Java中HTTP请求头怎么设置

在Java中，你可以使用多种库来发送HTTP请求并设置请求头。以下是使用两个流行的HTTP客户端库——Apache HttpClient和Java 11中的HttpClient——来设置HTTP请求头的示例。

使用Apache HttpClient

首先，确保你已经添加了Apache HttpClient的依赖。如果你使用Maven，可以在pom.xml文件中添加以下依赖：

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>5.1.3</version>
</dependency>

然后，你可以使用以下代码来创建一个HTTP请求并设置请求头：

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

public class HttpClientExample {
    public static void main(String[] args) throws Exception {
        HttpClient httpClient = HttpClients.createDefault();
        HttpGet request = new HttpGet("http://example.com");

        // 设置请求头
        request.setHeader("Accept", "application/json");
        request.setHeader("Authorization", "Bearer your_token_here");

        HttpResponse response = httpClient.execute(request);
        String responseBody = EntityUtils.toString(response.getEntity());

        System.out.println(responseBody);
        httpClient.getConnectionManager().shutdown();
    }
}

使用Java 11 HttpClient

如果你使用的是Java 11或更高版本，你可以使用内置的java.net.http.HttpClient来发送HTTP请求并设置请求头：

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class Java11HttpClientExample {
    public static void main(String[] args) throws Exception {
        HttpClient httpClient = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest.newBuilder()
                .uri(URI.create("http://example.com"))
                .header("Accept", "application/json")
                .header("Authorization", "Bearer your_token_here")
                .GET() // 或者使用其他HTTP方法，如.POST(), .PUT(), .DELETE()等
                .build();

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

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

在这两个例子中，我们都设置了Accept和Authorization请求头。你可以根据需要添加更多的请求头。只需使用setHeader方法（对于Apache HttpClient）或header方法（对于Java 11 HttpClient）即可。