This project shows how we can support arbitrary data formats with our JAX-RS web services.
The web service itself is identical in functionality to the Parolee service introduced in Example 05. However, this time, it's set up to exchange data between client and service using java serialization as the data format.
JAX-RS does not natively support this format, but can easily be extended to support arbitrary formats. We have created a class, SerializationMessageBodyReaderAndWriter, which implements the MessageBodyReader and MessageBodyWriter interfaces. We have also annotated the class with both a @Produces and @Consumes annotation for the "application/java-serialization" MIME type (defined by the APPLICATION_JAVA_SERIALIZED_OBJECT constant). We have then told JAX-RS about our new reader / writer class by adding it to the ParoleeApplication's classes list (lines 21, 25, 36).
Now, when we mark a method in our ParoleeResource class as consuming application/java-serialization, the incoming HTTP request body will be run through our reader's readFrom() method, and supplied directly as an argument to the endpoint method (e.g. ParoleeResource's createParolee() method). Similarly, when we mark a method as producing application/java-serialization, the method's return value will be serialized via our writer's writeTo() method before being sent back to the client in the HTTP response body.
If we want to build an HTTP client which supports our custom data format, JAX-RS also provides a way for us to do this. The ClientBuilder class, which allows us to create new HTTP Client instances, contains a register() method. This method allows us to reference any custom readers and writers we like. We can see an example of this in ParoleeResourceIT's createClient() method (line 52).