ThreadLocal解决事务线程安全问题(c3p0数据库连接池工具类)

ThreadLocal底层是Map集合，它的key是当前线程，value由自己设定，可以绑定Connection或其他对象等，保证本次同一线程使用同一Connection。

ThreadLocal类提供几个方法： get/set/remove

以下是ThreadLocal搭配c3p0连接数据库，保证线程安全工具类：

package com.shop.Utils;

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

import javax.sql.DataSource;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class DataSourceUtils {
private static DataSource dataSource = new ComboPooledDataSource();
private static ThreadLocal<Connection> tl = new ThreadLocal<>();

//将Connection绑定到当前线程
public static Connection getConnection() throws SQLException{
Connection conn = tl.get();
if(conn==null){
conn = dataSource.getConnection();
tl.set(conn);
}
return conn;
}

public static DataSource getDataSource(){
return dataSource;
}
//开启事务
public static void startTransaction() throws SQLException{
Connection conn = getConnection();
if(conn!=null)
conn.setAutoCommit(false); //开启事务
}
//回滚事务
public static void rollback() throws SQLException{
Connection conn = getConnection();
if(conn!=null)
conn.rollback();
}
//提交事务并释放资源
public static void commitAndRelease() throws SQLException{
Connection conn = getConnection();
if(conn!=null){
conn.commit();
conn.close();
tl.remove();
}
}
//关闭资源方法：conn, rs, stat
}