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在Java中，可以通过多种方式设置HTTP请求的header，具体取决于你使用的是哪种HTTP客户端。以下是几种常见的方法：

1. 使用原生HttpURLConnection

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(); } }

2. 使用 Apache HttpClient

首先添加依赖：

<!-- 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); } } } }

3. 使用 Spring RestTemplate

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()); } }

4. 使用 OkHttp

首先添加依赖：

<!-- 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()); } } }

5. 在Servlet中设置响应头

如果是在Servlet中处理HTTP请求，可以设置响应头：

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\"}"); } }

常用HTTP头字段

注意事项

1. Content-Type：发送JSON数据时通常设置为application/json

2. Authorization：用于身份验证，常见格式是Bearer token

3. 自定义头部：通常以X-开头，但不是强制要求

4. 字符编码：确保字符编码正确，建议使用UTF-8

5. 敏感信息：避免在URL中传递敏感信息，应放在请求头中

选择哪种方式取决于你的项目需求：

• 简单项目：使用HttpURLConnection

• 需要更多功能：使用 Apache HttpClient 或 OkHttp

• Spring项目：使用 RestTemplate

• Servlet项目：直接使用HttpServletResponse