How to get a jakarta.json.JsonObject Response using the Java 11 HttpClient?

Question

I want to fetch a jakarta.json.JsonObject in the HttpResponse itself using the Jakarta JSONP API. Right now, I have to fetch it as a String, feed the body into a reader and then get the JsonObject like the code below.

import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import jakarta.json.Json;
import jakarta.json.JsonObject;
import jakarta.json.JsonReader;

HttpRequest request = HttpRequest.newBuilder().uri(uri).GET().build();
HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());
JsonReader jsonReader = Json.createReader(new StringReader(response.body()));
JsonObject object = jsonReader.readObject();
jsonReader.close();

How do I get the response as HttpResponse<JsonObject> response directly? I don't want to use any external libraries other than the Jakarta JSONP one.

Edit: As an example, one could write their own BodyHandler like this:

import java.net.http.HttpResponse;
import java.net.http.HttpResponse.BodySubscriber;
import java.net.http.HttpResponse.BodySubscribers;
import java.net.http.HttpResponse.ResponseInfo;

import jakarta.json.JsonObject;

public class JsonObjectBodyHandler implements HttpResponse.BodyHandler<JsonObject> {

    @Override
    public BodySubscriber<JsonObject> apply(ResponseInfo responseInfo) {
        // How to implement this
    }

}

and then use it in the function like this:

HttpResponse<JsonObject> response = httpClient.send(request, new JsonObjectBodyHandler());

Does this answer your question? Deserializing JSON using Java 11 HttpClient and custom BodyHandler with Jackson halts and will not proceed — f1sh
– f1sh, Commented Feb 14, 2023 at 15:06
@f1sh That doesn't answer the question because it uses Jackson to serialize JSON Response bodies to POJOs and I want to simply convert the body to a JsonObject without any external library. — khateeb
– khateeb, Commented Feb 15, 2023 at 7:31

Johny · Accepted Answer · 2024-11-07 10:33:28Z

Based on f1sh comment's question, you can simply change the Jackson part with the JSON-P API:


import jakarta.json.Json;
import jakarta.json.JsonObject;
import java.io.StringReader;
import java.net.http.HttpResponse;
import java.nio.charset.StandardCharsets;

public class JsonBodyHandle implements HttpResponse.BodyHandler<JsonObject> {
    @Override
    public HttpResponse.BodySubscriber<JsonObject> apply(HttpResponse.ResponseInfo ri) {
        HttpResponse.BodySubscriber<String> upstream = HttpResponse.BodySubscribers.ofString(StandardCharsets.UTF_8);
        return HttpResponse.BodySubscribers.mapping(
            upstream, body -> Json.createReader(new StringReader(body)).readObject());
        }
    }

Then you use the JsonBodyHandle:

HttpResponse<JsonObject> res = client.send(request, new JsonBodyHandle());
JsonObject json = res.body();

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