JDBC连接池，jdbc,package org.

JDBC连接池，jdbc,package org.

package org.hwork.db;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;import java.util.Date;import java.util.Enumeration;import java.util.Vector;import org.apache.log4j.Logger;import org.hwork.utils.LoadProperties;import org.hwork.web.Constant;public class DbConnectionManager {    private DbConnectionPool pool;    private static DbConnectionManager dbConnectionManager = new DbConnectionManager();    /**     * 单实例模式     */    private DbConnectionManager(){        LoadProperties pro = new LoadProperties(Constant.propertiesName);        pool = new DbConnectionPool(pro.getValue("db.driverClass"), pro.getValue("db.url"), pro.getValue("db.userName"), pro.getValue("db.password"), Integer.valueOf(pro.getValue("db.minConns").trim()), Integer.valueOf(pro.getValue("db.maxConns").trim()));    }    public static DbConnectionManager newInstance(){        if(dbConnectionManager != null){            return dbConnectionManager;        }else{            return new DbConnectionManager();        }    }    public Connection getConnection(){        return pool.getConnection();    }    public void close(Connection conn){        pool.freeConnection(conn);    }    public void release(){        pool.release();    }    protected class DbConnectionPool {        private final Logger logger = Logger.getLogger(DbConnectionPool.class);        private Vector<Connection> freeConnections = new Vector<Connection>();        private String driverClass;        private String url;        private String userName;        private String password;        private int minConns;        private int maxConns;        private int isUsed = 0;        private int timeout = 15 * 1000;        public DbConnectionPool(String driverClass, String url,                String userName, String password, int minConns, int maxConns) {            this.driverClass = driverClass;            this.url = url;            this.userName = userName;            this.password = password;            this.minConns = minConns;            this.maxConns = maxConns;            initConnection();        }        private void initConnection(){            try {                Class.forName(driverClass); //加载驱动                for(int i = 0; i < minConns; i++){                    Connection conn = DriverManager.getConnection(url, userName, password);                    freeConnections.add(conn);                    System.out.println("初始化数据库连接放入连接池" + i);                }            } catch (ClassNotFoundException e) {                logger.error("驱动无法加载，请检查驱动是否存在，driver: " + driverClass, e);            } catch (SQLException e){                logger.error("数据库连接池初始化失败", e);            }        }        /**         * 获取连接         * @return         */        public synchronized Connection getConnection(){            System.out.println("已用 " + isUsed + " 个连接，空闲连接个数 " + freeConnections.size());            Connection conn = null;            if(freeConnections.size() > 0){                conn = freeConnections.firstElement();                try{                    if(conn.isClosed()){                        conn = getConnection();                    }                }catch(SQLException e){                    conn= getConnection();                }                freeConnections.removeElementAt(0);                isUsed++;                return conn;            }            if(isUsed < maxConns){                conn = newConnection();                isUsed++;                return conn;            }            if(isUsed >= maxConns){                //连接池已满                long startTime = System.currentTimeMillis();                try {                    wait(timeout);                } catch (InterruptedException e) {                    e.printStackTrace();                }                if(new Date().getTime() - startTime > timeout){                    logger.info("没有可获取的链接，正在重试...");                    conn = getConnection();                }            }            return conn;        }        /**         * 释放连接入连接池         * @param conn         */        public synchronized void freeConnection(Connection conn){            freeConnections.add(conn);            if(isUsed > 0) isUsed--;            notifyAll();            logger.info("释放连接!");        }        private Connection newConnection(){            Connection conn = null;            try {                conn = DriverManager.getConnection(url, userName, password);                logger.debug("创建了一个新的链接");            } catch (SQLException e) {                logger.error("获取数据库连接失败", e);            }            return conn;        }        public synchronized void release(){            Enumeration<Connection> enums = freeConnections.elements();            while(enums.hasMoreElements()){                try {                    enums.nextElement().close();                } catch (SQLException e) {                    logger.warn("关闭链接失败", e);                }            }            freeConnections.removeAllElements();            logger.debug("释放了所有的连接");        }        public int getIsUsed(){            return isUsed;        }    }}//该片段来自于http://byrx.net