FTPClient连接池的实现

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FTPClient连接池的实现

suifeng3051 2015-10-08 10:59:00 浏览990
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最近在写一个FTP上传工具,用到了Apache的FTPClient,为了提高上传效率,我采用了多线程的方式,但是每个线程频繁的创建和销毁FTPClient对象势必会造成不必要的开销,因此,此处最好使用一个FTPClient连接池。仔细翻了一下Apache的api,发现它并没有一个FTPClientPool的实现,所以,不得不自己写一个FTPClientPool。下面就大体介绍一下开发连接池的整个过程,供大家参考。

关于对象池

有些对象的创建开销是比较大的,比如数据库连接等。为了减少频繁创建、销毁对象带来的性能消耗,我们可以利用对象池的技术来实现对象的复用。对象池提供了一种机制,它可以管理对象池中对象的生命周期,提供了获取和释放对象的方法,可以让客户端很方便的使用对象池中的对象。

如果我们要自己实现一个对象池,一般需要完成如下功能:

1. 如果池中有可用的对象,对象池应当能返回给客户端
2. 客户端把对象放回池里后,可以对这些对象进行重用
3. 对象池能够创建新的对象来满足客户端不断增长的需求
4. 需要有一个正确关闭池的机制来结束对象的生命周期

Apache的对象池工具包

为了方便我们开发自己的对象池,Apache 提供的common-pool工具包,里面包含了开发通用对象池的一些接口和实现类。其中最基本的两个接口是ObjectPool PoolableObjectFactory

ObjectPool接口中有几个最基本的方法:

1. addObject() : 添加对象到池
2. borrowObject():客户端从池中借出一个对象
3. returnObject():客户端归还一个对象到池中
4. close():关闭对象池,清理内存释放资源等
5. setFactory(ObjectFactory factory):需要一个工厂来制造池中的对象

PoolableObjectFactory接口中几个最基本的方法:

1. makeObject():制造一个对象
2. destoryObject():销毁一个对象
3. validateObject():验证一个对象是否还可用

通过以上两个接口我们就可以自己实现一个对象池了。

实例:开发一个FTPClient对象池

最近在开发一个项目,需要把hdfs中的文件上传到一组ftp服务器,为了提高上传效率,自然考虑到使用多线程的方式进行上传。我上传ftp用的工具是Apache common-net包中的FTPClient,但Apache并没有提供FTPClientPool,于是为了减少FTPClient的创建销毁次数,我们就自己开发一个FTPClientPool来复用FTPClient连接。

通过上面的介绍,我们可以利用Apache提供的common-pool包来协助我们开发连接池。而开发一个简单的对象池,仅需要实现common-pool 包中的ObjectPool和PoolableObjectFactory两个接口即可。下面就看一下我写的实现:

写一个ObjectPool接口的实现FTPClientPool

import java.io.IOException;
import java.util.NoSuchElementException;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;

import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.pool.ObjectPool;
import org.apache.commons.pool.PoolableObjectFactory;

/**
* 实现了一个FTPClient连接池
* @author heaven
*/
public class FTPClientPool implements ObjectPool<FTPClient>{
 private static final int DEFAULT_POOL_SIZE = 10;
 private final BlockingQueue<FTPClient> pool;
 private final FtpClientFactory factory;

 /**
 * 初始化连接池,需要注入一个工厂来提供FTPClient实例
 * @param factory
 * @throws Exception
 */
 public FTPClientPool(FtpClientFactory factory) throws Exception{
      this(DEFAULT_POOL_SIZE, factory);
 }
 /**
 *
 * @param maxPoolSize
 * @param factory
 * @throws Exception
 */
 public FTPClientPool(int poolSize, FtpClientFactory factory) throws Exception {
      this.factory = factory;
      pool = new ArrayBlockingQueue<FTPClient>(poolSize*2);
      initPool(poolSize);
 }
 /**
 * 初始化连接池,需要注入一个工厂来提供FTPClient实例
 * @param maxPoolSize
 * @throws Exception
 */
 private void initPool(int maxPoolSize) throws Exception {
      for(int i=0;i<maxPoolSize;i++){
           //往池中添加对象
           addObject();
      }

 }
 /* (non-Javadoc)
 * @see org.apache.commons.pool.ObjectPool#borrowObject()
 */
 public FTPClient borrowObject() throws Exception, NoSuchElementException, IllegalStateException {
      FTPClient client = pool.take();
      if (client == null) {
           client = factory.makeObject();
           addObject();
      }else if(!factory.validateObject(client)){//验证不通过
           //使对象在池中失效
           invalidateObject(client);
           //制造并添加新对象到池中
           client = factory.makeObject();
           addObject();
      }
      return client;

 }

 /* (non-Javadoc)
 * @see org.apache.commons.pool.ObjectPool#returnObject(java.lang.Object)
 */
 public void returnObject(FTPClient client) throws Exception {
      if ((client != null) && !pool.offer(client,3,TimeUnit.SECONDS)) {
           try {
                factory.destroyObject(client);
           } catch (IOException e) {
                e.printStackTrace();
           }
      }
 }

 public void invalidateObject(FTPClient client) throws Exception {
      //移除无效的客户端
      pool.remove(client);
 }

 /* (non-Javadoc)
 * @see org.apache.commons.pool.ObjectPool#addObject()
 */
 public void addObject() throws Exception, IllegalStateException, UnsupportedOperationException {
      //插入对象到队列
      pool.offer(factory.makeObject(),3,TimeUnit.SECONDS);
 }

 public int getNumIdle() throws UnsupportedOperationException {
      return 0;
 }

 public int getNumActive() throws UnsupportedOperationException {
      return 0;
 }

 public void clear() throws Exception, UnsupportedOperationException {

 }

 /* (non-Javadoc)
 * @see org.apache.commons.pool.ObjectPool#close()
 */
 public void close() throws Exception {
      while(pool.iterator().hasNext()){
           FTPClient client = pool.take();
           factory.destroyObject(client);
      }
 }

 public void setFactory(PoolableObjectFactory<FTPClient> factory) throws IllegalStateException, UnsupportedOperationException {

 }

}

再写一个PoolableObjectFactory接口的实现FTPClientFactory

import java.io.IOException;
import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPReply;
import org.apache.commons.pool.PoolableObjectFactory;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.hdfstoftp.util.FTPClientException;

/**
* FTPClient工厂类,通过FTPClient工厂提供FTPClient实例的创建和销毁
* @author heaven
*/
public class FtpClientFactory implements PoolableObjectFactory<FTPClient> {
private static Logger logger = LoggerFactory.getLogger("file");
 private  FTPClientConfigure config;
 //给工厂传入一个参数对象,方便配置FTPClient的相关参数
 public FtpClientFactory(FTPClientConfigure config){
      this.config=config;
 }

 /* (non-Javadoc)
 * @see org.apache.commons.pool.PoolableObjectFactory#makeObject()
 */
 public FTPClient makeObject() throws Exception {
      FTPClient ftpClient = new FTPClient();
      ftpClient.setConnectTimeout(config.getClientTimeout());
      try {
           ftpClient.connect(config.getHost(), config.getPort());
           int reply = ftpClient.getReplyCode();
           if (!FTPReply.isPositiveCompletion(reply)) {
                ftpClient.disconnect();
                logger.warn("FTPServer refused connection");
                return null;
           }
           boolean result = ftpClient.login(config.getUsername(), config.getPassword());
           if (!result) {
                throw new FTPClientException("ftpClient登陆失败! userName:" + config.getUsername() + " ; password:" + config.getPassword());
           }
           ftpClient.setFileType(config.getTransferFileType());
           ftpClient.setBufferSize(1024);
           ftpClient.setControlEncoding(config.getEncoding());
           if (config.getPassiveMode().equals("true")) {
                ftpClient.enterLocalPassiveMode();
           }
      } catch (IOException e) {
           e.printStackTrace();
      } catch (FTPClientException e) {
           e.printStackTrace();
      }
      return ftpClient;
 }

 /* (non-Javadoc)
 * @see org.apache.commons.pool.PoolableObjectFactory#destroyObject(java.lang.Object)
 */
 public void destroyObject(FTPClient ftpClient) throws Exception {
      try {
           if (ftpClient != null && ftpClient.isConnected()) {
                ftpClient.logout();
           }
      } catch (IOException io) {
           io.printStackTrace();
      } finally {
           // 注意,一定要在finally代码中断开连接,否则会导致占用ftp连接情况
           try {
                ftpClient.disconnect();
           } catch (IOException io) {
                io.printStackTrace();
           }
      }
 }

 /* (non-Javadoc)
 * @see org.apache.commons.pool.PoolableObjectFactory#validateObject(java.lang.Object)
 */
 public boolean validateObject(FTPClient ftpClient) {
      try {
           return ftpClient.sendNoOp();
      } catch (IOException e) {
           throw new RuntimeException("Failed to validate client: " + e, e);
      }
 }

 public void activateObject(FTPClient ftpClient) throws Exception {
 }

 public void passivateObject(FTPClient ftpClient) throws Exception {

 }

}

最后,我们最好给工厂传递一个参数对象,方便我们设置FTPClient的一些参数

package org.apache.commons.pool.impl.contrib;

/**
 * FTPClient配置类,封装了FTPClient的相关配置
 *
 * @author heaven
 */
public class FTPClientConfigure {
  private String host;
  private int port;
  private String username;
  private String password;
  private String passiveMode;
  private String encoding;
  private int clientTimeout;
  private int threadNum;
  private int transferFileType;
  private boolean renameUploaded;
  private int retryTimes;

  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 String getPassiveMode() {
         return passiveMode;
  }

  public void setPassiveMode(String passiveMode) {
         this. passiveMode = passiveMode;
  }

  public String getEncoding() {
         return encoding;
  }

  public void setEncoding(String encoding) {
         this. encoding = encoding;
  }

  public int getClientTimeout() {
         return clientTimeout;
  }

  public void setClientTimeout( int clientTimeout) {
         this. clientTimeout = clientTimeout;
  }

  public int getThreadNum() {
         return threadNum;
  }

  public void setThreadNum( int threadNum) {
         this. threadNum = threadNum;
  }

  public int getTransferFileType() {
         return transferFileType;
  }

  public void setTransferFileType( int transferFileType) {
         this. transferFileType = transferFileType;
  }

  public boolean isRenameUploaded() {
         return renameUploaded;
  }

  public void setRenameUploaded( boolean renameUploaded) {
         this. renameUploaded = renameUploaded;
  }

  public int getRetryTimes() {
         return retryTimes;
  }

  public void setRetryTimes( int retryTimes) {
         this. retryTimes = retryTimes;
  }

  @Override
  public String toString() {
         return "FTPClientConfig [host=" + host + "\n port=" + port + "\n username=" + username + "\n password=" + password   + "\n passiveMode=" + passiveMode
                    + "\n encoding=" + encoding + "\n clientTimeout=" + clientTimeout + "\n threadNum=" + threadNum + "\n transferFileType="
                    + transferFileType + "\n renameUploaded=" + renameUploaded + "\n retryTimes=" + retryTimes + "]" ;
  }

}

FTPClientPool连接池类管理FTPClient对象的生命周期,负责对象的借出、规划、池的销毁等;FTPClientPool类依赖于FtpClientFactory类,由这个工程类来制造和销毁对象;FtpClientFactory又依赖FTPClientConfigure类,FTPClientConfigure负责封装FTPClient的配置参数。至此,我们的FTPClient连接池就开发完成了。

需要注意的是,FTPClientPool中用到了一个阻塞队列ArrayBlockingQueue来管理存放FTPClient对象,关于阻塞队列,请参考我的这篇文章:【Java并发之】BlockingQueue:http://blog.csdn.net/suifeng3051/article/details/48807423

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