对象池模式实现代码,Java代码库,德仔网

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【Java】对象池模式实现

作者:七色鱼 / 发布于2013/10/11/ 443

对象池模式经常用在频繁创建、销毁对象（并且对象创建、销毁开销很大）的场景，比如数据库连接池、线程池、任务队列池等。本代码简单实现了对象池模式，没有限制对象池大小。


	<strong>ObjectPool抽象父类</strong>

	

	<strong>import java.util.Iterator;</strong>

	<strong>import java.util.Vector;</strong>

	<strong>public abstract class ObjectPool<T> {
	
	 private Vector<T> locked, unlocked; // locked是已占用的对象集合，unlocked是可用对象集合
	
	 public ObjectPool() {
	 locked = new Vector<T>();
	 unlocked = new Vector<T>();
	 }</strong>

	<strong> // 创建对象
	 protected abstract T create();</strong>

	<strong> // 验证对象有效性
	 public abstract boolean validate(T o);</strong>

	<strong> // 使对象失效
	 public abstract void expire(T o);</strong>

	<strong> // 检出：从对象池获取对象
	 public synchronized T checkOut() {
	 T t;
	 if (unlocked.size() > 0) {
	 Iterator<T> iter = unlocked.iterator();
	 while(iter.hasNext()) {
	 t = iter.next();
	 if(validate(t)) { // 对象有效
	 unlocked.remove(t);
	 locked.add(t);
	
	 return t;
	 }
	 else { // 对象已经失效
	 unlocked.remove(t);
	 expire(t);
	 }
	 }
	 }
	
	 // 对象池塘没有可用对象，创建新对象
	 t = create();
	 locked.add(t);
	
	 return (t);
	 }</strong>

	<strong> // 检入：释放对象回对象池
	 public synchronized void checkIn(T t) {
	 locked.remove(t);
	 if(validate(t)) { // 如果对象仍有效则放回可用对象集合中
	 unlocked.add(t);
	 }
	 else { // 否则使对象失效
	 expire(t);
	 }
	 }
	
	}</strong>

	

	

	<strong>JDBCConnectionPool子类</strong>

	import java.sql.Connection;
	import java.sql.DriverManager;
	import java.sql.SQLException;

	public class JDBCConnectionPool extends ObjectPool<Connection> {
	
	private String url, usr, pwd;

	public JDBCConnectionPool(String driver, String url, String usr, String pwd) {
	 super();
	
	 // 加载对应的数据库驱动
	 try {
	 Class.forName(driver).newInstance();
	 }
	 catch(Exception e) {
	 e.printStackTrace();
	 }
	
	 this.url = url;
	 this.usr = usr;
	 this.pwd = pwd;
	}
	
	@Override
	protected Connection create() {
	 try {
	 return DriverManager.getConnection(url, usr, pwd);
	 }
	 catch(SQLException e) {
	 e.printStackTrace();
	 }
	
	 return null;
	}

	@Override
	public boolean validate(Connection o) {
	 try {
	 return o.isClosed();
	 }
	 catch(SQLException e) {
	 e.printStackTrace();
	 }
	
	 return false;
	}

	@Override
	public void expire(Connection o) {
	 try {
	 o.close();
	 }
	 catch(SQLException e) {
	 e.printStackTrace();
	 }
	 finally {
	 o = null;
	 }
	}
	
	public static void main(String[] args) {
	 JDBCConnectionPool dbConnPool = new JDBCConnectionPool("com.mysql.jdbc.Driver", "jdbc:mysql://127.0.0.1:3306/test", "root", "123");
	
	 // 获取数据库连接对象
	 Connection conn = dbConnPool.checkOut();
	
	 // 使用数据库连接对象
	 // ...
	
	 // 释放数据库连接对象
	 dbConnPool.checkIn(conn);
	
	}

	}

	

	[Java]代码

	

	class Pool {
	 private static final MAX_AVAILABLE = 100;
	 private final Semaphore available = new Semaphore(MAX_AVAILABLE, true);

	 public Object getItem() throws InterruptedException {
	 available.acquire();
	 return getNextAvailableItem();
	 }

	 public void putItem(Object x) {
	 if (markAsUnused(x))
	 available.release();
	 }

	 // Not a particularly efficient data structure; just for demo

	 protected Object[] items = ... whatever kinds of items being managed
	 protected boolean[] used = new boolean[MAX_AVAILABLE];

	 protected synchronized Object getNextAvailableItem() {
	 for (int i = 0; i < MAX_AVAILABLE; ++i) {
	 if (!used[i]) {
	 used[i] = true;
	 return items[i];
	 }
	 }
	 return null; // not reached
	 }

	 protected synchronized boolean markAsUnused(Object item) {
	 for (int i = 0; i < MAX_AVAILABLE; ++i) {
	 if (item == items[i]) {
	 if (used[i]) {
	 used[i] = false;
	 return true;
	 } else
	 return false;
	 }
	 }
	 return false;
	 }

	}

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　对象池模式　

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