Java 如何实现POST(x-www-form-urlencoded)请求

实现POST(x-www-form-urlencoded)请求的过程如下所示：

1. 构建URL和请求参数
2. 创建URL对象和HttpURLConnection对象
3. 设置请求头
4. 写入请求参数
5. 发起请求并接受服务器响应

以下为代码示例：

示例一

import java.net.*;
import java.io.*;

public class PostRequestExample {

    public static void main(String[] args) {

        try {
            //构建URL和请求参数
            String urlStr = "https://example.com/api";
            String params = "name=value1&foo=bar";

            //创建URL对象和HttpURLConnection对象
            URL url = new URL(urlStr);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();

            //设置请求头
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            conn.setRequestProperty("Content-Length", Integer.toString(params.getBytes().length));

            //写入请求参数
            conn.setDoOutput(true);
            DataOutputStream out = new DataOutputStream(conn.getOutputStream());
            out.writeBytes(params);
            out.flush();
            out.close();

            //发起请求并接受服务器响应
            BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String inputLine;
            StringBuffer response = new StringBuffer();
            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();

            //记录响应信息
            System.out.println(response.toString());

        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

示例二

import java.net.*;
import java.io.*;

public class PostRequestExample {

    public static void main(String[] args) {

        try {
            //构建URL和请求参数
            String urlStr = "https://example.com/api";
            String firstName = "John";
            String lastName = "Doe";
            String email = "[e-mail]";
            String params = "firstName=" + URLEncoder.encode(firstName, "UTF-8") 
                         + "&lastName=" + URLEncoder.encode(lastName, "UTF-8")
                         + "&email=" + URLEncoder.encode(email, "UTF-8");

            //创建URL对象和HttpURLConnection对象
            URL url = new URL(urlStr);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();

            //设置请求头
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            conn.setRequestProperty("Content-Length", Integer.toString(params.getBytes().length));

            //写入请求参数
            conn.setDoOutput(true);
            DataOutputStream out = new DataOutputStream(conn.getOutputStream());
            out.writeBytes(params);
            out.flush();
            out.close();

            //发起请求并接受服务器响应
            BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String inputLine;
            StringBuffer response = new StringBuffer();
            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();

            //记录响应信息
            System.out.println(response.toString());

        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

以上代码仅供参考，实际应用中需要根据具体的情况进行调整。