Accessing RESTful Services 1.2.3

Endpoints may communicate with remote services which offer a RESTful architecture for interfacing.

Assume that the sample endpoint below uses a JSON parser definition at the type-level.

####1. Defining RESTful Methods The usual @Request annotation should be replaced with the @Rest annotation which takes a sub-path and the HTTP method type associated with the request.

######Entity

public class Contact implements Serializable {

      private long id;
      private String username;
      private String mobile;

      
      /* serialVersionUID, Accessors, Mutators, 
       * hashCode() and equals() omitted */
      

      @Override
      public String toString() {
  
          StringBuilder builder = new StringBuilder();

          builder.append("{\\"id\\":");
          builder.append(String.valueOf(this.id));
          builder.append(", \\"username\\":\\"");
          builder.append(this.username);
          builder.append("\\", \\"mobile\\":\\"");
          builder.append(this.mobile);
          builder.append(\\"});

          return builder.toString();
      }
}

To transform complex entities to JSON, use a cached instance of Gson.

######Definition ```java @Rest(path = "/contacts/update", method = RequestMethod.HTTP_POST) public abstract void updateContact(@Param("contact") Contact contact); ``` > Headers are populated the usual way using `@Header` and `@HeaderSet`. The default HTTP method is GET.
######Invocation ```java Contact doctorWho = endpoint.readContact("TheDoctor"); doctorWho.setMobile("201184919");

endpoint.update(doctorWho);

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####2. Populating Path Parameters
Along with typical request parameters, the path to a RESTful resource may be parameterized as well. Such paths can be marked with <b>placeholders</b> to indicate the need for a parameter and supplied via variables annotated with the `@PathParam` annotation. 

> Placeholders are created by prefixing a name with a colon.   

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######Definition
```java
@Rest(path = "/contacts/read/:username")
public abstract Contact readContact(@PathParam("username") String username);

######Invocation

Contact riverSong = endpoint.readContact("RiverSong");