SpringBoot + SFTP 实现文件上传与下载实战-java下载文件

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);
 }
}

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;
}

@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);
 }
}