README.md

spring-GraphQL

This repo contains:

• GraphQL (query - mutation)
• Spring Data Jpa
• Pagination
• GraphQL test

This repo show how to use graphQL with spring for represent data, also show how to test it.

Instruction for use GraphQL

1. define graphql as directory on resources and create schema file into this directory
2. write type of object which represent in Rest-APIs base on your models.
   1. use type keyword for define objects
   2. use ID as type for id
   3. use ! to show this field have value and don't need check for null
   4. use [] to show this field has more than one data
   5. use input to define object that want use it in many request in mutation
3. define controller method and mapped query to the method
   1. use SchemaMapping -> @SchemaMapping(typeName = "Query", value = "allBooks")
   2. use QueryMapping -> @QueryMapping and set name of method as same as query that define in schema
4. sample query in UI

   query {
     findOne(id:2) {
       id
       title
       pages
       rating{
         star
       }
       author{
         firstName
         lastName
       }
     }
   }

5. sample mutation in UI

   mutation{ update(coffeeForUpdate: {
       id: 4
       name:"Hot Nescafe"
       size:TALL
     }) {
       name
       id
       size
     }
   }

6. Sample Mutation with array

   mutation BatchCreate { 
     batchCreate(coffees: [
       {name: "coffee One", size: SHORT},
       {name: "coffee two", size: TALL},    
       {name: "coffee three", size: SHORT}
     ]){
       id,
       name,
       size
     }
   }

How to extend scalar

if you want to extend scalar of graphQL, you must do this steps:

1. add graphql-java-extended-scalars in pom file
2. use scalar keyword in schema.graphqls file in order define new scalar -> scalar BigDecimal
3. create config class to define RuntimeWiringConfigurer bean, in order to wire scalar BigDecimal
4. Another library that is useful for date is Tailrocks graphql java datetime

How to write own handler for catch exception

1. define your own Exception which it extends from RuntimeException like PersonQLException
2. define a handler that it extends DataFetcherExceptionResolverAdapter and override resolveToSingleError method like PersonQLExceptionHandler
3. also you can use your handler class for handle constraint validation

customer as an extended scalar sample written by using those steps.

Note:

• Three Top level root Operation
  Query -> define query
  Mutation -> change data, creating, updating, deleting
  Subscription -> read data and keep connection open for when changes
  

• In order to use graphical UI , first enable spring.graphql.graphiql.enabled in application properties,
  and then write this URL in browser: http://localhost:8080/graphiql?path=/graphql

Special Thanks from Dan Vega for the tutorial about GraphQL