So verwenden Sie die Java GenericObjectPool-Objektpooling-Technologie

public interface ObjectPool<T> extends Closeable {
    /**
     * 从池中借走到一个对象
     */
    T borrowObject() throws Exception, NoSuchElementException, IllegalStateException;
    /**
     * 把对象归还给对象池
     */
    void returnObject(T var1) throws Exception;
    /**
     * 验证对象的有效性
     */
    void invalidateObject(T var1) throws Exception;

    /**
     * 往池中添加一个对象
     */
    void addObject() throws Exception, IllegalStateException, UnsupportedOperationException;
    /**
     * 返回对象池中有多少对象是空闲的，也就是能够被借走的对象的数量。
     */
    int getNumIdle();
    /**
     * 返回对象池中有对象对象是活跃的，也就是已经被借走的，在使用中的对象的数量。
     */
    int getNumActive();
    /**
     * 清理对象池。注意是清理不是清空，该方法要求的是，清理所有空闲对象，释放相关资源。
     */
    void clear() throws Exception, UnsupportedOperationException;
    /**
     * 关闭对象池。这个方法可以达到清空的效果，清理所有对象以及相关资源。
     */
    void close();
}

public interface PooledObjectFactory<T> {
    /**
     * 创建一个可由池提供服务的实例，并将其封装在由池管理的PooledObject中。
     */
    PooledObject<T> makeObject() throws Exception;

    /**
     *  销毁池不再需要的实例
     */
    void destroyObject(PooledObject<T> var1) throws Exception;

    /**
     * 确保实例可以安全地由池返回
     */
    boolean validateObject(PooledObject<T> var1);

    /**
     * 重新初始化池返回的实例
     */
    void activateObject(PooledObject<T> var1) throws Exception;

    /**
     * 取消初始化要返回到空闲对象池的实例
     */
    void passivateObject(PooledObject<T> var1) throws Exception;
}

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-pool2</artifactId>
    <version>2.7.0</version>
</dependency>

<!-- https://mvnrepository.com/artifact/com.jcraft/jsch -->
<dependency>
    <groupId>com.jcraft</groupId>
    <artifactId>jsch</artifactId>
    <version>0.1.55</version>
</dependency>

package com.vipsoft.sftp.exception;


/**
 * sftp连接池异常
 */
public class SftpPoolException extends RuntimeException {

    private static final long serialVersionUID = 1L;

    /**
     * Constructs a new runtime exception with {@code null} as its
     * detail message.  The cause is not initialized, and may subsequently be
     * initialized by a call to {@link #initCause}.
     */
    public SftpPoolException() {
    }

    /**
     * Constructs a new runtime exception with the specified detail message.
     * The cause is not initialized, and may subsequently be initialized by a
     * call to {@link #initCause}.
     *
     * @param message the detail message. The detail message is saved for
     *                later retrieval by the {@link #getMessage()} method.
     */
    public SftpPoolException(String message) {
        super(message);
    }

    /**
     * Constructs a new runtime exception with the specified detail message and
     * cause.  <p>Note that the detail message associated with
     * {@code cause} is <i>not</i> automatically incorporated in
     * this runtime exception&#39;s detail message.
     *
     * @param message the detail message (which is saved for later retrieval
     *                by the {@link #getMessage()} method).
     * @param cause   the cause (which is saved for later retrieval by the
     *                {@link #getCause()} method).  (A <tt>null</tt> value is
     *                permitted, and indicates that the cause is nonexistent or
     *                unknown.)
     * @since 1.4
     */
    public SftpPoolException(String message, Throwable cause) {
        super(message, cause);
    }

    /**
     * Constructs a new runtime exception with the specified cause and a
     * detail message of <tt>(cause==null ? null : cause.toString())</tt>
     * (which typically contains the class and detail message of
     * <tt>cause</tt>).  This constructor is useful for runtime exceptions
     * that are little more than wrappers for other throwables.
     *
     * @param cause the cause (which is saved for later retrieval by the
     *              {@link #getCause()} method).  (A <tt>null</tt> value is
     *              permitted, and indicates that the cause is nonexistent or
     *              unknown.)
     * @since 1.4
     */
    public SftpPoolException(Throwable cause) {
        super(cause);
    }

    /**
     * Constructs a new runtime exception with the specified detail
     * message, cause, suppression enabled or disabled, and writable
     * stack trace enabled or disabled.
     *
     * @param message            the detail message.
     * @param cause              the cause.  (A {@code null} value is permitted,
     *                           and indicates that the cause is nonexistent or unknown.)
     * @param enableSuppression  whether or not suppression is enabled
     *                           or disabled
     * @param writableStackTrace whether or not the stack trace should
     *                           be writable
     * @since 1.7
     */
    public SftpPoolException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
        super(message, cause, enableSuppression, writableStackTrace);
    }

}

package com.vipsoft.sftp.config;

import com.vipsoft.sftp.pool.SftpFactory;
import com.vipsoft.sftp.pool.SftpPool;
import com.vipsoft.sftp.utils.SftpUtil;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
@EnableConfigurationProperties(SftpProperties.class)
public class SftpConfig {
    // 工厂
    @Bean
    public SftpFactory sftpFactory(SftpProperties properties) {
        return new SftpFactory(properties);
    }

    // 连接池
    @Bean
    public SftpPool sftpPool(SftpFactory sftpFactory) {
        return new SftpPool(sftpFactory);
    }

    // 辅助类
    @Bean
    public SftpUtil sftpUtil(SftpPool sftpPool) {
        return new SftpUtil(sftpPool);
    }
}

package com.vipsoft.sftp.config;

import com.jcraft.jsch.ChannelSftp;
import org.apache.commons.pool2.impl.GenericObjectPoolConfig;
import org.springframework.boot.context.properties.ConfigurationProperties;

@ConfigurationProperties(prefix = "sftp")
public class SftpProperties {

    private String host;
    private int port = 22;
    private String username = "root";
    private String password = "root";
    private Pool pool = new Pool();

    public String getHost() {
        return host;
    }

    public void setHost(String host) {
        this.host = host;
    }

    public int getPort() {
        return port;
    }

    public void setPort(int port) {
        this.port = port;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Pool getPool() {
        return pool;
    }

    public void setPool(Pool pool) {
        this.pool = pool;
    }

    public static class Pool extends GenericObjectPoolConfig<ChannelSftp> {

        private int maxTotal = DEFAULT_MAX_TOTAL;
        private int maxIdle = DEFAULT_MAX_IDLE;
        private int minIdle = DEFAULT_MIN_IDLE;

        public Pool() {
            super();
        }
        @Override
        public int getMaxTotal() {
            return maxTotal;
        }
        @Override
        public void setMaxTotal(int maxTotal) {
            this.maxTotal = maxTotal;
        }
        @Override
        public int getMaxIdle() {
            return maxIdle;
        }
        @Override
        public void setMaxIdle(int maxIdle) {
            this.maxIdle = maxIdle;
        }
        @Override
        public int getMinIdle() {
            return minIdle;
        }
        @Override
        public void setMinIdle(int minIdle) {
            this.minIdle = minIdle;
        }
    }
}

package com.vipsoft.sftp.pool;

import com.jcraft.jsch.ChannelSftp;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.JSchException;
import com.jcraft.jsch.Session;
import com.vipsoft.sftp.config.SftpProperties;
import com.vipsoft.sftp.exception.SftpPoolException;
import org.apache.commons.pool2.BasePooledObjectFactory;
import org.apache.commons.pool2.PooledObject;
import org.apache.commons.pool2.impl.DefaultPooledObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Properties;

public class SftpFactory extends BasePooledObjectFactory<ChannelSftp> {

    private  final Logger logger = LoggerFactory.getLogger(this.getClass());

    private SftpProperties properties;

    public SftpProperties getProperties() {
        return properties;
    }

    public void setProperties(SftpProperties properties) {
        this.properties = properties;
    }

    public SftpFactory(SftpProperties properties) {
        this.properties = properties;
    }

    @Override
    public ChannelSftp create() {
        try {
            JSch jsch = new JSch();
            Session sshSession = jsch.getSession(properties.getUsername(), properties.getHost(), properties.getPort());
            sshSession.setPassword(properties.getPassword());
            Properties sshConfig = new Properties();
            sshConfig.put("StrictHostKeyChecking", "no");
            sshSession.setConfig(sshConfig);
            sshSession.connect();
            ChannelSftp channel = (ChannelSftp) sshSession.openChannel("sftp");
            channel.connect();
            return channel;
        } catch (JSchException e) {
            throw new SftpPoolException("连接sfpt失败", e);
        }
    }

    @Override
    public PooledObject<ChannelSftp> wrap(ChannelSftp channelSftp) {
        return new DefaultPooledObject<>(channelSftp);
    }

    // 销毁对象
    @Override
    public void destroyObject(PooledObject<ChannelSftp> p) {
        ChannelSftp channelSftp = p.getObject();
        channelSftp.disconnect();
    }
}

package com.vipsoft.sftp.pool;

import com.jcraft.jsch.ChannelSftp;
import org.apache.commons.pool2.impl.GenericObjectPool;

public class SftpPool<T> extends GenericObjectPool<ChannelSftp> {

    public SftpPool(SftpFactory factory) {
        super(factory,factory.getProperties().getPool());
    }

    /**
     * 获取一个sftp连接对象
     * @return sftp连接对象
     */
    @Override
    public ChannelSftp borrowObject() throws Exception {
        return super.borrowObject();
    }

    /**
     * 归还一个sftp连接对象
     * @param channelSftp sftp连接对象
     */
    @Override
    public void returnObject(ChannelSftp channelSftp) {
        if (channelSftp!=null) {
            super.returnObject(channelSftp);
        }
    }

}

package com.vipsoft.sftp.utils;

import com.jcraft.jsch.ChannelSftp;
import com.jcraft.jsch.SftpException;
import com.vipsoft.sftp.exception.SftpPoolException;
import com.vipsoft.sftp.pool.SftpPool;

import java.io.InputStream;

public class SftpUtil {

    private SftpPool pool;

    public SftpUtil(SftpPool pool) {
        this.pool = pool;
    }

    /**
     * 下载文件
     *
     * @param dir  远程目录
     * @param name 远程文件名
     * @return 文件字节数组
     */
    public byte[] download(String dir, String name) {
        ChannelSftp sftp = null;
        try {
            sftp = pool.borrowObject();
            sftp.cd(dir);
            InputStream in = sftp.get(name);
            return ByteUtil.inputStreamToByteArray(in);
        } catch (Exception e) {
            throw new SftpPoolException("sftp下载文件出错", e);
        } finally {
            pool.returnObject(sftp);
        }
    }

    /**
     * 上传文件
     *
     * @param dir  远程目录
     * @param name 远程文件名
     * @param in   输入流
     */
    public void upload(String dir, String name, InputStream in) {
        ChannelSftp sftp = null;
        try {
            sftp = pool.borrowObject();
            mkdirs(sftp, dir);
            sftp.cd(dir);
            sftp.put(in, name);
        } catch (Exception e) {
            throw new SftpPoolException("sftp上传文件出错", e);
        } finally {
            pool.returnObject(sftp);
        }
    }

    /**
     * 删除文件
     *
     * @param dir  远程目录
     * @param name 远程文件名
     */
    public void delete(String dir, String name) {
        ChannelSftp sftp = null;
        try {
            sftp = pool.borrowObject();
            sftp.cd(dir);
            sftp.rm(name);
        } catch (Exception e) {
            throw new SftpPoolException("sftp删除文件出错", e);
        } finally {
            pool.returnObject(sftp);
        }
    }

    /**
     * 递归创建多级目录
     *
     * @param dir 多级目录
     */
    private void mkdirs(ChannelSftp sftp, String dir) {
        String[] folders = dir.split("/");
        try {
            sftp.cd("/");
            for (String folder : folders) {
                if (folder.length() > 0) {
                    try {
                        sftp.cd(folder);
                    } catch (Exception e) {
                        sftp.mkdir(folder);
                        sftp.cd(folder);
                    }
                }
            }
        } catch (SftpException e) {
            throw new SftpPoolException("sftp创建目录出错", e);
        }
    }
}

package com.vipsoft.sftp;

import com.vipsoft.sftp.utils.SftpUtil;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
public class SftpTest {

    @Autowired
    private SftpUtil sftpUtil;

    @Test
    void downloadTest() {
        byte[] dockerfiles = sftpUtil.download("/opt/demo/", "Dockerfile");
        System.out.println("FileSize =>" + dockerfiles.length);
    }

}