Question

@Path("/hello")
public class Hello {

    @POST
    @Path("{id}")
    @Produces(MediaType.APPLICATION_JSON)
    @Consumes(MediaType.APPLICATION_JSON)
    public JSONObject sayPlainTextHello(@PathParam("id")JSONObject inputJsonObj) {

        String input = (String) inputJsonObj.get("input");
        String output="The input you sent is :"+input;
        JSONObject outputJsonObj = new JSONObject();
        outputJsonObj.put("output", output);

        return outputJsonObj;
    }
} 

This is my webservice (I am using Jersey API). But I could not figure out a way to call this method from a java rest client to send and receive the json data. I tried the following way to write the client

ClientConfig config = new DefaultClientConfig();
Client client = Client.create(config);
WebResource service = client.resource(getBaseURI());
JSONObject inputJsonObj = new JSONObject();
inputJsonObj.put("input", "Value");
System.out.println(service.path("rest").path("hello").accept(MediaType.APPLICATION_JSON).entity(inputJsonObj).post(JSONObject.class,JSONObject.class));

But this shows the following error

Exception in thread "main" com.sun.jersey.api.client.ClientHandlerException: com.sun.jersey.api.client.ClientHandlerException: A message body writer for Java type, class java.lang.Class, and MIME media type, application/octet-stream, was not found

Answer 1

Your use of @PathParam is incorrect. It does not follow these requirements as documented in the javadoc here. I believe you just want to POST the JSON entity. You can fix this in your resource method to accept JSON entity.

@Path("/hello")
public class Hello {

  @POST
  @Produces(MediaType.APPLICATION_JSON)
  @Consumes(MediaType.APPLICATION_JSON)
  public JSONObject sayPlainTextHello(JSONObject inputJsonObj) throws Exception {

    String input = (String) inputJsonObj.get("input");
    String output = "The input you sent is :" + input;
    JSONObject outputJsonObj = new JSONObject();
    outputJsonObj.put("output", output);

    return outputJsonObj;
  }
}

And, your client code should look like this:

  ClientConfig config = new DefaultClientConfig();
  Client client = Client.create(config);
  client.addFilter(new LoggingFilter());
  WebResource service = client.resource(getBaseURI());
  JSONObject inputJsonObj = new JSONObject();
  inputJsonObj.put("input", "Value");
  System.out.println(service.path("rest").path("hello").accept(MediaType.APPLICATION_JSON).post(JSONObject.class, inputJsonObj));