JDBC数据源(DataSource)的简单实现

前言：

    数据源技术是Java操作数据库的一个很关键技术，流行的持久化框架都离不开数据源的应用。

数据源提供了一种简单获取数据库连接的方式，并能在内部通过一个池的机制来复用数据库连接，这样就大大减少创建数据库连接的次数，提高了系统性能。

对于数据源的应用，一般都选择实用开源的数据源或数据库连接池来使用，比如，常见的有DBCP、C3P0、Proxool等等。但用起来有些笨重和麻烦。下面自己手动实现个精简的数据源，代码如下：

import org.apache.commons.logging.Log; 
import org.apache.commons.logging.LogFactory; 

import javax.sql.DataSource; 
import java.util.Collections; 
import java.util.LinkedList; 
import java.sql.Connection; 
import java.sql.SQLException; 
import java.sql.DriverManager; 
import java.io.PrintWriter; 

/** 
* 一个简单的DataSource实现 
* 
* @author leizhimin 2010-1-14 0:03:17 
*/ 
public class SimpleDateSource implements DataSource { 
        private static Log log = LogFactory.getLog(SimpleDateSource.class); 
        private static final String dirverClassName = "com.mysql.jdbc.Driver"; 
        private static final String url = "jdbc:mysql://127.0.0.1:3306/testdb"; 
        private static final String user = "root"; 
        private static final String pswd = "leizhimin"; 
        //连接池 
        private static LinkedList<Connection> pool = (LinkedList<Connection>) Collections.synchronizedList(new LinkedList<Connection>()); 
        private static SimpleDateSource instance = new SimpleDateSource(); 

        static { 
                try { 
                        Class.forName(dirverClassName); 
                } catch (ClassNotFoundException e) { 
                        log.error("找不到驱动类！", e); 
                } 
        } 

        private SimpleDateSource() { 
        } 

        /** 
         * 获取数据源单例 
         * 
         * @return 数据源单例 
         */ 
        public SimpleDateSource instance() { 
                if (instance == null) instance = new SimpleDateSource(); 
                return instance; 
        } 

        /** 
         * 获取一个数据库连接 
         * 
         * @return 一个数据库连接 
         * @throws SQLException 
         */ 
        public Connection getConnection() throws SQLException { 
                synchronized (pool) { 
                        if (pool.size() > 0) return pool.removeFirst(); 
                        else return makeConnection(); 
                } 
        } 

        /** 
         * 连接归池 
         * 
         * @param conn 
         */ 
        public static void freeConnection(Connection conn) { 
                pool.addLast(conn); 
        } 

        private Connection makeConnection() throws SQLException { 
                return DriverManager.getConnection(url, user, pswd); 
        } 

        public Connection getConnection(String username, String password) throws SQLException { 
                return DriverManager.getConnection(url, username, password); 
        } 

        public PrintWriter getLogWriter() throws SQLException { 
                return null; 
        } 

        public void setLogWriter(PrintWriter out) throws SQLException { 

        } 

        public void setLoginTimeout(int seconds) throws SQLException { 

        } 

        public int getLoginTimeout() throws SQLException { 
                return 0; 
        } 

        public <T> T unwrap(Class<T> iface) throws SQLException { 
                return null; 
        } 

        public boolean isWrapperFor(Class<?> iface) throws SQLException { 
                return false; 
        } 
}