4. Your First Client

The REST client calls the service from the previous page and parses the response into the same Pet bean. With that server still running, create src/main/java/com/example/demo/Client.java:

// Artifact: juneau-rest-client
package com.example.demo;

import org.apache.juneau.marshall.json5.*;
import org.apache.juneau.rest.client.*;

public class Client {
    public static void main(String[] args) throws Exception {
        try (RestClient client = RestClient.builder()
                .rootUrl("http://localhost:10000")
                .serializer(Json5Serializer.create().build())
                .parser(Json5Parser.create().build())
                .build()) {

            try (var resp = client.get("/pets/{id}").pathData("id", 1).run()) {
                resp.assertOk();
                Pet pet = resp.body().as(Pet.class);
                System.out.println(pet.id + " " + pet.name);
            }
        }
    }
}

Run it from a second terminal in the project directory:

mvn compile exec:java -Dexec.mainClass=com.example.demo.Client

It prints 1 Fido, followed by a log line for the request.

Always close the response (it holds the connection) and close the client at shutdown; the try blocks above do both.

Which client?

juneau-rest-client (org.apache.juneau.rest.client.RestClient) is the recommended REST client. It is generally available in 10.0.0, transport-agnostic, and uses the JDK HttpClient by default. juneau-rest-client-classic (org.apache.juneau.rest.client.classic.RestClient, Apache HttpClient 4.5) stays supported and is not deprecated; it is the stable choice for existing users. See Choosing a REST Client.

A typed proxy instead

For services you call often, declare an interface and let Juneau implement it. See Declarative Remote-Proxy Features.

Learn more

Requests, responses, assertions, and security.

Where next?

You now have a serializer, a REST resource, and a client. The Ecosystem Overview lists everything else, and the Starter Projects show a complete deployable app.

Next: pick a guide. The Guides each do one task end to end, from a Spring Boot API to a typed client.