简单工具类

查找到的简单工具类：c3p0配置文件，连接池工具类DataSourceUtils，需要的jar包：mysql-connector,c3p0,commons等jar包

c3p0-config.xml

<c3p0-config>
	<!-- 默认配置，如果没有指定则使用这个配置 -->
	<default-config>
		<!-- 基本配置 -->
		<property name="driverClass">com.mysql.jdbc.Driver</property>
		<property name="jdbcUrl">jdbc:mysql://localhost:3306/数据库名</property>
		<property name="user">用户名</property>
		<property name="password">密码</property>
	
		<!--扩展配置-->
		<property name="checkoutTimeout">30000</property>
		<property name="idleConnectionTestPeriod">30</property>
		<property name="initialPoolSize">10</property>
		<property name="maxIdleTime">30</property>
		<property name="maxPoolSize">100</property>
		<property name="minPoolSize">10</property>
		<property name="maxStatements">200</property>
	</default-config> 
	
	
	<!-- 命名的配置 -->
	<named-config name="itcast">
		<property name="driverClass">com.mysql.jdbc.Driver</property>
		<property name="jdbcUrl">jdbc:mysql://127.0.0.1:3306/xxxx</property>
		<property name="user">root</property>
		<property name="password">1234</property>
		
		
		<!-- 如果池中数据连接不够时一次增长多少个 -->
		<property name="acquireIncrement">5</property>
		<property name="initialPoolSize">20</property>
		<property name="minPoolSize">10</property>
		<property name="maxPoolSize">40</property>
		<property name="maxStatements">20</property>
		<property name="maxStatementsPerConnection">5</property>
	</named-config>
</c3p0-config> 

DataSourceUtils.java

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.sql.DataSource;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class DataSourceUtils {
	private static ComboPooledDataSource ds=new ComboPooledDataSource();
	private static ThreadLocal<Connection> tl=new ThreadLocal<>();
	
	/**
	 * 获取数据源
	 * @return 连接池
	 */
	public static DataSource getDataSource(){
		return ds;
	}
	
	/**
	 * 从当前线程上获取连接
	 * @return 连接
	 * @throws SQLException
	 */
	public static Connection getConnection() throws SQLException{
		Connection conn = tl.get();
		if(conn==null){
			//第一次获取 创建一个连接 和当前的线程绑定
			 conn=ds.getConnection();
			 
			 //绑定
			 tl.set(conn);
		}
		return conn;
	}
	
	
	
	/**
	 * 释放资源
	 * 
	 * @param conn
	 *            连接
	 * @param st
	 *            语句执行者
	 * @param rs
	 *            结果集
	 */
	public static void closeResource(Connection conn, Statement st, ResultSet rs) {
		closeResource(st, rs);
		closeConn(conn);
	}
	
	 
	public static void closeResource(Statement st, ResultSet rs) {
			closeResultSet(rs);
			closeStatement(st);
	}

	/**
	 * 释放连接
	 * 
	 * @param conn
	 *            连接
	 */
	public static void closeConn(Connection conn) {
		if (conn != null) {
			try {
				conn.close();
				//和当前的线程解绑
				tl.remove();
			} catch (SQLException e) {
				e.printStackTrace();
			}
			conn = null;
		}

	}

	/**
	 * 释放语句执行者
	 * 
	 * @param st
	 *            语句执行者
	 */
	public static void closeStatement(Statement st) {
		if (st != null) {
			try {
				st.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
			st = null;
		}

	}

	/**
	 * 释放结果集
	 * 
	 * @param rs
	 *            结果集
	 */
	public static void closeResultSet(ResultSet rs) {
		if (rs != null) {
			try {
				rs.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
			rs = null;
		}

	}
	
	/**
	 * 开启事务
	 * @throws SQLException
	 */
	public static void startTransaction() throws SQLException{
		//获取连接//开启事务
		getConnection().setAutoCommit(false);;
	}
	
	/**
	 * 事务提交
	 */
	public static void commitAndClose(){
		try {
			//获取连接
			Connection conn = getConnection();
			//提交事务
			conn.commit();
			//释放资源
			conn.close();
			//解除绑定
			tl.remove();
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 事务回滚
	 */
	public static void rollbackAndClose(){
		try {
			//获取连接
			Connection conn = getConnection();
			//事务回滚
			conn.rollback();
			//释放资源
			conn.close();
			//解除绑定
			tl.remove();
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
}