import org.slf4j.LoggerFactory;
/**
 * common-pool2 使用方式
 * <p/>
 * 假設這是一個建立TCP連接的對象，該對象的初始化時間平均為500ms，為了避免在程序中頻繁創(chuàng)建Conn對象，我們需要借助對象池管理Conn對象實例
 *
 * @author WangJun <wangjuntytl@163.com>
 * @version 1.0 15/10/28
 * @since 1.6
 */
public class Conn {
    /**
     * 記錄對象的創(chuàng)建時間
     */
    private long createTime;
    /**
     * 初始化Conn對象，模擬創(chuàng)建Conn對象平均消耗500ms
     * @throws InterruptedException
     */
    public Conn() throws InterruptedException {
        Thread.sleep(500);
        createTime = System.currentTimeMillis();
        LoggerFactory.getLogger(getClass()).debug(" init conn suc... " + createTime);
    }
    /**
     * 報告Conn對象信息
     */
    public void report() {
        LoggerFactory.getLogger(getClass()).info("this is a available conn " + createTime);
    }
}

package com.peaceful.pool.demo;
    import org.apache.commons.pool2.BasePooledObjectFactory;
    import org.apache.commons.pool2.PooledObject;
    import org.apache.commons.pool2.PooledObjectFactory;
    import org.apache.commons.pool2.impl.DefaultPooledObject;
    /**
     * common-pool2 使用方式
     * <p/>
     * 為了使用common-pool2對象池管理，我們必須實現{@link org.apache.commons.pool2.PooledObjectFactory}或者其子類
     * 這是一個工廠模式，告訴對象池怎樣去創(chuàng)建要管理的對象
     * <p/>
     * BasePooledObjectFactory 是對{@link org.apache.commons.pool2.PooledObjectFactory}的一個基本實現，我們可以繼承該類，減少一些方法的實現
     * <p/>
     * 在實現{@link org.apache.commons.pool2.PooledObjectFactory}接口時，我們一定要實現的接口方法是{@link PooledObjectFactory#makeObject()}方法。
     *
     * @author WangJun <wangjuntytl@163.com>
     * @version 1.0 15/10/28
     * @since 1.6
     */
    public class ConnFactory extends BasePooledObjectFactory<Conn> {
        /**
         * 間接實現{@link PooledObjectFactory#makeObject()}方法，表明怎樣創(chuàng)建需要管理對象
         */
        @Override
        public Conn create() throws Exception {
            return new Conn();
        }
        /**
         * 在common-pool2中為了統(tǒng)計管理的對象的一些信息，比如調用次數，空閑時間，上次使用時間等，需要對管理的對象進行包裝，然后在放入到對象池中
         *
         * @param obj 對象池要管理的對象
         * @return 返回包裝后的PooledObject對象
         */
        @Override
        public PooledObject<Conn> wrap(Conn obj) {
            return new DefaultPooledObject<Conn>(obj);
        }
    }

package com.peaceful.pool.demo;
    import org.apache.commons.pool2.impl.GenericObjectPoolConfig;
    /**
     * common-pool2 使用方式
     * <p/>
     * {@link org.apache.commons.pool2.impl.GenericObjectPool}支持個性化配置，我們可以配置對象池中總共的對象數，最大、最小空閑對象數等等
     * 這邊繼承{@link GenericObjectPoolConfig}是為了ConnPool也可以進行個性化的配置
     *
     * @author WangJun <wangjuntytl@163.com>
     * @version 1.0 15/10/28
     * @since 1.6
     */
    public class ConnPoolConfig extends GenericObjectPoolConfig {
        public ConnPoolConfig() {
            // defaults to make your life with connection pool easier :)
            setMinIdle(5);
            setTestOnBorrow(true);
        }
    }

package com.peaceful.pool.demo;
    import org.apache.commons.pool2.impl.GenericObjectPool;
    /**
     * common-pool2 使用方式
     * <p/>
     * Conn對象管理池，這里利用GenericObjectPool作為對象池
     *
     * @author WangJun <wangjuntytl@163.com>
     * @version 1.0 15/10/28
     * @since 1.6
     */
    public class ConnPool extends GenericObjectPool<Conn> {
        /**
         * 調用{@link GenericObjectPool}的構造方法，構造ConnPool
         */
        public ConnPool() {
            super(new ConnFactory(), new ConnPoolConfig());
        }
        /**
         * 調用{@link GenericObjectPool}的構造方法，構造ConnPool
         */
        public ConnPool(ConnPoolConfig connPoolConfig) {
            super(new ConnFactory(), connPoolConfig);
        }
    }

public class ConnDemo {
        public static void main(String[] args) throws Exception {
            ConnPoolConfig connPoolConfig = new ConnPoolConfig();
            connPoolConfig.setMinIdle(5);
            connPoolConfig.setMaxIdle(8);
            ConnPool connPool = new ConnPool(connPoolConfig);
            Conn conn1 = connPool.borrowObject();
            Conn conn2 = connPool.borrowObject();
            Conn conn3 = connPool.borrowObject();
            Conn conn4 = connPool.borrowObject();
            Conn conn5 = connPool.borrowObject();
            conn1.report();
            connPool.returnObject(conn1);
            conn2.report();
            connPool.returnObject(conn2);
            conn3.report();
            connPool.returnObject(conn3);
            conn4.report();
            connPool.returnObject(conn4);
            conn5.report();
            connPool.returnObject(conn5);
            conn5.report();
            // 被歸還的對象的引用，不可以在次歸還
            // java.lang.IllegalStateException: Object has already been retured to this pool or is invalid
            try {
                connPool.returnObject(conn5);
            }catch (Exception e){
                e.printStackTrace();
            }
        }
    }