Java FTPClient連接池的實現

更新時間：2018年06月26日 10:25:29 作者：Heaven-Wang

這篇文章主要介紹了Java FTPClient連接池的實現，小編覺得挺不錯的，現在分享給大家，也給大家做個參考。一起跟隨小編過來看看吧

最近在寫一個FTP上傳工具，用到了Apache的FTPClient，為了提高上傳效率，我采用了多線程的方式，但是每個線程頻繁的創(chuàng)建和銷毀FTPClient對象勢必會造成不必要的開銷，因此，此處最好使用一個FTPClient連接池。仔細翻了一下Apache的api，發(fā)現它并沒有一個FTPClientPool的實現，所以，不得不自己寫一個FTPClientPool。下面就大體介紹一下開發(fā)連接池的整個過程，供大家參考。

關于對象池

有些對象的創(chuàng)建開銷是比較大的，比如數據庫連接等。為了減少頻繁創(chuàng)建、銷毀對象帶來的性能消耗，我們可以利用對象池的技術來實現對象的復用。對象池提供了一種機制，它可以管理對象池中對象的生命周期，提供了獲取和釋放對象的方法，可以讓客戶端很方便的使用對象池中的對象。

如果我們要自己實現一個對象池，一般需要完成如下功能：

1. 如果池中有可用的對象，對象池應當能返回給客戶端
2. 客戶端把對象放回池里后，可以對這些對象進行重用
3. 對象池能夠創(chuàng)建新的對象來滿足客戶端不斷增長的需求
4. 需要有一個正確關閉池的機制來結束對象的生命周期

Apache的對象池工具包

為了方便我們開發(fā)自己的對象池，Apache 提供的common-pool工具包，里面包含了開發(fā)通用對象池的一些接口和實現類。其中最基本的兩個接口是ObjectPool 和PoolableObjectFactory。

ObjectPool接口中有幾個最基本的方法：

1. addObject() : 添加對象到池
2. borrowObject()：客戶端從池中借出一個對象
3. returnObject()：客戶端歸還一個對象到池中
4. close()：關閉對象池，清理內存釋放資源等
5. setFactory(ObjectFactory factory)：需要一個工廠來制造池中的對象

PoolableObjectFactory接口中幾個最基本的方法：

1. makeObject()：制造一個對象
2. destoryObject()：銷毀一個對象
3. validateObject()：驗證一個對象是否還可用

通過以上兩個接口我們就可以自己實現一個對象池了。

實例：開發(fā)一個FTPClient對象池

最近在開發(fā)一個項目，需要把hdfs中的文件上傳到一組ftp服務器，為了提高上傳效率，自然考慮到使用多線程的方式進行上傳。我上傳ftp用的工具是Apache common-net包中的FTPClient，但Apache并沒有提供FTPClientPool，于是為了減少FTPClient的創(chuàng)建銷毀次數，我們就自己開發(fā)一個FTPClientPool來復用FTPClient連接。

通過上面的介紹，我們可以利用Apache提供的common-pool包來協(xié)助我們開發(fā)連接池。而開發(fā)一個簡單的對象池，僅需要實現common-pool 包中的ObjectPool和PoolableObjectFactory兩個接口即可。下面就看一下我寫的實現：

寫一個ObjectPool接口的實現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;

/**
* 實現了一個FTPClient連接池
* @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;

 /**
 * 初始化連接池，需要注入一個工廠來提供FTPClient實例
 * @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);
 }
 /**
 * 初始化連接池，需要注入一個工廠來提供FTPClient實例
 * @param maxPoolSize
 * @throws Exception
 */
 private void initPool(int maxPoolSize) throws Exception {
   for(int i=0;i<maxPoolSize;i++){
      //往池中添加對象
      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)){//驗證不通過
      //使對象在池中失效
      invalidateObject(client);
      //制造并添加新對象到池中
      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 {
   //移除無效的客戶端
   pool.remove(client);
 }

 /* (non-Javadoc)
 * @see org.apache.commons.pool.ObjectPool#addObject()
 */
 public void addObject() throws Exception, IllegalStateException, UnsupportedOperationException {
   //插入對象到隊列
   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 {

 }
}

再寫一個PoolableObjectFactory接口的實現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工廠類，通過FTPClient工廠提供FTPClient實例的創(chuàng)建和銷毀
* @author heaven
*/
public class FtpClientFactory implements PoolableObjectFactory<FTPClient> {
private static Logger logger = LoggerFactory.getLogger("file");
 private FTPClientConfigure config;
 //給工廠傳入一個參數對象，方便配置FTPClient的相關參數
 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登陸失敗! 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代碼中斷開連接，否則會導致占用ftp連接情況
      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，我們最好給工廠傳遞一個參數對象，方便我們設置FTPClient的一些參數

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

/**
 * FTPClient配置類，封裝了FTPClient的相關配置
 *
 * @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連接池類管理FTPClient對象的生命周期，負責對象的借出、規(guī)劃、池的銷毀等；FTPClientPool類依賴于FtpClientFactory類，由這個工程類來制造和銷毀對象；FtpClientFactory又依賴FTPClientConfigure類，FTPClientConfigure負責封裝FTPClient的配置參數。至此，我們的FTPClient連接池就開發(fā)完成了。

需要注意的是，FTPClientPool中用到了一個阻塞隊列ArrayBlockingQueue來管理存放FTPClient對象，關于阻塞隊列，請參考我的這篇文章：【Java并發(fā)之】BlockingQueue

以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持腳本之家。

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