java使用post请求下载文件

在Java中，可以使用HttpURLConnection或Apache HttpClient来执行POST请求并下载文件。以下是使用HttpURLConnection的示例代码：

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

public class DownloadFile {
    public static void main(String[] args) {
        String url = "http://example.com/download/file";
        String filePath = "C:/downloads/file.txt";
        try {
            URL downloadUrl = new URL(url);
            HttpURLConnection httpConn = (HttpURLConnection) downloadUrl.openConnection();
            httpConn.setDoOutput(true);
            httpConn.setRequestMethod("POST");

            OutputStream outputStream = httpConn.getOutputStream();
            outputStream.write("param1=value1&param2=value2".getBytes());
            outputStream.flush();
            outputStream.close();

            int responseCode = httpConn.getResponseCode();
            if (responseCode == HttpURLConnection.HTTP_OK) {
                InputStream inputStream = httpConn.getInputStream();
                FileOutputStream outputStream = new FileOutputStream(filePath);
                byte[] buffer = new byte[4096];
                int bytesRead = -1;
                while ((bytesRead = inputStream.read(buffer)) != -1) {
                    outputStream.write(buffer, 0, bytesRead);
                }
                outputStream.close();
                inputStream.close();
                System.out.println("File downloaded successfully.");
            } else {
                System.out.println("Server returned response code: " + responseCode);
            }
            httpConn.disconnect();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

在上面的代码中，我们首先创建一个URL对象，然后使用HttpURLConnection打开连接。设置doOutput为true以启用输出流，并将请求方法设置为POST。接下来，我们将POST参数写入输出流中。然后，我们获取服务器响应代码，并检查是否为HTTP_OK（200）。如果是，我们将响应流复制到文件输出流中，从而将文件写入本地磁盘。最后，我们关闭所有流并断开连接。