day18-事务与连接池 3.jdbc中事务操作介绍

那么我们都是通过程序操作数据库。所以要了解jdbc下怎样对事务操作。jdbc如何操作事务?

自动事务false那就不开了呗相当于开启事务。

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package cn.itcast.transaction;

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

import cn.itcast.utils.JdbcUtils;
//代码加上事务了加上回滚了加上提交了

//jdbc中事务操作
public class TransactionTest1 {
    public static void main(String[] args) throws SQLException {

//修改id=2这个人的money=500;
String sql = "update account set money=500 where id=2";
Connection con = JdbcUtils.getConnection();

con.setAutoCommit(false);//开启事务,相当于start transaction;

Statement st = con.createStatement();
st.executeUpdate(sql);

//事务回滚
//con.rollback();

con.commit();//事务提交
st.close();
con.close();
}
}

package cn.itcast.transaction;

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

import cn.itcast.utils.JdbcUtils;
//代码加上事务了加上回滚了加上提交了

//jdbc中事务操作
public class TransactionTest2 {
    public static void main(String[] args) {

//修改id=2这个人的money=500;
String sql = "update account set money=500 where id=2";

//事务操作的异常不能说想抛就抛
Connection con = null;
Statement st  = null;

try {
    //如果数据库操作过程中捕获异常了,
     con = JdbcUtils.getConnection();
    con.setAutoCommit(false);//开启事务,相当于start transaction;
     st = con.createStatement();
     st.executeUpdate(sql);
} catch (SQLException e) {
    e.printStackTrace();
    //事务回滚 有异常就把事务回滚,有异常就说明出问题了
    //出问题就把数据恢复到原始,那就回滚吧
    try {
        con.rollback();
    } catch (SQLException e1) {
        e1.printStackTrace();
    }
}finally{//finally里面的内容肯定是能执行到的
    try {
        con.commit();//事务提交
        st.close();//资源关闭  释放资源操作
        con.close();//资源关闭
    } catch (SQLException e) {
        e.printStackTrace();
    }

}

}
}

package cn.itcast.utils;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ResourceBundle;

public class JdbcUtils {

    private static final String DRIVERCLASS;
    private static final String URL;
    private static final String USERNAME;
    private static final String PASSWORD;

    private static final ThreadLocal<Connection> tl = new ThreadLocal<Connection>();
    static {
        DRIVERCLASS = ResourceBundle.getBundle("jdbc").getString("driverClass");
        URL = ResourceBundle.getBundle("jdbc").getString("url");
        USERNAME = ResourceBundle.getBundle("jdbc").getString("username");
        PASSWORD = ResourceBundle.getBundle("jdbc").getString("password");
    }

    static {
        try {
            // 将加载驱动操作，放置在静态代码块中.这样就保证了只加载一次.
            Class.forName(DRIVERCLASS);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection() throws SQLException {
        Connection con = tl.get();// 从ThreadLocal中获取Connection。第一次获取得到的是null.

        if (con == null) {
            // 2.获取连接
            con = DriverManager.getConnection(URL, USERNAME, PASSWORD);
            tl.set(con); // 将con装入到ThreadLocal中。
        }

        // tl.remove(); //解除
        return con;
    }

    // 关闭操作
    public static void closeConnection(Connection con) throws SQLException {
        if (con != null) {
            con.close();
        }
    }

    public static void closeStatement(Statement st) throws SQLException {
        if (st != null) {
            st.close();
        }
    }

    public static void closeResultSet(ResultSet rs) throws SQLException {
        if (rs != null) {
            rs.close();
        }
    }
}