How do you create a REST client for Java?

java

http-client

rest-template

feign

byNikita Barsukov·Feb 14, 2025

For hurried problem-solvers, here's an efficient way to make a REST client using Spring's RestTemplate. Spring Web library is a prerequisite. Have a swift look at the snippet:

import org.springframework.web.client.RestTemplate;

public class RestClient {
    public static void main(String[] args) {
        // Because everything gets better with a freshly brewed RestTemplate, coffee anyone?
        RestTemplate restTemplate = new RestTemplate();
        
        // Let's fetch "Hello, World!" from the other end of the bridge
        String response = restTemplate.getForObject("http://api.example.com/data", String.class);
        System.out.println(response);
    }
}

This code fetches content from a REST endpoint with a GET request. Need POST? Replace getForObject with postForObject.

Making the right selection: Deciphering HTTP clients

When advanced tools save the day

Choosing an HTTP client shouldn't be a hasty decision. Spring’s RestTemplate is an easy-out for simpler requirements, but for more convoluted scenarios, consider modern and specialized clients when:

Concurrency is as high as my best score on Tetris. 💻
You need NIO (Non-blocking I/O) for a performance that's snappier than a crocodile.
Your project is feeling adventurous with HTTP/2 support.
Async operations are your project's best friends.

Unleashing the power of abstraction

When dealing with HTTP requests makes you cringe, Feign or Retrofit may come to your rescue. These tools possess higher-level abstractions allowing for declarative REST clients using decoy annotations. #Fancy

@GET("/users/{userId}/repos")
// Luckily, this isn't a scavenger hunt for repositories!
List<Repo> listRepos(@Path("userId") int userId);

Pro-Tip: Abstractions promote clean code, it’s like cleaning your room without actually doing it.

Framework alignment

Ensure the rest client you select integrates well with your existing framework and ecosystem. You wouldn't want an orange in a basket full of apples, would you?

Testing made simple: The 'Rest-assured' way

Rest-assured makes testing a breeze by providing a fluent interface that feels more like English than programming. It’s as simple as green eggs and ham.

// Here's hoping that 200 is always your lucky number
given().when().get("/data").then().assertThat().statusCode(200);

Pro-Tip: Good testing supports rock-solid integration with RESTful services.

Balancing for simplicity and performance: Best Practices

When Non-Blocking Rules

Are you managing a manifold of short-lived requests? Non-blocking I/O models could dramatically beef up throughput and scalability.

Go HTTP/2 for performance!

Harness an HTTP client supporting HTTP/2 to leverage features like multiplexed streams, server push, and header compression. It's as pleasing as a perfectly brewed coffee!