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ResCU - a lightweight Rest client utility for Java (JAX-RS)

ResCU enables the user to create a proxy Rest client in run-time directly from a JAX-RS annotated interface. ResCU is mostly focused on json-based services, and uses Jackson for json-to-object mapping.

Several other libraries do this (eg. Jersey and RESTEasy); the benefit of ResCU is that it is very lightweight with minimal dependencies. This makes it useful for quickly creating REST clients in Android apps etc.

Dependencies

  • jackson (json parser)
  • slf4j (logging interface)
  • jsr-311 (JAX-RS) (a set of REST-service specific annotations)
  • jsr-305 (a set of annotations)

Features and benefits

  • Lightweight, minimal dependencies.
  • JAX-RS-annotated server-side interfaces may be reused to create clients; basic support is provided for @GET, @POST, @PUT, @DELETE, @HEAD, @OPTIONS, @Path, @QueryParam, @FormParam, @HeaderParam, @PathParam, @Consumes and @Produces (application/json and text/plain only).
  • Support for basic HTTP authentication and some common request signing paradigms. See the Basic HTTP Authentication wiki.
  • Support for custom exceptions on API methods: on an exceptional HTTP response, rescu can deserialize the response body as an exception. See Exception handling wiki.
  • Suppoft for custom interceptors.

Limitations

  • Rescu is meant mostly for json-based REST services. The response body is always interpreted as json or plain text. No XML, no binary data, and no plans to add it.
  • JAX-RS: No support yet for the following annotations: @MatrixParam, @CookieParam, @ApplicationPath, @HttpMethod, @Encoded, @DefaultValue.

Logging

ResCU uses slf4j for logging. For best results, a supported logging implementation (eg. log4j, JUL, logback, ...) should be provided in runtime, though this is not required. See slf4j's documentation for more info.

See logback.xml in test sources for example configuration.

Set the logging level for rescu to debug or trace in logback.xml for debugging:

<logger name="si.mazi.rescu" level="trace"/>

Usage

Maven

Rescu is hosted in Maven Central so all you need to do is add this dependency to your pom:

<dependency>
    <groupId>com.github.mmazi</groupId>
    <artifactId>rescu</artifactId>
    <version>3.0</version>
</dependency>

Usage in code

  1. Create a JAX-RS-annotated interface (or get it from the REST service developer), eg. ExampleService.java.
  2. Call ExampleService service = RestProxyFactory.createProxy(ExampleService.class, "http://www.example.com/").
  3. That's it! Just use the service object you just got.

Examples

See the tests for some examples. ExampleService is an example of a JAX-RS-annotated interface.

For more working examples, see XChange, eg. BitstampTradeServiceRaw.java.

Settings

Rescu can be configured by adding a rescu.properties file in your classpath.

Supported settings with example values (copy this into your rescu.properties file):

rescu.http.readTimeoutMillis = 5000             # Read timeout in milliseconds when performing HTTP requests. The default is 30000 (30 seconds).
rescu.http.readProxyHost = www.example.com      # Proxy host. Both host and port must be set in order to use a proxy.
rescu.http.readProxyPort = 80                   # Proxy port. Both host and port must be set in order to use a proxy.
rescu.http.readProxyType = SOCKS                # Proxy type. Applied only when readProxyHost and readProxyPort are set. Allowed values: DIRECT, HTTP, SOCKS.
rescu.http.ignoreErrorCodes = true              # If set to true, the HTTP response body never be parsed as Exception but always as the method response type. Defaults to false.

License

Rescu is released under the MIT License. Please see LICENSE.txt for the full text.