一、实现功能
通过模拟 银行转账业务，来熟悉对mybatis的使用
二、环境搭建
1、引入依赖
<dependencies>
<!--mybatis依赖-->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.10</version>
</dependency>
<!--数据库驱动-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.30</version>
</dependency>
<!--引入logback日志框架依赖，这个日志框架实现了slf4j规范-->
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.11</version>
</dependency>
<!--servlet依赖-->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
</dependency>
</dependencies>
2、添加mybatis-config.xml核心配置文件
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<properties resource="jdbc.properties"/>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="AccountMapper.xml"/>
</mappers>
</configuration>
3、添加jdbc.properties文件
jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/powernode?useUnicode=true&characterEncoding=utf-8
jdbc.username=root
jdbc.password=root
4、添加日志文件logback.xml
<?xml version="1.0" encoding="UTF-8"?>
<configuration debug="false">
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
<pattern>%d{HH:mm:ss.SSS} %contextName [%thread] %-5level %logger{36} - %msg%n
</pattern>
</encoder>
</appender>
<logger name="com.apache.ibatis" level="TRACE"/>
<logger name="java.sql.Connection" level="DEBUG"/>
<logger name="java.sql.Statement" level="DEBUG"/>
<logger name="java.sql.PreparedStatement" level="DEBUG"/>
<root level="DEBUG">
<appender-ref ref="STDOUT" />
<appender-ref ref="FILE" />
</root>
</configuration>
5、添加AccountMapper.xml文件
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="account">
</mapper>
6、添加简单页面文件 index.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>银行转账</title>
</head>
<body>
<form action="/bank/transfer" method="post">
转出账号：<input type="text" name="fromActno"><br>
转入账号：<input type="text" name="toActno"><br>
转账金额：<input type="text" name="money"><br>
<input type="submit" value="转账"><br>
</form>
</body>
</html>
7、增加工具类SqlSessionUtil
package com.powernode.bank.util;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
public class SqlSessionUtil {
private SqlSessionUtil(){
};
private static SqlSessionFactory sqlSessionFactory;
static {
try {
sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 获取会话对象，
* @return
*/
public static SqlSession openSqlSession(){
return sqlSessionFactory.openSession();
}
}
8、增加实体类 Account
package com.powernode.bank.pojo;
public class Account {
private Long id ;
private String actno;
private Double balance;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getActno() {
return actno;
}
public void setActno(String actno) {
this.actno = actno;
}
public Double getBalance() {
return balance;
}
public void setBalance(Double balance) {
this.balance = balance;
}
}
9、mysql建表 t_act
SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;
-- ----------------------------
-- Table structure for t_act
-- ----------------------------
DROP TABLE IF EXISTS t_act;
CREATE TABLE t_act (
id bigint(0) NOT NULL AUTO_INCREMENT,
actno varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL COMMENT '账号',
balance decimal(15, 2) NULL DEFAULT NULL COMMENT '余额',
PRIMARY KEY (id) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 3 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci ROW_FORMAT = Dynamic;
-- ----------------------------
-- Records of t_act
-- ----------------------------
INSERT INTO t_act VALUES (1, 'act001', 30002.00);
INSERT INTO t_act VALUES (2, 'act002', 19998.00);
SET FOREIGN_KEY_CHECKS = 1;
10、展示项目目录结构
三、后台代码实现
1、创建AccountServlet
package com.powernode.bank.web;
import com.powernode.bank.exceptions.MoneyNotEnoughException;
import com.powernode.bank.exceptions.TransferException;
import com.powernode.bank.service.AccountServiceImpl;
import com.powernode.bank.service.IAccount;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/transfer")
public class AccountServlet extends HttpServlet {
private IAccount accountService = new AccountServiceImpl();
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取表单数据
String fromActno = request.getParameter("fromActno");
String toActno = request.getParameter("toActno");
double money = Double.parseDouble(request.getParameter("money"));
try {
//调用service的转账方法完成转账（调用业务层）
accountService.transfer(fromActno,toActno,money);
//调用视图层view展示结果
response.sendRedirect(request.getContextPath() + "/success.html");
} catch (MoneyNotEnoughException e) {
response.sendRedirect(request.getContextPath() + "/error1.html");
} catch (TransferException e) {
response.sendRedirect(request.getContextPath() + "/error2.html");
}
}
}
2、创建业务接口IAccount
package com.powernode.bank.service;
import com.powernode.bank.exceptions.MoneyNotEnoughException;
import com.powernode.bank.exceptions.TransferException;
/**
* 账户业务类
*/
public interface IAccount {
//转账
void transfer(String fromActno, String toActno, double money) throws MoneyNotEnoughException, TransferException;
}
3、创建业务接口实现类AccountServiceImpl
package com.powernode.bank.service;
import com.powernode.bank.dao.AccountDao;
import com.powernode.bank.dao.impl.AccountDaoImpl;
import com.powernode.bank.exceptions.MoneyNotEnoughException;
import com.powernode.bank.exceptions.TransferException;
import com.powernode.bank.pojo.Account;
public class AccountServiceImpl implements IAccount {
private AccountDao accountDao = new AccountDaoImpl();
@Override
public void transfer(String fromActno, String toActno, double money) throws MoneyNotEnoughException, TransferException {
Account fromAct = accountDao.selectByActno(fromActno);
if(fromAct.getBalance() < money){
throw new MoneyNotEnoughException("对不起，余额不足");
}
//先更新内存中java对象的余额
Account toAct = accountDao.selectByActno(toActno);
fromAct.setBalance(fromAct.getBalance() - money);
toAct.setBalance(toAct.getBalance() + money);
int count = accountDao.updateByActno(fromAct);
count += accountDao.updateByActno(toAct);
if(count != 2){
throw new TransferException("对不起，转账异常");
}
}
}
4、创建持久层接口AccountDao，以及实现类AccountDaoImpl
package com.powernode.bank.dao;
import com.powernode.bank.pojo.Account;
public interface AccountDao {
Account selectByActno(String actno);
int updateByActno(Account act);
}
package com.powernode.bank.dao.impl;
import com.powernode.bank.dao.AccountDao;
import com.powernode.bank.pojo.Account;
import com.powernode.bank.util.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;
public class AccountDaoImpl implements AccountDao {
@Override
public Account selectByActno(String actno) {
SqlSession sqlSession = SqlSessionUtil.openSqlSession();
Account account = sqlSession.selectOne("account.selectByActno", actno);
sqlSession.commit();
sqlSession.close();
return account;
}
@Override
public int updateByActno(Account act) {
SqlSession sqlSession = SqlSessionUtil.openSqlSession();
int count = sqlSession.update("account.updateByActno", act);
sqlSession.commit();
sqlSession.close();
return count;
}
}
5、增加两个异常类
MoneyNotEnoughException
package com.powernode.bank.exceptions;
/**
* 余额不足异常
*/
public class MoneyNotEnoughException extends Exception {
public MoneyNotEnoughException() {
}
public MoneyNotEnoughException(String message) {
super(message);
}
}
TransferException
package com.powernode.bank.exceptions;
/**
* 转账异常
*/
public class TransferException extends Exception {
public TransferException() {
}
public TransferException(String message) {
super(message);
}
}
6、运行测试页面
转账前
转账后
四、加入事务控制
如果转账过程中，出现了异常，此时代码是有问题的，我们对原有代码进行改造
SqlSessionUtil 改造
1、将SqlSession放到ThreadLocal中，确保同一个线程当中，获取到的SqlSession对象是同一个。
2、关闭连接的时候，记得从ThreadLocal中移除当前线程中的SqlSession对象，因为tomcat服务器是支持多线程的。
package com.powernode.bank.util;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
public class SqlSessionUtil {
private SqlSessionUtil(){
};
private static SqlSessionFactory sqlSessionFactory;
static {
try {
sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
} catch (IOException e) {
e.printStackTrace();
}
}
//全局的，服务器级别的，一个服务器当中定义一个即可
private static ThreadLocal<SqlSession> threadLocal = new ThreadLocal<>();
/**
* 获取会话对象，
* @return
*/
public static SqlSession openSqlSession(){
SqlSession sqlSession = threadLocal.get();
if(sqlSession == null){
sqlSession = sqlSessionFactory.openSession();
threadLocal.set(sqlSession);
}
return sqlSession;
}
public static void close(SqlSession sqlSession){
if(sqlSession != null){
sqlSession.close();
threadLocal.remove();
}
}
}
AccountServiceImpl
package com.powernode.bank.service;
import com.powernode.bank.dao.AccountDao;
import com.powernode.bank.dao.impl.AccountDaoImpl;
import com.powernode.bank.exceptions.MoneyNotEnoughException;
import com.powernode.bank.exceptions.TransferException;
import com.powernode.bank.pojo.Account;
import com.powernode.bank.util.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;
public class AccountServiceImpl implements IAccount {
private AccountDao accountDao = new AccountDaoImpl();
@Override
public void transfer(String fromActno, String toActno, double money) throws MoneyNotEnoughException, TransferException {
SqlSession sqlSession = SqlSessionUtil.openSqlSession();
Account fromAct = accountDao.selectByActno(fromActno);
if(fromAct.getBalance() < money){
throw new MoneyNotEnoughException("对不起，余额不足");
}
//先更新内存中java对象的余额
Account toAct = accountDao.selectByActno(toActno);
fromAct.setBalance(fromAct.getBalance() - money);
toAct.setBalance(toAct.getBalance() + money);
int count = accountDao.updateByActno(fromAct);
count += accountDao.updateByActno(toAct);
if(count != 2){
throw new TransferException("对不起，转账异常");
}
sqlSession.commit();
SqlSessionUtil.close(sqlSession);
}
}
AccountDaoImpl 改造
package com.powernode.bank.dao.impl;
import com.powernode.bank.dao.AccountDao;
import com.powernode.bank.pojo.Account;
import com.powernode.bank.util.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;
public class AccountDaoImpl implements AccountDao {
@Override
public Account selectByActno(String actno) {
SqlSession sqlSession = SqlSessionUtil.openSqlSession();
Account account = sqlSession.selectOne("account.selectByActno", actno);
return account;
}
@Override
public int updateByActno(Account act) {
SqlSession sqlSession = SqlSessionUtil.openSqlSession();
int count = sqlSession.update("account.updateByActno", act);
return count;
}
}