java设置HTTP请求header的多种实现方式详解

import java.net.HttpURLConnection;
import java.net.URL;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;

public class HttpURLConnectionExample {
    public static void main(String[] args) throws Exception {
        URL url = new URL("http://example.com/api");
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        
        // 设置请求方法
        connection.setRequestMethod("POST");
        
        // 设置请求头
        connection.setRequestProperty("Content-Type", "application/json");
        connection.setRequestProperty("Authorization", "Bearer token123");
        connection.setRequestProperty("User-Agent", "MyApp/1.0");
        connection.setRequestProperty("X-Custom-Header", "CustomValue");
        
        // 设置连接超时
        connection.setConnectTimeout(5000);
        connection.setReadTimeout(5000);
        
        // 发送请求体（如果是POST/PUT）
        connection.setDoOutput(true);
        String jsonInput = "{\"key\": \"value\"}";
        try (OutputStream os = connection.getOutputStream()) {
            byte[] input = jsonInput.getBytes("utf-8");
            os.write(input, 0, input.length);
        }
        
        // 获取响应
        int responseCode = connection.getResponseCode();
        System.out.println("Response Code: " + responseCode);
        
        // 读取响应
        try (BufferedReader br = new BufferedReader(
                new InputStreamReader(connection.getInputStream(), "utf-8"))) {
            StringBuilder response = new StringBuilder();
            String responseLine;
            while ((responseLine = br.readLine()) != null) {
                response.append(responseLine.trim());
            }
            System.out.println("Response: " + response.toString());
        }
        
        connection.disconnect();
    }
}

<!-- Maven -->
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.13</version>
</dependency>

import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.util.EntityUtils;

public class ApacheHttpClientExample {
    public static void main(String[] args) throws Exception {
        try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
            HttpPost httpPost = new HttpPost("http://example.com/api");
            
            // 设置请求头
            httpPost.setHeader("Content-Type", "application/json");
            httpPost.setHeader("Authorization", "Bearer token123");
            httpPost.setHeader("X-Custom-Header", "CustomValue");
            httpPost.setHeader("User-Agent", "MyApp/1.0");
            
            // 设置请求体
            String json = "{\"key\": \"value\"}";
            StringEntity entity = new StringEntity(json);
            httpPost.setEntity(entity);
            
            // 执行请求
            try (CloseableHttpResponse response = httpClient.execute(httpPost)) {
                System.out.println("Status: " + response.getStatusLine());
                String responseBody = EntityUtils.toString(response.getEntity());
                System.out.println("Response: " + responseBody);
            }
        }
    }
}

import org.springframework.http.*;
import org.springframework.web.client.RestTemplate;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import java.util.Collections;

public class RestTemplateExample {
    public static void main(String[] args) {
        RestTemplate restTemplate = new RestTemplate();
        
        // 设置请求头
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        headers.set("Authorization", "Bearer token123");
        headers.set("X-Custom-Header", "CustomValue");
        headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
        
        // 设置请求体
        String requestBody = "{\"key\": \"value\"}";
        HttpEntity<String> requestEntity = new HttpEntity<>(requestBody, headers);
        
        // 发送请求
        ResponseEntity<String> response = restTemplate.exchange(
            "http://example.com/api",
            HttpMethod.POST,
            requestEntity,
            String.class
        );
        
        System.out.println("Status: " + response.getStatusCode());
        System.out.println("Response: " + response.getBody());
    }
}

<!-- Maven -->
<dependency>
    <groupId>com.squareup.okhttp3</groupId>
    <artifactId>okhttp</artifactId>
    <version>4.9.3</version>
</dependency>

import okhttp3.*;

public class OkHttpExample {
    public static void main(String[] args) throws Exception {
        OkHttpClient client = new OkHttpClient();
        
        // 创建请求体
        MediaType mediaType = MediaType.parse("application/json");
        String json = "{\"key\": \"value\"}";
        RequestBody body = RequestBody.create(mediaType, json);
        
        // 构建请求
        Request request = new Request.Builder()
            .url("http://example.com/api")
            .post(body)
            .addHeader("Content-Type", "application/json")
            .addHeader("Authorization", "Bearer token123")
            .addHeader("X-Custom-Header", "CustomValue")
            .addHeader("User-Agent", "MyApp/1.0")
            .build();
        
        // 发送请求
        try (Response response = client.newCall(request).execute()) {
            System.out.println("Code: " + response.code());
            System.out.println("Response: " + response.body().string());
        }
    }
}

import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;

@WebServlet("/api")
public class MyServlet extends HttpServlet {
    
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) 
            throws IOException {
        
        // 设置响应头
        response.setHeader("Content-Type", "application/json");
        response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate");
        response.setHeader("Pragma", "no-cache");
        response.setHeader("Expires", "0");
        response.setHeader("X-Custom-Header", "CustomValue");
        
        // 或者使用setHeader的便捷方法
        response.setContentType("application/json");
        response.setCharacterEncoding("UTF-8");
        
        // 添加多个相同名称的头
        response.addHeader("Set-Cookie", "token=abc123");
        response.addHeader("Set-Cookie", "session=xyz789");
        
        // 写入响应体
        response.getWriter().write("{\"status\": \"success\"}");
    }
}