jdbc 12: 悲观锁

jdbc连接mysql，简单演示行级锁

通过debug模式进行演示

在Test1程序设置断点，让程序1,查询并锁定数据，且程序不执行完(此时停在debug断点处)

这时启动Test2程序，去修改已经被锁定的数据，发现此时，程序2出现等待情况

让程序1的断点结束，此时程序2可以顺利修改数据

原因: 程序1的行级锁已经释放

Test1

package com.examples.jdbc.o12_悲观锁;

import com.examples.jdbc.utils.DBUtils;

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

/**

 * 简单的行级锁的演示

 */

public class Test1 {

    public static void main(String[] args) {

        //3个数据库资源对象

        Connection connection = null;

        PreparedStatement preparedStatement = null;

        ResultSet resultSet = null;

        //jdbc数据库操作

        try {

            //1.

            connection = DBUtils.getConnection();

            connection.setAutoCommit(false);

            //2.

            String sql = "select * from tb_user where uname like ? for update";

            preparedStatement = connection.prepareStatement(sql);

            preparedStatement.setString(1, "_");

            //3.

            resultSet = preparedStatement.executeQuery();

            while(resultSet.next()){

                int id = resultSet.getInt("id");

                String uname = resultSet.getString("uname");

                String upasswd = resultSet.getString("upasswd");

                System.out.println("id: " + id + " uname: " + uname + " upasswd: " + upasswd);

            }

            connection.commit();

        } catch (SQLException e) {

            if(connection != null){

                try {

                    connection.rollback();

                } catch (SQLException ex) {

                    ex.printStackTrace();

                }

            }

            e.printStackTrace();

        }finally {

            //4.

            DBUtils.close(connection, preparedStatement, resultSet);

        }

    }

}

Test2

package com.examples.jdbc.o12_悲观锁;

import com.examples.jdbc.utils.DBUtils;

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.SQLException;

/**

 * 模拟在行级锁起作用期间，修改被锁定的数据

 */

public class Test2 {

    public static void main(String[] args) {

        //2个jdbc资源对象

        Connection connection = null;

        PreparedStatement preparedStatement = null;

        //jdbc操作

        try {

            //1.

            connection = DBUtils.getConnection();

            connection.setAutoCommit(false);

            //2.

            String sql = "update tb_user set upasswd = ? where uname like ?";

            preparedStatement = connection.prepareStatement(sql);

            preparedStatement.setString(1, "xun");

            preparedStatement.setString(2, "_");

            //3.

            int num = preparedStatement.executeUpdate();

            System.out.println(num == 1 ? "修改成功" : "修改失败");

            connection.commit();

        } catch (SQLException e) {

            if(connection != null){

                try {

                    connection.rollback();

                } catch (SQLException ex) {

                    ex.printStackTrace();

                }

            }

            e.printStackTrace();

        }finally {

            //4.

            DBUtils.close(connection, preparedStatement, null);

        }

    }

}

巴特西

jdbc 12: 悲观锁

jdbc连接mysql，简单演示行级锁

通过debug模式进行演示

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