事务
为什要用到Spring中AOP事务?
首先举个例子了解一下什么是事务操作?以及出现的问题?课程中老师用到的例子是转账的事务例子,A将钱转给B,此时service层提供一个方法用来在数据库中进行减操作、B收到钱后会开启一个事务用来加操作,但是如果A在赚钱给B操作过程中出现了异常,此时很可能是A中的减操作已经执行完毕,而B却没有收到钱,那么此时钱就不翼而飞了,那么此时我们就应该提供一种解决方案,让A出现异常后不会执行减操作这样不就可以避免上述情况的发生,通过AOP的学习,我们可以通过SpringAOP来对service层中的加减方法的功能进行加强,开始学习吧!
事物的特性
原子性(Atomicity)、一致性(Consistency)、隔离性(Isolation)、持久性(Durability)
事务并发问题
脏读、不可重复读、幻读 名词解释: 博客地址
事务的隔离级别
1 读未提交
2 读已提交
4 可重复读
8 串行化
名词解释
spring封装了事务管理代码
事务操作
- 打开事务
- 提交事务
- 回滚事务
在执行SQL语句之前,先执行start transaction,这就开启了一个事务(事务的起点),然后可以去执行多条SQL语句,最后要结束事务,commit表示提交,即事务中的多条SQL语句所做出的影响会持久化到数据库中。或者rollback,表示回滚,即回滚到事务的起点,之前做的所有操作都被撤消了!
事务操作对象
因为在不同平台,操作事务的代码各不相同.spring提供了一个接口
- DataSourceTransactionManager
- HibernateTransitionmanager
注意:在spring中玩事务管理.最为核心的对象就是TransactionManager对象
spring管理事务的属性介绍
- 事务的隔离级别
- 是否只读:true 只读、false 可操作
- 事务的传播行为
spring管理事务方式
编码式
1.将核心事务管理器配置到spring容器
<!-- 事物核心管理器 ,封装了所有的事物操作依赖于连接池-->
<bean name="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource"></property>
</bean>
2.配置TransactionTemplate模板
<!-- 事务模板对象 -->
<bean name="transactionTemplate" class="org.springframework.transaction.support.TransactionTemplate">
<property name="transactionManager" ref="transactionManager"></property>
</bean>
3.将事务模板注入Service
<!-- 3.Service-->
<bean name="accountService" class="cn.itcast.service.AccountServiceImpl" >
<property name="ad" ref="accountDao" ></property>
<property name="tt" ref="transactionTemplate" ></property>
</bean>
4.在Service中调用模板
public void transfer(final Integer from,final Integer to,final Double money) {
tt.execute(new TransactionCallbackWithoutResult() {
@Override
protected void doInTransactionWithoutResult(TransactionStatus arg0) {
//减钱
ad.decreaseMoney(from, money);
int i = 1/0;
//加钱
ad.increaseMoney(to, money);
}
});
}
xml配置(aop)
1.导包:
2.导入新的约束(tx)
beans: 最基本
context:读取properties配置
aop:配置aop
tx:配置事务通知
3.配置通知
<!-- 配置事务通知 -->
<tx:advice id="txAdvice" transaction-manager="transactionManager" >
<tx:attributes>
<!-- 以方法为单位,指定方法应用什么事务属性
isolation:隔离级别
propagation:传播行为
read-only:是否只读
-->
<tx:method name="save*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="false" />
<tx:method name="persist*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="false" />
<tx:method name="update*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="false" />
<tx:method name="modify*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="false" />
<tx:method name="delete*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="false" />
<tx:method name="remove*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="false" />
<tx:method name="get*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="true" />
<tx:method name="find*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="true" />
<tx:method name="transfer" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="false" />
</tx:attributes>
</tx:advice>
4.配置将通知织入目标
<!-- 配置织入 -->
<aop:config >
<!-- 配置切点表达式 -->
<aop:pointcut expression="execution(* cn.itcast.service.*ServiceImpl.*(..))" id="txPc"/>
<!-- 配置切面 : 通知+切点
advice-ref:通知的名称
pointcut-ref:切点的名称
-->
<aop:advisor advice-ref="txAdvice" pointcut-ref="txPc" />
</aop:config>
注解配置
在注解配置ApplicationContext.xml的时候需要把上述方式中xml配置注入中的配置事务通知、配置织入去掉,
然后在service实现类方法中添加注解即可。
第一种方式注解在方法上添加:
@Override
@Transactional(isolation=Isolation.REPEATABLE_READ,propagation=Propagation.REQUIRED,readOnly=false)
public void transfer(final Integer from,final Integer to,final Double money) {
//减钱
ad.decreaseMoney(from, money);
int i = 1/0;
//加钱
ad.increaseMoney(to, money);
}
第一种方式注解在类上添加:为了避免每次重写方法的时候都需要手动添加注解,用这种方式会统一给每个方法都注入,如果想改变某一个方法的注解内容如只读属性改成可操作,在方法上再添加注解即可
//统一配置
@Transactional(isolation=Isolation.REPEATABLE_READ,propagation=Propagation.REQUIRED,readOnly=true)
public class AccountServiceImpl implements AccountService {
private AccountDao ad ;
private TransactionTemplate tt;
//只读属性改成可操作
@Override
@Transactional(isolation=Isolation.REPEATABLE_READ,propagation=Propagation.REQUIRED,readOnly=false)
public void transfer(final Integer from,final Integer to,final Double money) {
//减钱
ad.decreaseMoney(from, money);
int i = 1/0;
//加钱
ad.increaseMoney(to, money);
}
}
逻辑关系图:
练习代码:
xml配置注入applicationContext.xml:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.2.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.2.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.2.xsd ">
<!-- 指定spring读取db.properties配置 -->
<context:property-placeholder location="classpath:db.properties" />
<!-- 事务核心管理器,封装了所有事务操作. 依赖于连接池 -->
<bean name="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager" >
<property name="dataSource" ref="dataSource" ></property>
</bean>
<!-- 事务模板对象 -->
<bean name="transactionTemplate" class="org.springframework.transaction.support.TransactionTemplate" >
<property name="transactionManager" ref="transactionManager" ></property>
</bean>
<!-- 配置事务通知 -->
<tx:advice id="txAdvice" transaction-manager="transactionManager" >
<tx:attributes>
<!-- 以方法为单位,指定方法应用什么事务属性
isolation:隔离级别
propagation:传播行为
read-only:是否只读
-->
<tx:method name="save*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="false" />
<tx:method name="persist*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="false" />
<tx:method name="update*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="false" />
<tx:method name="modify*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="false" />
<tx:method name="delete*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="false" />
<tx:method name="remove*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="false" />
<tx:method name="get*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="true" />
<tx:method name="find*" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="true" />
<tx:method name="transfer" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="false" />
</tx:attributes>
</tx:advice>
<!-- 配置织入 -->
<aop:config >
<!-- 配置切点表达式 -->
<aop:pointcut expression="execution(* cn.itcast.service.*ServiceImpl.*(..))" id="txPc"/>
<!-- 配置切面 : 通知+切点
advice-ref:通知的名称
pointcut-ref:切点的名称
-->
<aop:advisor advice-ref="txAdvice" pointcut-ref="txPc" />
</aop:config>
<!-- 1.将连接池 -->
<bean name="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" >
<property name="jdbcUrl" value="${jdbc.jdbcUrl}" ></property>
<property name="driverClass" value="${jdbc.driverClass}" ></property>
<property name="user" value="${jdbc.user}" ></property>
<property name="password" value="${jdbc.password}" ></property>
</bean>
<!-- 2.Dao-->
<bean name="accountDao" class="cn.itcast.dao.AccountDaoImpl" >
<property name="dataSource" ref="dataSource" ></property>
</bean>
<!-- 3.Service-->
<bean name="accountService" class="cn.itcast.service.AccountServiceImpl" >
<property name="ad" ref="accountDao" ></property>
<property name="tt" ref="transactionTemplate" ></property>
</bean>
</beans>
手动注解注入applicationContext2.xml:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.2.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.2.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.2.xsd ">
<!-- 指定spring读取db.properties配置 -->
<context:property-placeholder location="classpath:db.properties" />
<!-- 事务核心管理器,封装了所有事务操作. 依赖于连接池 -->
<bean name="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager" >
<property name="dataSource" ref="dataSource" ></property>
</bean>
<!-- 事务模板对象 -->
<bean name="transactionTemplate" class="org.springframework.transaction.support.TransactionTemplate" >
<property name="transactionManager" ref="transactionManager" ></property>
</bean>
<!-- 开启使用注解管理aop事务 -->
<tx:annotation-driven/>
<!-- 1.将连接池 -->
<bean name="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" >
<property name="jdbcUrl" value="${jdbc.jdbcUrl}" ></property>
<property name="driverClass" value="${jdbc.driverClass}" ></property>
<property name="user" value="${jdbc.user}" ></property>
<property name="password" value="${jdbc.password}" ></property>
</bean>
<!-- 2.Dao-->
<bean name="accountDao" class="cn.itcast.dao.AccountDaoImpl" >
<property name="dataSource" ref="dataSource" ></property>
</bean>
<!-- 3.Service-->
<bean name="accountService" class="cn.itcast.service.AccountServiceImpl" >
<property name="ad" ref="accountDao" ></property>
<property name="tt" ref="transactionTemplate" ></property>
</bean>
</beans>
DAO层:目标对象
AccountDao和AccountDaoImpl
package cn.itcast.dao;
public interface AccountDao {
//加钱
void increaseMoney(Integer id,Double money);
//减钱
void decreaseMoney(Integer id,Double money);
}
package cn.itcast.dao;
import org.springframework.jdbc.core.support.JdbcDaoSupport;
public class AccountDaoImpl extends JdbcDaoSupport implements AccountDao {
@Override
public void increaseMoney(Integer id, Double money) {
getJdbcTemplate().update("update t_account set money = money+? where id = ? ", money,id);
}
@Override
public void decreaseMoney(Integer id, Double money) {
getJdbcTemplate().update("update t_account set money = money-? where id = ? ", money,id);
}
}
service层:业务处理
AccountService与AccountServiceImpl
package cn.itcast.service;
public interface AccountService {
//转账方法
void transfer(Integer from,Integer to,Double money);
}
package cn.itcast.service;
import org.springframework.transaction.TransactionStatus;
import org.springframework.transaction.annotation.Isolation;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.transaction.support.TransactionCallback;
import org.springframework.transaction.support.TransactionCallbackWithoutResult;
import org.springframework.transaction.support.TransactionTemplate;
import cn.itcast.dao.AccountDao;
@Transactional(isolation=Isolation.REPEATABLE_READ,propagation=Propagation.REQUIRED,readOnly=true)
public class AccountServiceImpl implements AccountService {
private AccountDao ad ;
private TransactionTemplate tt;
//只读属性改成可操作
@Override
@Transactional(isolation=Isolation.REPEATABLE_READ,propagation=Propagation.REQUIRED,readOnly=false)
public void transfer(final Integer from,final Integer to,final Double money) {
//减钱
ad.decreaseMoney(from, money);
int i = 1/0;
//加钱
ad.increaseMoney(to, money);
}
/* @Override
public void transfer(final Integer from,final Integer to,final Double money) {
tt.execute(new TransactionCallbackWithoutResult() {
@Override
protected void doInTransactionWithoutResult(TransactionStatus arg0) {
//减钱
ad.decreaseMoney(from, money);
int i = 1/0;
//加钱
ad.increaseMoney(to, money);
}
});
}
*/
public void setAd(AccountDao ad) {
this.ad = ad;
}
public void setTt(TransactionTemplate tt) {
this.tt = tt;
}
}
测试类:
xml配置测试类
package cn.itcast.tx;
import javax.annotation.Resource;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import cn.itcast.service.AccountService;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:applicationContext.xml")
public class Demo {
@Resource(name="accountService")
private AccountService as;
@Test
public void fun1(){
as.transfer(1, 2, 100d);
}
}
注解测试类:
package cn.itcast.tx;
import javax.annotation.Resource;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import cn.itcast.service.AccountService;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:applicationContext2.xml")
public class Demo2 {
@Resource(name="accountService")
private AccountService as;
@Test
public void fun1(){
as.transfer(1, 2, 100d);
}
}