前面的操作都是在持久层使用事务。下面演示一个例子:
假设账户“小王”和“小张”各1000元。
小王去银行给小张转账100元,结果应该是:小王的金额900元,而小张的金额是1100元。
如果我们这么实现,结果会怎么样?
实体类:
package com.mantishell.domain;
public class Account {
private Integer id;
private String name;
private Float money;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Float getMoney() {
return money;
}
public void setMoney(Float money) {
this.money = money;
}
@Override
public String toString() {
return "Account{" +
"id=" + id +
", name=‘" + name + ‘\‘‘ +
", money=" + money +
‘}‘;
}
}
持久层:
IAccountDao.java
package com.mantishell.dao;
import com.mantishell.domain.Account;
/**
* 持久层接口
*/
public interface IAccountDao {
/**
* 更新
* @param account
*/
void updateAccount(Account account);
/**
* 根据名称查询账户
* @param accountName
* @return 如果有唯一的一个结果就返回,如果没有结果就返回null
* 如果结果集超过一个就抛异常
*/
Account findAccountByName(String accountName);
}
AccountDaoImpl.java
package com.mantishell.dao.impl;
import com.mantishell.dao.IAccountDao;
import com.mantishell.domain.Account;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import java.util.List;
public class AccountDaoImpl implements IAccountDao {
private QueryRunner runner;
public void setRunner(QueryRunner runner){
this.runner = runner;
}
public void updateAccount(Account account) {
try{
runner.update("update account set name=?,money=? where id=?",account.getName(),account.getMoney(),account.getId());
}catch (Exception e){
throw new RuntimeException(e);
}
}
public Account findAccountByName(String accountName) {
try{
List<Account> accounts = runner.query("select * from account where name=?",new BeanListHandler<Account>(Account.class),accountName);
if(accounts == null || accounts.size() == 0){
return null;
}
if(accounts.size() > 1){
throw new RuntimeException("结果集不唯一,数据有问题");
}
return accounts.get(0);
}catch (Exception e){
throw new RuntimeException(e);
}
}
}
业务层:
IAccountService.java
package com.mantishell.service;
import com.mantishell.domain.Account;
/**
* 业务层接口
*/
public interface IAccountService {
/**
* 更新
* @param account
*/
void updateAccount(Account account);
/**
* 转账
* @param sourceName 转出账户名称
* @param destName 转入账户名称
* @param money 转账金额
*/
void transfer(String sourceName,String destName,Float money);
}
AccountServiceImpl.java
package com.mantishell.service.impl;
import com.mantishell.dao.IAccountDao;
import com.mantishell.domain.Account;
import com.mantishell.service.IAccountService;
public class AccountServiceImpl implements IAccountService {
private IAccountDao accountDao;
public void setAccountDao(IAccountDao accountDao){
this.accountDao = accountDao;
}
public void updateAccount(Account account) {
accountDao.updateAccount(account);
}
public void transfer(String sourceName, String destName, Float money) {
Account source = accountDao.findAccountByName(sourceName);
Account dest = accountDao.findAccountByName(destName);
source.setMoney(source.getMoney()-money);
dest.setMoney(dest.getMoney()+money);
accountDao.updateAccount(source);
accountDao.updateAccount(dest);
}
}
配置文件:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
<!-- 配置Service -->
<bean id="accountService" class="com.mantishell.service.impl.AccountServiceImpl">
<!-- 注入dao -->
<property name="accountDao" ref="accountDao"></property>
</bean>
<!--配置Dao对象-->
<bean id="accountDao" class="com.mantishell.dao.impl.AccountDaoImpl">
<!-- 注入QueryRunner -->
<property name="runner" ref="runner"></property>
</bean>
<!--配置QueryRunner-->
<bean id="runner" class="org.apache.commons.dbutils.QueryRunner" scope="prototype">
<!--注入数据源-->
<constructor-arg name="ds" ref="dataSource"/>
</bean>
<!-- 配置数据源 -->
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
<!--连接数据库的必备信息-->
<property name="driverClass" value="com.mysql.jdbc.Driver"></property>
<property name="jdbcUrl" value="jdbc:mysql://localhost:3306/db4"></property>
<property name="user" value="root"></property>
<property name="password" value="123456"></property>
</bean>
</beans>
测试:
package com.mantishell.test;
import com.mantishell.service.IAccountService;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:bean.xml")
public class AccountTest {
@Autowired
private IAccountService as;
@Test
public void testTransfer(){
as.transfer("小王","小张",100f);
}
}
pom文件:
<packaging>jar</packaging>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>5.0.2.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-test</artifactId>
<version>5.0.2.RELEASE</version>
</dependency>
<dependency>
<groupId>commons-dbutils</groupId>
<artifactId>commons-dbutils</artifactId>
<version>1.4</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.6</version>
</dependency>
<dependency>
<groupId>c3p0</groupId>
<artifactId>c3p0</artifactId>
<version>0.9.1.2</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
</dependencies>
运行测试发现竟然是正确的。但是这里不是很严谨,比如网络不是很好,导致小王把钱转出去了,但小张却没收到。那么他俩加起来的总额就不等于2000元了。
为了看的更清楚,这里在业务层的实现方法上人为造一个异常:
public void transfer(String sourceName, String destName, Float money) {
Account source = accountDao.findAccountByName(sourceName);
Account dest = accountDao.findAccountByName(destName);
source.setMoney(source.getMoney()-money);
dest.setMoney(dest.getMoney()+money);
accountDao.updateAccount(source);
int a = 10/0;
accountDao.updateAccount(dest);
}
再次测试发现,真的变成了小王的金额900元,小张的金额1000元。
难道是没用事务吗?不对啊,没有用事务的话,小王就不会减去100元了。为什么呢?
因为没有在业务层使用事务,把他俩转账捆在一起,一旦一方失败,那么数据回滚,不会造成数据错误。这就是为什么要在业务层使用事务了。
下面修改为业务层控制事务
1、添加工具类
连接工具类:
package com.mantishell.utils;
import javax.sql.DataSource;
import java.sql.Connection;
/**
* 连接的工具类,它用于从数据源中获取一个连接,并且实现和线程的绑定
*/
public class ConnectionUtils {
private ThreadLocal<Connection> tl = new ThreadLocal<Connection>();
private DataSource dataSource;
public void setDataSource(DataSource dataSource) {
this.dataSource = dataSource;
}
/**
* 获取当前线程上的连接
* @return
*/
public Connection getThreadConnection() {
try{
//1.先从ThreadLocal上获取
Connection conn = tl.get();
//2.判断当前线程上是否有连接
if (conn == null) {
//3.从数据源中获取一个连接,并且存入ThreadLocal中
conn = dataSource.getConnection();
tl.set(conn);
}
//4.返回当前线程上的连接
return conn;
}catch (Exception e){
throw new RuntimeException(e);
}
}
/**
* 把连接和线程解绑
*/
public void removeConnection(){
tl.remove();
}
}
事务管理类:
package com.mantishell.utils;
/**
* 和事务管理相关的工具类,它包含了,开启事务,提交事务,回滚事务和释放连接
*/
public class TransactionManager {
private ConnectionUtils connectionUtils;
public void setConnectionUtils(ConnectionUtils connectionUtils) {
this.connectionUtils = connectionUtils;
}
/**
* 开启事务
*/
public void beginTransaction(){
try {
connectionUtils.getThreadConnection().setAutoCommit(false);
}catch (Exception e){
e.printStackTrace();
}
}
/**
* 提交事务
*/
public void commit(){
try {
connectionUtils.getThreadConnection().commit();
}catch (Exception e){
e.printStackTrace();
}
}
/**
* 回滚事务
*/
public void rollback(){
try {
connectionUtils.getThreadConnection().rollback();
}catch (Exception e){
e.printStackTrace();
}
}
/**
* 释放连接
*/
public void release(){
try {
connectionUtils.getThreadConnection().close();//还回连接池中
connectionUtils.removeConnection();
}catch (Exception e){
e.printStackTrace();
}
}
}
## 2、业务实现修改
public class AccountServiceImpl implements IAccountService {
private IAccountDao accountDao;
private TransactionManager txManager;
public void setTxManager(TransactionManager txManager) {
this.txManager = txManager;
}
public void setAccountDao(IAccountDao accountDao){
this.accountDao = accountDao;
}
public void updateAccount(Account account) {
accountDao.updateAccount(account);
}
public void transfer(String sourceName, String destName, Float money) {
/*Account source = accountDao.findAccountByName(sourceName);
Account dest = accountDao.findAccountByName(destName);
source.setMoney(source.getMoney()-money);
dest.setMoney(dest.getMoney()+money);
accountDao.updateAccount(source);
int a = 10/0;
accountDao.updateAccount(dest);*/
try {
//1.开启事务
txManager.beginTransaction();
//2.执行操作
//2.1根据名称查询转出账户
Account source = accountDao.findAccountByName(sourceName);
//2.2根据名称查询转入账户
Account dest = accountDao.findAccountByName(destName);
//2.3转出账户减钱
source.setMoney(source.getMoney()-money);
//2.4转入账户加钱
dest.setMoney(dest.getMoney()+money);
//2.5更新转出账户
accountDao.updateAccount(source);
int i=1/0;
//2.6更新转入账户
accountDao.updateAccount(dest);
//3.提交事务
txManager.commit();
}catch (Exception e){
//4.回滚操作
txManager.rollback();
e.printStackTrace();
}finally {
//5.释放连接
txManager.release();
}
}
}
## 3、持久层修改
public class AccountDaoImpl implements IAccountDao {
private QueryRunner runner;
private ConnectionUtils connectionUtils;
public void setConnectionUtils(ConnectionUtils connectionUtils) {
this.connectionUtils = connectionUtils;
}
public void setRunner(QueryRunner runner){
this.runner = runner;
}
public void updateAccount(Account account) {
try{
runner.update(connectionUtils.getThreadConnection(),"update account set name=?,money=? where id=?",account.getName(),account.getMoney(),account.getId());
}catch (Exception e){
throw new RuntimeException(e);
}
}
public Account findAccountByName(String accountName) {
try{
List<Account> accounts = runner.query(connectionUtils.getThreadConnection(),"select * from account where name = ? ",new BeanListHandler<Account>(Account.class),accountName);
if(accounts == null || accounts.size() == 0){
return null;
}
if(accounts.size() > 1){
throw new RuntimeException("结果集不唯一,数据有问题");
}
return accounts.get(0);
}catch (Exception e){
throw new RuntimeException(e);
}
}
}
4、修改配置文件
<bean id="accountService" class="com.mantishell.service.impl.AccountServiceImpl">
<!-- 注入dao -->
<property name="accountDao" ref="accountDao"/>
<property name="txManager" ref="txManager"/>
</bean>
<!--配置Dao对象-->
<bean id="accountDao" class="com.mantishell.dao.impl.AccountDaoImpl">
<!-- 注入QueryRunner -->
<property name="runner" ref="runner"/>
<!-- 注入ConnectionUtils -->
<property name="connectionUtils" ref="connectionUtils"/>
</bean>
<!--配置QueryRunner-->
<bean id="runner" class="org.apache.commons.dbutils.QueryRunner" scope="prototype">
<!--注入数据源-->
</bean>
<!-- 配置数据源 -->
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
<!--连接数据库的必备信息-->
<property name="driverClass" value="com.mysql.jdbc.Driver"/>
<property name="jdbcUrl" value="jdbc:mysql://localhost:3306/db4?useUnicode=true&characterEncoding=utf8"/>
<property name="user" value="root"/>
<property name="password" value="123456"/>
</bean>
<!-- 配置事务管理器-->
<bean id="txManager" class="com.mantishell.utils.TransactionManager">
<!-- 注入ConnectionUtils-->
<property name="connectionUtils" ref="connectionUtils"/>
</bean>
<!-- 配置Connection的工具类 ConnectionUtils -->
<bean id="connectionUtils" class="com.mantishell.utils.ConnectionUtils">
<!-- 注入数据源-->
<property name="dataSource" ref="dataSource"/>
</bean>
即使我们人为在业务里添加一条异常的语句:`int i=1/0;`,执行后碰到异常,事务回滚,俩人仍然分别是1000元。
这里的service用到事务管理器,dao用到connectionutils,事务管理器也用到connectionutils,
原文地址:https://www.cnblogs.com/mantishell/p/12598812.html
时间: 2024-10-29 00:56:26