关于 SSM 事务配置失效

1.在Mysql中，只有当表的类型是INNODB的时候，才支持事务，所以需要把表的类型设置为INNODB,否则无法观察到事务.

修改表的类型为INNODB的SQL：

alter table hero ENGINE = innodb;
查看表的类型的SQL

show table status from tablename;

2.

 applicationContext.xml

<!-- 开启事务注解，标注@Transactional的类和方法将具有事务性 -->
<tx:annotation-driven transaction-manager="txManager"  proxy-target-class="true" />
<bean id="txManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
    <property name="dataSource" ref="dataSource" />
</bean>

<!--spring的配置文件application.xml中包扫描不需要扫描@Controller注解的， 具体如下：-->
<context:component-scan base-package="com.crossoverJie">
    <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
    <context:exclude-filter type="annotation" expression="org.springframework.web.bind.annotation.ControllerAdvice"/>
    <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Repository"/>
</context:component-scan>

3.SpringMVC.xml

<!--springMVC配置文件springMVC-servlet.xml中只需要扫描@Controller注解的，具体如下：-->
<context:component-scan base-package="com.crossoverJie">
    <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
    <context:include-filter type="annotation" expression="org.springframework.web.bind.annotation.ControllerAdvice"/>
    <!--下面这个是防止事务没起作用，spring.xml的父容器先于Servlet的子容器生效，将Service提前加载了。这里不用再进行加载装配-->
    <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Service" />
</context:component-scan>

4.test

在方法上加上注解：

@Transactional(propagation = Propagation.REQUIRED, rollbackFor = Throwable.class)
@Override
public void addTwo() {
        addOne();
    Category c1 = new Category();
    c1.setName("短的名字");
    categoryMapper.add(c1);

}
@Transactional(propagation = Propagation.REQUIRED, rollbackFor = Throwable.class)
@Override
public void addOne() {
    Category c2 = new Category();
    c2.setName("名字长对应字段放不下");
    categoryMapper.add(c2);
    int i = 9 / 0; //这里会抛出异常
}

执行并查看日志：

java.lang.NullPointerException //异常信息

DEBUG [main] (AbstractPlatformTransactionManager.java:847) - Initiating transaction rollback //回滚
DEBUG [main] (DataSourceTransactionManager.java:284) - Rolling back JDBC transaction on Connection [com.mysql.jdbc.JDBC4Connection@6ea2bc93]
DEBUG [main] (DataSourceTransactionManager.java:327) - Releasing JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ea2bc93] after transaction
DEBUG [main] (DataSourceUtils.java:327) - Returning JDBC Connection to DataSource //返回连接到连接池
说明事务生效了，遇到异常回滚。