SpringBoot + SFTP 实现文件上传与下载实战

背景

近期在工作中需要实现文件的上传与下载，一开始打算使用一些高级的文件系统，比如：FastDFS，GlusterFS，CephFS，这些高级厉害的文件存储系统，当然博主也花了两周的时间把这三个FS都玩了一遍。个人认为FastDFS使用以及部署最简单，比较适合存储图片以及中小型文件（<500M），毕竟是国产框架(点赞)；而GlusterFS和CephFS，GlusterFS部署和Java对接起来较为简单，CephFS部署很费劲，对Java使用不太友好(不太方便)。当然很大原因是博主技术不够，玩不过来。在使用这些框架之后，Leader感觉公司目前的技术储备还不够成熟，最终使用常用的SFTP实现文件上传和下载。背景介绍就到这里，接下来实战吧！

SFTP介绍

• SFTP是Secure File Transfer Protocol的缩写，安全文件传送协议。可以为传输文件提供一种安全的加密方法，语法几乎和FTP一致。
• 相比于FTP，SFTP更安全，但更安全带来副作用就是的效率比FTP要低些。
• SFTP是SSH的一部分，内部是采用SSH连接，所以在以下代码中进行文件的操作都会先cd到SFTP存放文件的根路径下。
• Reference：SFTP与FTP比较、浅谈SFTP与FTP。

实战

1. 相关依赖（基于SpringBoot）

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
    <dependency>
        <groupId>com.jcraft</groupId>
        <artifactId>jsch</artifactId>
        <version>0.1.54</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.apache.commons</groupId>
        <artifactId>commons-lang3</artifactId>
    </dependency>
</dependencies>

2. 相关配置

#============================================================================
# SFTP Client Setting
#============================================================================
# 协议
sftp.client.protocol=sftp
# ip地址
sftp.client.host=127.0.0.1
# 端口
sftp.client.port=22
# 用户名
sftp.client.username=sftp
# 密码
sftp.client.password=sftp
# 根路径
sftp.client.root=/home/sftp/
# 密钥文件路径
sftp.client.privateKey=
# 密钥的密码
sftp.client.passphrase=
# 
sftp.client.sessionStrictHostKeyChecking=no
# session连接超时时间
sftp.client.sessionConnectTimeout=15000
# channel连接超时时间
sftp.client.channelConnectedTimeout=15000

• 这里暂时没有使用到使用加密密钥的方式登陆，所以暂不填写

3. 将application.properties中配置转为一个Bean

@Getter
@Setter
@Component
@ConfigurationProperties(ignoreUnknownFields = false, prefix = "sftp.client")
public class SftpProperties {
    private String host;

    private Integer port;

    private String protocol;

    private String username;

    private String password;

    private String root;

    private String privateKey;

    private String passphrase;

    private String sessionStrictHostKeyChecking;

    private Integer sessionConnectTimeout;

    private Integer channelConnectedTimeout;
}

4. 将上传下载文件封装成Service

• FileSystemService

/**
 * @author jason.tang
 * @create 2019-03-07 13:33
 * @description
 */
public interface FileSystemService {

    boolean uploadFile(String targetPath, InputStream inputStream) throws Exception;

    boolean uploadFile(String targetPath, File file) throws Exception;

    File downloadFile(String targetPath) throws Exception;

    boolean deleteFile(String targetPath) throws Exception;
}

• 实现类：FileSystemServiceImpl（此处省略相关上传下载代码）

/**
 * @author jason.tang
 * @create 2019-03-07 13:33
 * @description
 */
@Slf4j
@Service("fileSystemService")
public class FileSystemServiceImpl implements FileSystemService {

    @Autowired
    private SftpProperties config;

    // 设置第一次登陆的时候提示，可选值：(ask | yes | no)
    private static final String SESSION_CONFIG_STRICT_HOST_KEY_CHECKING = "StrictHostKeyChecking";

    /**
     * 创建SFTP连接
     * @return
     * @throws Exception
     */
    private ChannelSftp createSftp() throws Exception {
        JSch jsch = new JSch();
        log.info("Try to connect sftp[" + config.getUsername() + "@" + config.getHost() + "], use password[" + config.getPassword() + "]");

        Session session = createSession(jsch, config.getHost(), config.getUsername(), config.getPort());
        session.setPassword(config.getPassword());
        session.connect(config.getSessionConnectTimeout());

        log.info("Session connected to {}.", config.getHost());

        Channel channel = session.openChannel(config.getProtocol());
        channel.connect(config.getChannelConnectedTimeout());

        log.info("Channel created to {}.", config.getHost());

        return (ChannelSftp) channel;
    }

    /**
     * 加密秘钥方式登陆
     * @return
     */
    private ChannelSftp connectByKey() throws Exception {
        JSch jsch = new JSch();

        // 设置密钥和密码 ,支持密钥的方式登陆
        if (StringUtils.isNotBlank(config.getPrivateKey())) {
            if (StringUtils.isNotBlank(config.getPassphrase())) {
                // 设置带口令的密钥
                jsch.addIdentity(config.getPrivateKey(), config.getPassphrase());
            } else {
                // 设置不带口令的密钥
                jsch.addIdentity(config.getPrivateKey());
            }
        }
        log.info("Try to connect sftp[" + config.getUsername() + "@" + config.getHost() + "], use private key[" + config.getPrivateKey()
                + "] with passphrase[" + config.getPassphrase() + "]");

        Session session = createSession(jsch, config.getHost(), config.getUsername(), config.getPort());
        // 设置登陆超时时间
        session.connect(config.getSessionConnectTimeout());
        log.info("Session connected to " + config.getHost() + ".");

        // 创建sftp通信通道
        Channel channel = session.openChannel(config.getProtocol());
        channel.connect(config.getChannelConnectedTimeout());
        log.info("Channel created to " + config.getHost() + ".");
        return (ChannelSftp) channel;
    }

    /**
     * 创建session
     * @param jsch
     * @param host
     * @param username
     * @param port
     * @return
     * @throws Exception
     */
    private Session createSession(JSch jsch, String host, String username, Integer port) throws Exception {
        Session session = null;

        if (port <= 0) {
            session = jsch.getSession(username, host);
        } else {
            session = jsch.getSession(username, host, port);
        }

        if (session == null) {
            throw new Exception(host + " session is null");
        }

        session.setConfig(SESSION_CONFIG_STRICT_HOST_KEY_CHECKING, config.getSessionStrictHostKeyChecking());
        return session;
    }

    /**
     * 关闭连接
     * @param sftp
     */
    private void disconnect(ChannelSftp sftp) {
        try {
            if (sftp != null) {
                if (sftp.isConnected()) {
                    sftp.disconnect();
                } else if (sftp.isClosed()) {
                    log.info("sftp is closed already");
                }
                if (null != sftp.getSession()) {
                    sftp.getSession().disconnect();
                }
            }
        } catch (JSchException e) {
            e.printStackTrace();
        }
    }
}

5. 上传文件

• 5.1 将inputStream上传到指定路径下(单级或多级目录)

@Override
public boolean uploadFile(String targetPath, InputStream inputStream) throws Exception {
    ChannelSftp sftp = this.createSftp();
    try {
        sftp.cd(config.getRoot());
        log.info("Change path to {}", config.getRoot());

        int index = targetPath.lastIndexOf("/");
        String fileDir = targetPath.substring(0, index);
        String fileName = targetPath.substring(index + 1);
        boolean dirs = this.createDirs(fileDir, sftp);
        if (!dirs) {
            log.error("Remote path error. path:{}", targetPath);
            throw new Exception("Upload File failure");
        }
        sftp.put(inputStream, fileName);
        return true;
    } catch (Exception e) {
        log.error("Upload file failure. TargetPath: {}", targetPath, e);
        throw new Exception("Upload File failure");
    } finally {
        this.disconnect(sftp);
    }
}

• 5.2 创建多级目录

private boolean createDirs(String dirPath, ChannelSftp sftp) {
    if (dirPath != null && !dirPath.isEmpty()
                && sftp != null) {
        String[] dirs = Arrays.stream(dirPath.split("/"))
               .filter(StringUtils::isNotBlank)
               .toArray(String[]::new);

        for (String dir : dirs) {
            try {
                sftp.cd(dir);
                log.info("Change directory {}", dir);
            } catch (Exception e) {
                try {
                    sftp.mkdir(dir);
                    log.info("Create directory {}", dir);
                } catch (SftpException e1) {
                     log.error("Create directory failure, directory:{}", dir, e1);
                     e1.printStackTrace();
                }
                try {
                    sftp.cd(dir);
                    log.info("Change directory {}", dir);
                } catch (SftpException e1) {
                    log.error("Change directory failure, directory:{}", dir, e1);
                    e1.printStackTrace();
                }
            }
        }
        return true;
    }
    return false;
}

• 5.3 将文件上传到指定目录

@Override
public boolean uploadFile(String targetPath, File file) throws Exception {
    return this.uploadFile(targetPath, new FileInputStream(file));
}

6. 下载文件

@Override
public File downloadFile(String targetPath) throws Exception {
    ChannelSftp sftp = this.createSftp();
    OutputStream outputStream = null;
    try {
        sftp.cd(config.getRoot());
        log.info("Change path to {}", config.getRoot());

        File file = new File(targetPath.substring(targetPath.lastIndexOf("/") + 1));

        outputStream = new FileOutputStream(file);
        sftp.get(targetPath, outputStream);
        log.info("Download file success. TargetPath: {}", targetPath);
        return file;
    } catch (Exception e) {
        log.error("Download file failure. TargetPath: {}", targetPath, e);
         throw new Exception("Download File failure");
    } finally {
        if (outputStream != null) {
            outputStream.close();
        }
        this.disconnect(sftp);
    }
}

7. 删除文件

/**
     * 删除文件
     * @param targetPath
     * @return
     * @throws Exception
     */
@Override
public boolean deleteFile(String targetPath) throws Exception {
    ChannelSftp sftp = null;
    try {
        sftp = this.createSftp();
        sftp.cd(config.getRoot());
        sftp.rm(targetPath);
        return true;
    } catch (Exception e) {
        log.error("Delete file failure. TargetPath: {}", targetPath, e);
        throw new Exception("Delete File failure");
    } finally {
        this.disconnect(sftp);
    }
}

8. 最后

• 具体测试请看源码，这里不贴出相关测试，避免篇幅太长。
• 涉及到对文件的操作，一定记得将流关闭。
• 在使用中比如下载文件，请将生成的文件在使用后删除（file.delete()），避免在服务器中占据大量资源。
• application.proerties中SFTP相关配置，请自行更换。如有不对之处，请指出，感谢阅读！