Java 上传文件到远程服务器

在 Java 中，有几种常见的方法可以将文件上传到远程服务器，以下是几种实现方式：

使用 HTTP/HTTPS (基于 Web 服务)

使用 Apache HttpClient

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.entity.mime.content.FileBody;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import java.io.File;
import java.io.IOException;
public class FileUploader {
    public static void main(String[] args) {
        String serverUrl = "http://example.com/upload";
        File fileToUpload = new File("path/to/your/file.txt");
        try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
            HttpPost uploadFile = new HttpPost(serverUrl);
            FileBody fileBody = new FileBody(fileToUpload);
            HttpEntity entity = MultipartEntityBuilder.create()
                    .addPart("file", fileBody)
                    .build();
            uploadFile.setEntity(entity);
            HttpResponse response = httpClient.execute(uploadFile);
            HttpEntity responseEntity = response.getEntity();
            String responseString = EntityUtils.toString(responseEntity);
            System.out.println("Server response: " + responseString);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

添加依赖 (Maven)

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.13</version>
</dependency>
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpmime</artifactId>
    <version>4.5.13</version>
</dependency>

使用 FTP/SFTP

使用 Apache Commons Net (FTP)

import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;
import java.io.FileInputStream;
import java.io.IOException;
public class FtpUploader {
    public static void main(String[] args) {
        String server = "ftp.example.com";
        int port = 21;
        String user = "username";
        String pass = "password";
        String remoteFilePath = "/remote/path/file.txt";
        String localFilePath = "path/to/your/file.txt";
        FTPClient ftpClient = new FTPClient();
        try {
            ftpClient.connect(server, port);
            ftpClient.login(user, pass);
            ftpClient.enterLocalPassiveMode();
            ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
            FileInputStream inputStream = new FileInputStream(localFilePath);
            boolean done = ftpClient.storeFile(remoteFilePath, inputStream);
            inputStream.close();
            if (done) {
                System.out.println("File uploaded successfully");
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (ftpClient.isConnected()) {
                    ftpClient.logout();
                    ftpClient.disconnect();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

添加依赖 (Maven)

<dependency>
    <groupId>commons-net</groupId>
    <artifactId>commons-net</artifactId>
    <version>3.8.0</version>
</dependency>

使用 JSch (SFTP)

import com.jcraft.jsch.*;
import java.io.FileInputStream;
import java.io.InputStream;
public class SftpUploader {
    public static void main(String[] args) {
        String host = "sftp.example.com";
        int port = 22;
        String user = "username";
        String password = "password";
        String remoteFilePath = "/remote/path/file.txt";
        String localFilePath = "path/to/your/file.txt";
        JSch jsch = new JSch();
        Session session = null;
        Channel channel = null;
        InputStream inputStream = null;
        try {
            session = jsch.getSession(user, host, port);
            session.setPassword(password);
            session.setConfig("StrictHostKeyChecking", "no");
            session.connect();
            channel = session.openChannel("sftp");
            channel.connect();
            ChannelSftp sftpChannel = (ChannelSftp) channel;
            inputStream = new FileInputStream(localFilePath);
            sftpChannel.put(inputStream, remoteFilePath);
            System.out.println("File uploaded successfully");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (inputStream != null) inputStream.close();
                if (channel != null) channel.disconnect();
                if (session != null) session.disconnect();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

添加依赖 (Maven)

<dependency>
    <groupId>com.jcraft</groupId>
    <artifactId>jsch</artifactId>
    <version>0.1.55</version>
</dependency>

使用 SSH (SCP)

import com.jcraft.jsch.*;
public class ScpUploader {
    public static void main(String[] args) {
        String host = "ssh.example.com";
        int port = 22;
        String user = "username";
        String password = "password";
        String remoteFilePath = "/remote/path/file.txt";
        String localFilePath = "path/to/your/file.txt";
        JSch jsch = new JSch();
        Session session = null;
        Channel channel = null;
        try {
            session = jsch.getSession(user, host, port);
            session.setPassword(password);
            session.setConfig("StrictHostKeyChecking", "no");
            session.connect();
            String command = "scp -p " + localFilePath + " " + user + "@" + host + ":" + remoteFilePath;
            channel = session.openChannel("exec");
            ((ChannelExec) channel).setCommand(command);
            channel.connect();
            System.out.println("File uploaded successfully");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (channel != null) channel.disconnect();
            if (session != null) session.disconnect();
        }
    }
}

使用 Spring Boot (Web 服务端)

如果你需要构建一个完整的上传服务,可以使用 Spring Boot：

import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;
import java.io.File;
import java.io.IOException;
@RestController
public class FileUploadController {
    @PostMapping("/upload")
    public String handleFileUpload(@RequestParam("file") MultipartFile file) {
        try {
            // 保存文件到本地或远程服务器
            String fileName = file.getOriginalFilename();
            File dest = new File("/path/to/save/" + fileName);
            file.transferTo(dest);
            return "File uploaded successfully: " + fileName;
        } catch (IOException e) {
            return "Failed to upload file: " + e.getMessage();
        }
    }
}

注意事项

1. 安全性：在生产环境中，不要硬编码凭据，应使用配置文件或环境变量
2. 错误处理：添加适当的错误处理和日志记录
3. 性能：对于大文件，考虑使用分块上传或进度监控
4. 超时设置：根据网络环境设置合理的超时时间
5. SSL/TLS：对于敏感数据，始终使用加密连接

选择哪种方法取决于你的具体需求,如服务器类型、安全要求和网络环境等。