Java http 接口请求详解

Java 中进行 HTTP 接口请求的方式有多种，常用的方式包括使用 Java 原生的 HttpURLConnection 类、Apache HttpClient 库和 Spring 的 RestTemplate。

1. 使用 HttpURLConnection 类进行 HTTP 接口请求：

   import java.io.BufferedReader;
   import java.io.InputStreamReader;
   import java.net.HttpURLConnection;
   import java.net.URL;
   
   public class HttpUrlConnectionExample {
       public static void main(String[] args) {
           try {
               // 创建 URL 对象
               URL url = new URL("http://example.com/api/endpoint");
   
               // 打开连接
               HttpURLConnection connection = (HttpURLConnection) url.openConnection();
   
               // 设置请求方法
               connection.setRequestMethod("GET");
   
               // 发送请求
               int responseCode = connection.getResponseCode();
   
               // 读取响应
               BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
               String line;
               StringBuilder response = new StringBuilder();
               while ((line = reader.readLine()) != null) {
                   response.append(line);
               }
               reader.close();
   
               // 关闭连接
               connection.disconnect();
   
               // 处理响应
               System.out.println("Response Code: " + responseCode);
               System.out.println("Response Body: " + response.toString());
           } catch (Exception e) {
               e.printStackTrace();
           }
       }
   }
   

2. 使用 Apache HttpClient 库进行 HTTP 接口请求：

   import org.apache.http.HttpEntity;
   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 ApacheHttpClientExample {
       public static void main(String[] args) {
           try {
               // 创建 HttpClient 对象
               HttpClient httpClient = HttpClients.createDefault();
   
               // 创建 HttpGet 请求对象
               HttpGet httpGet = new HttpGet("http://example.com/api/endpoint");
   
               // 发送请求并获取响应
               HttpResponse response = httpClient.execute(httpGet);
   
               // 读取响应
               HttpEntity entity = response.getEntity();
               String responseBody = EntityUtils.toString(entity);
   
               // 处理响应
               System.out.println("Response Code: " + response.getStatusLine().getStatusCode());
               System.out.println("Response Body: " + responseBody);
           } catch (Exception e) {
               e.printStackTrace();
           }
       }
   }
   

3. 使用 Spring 的 RestTemplate 进行 HTTP 接口请求（需要添加相关依赖）：

   import org.springframework.http.ResponseEntity;
   import org.springframework.web.client.RestTemplate;
   
   public class RestTemplateExample {
       public static void main(String[] args) {
           try {
               // 创建 RestTemplate 对象
               RestTemplate restTemplate = new RestTemplate();
   
               // 发送 GET 请求并获取响应
               ResponseEntity<String> response = restTemplate.getForEntity("http://example.com/api/endpoint", String.class);
   
               // 处理响应
               System.out.println("Response Code: " + response.getStatusCode());
               System.out.println("Response Body: " + response.getBody());
           } catch (Exception e) {
               e.printStackTrace();
           }
       }
   }