Java FTPClient連接池的實現

2024-07-14 08:41:21

字體：大中小

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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連接池的整個過程，供大家參考。

關于對象池

有些對象的創建開銷是比較大的，比如數據庫連接等。為了減少頻繁創建、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

為了方便我們開發自己的對象池，Apache 提供的common-pool工具包，里面包含了開發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：開發一個FTPClient對象池

最近在開發一個項目，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的創建銷毀次數，我們就自己開發一個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包來協助我們開發連接池。而開發一個簡單的對象池，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VeVb武林網。

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