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URLConnection发送HTTP请求

wen java案例 1

本文目录导读：

URLConnection发送HTTP请求

  1. 基本 GET 请求
  2. POST 请求（带参数）
  3. JSON 格式的 POST 请求
  4. PUT 请求（更新数据）
  5. DELETE 请求
  6. 带超时和自动重定向的封装类
  7. 注意事项

我来详细介绍使用 URLConnection 发送 HTTP 请求的方法。

基本 GET 请求

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
public class HttpGetExample {
    public static void main(String[] args) {
        try {
            // 创建 URL 对象
            URL url = new URL("https://api.example.com/users");
            // 打开连接
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            // 设置请求方法
            connection.setRequestMethod("GET");
            // 设置请求头
            connection.setRequestProperty("User-Agent", "Mozilla/5.0");
            connection.setRequestProperty("Accept", "application/json");
            // 设置超时时间
            connection.setConnectTimeout(5000);
            connection.setReadTimeout(5000);
            // 获取响应码
            int responseCode = connection.getResponseCode();
            System.out.println("响应码: " + responseCode);
            // 读取响应
            if (responseCode == HttpURLConnection.HTTP_OK) {
                BufferedReader in = new BufferedReader(
                    new InputStreamReader(connection.getInputStream()));
                String inputLine;
                StringBuilder response = new StringBuilder();
                while ((inputLine = in.readLine()) != null) {
                    response.append(inputLine);
                }
                in.close();
                System.out.println("响应内容: " + response.toString());
            } else {
                System.out.println("请求失败");
            }
            // 断开连接
            connection.disconnect();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

POST 请求（带参数）

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
public class HttpPostExample {
    public static void main(String[] args) {
        try {
            URL url = new URL("https://api.example.com/users");
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            // 设置 POST 请求
            connection.setRequestMethod("POST");
            connection.setDoOutput(true);
            connection.setDoInput(true);
            // 设置请求头
            connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            connection.setRequestProperty("Accept", "application/json");
            connection.setRequestProperty("Charset", "UTF-8");
            // 构建请求参数
            String urlParameters = "username=" + URLEncoder.encode("张三", "UTF-8")
                    + "&password=" + URLEncoder.encode("123456", "UTF-8")
                    + "&age=" + URLEncoder.encode("25", "UTF-8");
            // 发送 POST 参数
            DataOutputStream wr = new DataOutputStream(connection.getOutputStream());
            wr.writeBytes(urlParameters);
            wr.flush();
            wr.close();
            // 获取响应
            int responseCode = connection.getResponseCode();
            BufferedReader in = new BufferedReader(
                new InputStreamReader(connection.getInputStream()));
            StringBuilder response = new StringBuilder();
            String inputLine;
            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();
            System.out.println("响应码: " + responseCode);
            System.out.println("响应内容: " + response.toString());
            connection.disconnect();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

JSON 格式的 POST 请求

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
public class HttpPostJsonExample {
    public static void main(String[] args) {
        try {
            URL url = new URL("https://api.example.com/users");
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            // 设置请求头
            connection.setRequestMethod("POST");
            connection.setRequestProperty("Content-Type", "application/json");
            connection.setRequestProperty("Accept", "application/json");
            connection.setDoOutput(true);
            // 构建 JSON 数据
            String jsonInputString = "{\"name\": \"张三\", \"age\": 25, \"email\": \"zhangsan@example.com\"}";
            // 发送 JSON 数据
            try (DataOutputStream wr = new DataOutputStream(connection.getOutputStream())) {
                byte[] input = jsonInputString.getBytes("utf-8");
                wr.write(input, 0, input.length);
            }
            // 读取响应
            int responseCode = connection.getResponseCode();
            // 根据响应码选择输入流
            BufferedReader in;
            if (responseCode >= 200 && responseCode < 300) {
                in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            } else {
                in = new BufferedReader(new InputStreamReader(connection.getErrorStream()));
            }
            StringBuilder response = new StringBuilder();
            String line;
            while ((line = in.readLine()) != null) {
                response.append(line);
            }
            in.close();
            System.out.println("响应码: " + responseCode);
            System.out.println("响应内容: " + response.toString());
            connection.disconnect();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

PUT 请求（更新数据）

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
public class HttpPutExample {
    public static void main(String[] args) {
        try {
            URL url = new URL("https://api.example.com/users/123");
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            // 设置 PUT 请求
            connection.setRequestMethod("PUT");
            connection.setRequestProperty("Content-Type", "application/json");
            connection.setDoOutput(true);
            // 要更新的数据
            String updateData = "{\"name\": \"李四\", \"age\": 30}";
            // 发送数据
            try (DataOutputStream wr = new DataOutputStream(connection.getOutputStream())) {
                byte[] input = updateData.getBytes("utf-8");
                wr.write(input, 0, input.length);
            }
            int responseCode = connection.getResponseCode();
            System.out.println("响应码: " + responseCode);
            connection.disconnect();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

DELETE 请求

import java.net.HttpURLConnection;
import java.net.URL;
public class HttpDeleteExample {
    public static void main(String[] args) {
        try {
            URL url = new URL("https://api.example.com/users/123");
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            // 设置 DELETE 请求
            connection.setRequestMethod("DELETE");
            int responseCode = connection.getResponseCode();
            if (responseCode == 200 || responseCode == 204) {
                System.out.println("删除成功");
            } else {
                System.out.println("删除失败，响应码: " + responseCode);
            }
            connection.disconnect();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

带超时和自动重定向的封装类

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Map;
public class HttpClientUtil {
    private static final int CONNECT_TIMEOUT = 5000;
    private static final int READ_TIMEOUT = 5000;
    /**
     * 发送 GET 请求
     */
    public static String doGet(String url, Map<String, String> headers) throws Exception {
        HttpURLConnection connection = null;
        try {
            URL requestUrl = new URL(url);
            connection = (HttpURLConnection) requestUrl.openConnection();
            // 设置基础属性
            connection.setRequestMethod("GET");
            connection.setConnectTimeout(CONNECT_TIMEOUT);
            connection.setReadTimeout(READ_TIMEOUT);
            connection.setInstanceFollowRedirects(true); // 自动重定向
            // 设置请求头
            if (headers != null && !headers.isEmpty()) {
                for (Map.Entry<String, String> entry : headers.entrySet()) {
                    connection.setRequestProperty(entry.getKey(), entry.getValue());
                }
            }
            // 获取响应
            return getResponse(connection);
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
        }
    }
    /**
     * 发送 POST 请求
     */
    public static String doPost(String url, String data, String contentType, 
                                Map<String, String> headers) throws Exception {
        HttpURLConnection connection = null;
        try {
            URL requestUrl = new URL(url);
            connection = (HttpURLConnection) requestUrl.openConnection();
            // 设置基础属性
            connection.setRequestMethod("POST");
            connection.setConnectTimeout(CONNECT_TIMEOUT);
            connection.setReadTimeout(READ_TIMEOUT);
            connection.setDoOutput(true);
            connection.setDoInput(true);
            // 设置请求头
            if (contentType != null) {
                connection.setRequestProperty("Content-Type", contentType);
            }
            if (headers != null && !headers.isEmpty()) {
                for (Map.Entry<String, String> entry : headers.entrySet()) {
                    connection.setRequestProperty(entry.getKey(), entry.getValue());
                }
            }
            // 发送数据
            if (data != null && !data.isEmpty()) {
                try (DataOutputStream wr = new DataOutputStream(connection.getOutputStream())) {
                    byte[] input = data.getBytes("utf-8");
                    wr.write(input, 0, input.length);
                }
            }
            // 获取响应
            return getResponse(connection);
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
        }
    }
    /**
     * 获取响应内容
     */
    private static String getResponse(HttpURLConnection connection) throws IOException {
        int responseCode = connection.getResponseCode();
        // 根据响应码选择输入流
        InputStream inputStream;
        if (responseCode >= 200 && responseCode < 300) {
            inputStream = connection.getInputStream();
        } else {
            inputStream = connection.getErrorStream();
        }
        // 读取响应
        StringBuilder response = new StringBuilder();
        if (inputStream != null) {
            try (BufferedReader reader = new BufferedReader(
                    new InputStreamReader(inputStream, "UTF-8"))) {
                String line;
                while ((line = reader.readLine()) != null) {
                    response.append(line);
                }
            }
        }
        return response.toString();
    }
    // 使用示例
    public static void main(String[] args) {
        try {
            // GET 请求
            String getResult = doGet("https://api.example.com/data", null);
            System.out.println("GET 结果: " + getResult);
            // POST 请求
            String jsonData = "{\"key\": \"value\"}";
            String postResult = doPost("https://api.example.com/data", 
                                      jsonData, 
                                      "application/json", 
                                      null);
            System.out.println("POST 结果: " + postResult);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

注意事项

  1. 设置超时时间：避免请求长时间挂起
  2. 处理字符编码：确保使用 UTF-8
  3. 关闭连接：使用完必须调用 disconnect()
  4. 错误处理：检查响应码并处理错误流
  5. 安全性：不要在 URL 中传递敏感信息

代码覆盖了常见的 HTTP 请求场景，可以根据实际需求选择使用。

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