JDBC实现JDBC实现银行的转账事务

Posted 2020-09-20

JDBC中的事务是默认提交的，也就是说每执行一次PreparedStatement,那么数据就会被写入到磁盘。如果需要关闭默认提交，使用  void setAutoCommit(false)  .

db.properties

driverClassName=oracle.jdbc.OracleDriver
url=jdbc:oracle:thin:@localhost:1521:xe
username=system
password=517839

db.properties

JDBCUtilProperties.java

package com.xdl.util;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
public class JDBCUtilProperties {
    public  static   String   driverClassName;
    public  static   String   url;
    public  static   String   username;
    public  static   String   password;
    static {
        try {
            // 读取 db.properties 文件 ,路径是相对于项目的路径
            InputStream  inputStream = JDBCUtilProperties.class.getClassLoader().
                getResourceAsStream("com/xdl/util/db.properties");
            /* Properties  就是一个key value 结构  */
            Properties  pro = new Properties();
            try {
                pro.load(inputStream);
                driverClassName = pro.getProperty("driverClassName");
                url = pro.getProperty("url");
                username = pro.getProperty("username");
                password = pro.getProperty("password");
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            Class.forName(driverClassName);
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }  
    /* 获取数据库 连接的方法  */
    public  static  Connection   getConnection(){
        Connection  conn  = null;
        try {
            conn = DriverManager.getConnection(url, username, password);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return  conn;
    }
    /* 释放资源的方法  */
    public  static  void  releaseResource(Connection conn,Statement st,ResultSet rs){
        if(rs != null){
            try {
                rs.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }finally{
                rs = null;
            }
        }
        if(st != null){
            try {
                st.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }finally{
                st = null;
            }
        }
        if(conn != null){
            try {
                conn.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }finally{
                conn = null;
            }
        }
    }
}

JDBCUtilProperties.java

Test.java

package com.xdl.test;

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

import com.xdl.util.JDBCUtilProperties;

public class Test {
    /* 转账的案例  
       create  table   bankAccount(
           id   number  primary key,
           name  varchar2(30),
           money   number);
       insert  into  bankAccount values(1,‘name1‘,10000000);
       insert  into  bankAccount values(2,‘name2‘,10000000);
       commit;
     */
    public  static void   test(){
        // 1.获取连接 
        Connection   conn  = null;
        PreparedStatement   ps = null;
        PreparedStatement   ps2 = null;
        conn = JDBCUtilProperties.getConnection();
        try {
            //关闭自动提交
            conn.setAutoCommit(false);
            double  m = 1000000;
            //从name1账户中扣钱
            ps = conn.prepareStatement
               ("update bankaccount set money=money-? where id=1 and name=‘name1‘");
            ps.setDouble(1, m);
            //得到影响的行数
            int rows = ps.executeUpdate();
            //往name2账户中加钱
            ps2 = conn.prepareStatement
                ("update bankaccount set money=money+? where id=2 and name=‘namw2‘");
            ps2.setDouble(1, m);
            //得到影响的行数
            int rows2 = ps2.executeUpdate();
            //如果两个语句得到影响行数都是1，那么提交事务
            if(rows == 1 && rows2 == 1 ){
                System.out.println("转账成功");
                conn.commit();
            }else{
                //若不满足条件，则对两个语句回归
                System.out.println("转账失败");
                conn.rollback();
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            try {
                conn.rollback();
            } catch (SQLException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            e.printStackTrace();
        }finally {
            JDBCUtilProperties.releaseResource(conn, ps, null);
            JDBCUtilProperties.releaseResource(conn, ps2, null);
        }
    }
    public static void main(String[] args) {
        test();
    }

}

Test.java