6.4. HttpClient

来源：cnblogs　　作者：博客0214　　时间：2023/6/2 11:08:04　　对本文有异议

1. 什么是HttpClient？

HttpClient是Java 11中引入的一个新特性，用于支持同步和异步发送HTTP请求以及处理HTTP响应。它提供了简单易用的API，使得发送HTTP请求变得非常简单。

2. HttpClient的主要组件

HttpClient由以下几个主要组件组成：

HttpClient：用于发送请求的主要类。
HttpRequest：表示一个HTTP请求。
HttpResponse：表示一个HTTP响应。

3. 发送GET请求

要使用HttpClient发送GET请求，可以创建一个HttpClient对象，然后创建一个HttpRequest对象并设置请求方法为GET。最后，使用HttpClient的send()方法发送请求并获取响应。以下是一个简单示例：

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
public class HttpClientGetExample {
    public static void main(String[] args) {
        try {
            HttpClient client = HttpClient.newHttpClient();
            HttpRequest request = HttpRequest.newBuilder()
                    .uri(URI.create("https://www.example.com/"))
                    .GET()
                    .build();
            HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
            System.out.println(response.statusCode());
            System.out.println(response.body());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

4. 发送POST请求

要使用HttpClient发送POST请求，可以创建一个HttpClient对象，然后创建一个HttpRequest对象并设置请求方法为POST。还需要设置请求体，例如表单数据或JSON数据。最后，使用HttpClient的send()方法发送请求并获取响应。以下是一个简单示例：

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.nio.charset.StandardCharsets;
public class HttpClientPostExample {
    public static void main(String[] args) {
        try {
            HttpClient client = HttpClient.newHttpClient();
            String postData = "username=user&password=pass";
            HttpRequest request = HttpRequest.newBuilder()
                    .uri(URI.create("https://www.example.com/login"))
                    .header("Content-Type", "application/x-www-form-urlencoded")
                    .POST(HttpRequest.BodyPublishers.ofString(postData))
                    .build();
            HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
            System.out.println(response.statusCode());
            System.out.println(response.body());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

5. 异步请求

HttpClient还支持异步发送HTTP请求。要发送异步请求，可以使用HttpClient的sendAsync()方法。以下是一个简单示例：

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
public class HttpClientAsyncExample {
    public static void main(String[] args) {
        try {
            HttpClient client = HttpClient.newHttpClient();
            HttpRequest request = HttpRequest.newBuilder()
                    .uri(URI.create("https://www.example.com/"))
                    .GET()
                    .build();
            client.sendAsync(request, HttpResponse.BodyHandlers.ofString())
                    .thenApply(HttpResponse::body)
                    .thenAccept(System.out::println)
                    .join();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

6. 自定义HttpClient

可以通过HttpClient.Builder类自定义HttpClient，例如设置超时、代理、重定向策略等。以下是一个简单示例，演示如何设置超时和代理：

import java.net.InetSocketAddress;
import java.net.ProxySelector;
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 CustomHttpClientExample {
    public static void main(String[] args) {
        try {
            HttpClient client = HttpClient.newBuilder()
                    .connectTimeout(Duration.ofSeconds(5))
                    .proxy(ProxySelector.of(new InetSocketAddress("myproxy.example.com", 8080)))
                    .build();
            HttpRequest request = HttpRequest.newBuilder()
                    .uri(URI.create("https://www.example.com/"))
                    .GET()
                    .build();
            HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
            System.out.println(response.statusCode());
            System.out.println(response.body());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}