                .content(objectMapper.writeValueAsString(PostForm.builder().title("my first post").content("my content of my post").build()))
                                .contentType(MediaType.APPLICATION_JSON)
                )
                .andExpect(status().isUnauthorized())
                .andReturn();

        log.debug("mvc result::" + result.getResponse().getContentAsString());

        verify(this.postService, times(0)).createPost(any(PostForm.class));
        verifyNoMoreInteractions(this.postService);
    }

    @Test
    @WithMockUser
    public void createPostWithMockUser() throws Exception {
        Post _data = Post.builder().title("my first post").content("my content of my post").build();
        given(this.postService.createPost(any(PostForm.class)))
                .willReturn(_data);

        MvcResult result = this.mockMvc
                .perform(
                        post("/posts")
                                .content(objectMapper.writeValueAsString(PostForm.builder().title("my first post").content("my content of my post").build()))
                                .contentType(MediaType.APPLICATION_JSON)
                )
                .andExpect(status().isCreated())
                .andExpect(header().string(HttpHeaders.LOCATION, containsString("/posts")))
                .andReturn();

        log.debug("mvc result::" + result.getResponse().getContentAsString());

        verify(this.postService, times(1)).createPost(any(PostForm.class));
    }

}

Similarly you can build a MockMvc object using MockMvcBuilders.webAppContextSetup.

this.mockMvc = webAppContextSetup(this.wac)
    .alwaysDo(print())
    .apply(springSecurity(springSecurityFilterChain))
    .build();

RestAssured also extends the MockMvc support through io.rest-assured:spring-mock-mvc module, explore the RestAsssured MockMVC integration example yourself.

Next let's move on a small feature, I've created a View class to limit the result in the final JSON view. Let's create a test for verify it. Spring Boot provides a @JsonTest and allow you test the JSON serialization and deserialization.

@RunWith(SpringRunner.class)
@JsonTest
@Slf4j
public class JsonViewTest {

    @Autowired
    private JacksonTester<Post> json;

    @Test
    public void serializeJson() throws IOException {
        Post details = Post.builder().title("test title").content("test content").build();

        assertThat(this.json.write(details)).extractingJsonPathStringValue("@.title")
                .isEqualTo("test title");
        assertThat(this.json.write(details)).extractingJsonPathStringValue("@.content")
                .isEqualTo("test content");

    }

    @Test
    public void serializeJsonWithView() throws IOException {
        Post details = Post.builder().title("test title").content("test content").build();

        ObjectMapper mapper = new ObjectMapper();
        String result = mapper
                .writerWithView(View.Summary.class)
                .writeValueAsString(details);
        log.debug("result:::" + result);

        assertTrue(result.contains("test title"));
        assertTrue(!result.contains("test content"));

    }
}

Integration Tests

Now web run the application with all dependent services, esp. with the real database.

The following is a sample integration tests.

@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
@RunWith(SpringRunner.class)
@Slf4j
public class IntegrationTests {

    @LocalServerPort
    int port;

    @Autowired
    PostRepository posts;

    @Autowired
    CommentRepository comments;

    String test_title = "test title";
    String test_content = "test content";
    String test_comment = "test_comment";
    String slug = "";

    @Before
    public void setup() {
        RestAssured.reset();
        RestAssured.port = this.port;
        this.comments.deleteAllInBatch();
        this.posts.deleteAllInBatch();

        Post post = posts.save(
                Post.builder()
                        .title(test_title)
                        .content(test_content)
                        .build()
        );
        log.debug("saved post:" + post);
        this.slug = post.getSlug();

        log.debug("print all posts:");
        posts.findAll().forEach(System.out::println);

        Comment comment = this.comments.save(
                Comment.builder()
                        .content(test_comment)
                        .post(new PostSlug(this.slug))
                        .build()
        );
        log.debug("saved comment:" + comment);
    }

    @Test
    public void testGetNoneExistingPost_shouldReturn404() throws Exception {
        //@formatter:off
        when()
            .get("/posts/100000")
        .then()
            .statusCode(HttpStatus.SC_NOT_FOUND);
        //@formatter:on
    }


    @Test
    public void testGetAllPosts_shouldBeOK() throws Exception {
        //@formatter:off
        when()
            .get("/posts")
        .then()
            .body("content[0].title", is(test_title))
            .statusCode(HttpStatus.SC_OK);
        //@formatter:on
    }

    @Test
    public void testGetPostBySlug_shouldBeOK() throws Exception {
        //@formatter:off
        when()
            .get("/posts/"+ this.slug)
        .then()
            .body("title", is(test_title))
            .body("content", is(test_content))
            .statusCode(HttpStatus.SC_OK);
        //@formatter:on
    }

    @Test
    public void testGetCommentsOfPostBySlug_shouldBeOK() throws Exception {
        //@formatter:off
        when()
            .get("/posts/"+ this.slug+"/comments")
        .then()
            .body("content[0].content", is(test_comment))
            .statusCode(HttpStatus.SC_OK);
        //@formatter:on
    }

    //-------------- test with auth -----------------------
    @Test
    public void testCreateAPost_withoutUserAuth_shouldReturn401() throws Exception {
        PostForm _data = PostForm.builder().title(test_title).content(test_content).build();

        //@formatter:off
        given()
            //.auth().basic("user", "password")
            .body(_data)
            .contentType(ContentType.JSON)
        .when()
            .post("/posts")
        .then()
            .statusCode(HttpStatus.SC_UNAUTHORIZED);
        //@formatter:on
    }

    @Test
    public void testCreateAPost_withUserAuth_shouldBeOK() throws Exception {
        PostForm _data = PostForm.builder().title(test_title).content(test_content).build();

        //@formatter:off
        given()
            .auth().basic("user", "password")
            .body(_data)
            .contentType(ContentType.JSON)
        .when()
            .post("/posts")
        .then()
            .header("Location", containsString("/posts"))
            .statusCode(HttpStatus.SC_CREATED);
        //@formatter:on
    }


    @Test
    public void testUpdateAPost_withoutUserAuth_shouldReturn401() throws Exception {
        PostForm _data = PostForm.builder().title(test_title).content(test_content).build();

        //@formatter:off
        given()
            //.auth().basic("user", "password")
            .body(_data)
            .contentType(ContentType.JSON)
        .when()
            .put("/posts/"+ this.slug)
        .then()
            .statusCode(HttpStatus.SC_UNAUTHORIZED);
        //@formatter:on
    }

    @Test
    public void testUpdateAPost_withUserAuth_shouldBeOK() throws Exception {
        PostForm _data = PostForm.builder().title(test_title).content(test_content).build();

        //@formatter:off
        given()
            .auth().basic("user", "password")
            .body(_data)
            .contentType(ContentType.JSON)
        .when()
            .put("/posts/"+ this.slug)
        .then()
            .statusCode(HttpStatus.SC_NO_CONTENT);
        //@formatter:on
    }


    @Test
    public void testDeleteAPost_withoutAuth_shouldReturn401() throws Exception {

        //@formatter:off
        when()
            .delete("/posts/"+ this.slug)
        .then()
            .statusCode(HttpStatus.SC_UNAUTHORIZED);
        //@formatter:on
    }

    @Test
    public void testDeleteAPost_withUserAuth_shouldReturn403() throws Exception {

        //@formatter:off
        given()
            .auth().basic("user", "password")
        .when()
            .delete("/posts/"+ this.slug)
        .then()
            .statusCode(HttpStatus.SC_FORBIDDEN);
        //@formatter:on
    }


    @Test
    public void testDeleteAPost_withAdminAuth_shouldOK() throws Exception {

        //@formatter:off
        given()
            .auth().basic("admin", "password")
        .when()
            .delete("/posts/"+ this.slug)
        .then()
            .statusCode(HttpStatus.SC_NO_CONTENT);
        //@formatter:on
    }


    @Test
    public void testCreateACommentsOfPostBySlug_withoutAuth_shouldReturn401() throws Exception {
        CommentForm _data = CommentForm.builder().content(test_comment).build();

        //@formatter:off
        given()
            .body(_data)
            .contentType(ContentType.JSON)
        .when()
            .post("/posts/"+ this.slug+"/comments")
        .then()
            .statusCode(HttpStatus.SC_UNAUTHORIZED);
        //@formatter:on
    }

    @Test
    public void testCreateACommentsOfPostBySlug_withUserAuth_shouldBeOk() throws Exception {
        CommentForm _data = CommentForm.builder().content(test_comment).build();

        //@formatter:off
        given()
            .auth().basic("user", "password")
            .body(_data)
            .contentType(ContentType.JSON)
        .when()
            .post("/posts/"+ this.slug+"/comments")
        .then()
            .header("Location", containsString("/posts/"+ this.slug+"/comments"))
            .statusCode(HttpStatus.SC_CREATED);
        //@formatter:on
    }

    
    @TestComponent
    @Slf4j
    static class TestUserDetailsService implements UserDetailsService {

        private final PasswordEncoder passwordEncoder;

        TestUserDetailsService(PasswordEncoder passwordEncoder) {
            this.passwordEncoder = passwordEncoder;
        }

        @Override
        public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
            UserDetails user = User.withUsername("user")
                    .password(passwordEncoder.encode("password"))
                    .roles("USER")
                    .accountExpired(false)
                    .accountLocked(false)
                    .credentialsExpired(false)
                    .disabled(false)
                    .build();

            UserDetails admin = User.withUsername("admin")
                    .password(passwordEncoder.encode("password"))
                    .roles("ADMIN")
                    .accountExpired(false)
                    .accountLocked(false)
                    .credentialsExpired(false)
                    .disabled(false)
                    .build();

            log.debug("dummy user:" + user);
            log.debug("dummy admin:" + admin);


            if ("user".equals(username)) {
                return user;
            } else {
                return admin;
            }
        }
    }

    @TestConfiguration
    @Slf4j
    @Import(TestUserDetailsService.class)
    @Order(-1)
    static class TestSecurityConfig extends WebSecurityConfigurerAdapter {

        @Autowired
        PasswordEncoder passwordEncoder;

        @Autowired
        UserDetailsService userDetailsService;

        @Override
        protected void configure(HttpSecurity http) throws Exception {
            http
                    .httpBasic()
                    .and()
                    .authorizeRequests()
                    .antMatchers(HttpMethod.GET, "/posts/**").permitAll()
                    .antMatchers(HttpMethod.DELETE, "/posts/**").hasRole("ADMIN")
                    .anyRequest().authenticated()
                    .and()
                    .csrf().disable();
        }

        @Override
        protected void configure(AuthenticationManagerBuilder auth) throws Exception {
            auth.userDetailsService(userDetailsService).passwordEncoder(passwordEncoder);
        }

        @Override
        @Bean
        public AuthenticationManager authenticationManagerBean() throws Exception {
            return super.authenticationManagerBean();
        }

    }
}

From the former sections, we have introduced how to get authentication from the auth-service. In the above codes, we add some custom Security configuration to override Spring Security Config to isolate the authentication from auth-service. Here we use a simple HTTP Basic authentication instead.

Testing against External Service

In our application, the auth service depends on user service to complete the authentication process. There is a UserServiceClient in the auth service used for signup and authentication.

@Component
public class UserServiceClient {

    private RestTemplate restTemplate;

    private ObjectMapper objectMapper;

    @Value("${services.user-service-url}")
    private String userServiceUrl;

    public UserServiceClient(RestTemplateBuilder builder, ObjectMapper objectMapper) {
        this.restTemplate = builder.build();
        this.objectMapper = objectMapper;
    }

    public void handleSignup(SignupForm form) {
        try {
            ResponseEntity<Void> response = this.restTemplate.postForEntity(userServiceUrl + "/users", form, Void.class);
        } catch (HttpClientErrorException e) {
            if (e.getStatusCode() == CONFLICT) {
                Map map = null;
                try {
                    map = objectMapper.readValue(e.getResponseBodyAsByteArray(), Map.class);
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
                throw new SignupConflictException((String) map.get("message"));
            }
        }
    }

    public User findByUsername(String username) {
        try {
            ResponseEntity<User> response = this.restTemplate.getForEntity(userServiceUrl + "/users/{username}", User.class, username);
            return response.getBody();
        } catch (HttpClientErrorException e) {
            if (e.getStatusCode() == NOT_FOUND) {
                return null;
            }
        }
        return null;
    }
}

In the above codes, we use RestTemplate to access the remote user service. To test UserServiceClient, we have to mock a remote rest server to ensure the endpoints is available when running the tests. There are some several approaches to archive this.

  • Spring provides a MockRestServiceServer to setup a mock rest service easily.
  • WireMock is a more common solution for mocking HTTP endpoints.

Next, let's explore them one by one.

MockRestServiceServer

The following is an example using MockRestServiceServer. The stubbing step is similar to the Mockito when/given, set the mocked data when submitting a specific request.

@RunWith(SpringRunner.class)
@RestClientTest(UserServiceClient.class)
@Slf4j
public class UserServiceClientTest {

    @Value("${services.user-service-url:http://localhost:8001}")
    private String userServiceUrl;

    @Autowired
    private UserServiceClient client;

    @Autowired
    private MockRestServiceServer server;

    @Test
    public void testFindbyUsername() {
        this.server.expect(requestTo(userServiceUrl + "/users/user"))
            .andRespond(withSuccess(new ClassPathResource("/find-user-by-username.json"), MediaType.APPLICATION_JSON_UTF8));
            //.andRespond(withSuccess("{\"username\":\"user\",\"password\":\"password\",\"email\":\"user@example.com\"}", MediaType.APPLICATION_JSON_UTF8));

        User user = this.client.findByUsername("user");
        assertNotNull(user);
        assertEquals("user", user.getUsername());

        this.server.verify();
    }

    @Test
    public void testFindbyUsername_notFound() {
        this.server.expect(requestTo(userServiceUrl + "/users/user1"))
            .andRespond(withStatus(NOT_FOUND));

        User user = this.client.findByUsername("user1");
        assertNull(user);

        this.server.verify();
    }
}

Similar to Spring Boot @WebMvcTest, @DataJpaTest, etc. The @RestClientTest is also a slice test utility which only provides a RestTemplateBuilder in the test context.

WireMock

WireMock is a general purpose solution for mocking HTTP endpoints.

There is an example of using WireMock to test UserServiceClient .

@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
@Slf4j
public class UserServiceClientWireMockTest {

    @Value("${services.user-service-url:http://localhost:8001}")
    private String userServiceUrl;

    @Autowired
    private UserServiceClient client;

    @Rule
    public WireMockRule wireMockRule = new WireMockRule(options().port(8001));

    @Before
    public void setup() {
        WireMock.reset();
    }

    @Test
    public void testFindbyUsername() {

        stubFor(
            get("/users/user")
                //.withHeader("Accept", equalTo(MediaType.APPLICATION_JSON_VALUE))
                .willReturn(
                    okJson("{\"username\":\"user\",\"password\":\"password\",\"email\":\"user@example.com\"}")
                )
        );

        User user = this.client.findByUsername("user");
        assertNotNull(user);
        assertEquals("user", user.getUsername());

        verify(1, getRequestedFor(urlMatching( "/users/user")));
    }

    @Test
    public void testFindbyUsername_notFound() {
        stubFor(
            get( "/users/user1")
                //.withHeader("Accept", equalTo(MediaType.APPLICATION_JSON_VALUE))
                .willReturn(
                    aResponse()
                        .withStatus(HttpStatus.SC_NOT_FOUND)
                )
        );

        User user = this.client.findByUsername("user1");
        assertNull(user);

        verify(1, getRequestedFor(urlMatching( "/users/user1")));
    }
}

In the above codes, WireMock provides a @Rule to wire the stubbing into the lifecycle of the JUnit runner.

Testing Service-to-Service Communication

The above MockRestServiceServer or WireMock is widely used when the existing external service is out of control, eg. it is from the 3rd party company or organization.

In our application, the auth service and user service are developed by ourselves, but may be produced by two different teams.

Assume when the auth service requires to embed the result of a /users endpoints that should be provided by user service, but at that moment such an AP does not exist in the user service at all. To resolve the problem, the best way is the developers from two sides sit down at a table and sign a contract about the communication details between these two services. Firstly the auth service developer lists all required HTTP endpoints that should be provided by the user service. For example.

  • When sending a GET request on the endpoints /users/user1, then return a response with the json content like this: {'username':'uesr', roles:'USER'}, etc.
  • When the requesting endpoint is /users/noneexisting, then return a 404 error.
  • ...

The user service developer reviews the requirements, and confirm the items one by one, and make sure they are on the same page.

Then they are back to work and focus on their own development. When the development(both side) is done, they can use a real world environment to verify if they have complied with the rules defined in the contracts they have signed.

In the software development world, this kind of scene is called Consumer Driven Contracts. In the CDC world, the auth service is called the API consumer, and the user service is the API producer/provider. In these years, CDC/Contracts testing becomes more and more popular.

Obviously, an advantage of applying this pattern is the consumer side can start work immediately when the contract is signed and do not need to wait for the complete work from the producer side.

There are a few projects available to improve the CDC development process.

  • Spring Cloud includes a Spring Cloud Contracts subproject, which is heavily dependent on the Spring ecosystem.
  • Pact is a general HTTP endpoints contracts verification solution, not limited to Spring ecosystem.

Spring Cloud Contracts

Spring Cloud Contracts Workshop provides the best practice when introducing Spring Cloud Contracts into your Microservices project.

Pact

Deploying Microservices application

In this section, we will explore how to deploy the services to the popular container platform, including Docker Swarm and Kubernetes.

Publishing Docker Images to Docker Hub

Create an account on the official Docker Hub, after the account is created, you will get a special namespace for yourself.

In former steps, we have set the image name with a hantsy/ prefix where the hantsy is the account name in the DockerHub.

After the Docker is installed, you can login to docker hub in the terminal.

docker login

// follow the guide to input user name and password to log in.

Then run the following command to publish your Docker images to the public Docker Hub.

docker push hantsy/post-service
docker push hantsy/user-service
docker push hantsy/auth-service
docker push hantsy/ngnix-proxy

When all are finished, go to Docker Hub, login and you will see the uploaded Docker images.

To verify the Docker Images is available via DockerHub, run the following commands to pull them from Docker Hub.

//remove the existing images.
docker rmi post-service

//pull the docker images
docker pull hantsy/post-service

If you do not want to expose your docker images to the public, choose a paid service or setup a private Docker registry server.

No panic the official docker registry is available as a Docker image, follow the official guide to deploy a docker registry server.

Besides the official Docker Hub and private Docker registry, almost all cloud platforms provide private Docker registry service for the customers.

And Github and GitLab provides a Packages feature which includes hosting Docker images services, check the following docs:

Deploying to Docker Swarm

Use Docker Machine to create multiple nodes.

These steps are tested on the legacy Docker Toolbox and use VritualBox as virtual machines. If you are using Docker Desktop for Windows, use Hyper-V instead.

In order to demonstrate running this project in Swarm mode, we will create two managers and three workers.

$ docker-machine create -d virtualbox --engine-registry-mirror https://docker.mirrors.ustc.edu.cn manager1
$ docker-machine create -d virtualbox --engine-registry-mirror https://docker.mirrors.ustc.edu.cn manager2
$ docker-machine create -d virtualbox --engine-registry-mirror https://docker.mirrors.ustc.edu.cn worker1
$ docker-machine create -d virtualbox --engine-registry-mirror https://docker.mirrors.ustc.edu.cn worker2
$ docker-machine create -d virtualbox --engine-registry-mirror https://docker.mirrors.ustc.edu.cn worker3

List all docker machines you just created.

$ docker-machine ls
NAME       ACTIVE   DRIVER       STATE     URL                         SWARM   DOCKER        ERRORS
manager1   -        virtualbox   Running   tcp://192.168.99.101:2376           v17.05.0-ce
manager2   -        virtualbox   Running   tcp://192.168.99.102:2376           v17.05.0-ce
worker1    -        virtualbox   Running   tcp://192.168.99.103:2376           v17.05.0-ce
worker2    -        virtualbox   Running   tcp://192.168.99.104:2376           v17.05.0-ce
worker3    -        virtualbox   Running   tcp://192.168.99.105:2376           v17.05.0-ce

Switch to machine manager1.

eval "$(docker-manager env manager1)"

Try to initialize a Docker Swarm host.

$ docker swarm init --listen-addr 192.168.99.101 --advertise-addr 192.168.99.101
Swarm initialized: current node (t36lxk020fasw5tdes4gm9ucf) is now a manager.

To add a worker to this swarm, run the following command:

    docker swarm join \
    --token SWMTKN-1-10bwwj2u6erepp9oc0qlkwao4o79vogifon51qkhdqfsl7zkkd-810eddvkzt2g8vvxb4gul4pnb \
    192.168.99.101:2377

To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.

We want to add manager2 as manager in this swarm. Follow the above info. Execute docker swarm join-token manager, it will show the guide to add more managers.

$ docker swarm join-token manager
To add a manager to this swarm, run the following command:

    docker swarm join \
    --token SWMTKN-1-10bwwj2u6erepp9oc0qlkwao4o79vogifon51qkhdqfsl7zkkd-4xus5y6wa7a4ass0f5bt20pym \
    192.168.99.101:2377

Let us switch to machine manager2.

eval "$(docker-machine env manager2)"

Copy and paste the docker swarm join command lines and execute it.

$ docker swarm join \
     --token SWMTKN-1-10bwwj2u6erepp9oc0qlkwao4o79vogifon51qkhdqfsl7zkkd-4xus5y6wa7a4ass0f5bt20pym \
     192.168.99.101:2377
This node joined a swarm as a manager.

Switch to worker1, worker2, and worker3, join this swarm as a worker.

    docker swarm join \
    --token SWMTKN-1-10bwwj2u6erepp9oc0qlkwao4o79vogifon51qkhdqfsl7zkkd-810eddvkzt2g8vvxb4gul4pnb \
    192.168.99.101:2377

Switch to any manager machine, and you can show all running nodes.

$ docker node ls
ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS
9d07by6czpem6hx55ke3ks1v1     manager2            Ready               Active              Reachable
er9klqvww0kdwyfaxr5f7n15l     worker1             Ready               Active
hsmaugexj4l7p5ighl9nega8q     worker2             Ready               Active
lknqw5dg5jyxw3j2camcpnb0v *   manager1            Ready               Active              Leader
ovqfs7ymrgbeyfqu8db8n6apc     worker3             Ready               Active

Switch to any manager machine, deploy all service via docker stack command.

docker stack deploy -c docker-stack.yml blogapp

The services will be scheduled to deploy in this swarm.

The docker-stack.yml file includes a visualizer service to visualize all services. It can be accessed via http://<any manager ip>:8080, you will see the deployment progress.

visualizer

#curl http://192.168.99.102/user -u user:test123
{"roles":["ROLE_USER"],"name":"user"}

Remove this stack by the following command.

docker stack rm blogapp

Deploying to Kubernetes