FavTuts

Favourite tutorials for developers

Java Basics

Java 11 HttpClient Examples

ByFavTuts Editorial

May 10, 2022 #HTTP, #http form, #HTTP Request, #java, #Java 11, #JSON, #redirect

This article shows you how to use the new Java 11 HttpClient APIs to send HTTP GET/POST requests, and some frequent used examples.

  HttpClient httpClient = HttpClient.newBuilder()
        .version(HttpClient.Version.HTTP_2)
        .followRedirects(HttpClient.Redirect.NORMAL)
        .connectTimeout(Duration.ofSeconds(20))
        .proxy(ProxySelector.of(new InetSocketAddress("proxy.yourcompany.com", 80)))
        .authenticator(Authenticator.getDefault())
        .build();

1. Synchronous Example

This example sends a GET request to https://httpbin.org/get, and print out the response header, status code, and body.

HttpClientSynchronous.java

package com.favtuts.http;

import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpHeaders;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.time.Duration;

public class HttpClientSynchronous {

    private static final HttpClient httpClient = HttpClient.newBuilder()
        .version(HttpClient.Version.HTTP_1_1)
        .connectTimeout(Duration.ofSeconds(10))
        .build();
    
    public static void main(String[] args) throws IOException, InterruptedException {
        
        HttpRequest request = HttpRequest.newBuilder()
            .GET()
            .uri(URI.create("https://httpbin.org/get"))
            .setHeader("User-Agent", "Java 11 HttpClient Bot") // add request header
            .build();
        
        HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());

        // print response headers
        HttpHeaders headers = response.headers();
        headers.map().forEach((k, v) -> System.out.println(k + ":" + v));

        // print status code
        System.out.println(response.statusCode());

        // print response body
        System.out.println(response.body());
    }
}

Output

access-control-allow-credentials:[true]
access-control-allow-origin:[*]
connection:[keep-alive]
content-length:[271]
content-type:[application/json]
date:[Tue, 10 May 2022 09:46:13 GMT]
server:[gunicorn/19.9.0]
200
{
  "args": {}, 
  "headers": {
    "Content-Length": "0", 
    "Host": "httpbin.org", 
    "User-Agent": "Java 11 HttpClient Bot", 
    "X-Amzn-Trace-Id": "Root=1-627a3465-59aa4d452eda31397a009a77"
  }, 
  "origin": "14.162.33.98", 
  "url": "https://httpbin.org/get"
}

2. Asynchronous Example

2.1 HttpClient.sendAsync() to send a GET request asynchronous, it will return a CompletableFuture

HttpClientAsynchronous.java

package com.favtuts.http;

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.time.Duration;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.TimeUnit;

public class HttpClientAsynchronous {

    private static final HttpClient httpClient = HttpClient.newBuilder()
            .version(HttpClient.Version.HTTP_2)
            .connectTimeout(Duration.ofSeconds(10))
            .build();
    
    public static void main(String[] args) throws Exception {
        
        HttpRequest request = HttpRequest.newBuilder()
                .GET()
                .uri(URI.create("https://httpbin.org/get"))
                .setHeader("User-Agent", "Java 11 HttpClient Bot")
                .build();
        
        CompletableFuture<HttpResponse<String>> response =
            httpClient.sendAsync(request, HttpResponse.BodyHandlers.ofString());
        
        String result = response.thenApply(HttpResponse::body).get(5, TimeUnit.SECONDS);

        System.out.println(result);
    }
}

Output

{
  "args": {},
  "headers": {
    "Host": "httpbin.org",
    "User-Agent": "Java 11 HttpClient Bot",
    "X-Amzn-Trace-Id": "Root=1-5ec0fb51-2c5dcf98167c6418bd555548"
  },
  "origin": "124.82.107.103",
  "url": "https://httpbin.org/get"
}

3. Custom Executor + Concurrent Requests

3.1 Add a custom executor.

	private final ExecutorService executorService = Executors.newFixedThreadPool(5);

  private final HttpClient httpClient = HttpClient.newBuilder()
          .executor(executorService)
          .build();

3.2 Send multiple concurrent requests asynchronously.

HttpClientCustomExecutor.java

package com.favtuts.http;

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.time.Duration;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.stream.Collectors;

public class HttpClientCustomExecutor {

    // custom executor
    private static final ExecutorService executorService = Executors.newFixedThreadPool(5);

    private static final HttpClient httpClient = HttpClient.newBuilder()
        .executor(executorService)
        .version(HttpClient.Version.HTTP_2)
        .connectTimeout(Duration.ofSeconds(10))
        .build();
    
    public static void main(String[] args) throws Exception {
        
        List<URI> targets = Arrays.asList(
            new URI("https://httpbin.org/get?name=favtuts1"),
            new URI("https://httpbin.org/get?name=favtuts2"),
            new URI("https://httpbin.org/get?name=favtuts3")
        );

        List<CompletableFuture<String>> result = targets.stream()
            .map(url -> httpClient.sendAsync(
                HttpRequest.newBuilder(url)
                    .GET()
                    .setHeader("User-Agent", "Java 11 HttpClient Bot")
                    .build()
                    , 
                HttpResponse.BodyHandlers.ofString())
                .thenApply(response -> response.body())         
            )
            .collect(Collectors.toList());
        
        for (CompletableFuture<String> future : result) {
            System.out.println(future.get());
        }
    }
    
}

Output

{
  "args": {
    "name": "favtuts1"
  }, 
  "headers": {
    "Host": "httpbin.org", 
    "User-Agent": "Java 11 HttpClient Bot", 
    "X-Amzn-Trace-Id": "Root=1-627a753c-14ae27021dbdabc23f2f6c4a"
  }, 
  "origin": "14.162.33.98", 
  "url": "https://httpbin.org/get?name=favtuts1"
}

{
  "args": {
    "name": "favtuts2"
  }, 
  "headers": {
    "Host": "httpbin.org", 
    "User-Agent": "Java 11 HttpClient Bot", 
    "X-Amzn-Trace-Id": "Root=1-627a753c-2ce53d22544b7da802f368d0"
  }, 
  "origin": "14.162.33.98", 
  "url": "https://httpbin.org/get?name=favtuts2"
}

{
  "args": {
    "name": "favtuts3"
  }, 
  "headers": {
    "Host": "httpbin.org", 
    "User-Agent": "Java 11 HttpClient Bot", 
    "X-Amzn-Trace-Id": "Root=1-627a753c-4d63aa946ec2103234231fb7"
  }, 
  "origin": "14.162.33.98", 
  "url": "https://httpbin.org/get?name=favtuts3"
}

4. POST Form Parameters

4.1 Java 11 HttpClient didn’t provide API for the form data, we have to construct it manually.

HttpClientPostForm.java

package com.favtuts.http;

import java.io.IOException;
import java.net.URI;
import java.net.URLEncoder;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.nio.charset.StandardCharsets;
import java.time.Duration;
import java.util.HashMap;
import java.util.Map;

public class HttpClientPostForm {
    
    private static final HttpClient httpClient = HttpClient.newBuilder()
            .version(HttpClient.Version.HTTP_2)
            .connectTimeout(Duration.ofSeconds(10))
            .build();

    public static void main(String[] args) throws IOException, InterruptedException {
        
        // form parameters
        Map<Object, Object> data = new HashMap<>();
        data.put("username", "abc");
        data.put("password", "123");
        data.put("custom", "secret");
        data.put("ts", System.currentTimeMillis());

        HttpRequest request = HttpRequest.newBuilder()
                .POST(ofFormData(data))
                .uri(URI.create("https://httpbin.org/post"))
                .setHeader("User-Agent", "Java 11 HttpClient Bot") // add request header
                .header("Content-Type", "application/x-www-form-urlencoded")
                .build();

        HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());

        // print status code
        System.out.println(response.statusCode());

        // print response body
        System.out.println(response.body());
    }

    // Sample: 'password=123&custom=secret&username=abc&ts=1570704369823'
    public static HttpRequest.BodyPublisher ofFormData(Map<Object, Object> data) {
        var builder = new StringBuilder();
        for (Map.Entry<Object, Object> entry : data.entrySet()) {
            if (builder.length() > 0) {
                builder.append("&");
            }
            builder.append(URLEncoder.encode(entry.getKey().toString(), StandardCharsets.UTF_8));
            builder.append("=");
            builder.append(URLEncoder.encode(entry.getValue().toString(), StandardCharsets.UTF_8));
        }
        return HttpRequest.BodyPublishers.ofString(builder.toString());
    }
}

Output

200
{
  "args": {}, 
  "data": "", 
  "files": {}, 
  "form": {
    "custom": "secret", 
    "password": "123", 
    "ts": "1652193037757", 
    "username": "abc"
  }, 
  "headers": {
    "Content-Length": "56", 
    "Content-Type": "application/x-www-form-urlencoded", 
    "Host": "httpbin.org", 
    "User-Agent": "Java 11 HttpClient Bot", 
    "X-Amzn-Trace-Id": "Root=1-627a770f-6fbdfa77156ce12779ae2ae0"
  }, 
  "json": null, 
  "origin": "14.162.33.98", 
  "url": "https://httpbin.org/post"
}

5. POST JSON

HttpClientPostJSON.java

package com.favtuts.http;

import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.time.Duration;

public class HttpClientPostJSON {

    private static final HttpClient httpClient = HttpClient.newBuilder()
            .version(HttpClient.Version.HTTP_2)
            .connectTimeout(Duration.ofSeconds(10))
            .build();

    public static void main(String[] args) throws IOException, InterruptedException {

        // json formatted data
        String json = new StringBuilder()
                .append("{")
                .append("\"name\":\"favtuts\",")
                .append("\"notes\":\"hello\"")
                .append("}").toString();

        // add json header
        HttpRequest request = HttpRequest.newBuilder()
                .POST(HttpRequest.BodyPublishers.ofString(json))
                .uri(URI.create("https://httpbin.org/post"))
                .setHeader("User-Agent", "Java 11 HttpClient Bot") // add request header
                .header("Content-Type", "application/json")
                .build();

        HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());

        // print status code
        System.out.println(response.statusCode());

        // print response body
        System.out.println(response.body());

    }
}

Output

200
{
  "args": {}, 
  "data": "{\"name\":\"favtuts\",\"notes\":\"hello\"}", 
  "files": {}, 
  "form": {}, 
  "headers": {
    "Content-Length": "34", 
    "Content-Type": "application/json", 
    "Host": "httpbin.org", 
    "User-Agent": "Java 11 HttpClient Bot", 
    "X-Amzn-Trace-Id": "Root=1-627a784a-0b2535867b89813140fca0c7"
  }, 
  "json": {
    "name": "favtuts", 
    "notes": "hello"
  }, 
  "origin": "14.162.33.98", 
  "url": "https://httpbin.org/post"
}

6. Authentication

6.1 Start a simple Spring Security WebApp provides HTTP basic authentication, and test it with the new Java 11 HttpClient APIs

HttpClientAuthentication.java

package com.favtuts.http;

import java.io.IOException;
import java.net.Authenticator;
import java.net.PasswordAuthentication;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.time.Duration;

public class HttpClientAuthentication {
    
    private static final HttpClient httpClient = HttpClient.newBuilder()
            .authenticator(new Authenticator() {
                @Override
                protected PasswordAuthentication getPasswordAuthentication() {
                    return new PasswordAuthentication(
                            "user",
                            "password".toCharArray());
                }

            })
            .connectTimeout(Duration.ofSeconds(10))
            .build();
    
    public static void main(String[] args) throws IOException, InterruptedException {

        HttpRequest request = HttpRequest.newBuilder()
                .GET()
                .uri(URI.create("http://localhost:8080/books"))
                .setHeader("User-Agent", "Java 11 HttpClient Bot") // add request header
                .build();

        HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());

        // print status code
        System.out.println(response.statusCode());

        // print response body
        System.out.println(response.body());

    }
}

7. FAQs

7.1 Disabled Redirect.

	private final HttpClient httpClient = HttpClient.newBuilder()
            .followRedirects(HttpClient.Redirect.NEVER)
            .build();

Read this HttpClient.Redirect JavaDoc

7.2 Timeout, 5 seconds.

	private final HttpClient httpClient = HttpClient.newBuilder()
            .connectTimeout(Duration.ofSeconds(5))
            .build();

7.3 Set a Proxy.

	private final HttpClient httpClient = HttpClient.newBuilder()
            .proxy(ProxySelector.of(new InetSocketAddress("your-company-proxy.com", 8080)))
            .build();

Download Source Code

$ git clone https://github.com/favtuts/java-core-tutorials-examples

$ cd java-misc/http

References

By FavTuts Editorial

Related Post

Java Basics

The Java Archive Tool (JAR) Examples

Jun 19, 2022 FavTuts Editorial
Java Basics

How to add a manifest into a Jar file

Jun 19, 2022 FavTuts Editorial
Java Basics

How to make a Java exe file or executable JAR file

Jun 19, 2022 FavTuts Editorial

Leave a Reply

Your email address will not be published. Required fields are marked *

You missed

Spring Boot

Validation with Spring Boot – the Complete Guide

December 10, 2024 FavTuts Editorial
Spring Boot

How to Record Request and Response Bodies in Sping Boot Applications

December 8, 2024 FavTuts Editorial
Spring Boot

How to create a Spring Boot console application

December 4, 2024 FavTuts Editorial
PHP

How To Change Your PHP Settings on Ubuntu

November 30, 2024 FavTuts Editorial