java写一段文件上传的代码

好的，以下是Java写一段文件上传的代码示例：

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class FileUploader {
    public static void main(String[] args) throws IOException {
        String targetURL = "http://example.com/upload"; // 替换为实际的上传URL
        String filePath = "path/to/file"; // 替换为实际的文件路径
        File uploadFile = new File(filePath);
        
        HttpURLConnection connection = null;
        InputStream inputStream = null;
        
        try {
            // 创建连接
            URL url = new URL(targetURL);
            connection = (HttpURLConnection) url.openConnection();
            connection.setDoOutput(true);
            connection.setRequestMethod("POST");
            connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=---------------------------7da2137580612");
            
            // 构建请求体
            String boundary = "---------------------------7da2137580612";
            String fileName = uploadFile.getName();
            String body = "--" + boundary + "\r\n"
                    + "Content-Disposition: form-data; name=\"file\"; filename=\"" + fileName + "\"\r\n"
                    + "Content-Type: application/octet-stream\r\n\r\n";
            byte[] bodyBytes = body.getBytes("UTF-8");
            byte[] fileBytes = new byte[(int) uploadFile.length()];
            inputStream = new FileInputStream(uploadFile);
            inputStream.read(fileBytes);
            byte[] endBytes = ("\r\n--" + boundary + "--\r\n").getBytes("UTF-8");
            byte[] dataBytes = new byte[bodyBytes.length + fileBytes.length + endBytes.length];
            System.arraycopy(bodyBytes, 0, dataBytes, 0, bodyBytes.length);
            System.arraycopy(fileBytes, 0, dataBytes, bodyBytes.length, fileBytes.length);
            System.arraycopy(endBytes, 0, dataBytes, bodyBytes.length + fileBytes.length, endBytes.length);
            
            // 发送请求
            connection.getOutputStream().write(dataBytes);
            
            // 处理响应
            if (connection.getResponseCode() == HttpURLConnection.HTTP_OK) {
                // 上传成功
                System.out.println("上传成功");
            } else {
                // 上传失败
                System.out.println("上传失败");
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
            if (inputStream != null) {
                inputStream.close();
            }
        }
    }
}

请注意将`targetURL`和`filePath`替换为实际的值，并确保请求头中的`boundary`值与请求体中的分隔符一致。此代码只是一个示例，具体实现可能因情况而异。