JDBCUtils工具类（转）

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

import javax.sql.DataSource;

import com.mchange.v2.c3p0.ComboPooledDataSource;
/**
 * 依赖：
 *        + c3p0-config.xml
 *        + c3p0-0.9.2-pre1.jar
 *        + mchange-commons-0.2.jar
 * 版本1.3 
 * 更新日期：2018/07/03
 * @author CeoBai
 *
 */
public class JdbcUtils {
    //ComboPooledDataSource(String configName)的参数configName指的是配置文件c3p0-config.xml中的 <named-config name="mysql">...</named-config>
    //如果没有输入configName参数，那么就采用默认的<default-config>...</defalut-config>，那么就可以为空不传参数
    private static ComboPooledDataSource dataSource = new ComboPooledDataSource("mysql");
    private static Connection con = null;
    private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>();
    /**
     * 获取连接对象
     * @return
     * @throws SQLException
     */
    public static Connection getConnection() throws SQLException{
        con = tl.get();
        if(con != null){return con;}
        return dataSource.getConnection();
    }
    /**
     * 获取连接池对象
     * @return
     */
    public static DataSource getDataSource(){
        return dataSource;
    }
    /**
     * 开启事务
     * @throws SQLException
     */
    public static void beginTransaction() throws SQLException{
        con = tl.get();
        if(con != null){throw new RuntimeException("事务已经开启！不能重复开启！");}
        con = getConnection();
        con.setAutoCommit(false);
        tl.set(con);
    }
    /**
     * 提交事务
     * @throws SQLException
     */
    public static void commitTransaction() throws SQLException{
        con = tl.get();
        if(con == null){throw new RuntimeException("事务还没开启！不能提交！");}
        con.commit();
        con.close();//归还连接对象到连接池
        tl.remove();//移除连接对象con。那么tl.get() == null
    }
    /**
     * 回滚事务
     * @throws SQLException
     */
    public static void rollbackTransaction() throws SQLException{
        con = tl.get();
        if(con == null){throw new RuntimeException("事务还没开启！不能回滚！");}
        con.rollback();
        con.close();
        tl.remove();
    }
    /**
     * 关闭 非事务专用的连接
     * @param connection
     * @throws SQLException
     */
    public static void releaseConnection(Connection connection) throws SQLException{
        con = tl.get();//获取事务专用连接
        if(con == null){connection.close();}
        if(con != connection){connection.close();}
    } 
}

<?xml version="1.0" encoding="UTF-8" ?>
<c3p0-config>
    <!-- c3p0有两种配置方式，一种是默认的default-config，一种是按名字区分：named-config需要添加一个属性值name -->
    <default-config> 
        <property name="jdbcUrl">jdbc:oracle:thin:username/password@amrood:1521:EMP</property>
        <property name="driverClass">oracle.jdbc.driver.OracleDriver</property>
        <property name="user">root</property>
        <property name="password"></property>
        
        <property name="acquireIncrement">3</property>
        <property name="initialPoolSize">10</property>
        <property name="minPoolSize">2</property>
        <property name="maxPoolSize">10</property>
    </default-config>
    <named-config name="mysql"> 
        <property name="jdbcUrl">jdbc:mysql://localhost:3306/db_user</property>
        <property name="driverClass">com.mysql.jdbc.Driver</property>
        <property name="user">root</property>
        <property name="password"></property>
        
        <property name="acquireIncrement">3</property>
        <property name="initialPoolSize">10</property>
        <property name="minPoolSize">2</property>
        <property name="maxPoolSize">10</property>
    </named-config>
</c3p0-config>