Receiving data as JSON object

Question

I in my controller class a have the following method:

import javax.json.Json;
import javax.servlet.http.HttpServletRequest;
import javax.ws.rs.Consumes;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.MediaType;


@POST
@Consumes({MediaType.APPLICATION_JSON})
@Produces({MediaType.TEXT_PLAIN})
@Path("/message")
public String postMessage(Json json,
    @Context HttpServletRequest request) {
   System.out.println("message");
   return "ok";
}

The problem is when I send POST by executing curl by:

curl -H "Content-Type: application/json" -X 
POST -d '{"key":"value"}' http://localhost:8080/message

I get HTTP Status 415 - Unsupported Media Type as if I didn't send JSON. When I change Json json, to String body the controller works fine.

In web.xml I have:

<servlet>
        <servlet-name>jersey-serlvet</servlet-name>
        <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
        <init-param>
            <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
            <param-value>true</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

EDIT

I had wrong JSON as suggested in the comments. However, even with a correct one like {"key":"value"} the code won't work.

Do you have JSON mapping enabled in your JAX-RS implementation? — Florian Albrecht, Mar 26 '18 at 11:45
Is it the correct url you are using? From the code you posted it should be `http://localhost:8080/message` rather than `http://localhost:8080/get/message` — Michal Lonski, Mar 26 '18 at 11:50
It's different. I changed it to `http://localhost:8080/message` now for convenience. — menteith, Mar 26 '18 at 11:51
@FlorianAlbrecht I think I have. Please check my updated post. — menteith, Mar 26 '18 at 11:52
You are also sending incorrect json: `'{"key":"value", "user"}'` - is is not a valid one, add a value to 'user'. — Michal Lonski, Mar 26 '18 at 11:53
Did you try to expect as parameter a POJO instead of javax.json.Json? Something like `public String postMessage(MyMessage msg) { }` where `MyMessage` is a class with `String key` field. — Michal Lonski, Mar 26 '18 at 12:12

Michal Lonski · Answer 1 · 2018-03-26T13:24:15.633

As far as I know jersey uses jackson's ObjectMapper to deserialize stuff. I think the problem may be that object mapper dont know how to map your request to javax.json.Json object, a simple test:

import javax.json.Json;
import com.fasterxml.jackson.databind.ObjectMapper;
// (...)
ObjectMapper mapper = new ObjectMapper();
Json json = mapper.readValue("{\"key\": \"value\"}", Json.class);

This produces an exception:

UnrecognizedPropertyException: Unrecognized field "key" (class javax.json.Json)

I think you should create a POJO instead of raw json objects, for example:

class MyMessage {
  public String key; //for simplicity, you probably will use accessor methods
}

And the same test works fine:

MyMessage msg = mapper.readValue("{\"key\": \"value\"}", MyMessage.class);

and then your controller method should look like this:

@POST
@Consumes({MediaType.APPLICATION_JSON})
@Produces({MediaType.TEXT_PLAIN})
@Path("/message")
public String postMessage(MyMessage msg) {
  System.out.println(msg.key);
  return "ok";
}

You were right about object mapper not knowing how to map. I had missing dependencies and I [solved it](https://stackoverflow.com/a/46406070/2657875). Now `MyMessage msg = mapper.readValue("{\"key\": \"value\"}", MyMessage.class); ` works great. However, I still get an error `Unsupported Media Type`. I'm using your controller. — menteith, Mar 26 '18 at 13:46

score 1 · Answer 2 · answered Mar 27 '18 at 09:02

I solved the problem. In a class that extends ResourceConfig there has to be register(JacksonFeature.class) instruction, e.g.:

public class ApplicationConfig extends ResourceConfig {

    public ApplicationConfig() {
        super(MyController.class);

        property(CommonProperties.FEATURE_AUTO_DISCOVERY_DISABLE, true);
        register(JacksonFeature.class);
    }
}

score 0 · Answer 3 · edited Jun 20 '20 at 09:12

0

Make sure that you have an implementation of MessageBodyReader in your classpath, that could consume JSON

edited Jun 20 '20 at 09:12

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answered Mar 26 '18 at 11:57

Nikolai Shevchenko

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Receiving data as JSON object

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