How to add a body to a GET request in JAX-RS

Question

I'm trying to consume a REST API that requires a body with a GET request. But as a GET usually doesn't have a body, I can't find a way to attach a body in my request. I am also building the REST API, but the professor won't allow us to change the method to POST (he gave us a list of the endpoints we are to create, no more, no less).

I'm trying to do it like this:

Response r = target.request().method(method, Entity.text(body));

Where I set the method to GET and the body to my get body. However, using this approach I get an exception:

javax.ws.rs.ProcessingException: RESTEASY004565: A GET request cannot have a body.

Is there any way to do this with JAX-RS? We learned to use JAX-RS so I would prefer a solution using this, as I'm not sure my professor would allow us to use any other REST client. I'm currently using RESTEasy, provided by the WildFly server.

(This is not a duplicate of HTTP GET with request body because I'm asking on how to create a GET request with body in JAX-RS, not if it should be done.)

Answer 1

This depends on what is your JAX-RS implementation. This check can be disabled in Jersey 2.25 using SUPPRESS_HTTP_COMPLIANCE_VALIDATION property:

ClientConfig config = new ClientConfig();
config.property(ClientProperties.SUPPRESS_HTTP_COMPLIANCE_VALIDATION, true);
JerseyClient client = JerseyClientBuilder.createClient(config);
WebTarget target = client.target(URI.create("https://www.stackoverflow.com"));
Response response = target.request().method("GET", Entity.text("BODY HERE"));

Instead of exception you will get an INFO log

INFO: Detected non-empty entity on a HTTP GET request. The underlying HTTP transport connector may decide to change the request method to POST.

However in RESTEasy 3.5.0.Final there is a hardcoded check in both URLConnectionEngine and ApacheHttpClient4Engine:

if (request.getEntity() != null)
{
  if (request.getMethod().equals("GET")) throw new ProcessingException(Messages.MESSAGES.getRequestCannotHaveBody());

You would have to create your own implementation of the ClientHttpEngine to skip this. Then you need to supply it when building the client:

ClientHttpEngine engine = new MyEngine();
ResteasyClient client = new ResteasyClientBuilder().httpEngine(engine).build();