1.基于XML的声明式事务控制
1.1 什么是声明式事务控制
Spring的声明式事务顾名思义就是采用声明的方式来处理事务。这里所说的声明,就是指在配置文件中声明,用在Spring配置文件中声明式的处理事务来代替代码式的处理事务
1.2 声明式事务处理的作用
(1)事务管理不侵入开发的组件(即,业务代码和事务控制通过配置的方式松耦合,代码运行时候,业务逻辑又能完成对应的事务控制,这是AOP思想,事务控制是增强方法,业务代码是被增强)。具体来说,业务逻辑对象就不会意识到正在事务管理中,事实上也应该如此,因为事务管理是属于系统层面的服务,而不是业务逻辑的一部分,如果想要改变事务管理策划的话,也只需要在定义文件中重新配置即可。
(2)不需要事务管理的时候,只要在设定文件上修改一下,即可移去事务管理服务,无需改变代码的重新编译,这样维护起来极其方便。只需要在配置文件中,删掉那个事务控制就可以了。
转账案例:
AccountController.java
package com.company.controller; import com.company.service.AccountService; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class AccountController { public static void main(String[] args) { ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); AccountService accountService = applicationContext.getBean(AccountService.class); accountService.transfer("tom", "lisi", 200); } }
AccountDao.java
package com.company.dao; public interface AccountDao { void out(String outMan, double money); void in(String inMan, double money); }
AccountDaoImpl.java
package com.company.dao.impl; import com.company.dao.AccountDao; import org.springframework.jdbc.core.JdbcTemplate; public class AccountDaoImpl implements AccountDao { private JdbcTemplate jdbcTemplate; public void setJdbcTemplate(JdbcTemplate jdbcTemplate) { this.jdbcTemplate = jdbcTemplate; } public void out(String outMan, double money) { jdbcTemplate.update("update account set money=money-? where name=? ", money, outMan); } public void in(String inMan, double money) { jdbcTemplate.update("update account set money=money+? where name=?",money, inMan); } }
Account.java
package com.company.domain; public class Account { private String name; private double money; public String getName() { return name; } public void setName(String name) { this.name = name; } public double getMoney() { return money; } public void setMoney(double money) { this.money = money; } }
AccountService.java
package com.company.service; public interface AccountService { void transfer(String outMan, String inMan, double money); }
AccountServiceImpl.java
package com.company.service.impl; import com.company.dao.AccountDao; import com.company.service.AccountService; public class AccountServiceImpl implements AccountService { private AccountDao accountDao; public void setAccountDao(AccountDao accountDao) { this.accountDao = accountDao; } public void transfer(String outMan, String inMan, double money) { accountDao.out(outMan, money); accountDao.in(inMan, money); } }
applicationContext.xml
<?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"> <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"> <property name="driverClass" value="com.mysql.jdbc.Driver"/> <property name="jdbcUrl" value="jdbc:mysql://localhost:3306/test"/> <property name="user" value="root"/> <property name="password" value="123456"/> </bean> <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate"> <property name="dataSource" ref="dataSource"/> </bean> <bean id="accountDao" class="com.company.dao.impl.AccountDaoImpl"> <property name="jdbcTemplate" ref="jdbcTemplate"/> </bean> <bean id="accountService" class="com.company.service.impl.AccountServiceImpl"> <property name="accountDao" ref="accountDao"/> </bean> </beans>
上面的案例存在一个问题
如果出现上面的问题,out已经执行了,但是in没有执行,导致账户不对。
因此需要事务来保证原子性
案例解决方案:使用基于xml声明式事务控制
1.3 声明式事务控制的实现
声明式事务控制明确事项:
谁是切点?被增强的方法,这里的是业务方法,就是transfer
谁是通知?就是事务控制,事务的增强
配置切面?切点和通知进行配置
主要是在核心配置文件applicationContext.xml中进行相应的改变
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 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.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd "> <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"> <property name="driverClass" value="com.mysql.jdbc.Driver"/> <property name="jdbcUrl" value="jdbc:mysql://localhost:3306/test"/> <property name="user" value="root"/> <property name="password" value="123456"/> </bean> <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate"> <property name="dataSource" ref="dataSource"/> </bean> <bean id="accountDao" class="com.company.dao.impl.AccountDaoImpl"> <property name="jdbcTemplate" ref="jdbcTemplate"/> </bean> <!--目标对象,内部的方法就是切点--> <bean id="accountService" class="com.company.service.impl.AccountServiceImpl"> <property name="accountDao" ref="accountDao"/> </bean> <!--配置平台事务管理器--> <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager"> <property name="dataSource" ref="dataSource"/> </bean> <!--通知,事务的增强--> <tx:advice id="txAdvice" transaction-manager="transactionManager"> <tx:attributes> <tx:method name="*"/> </tx:attributes> </tx:advice> <!-- 配置AOP事务织入--> <aop:config> <aop:advisor advice-ref="txAdvice" pointcut="execution(* com.company.service.impl.*.*(..))"></aop:advisor> </aop:config> </beans>
下面重点介绍下设置事务的属性信息,也就是事务控制的三大对象中TransactionDefinition
如果要指定方法,可以这样配置:
<!--通知,事务的增强--> <tx:advice id="txAdvice" transaction-manager="transactionManager"> <tx:attributes> <tx:method name="transfer" isolation="REPEATABLE_READ" propagation="REQUIRED" read-only="false"/> <tx:method name="*"/> </tx:attributes> </tx:advice>
pom.xml
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>org.example</groupId> <artifactId>spring_tx</artifactId> <version>1.0-SNAPSHOT</version> <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>5.2.9.RELEASE</version> </dependency> <dependency> <groupId>org.aspectj</groupId> <artifactId>aspectjweaver</artifactId> <version>1.9.6</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-jdbc</artifactId> <version>5.2.9.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-tx</artifactId> <version>5.2.9.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-test</artifactId> <version>5.2.9.RELEASE</version> </dependency> <dependency> <groupId>com.mchange</groupId> <artifactId>c3p0</artifactId> <version>0.9.5.4</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.44</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> <scope>test</scope> </dependency> </dependencies> </project>