jdbc 事物管理回滚

一,最近项目中,spring事物的管理,引发好奇,就是在事物回滚之前,对数据的插入更新操作,只要   
未提交,都不更改数据库,但是在查询时得到的结果却是插入更新之后的,带着疑问我做一下的例子.

二,JDBCHelper类
  

package com.ming.test.two;

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

public class JDBCHelper {
	
	public static ThreadLocal<Connection> local = new ThreadLocal<Connection>();
	//启动时 加载驱动
	static{
		try {
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			System.out.println("mysql驱动不存在!");
		}
	}
	
	public static Connection getConnection(){
		Connection connection = local.get();//在当前线程找 
		try {
			if(connection==null){
				connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/test?zeroDateTimeBehavior=convertToNull", "root","root");
				local.set(connection);
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			System.out.println("connection获取失败!");
		}
		return connection;
	}
	public static void closeConnection(Connection connection ){
		try {
			if(connection!=null){
				connection.close();
				local.remove();
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
}

test类
 

package com.ming.test.two;

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

public class Test {
	public static String id="12";
	public static void main(String[] args) {
		Connection con = JDBCHelper.getConnection();
		try {
//			con.createStatement();
//			con.prepareStatement("");
			con.setAutoCommit(false);//现将事物自动提交设为false
			con.setTransactionIsolation(con.TRANSACTION_READ_COMMITTED);
			PreparedStatement p = con.prepareStatement("insert into account(accountId,id,username) values("+id+",1,'jacky"+id+"')");
			p.execute();
			//con.prepareStatement("select * from account where accountId=7");
			PreparedStatement p1 = con.prepareStatement("select * from account where accountId="+id);
			ResultSet set = p1.executeQuery();
			while(set.next()){
				System.out.println(set.getRow()+"-"+set.getString(1)+"-"+set.getString(2)+"-"+set.getString(3));
				
			}
			int i =1/0;
			con.commit();//提交
			
		} catch (Exception e) {
			System.out.println("exception");
			// TODO Auto-generated catch block
			try {
				con.rollback();
			} catch (SQLException e1) {
				// TODO Auto-generated catch block
				e1.printStackTrace();
			}
		}
		
	}
}

三,结论以及注意
   注意事项：autocommot必须设置为false;
   com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException : Can't call rollback when autocommit=true
    而且异常的发生必须是在commit之前,否则也失效的.
    结论就是,在事物回滚时,所有的更新新增操作都是无效,但是在con查询中这些都是最新影响的数据。