1.代码中事务控制的3种方式[1]
- 编程式事务：就是直接在代码里手动开启事务，手动提交，手动回滚。优点就是可以灵活控制，缺点就是太麻烦了，太多重复的代码了。
- 声明式事务：就是使用SpringAop配置事务，这种方式大大的简化了编码。需要注意的是切入点表达式一定要写正确。
- 注解事务：直接在Service层的方法上面加上@Transactional注解，个人比较喜欢用这种方式。
2.事务不回滚的原因
在工作中，看过别人写的代码出现了事务不回滚的现象。当然，事务不回滚的都是采用的声明式事务或者是注解事务；编程式事务都是自己写代码手动回滚的，因此是不会出现不回滚的现象。
再说下声明式事务和注解事务回滚的原理：当被切面切中或者是加了注解的方法中抛出了RuntimeException异常时，Spring会进行事务回滚。默认情况下是捕获到方法的RuntimeException异常，也就是说抛出只要属于运行时的异常（即RuntimeException及其子类）都能回滚；但当抛出一个不属于运行时异常时，事务是不会回滚的。
下面说说我经常见到的3种事务不回滚的产生原因：
- （1）声明式事务配置切入点表达式写错了，没切中Service中的方法
- （2）Service方法中，把异常给try catch了，但catch里面只是打印了异常信息，没有手动抛出RuntimeException异常
- （3）Service方法中，抛出的异常不属于运行时异常（如IO异常），因为Spring默认情况下是捕获到运行时异常就回滚
代码实践
1.不捕获异常(一般处理方式)[2]
代码，其中contentMappger.updateWithErrTest(31L); 是SQL语句错误，用来测试回滚。
/** * 删除多条记录 */ @Override public ShopResult deleteContentGroup(String[] ids) { if (null == ids || ids.length == 0) { return ShopResult.error(); } for (String idStr : ids) { Long id = new Long(idStr); contentMappger.deleteByPrimaryKey(id); } contentMappger.updateWithErrTest(31L); //错误代码，SQL语句错误。用来测试事务，看是否回滚 return ShopResult.ok(); }
运行结果：报错，事务发生了回滚，即由于错误代码，前面的for循环删除记录事务被回滚了。
### SQL: delete form tb_content where kid = ? ### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'tb_content where kid = 31' at line 1 ; bad SQL grammar []; nested exception is com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'tb_content where kid = 31' at line 1] with root cause com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'tb_content where kid = 31' at line 1 at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:423) at com.mysql.jdbc.Util.handleNewInstance(Util.java:406) at com.mysql.jdbc.Util.getInstance(Util.java:381) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1030) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3536) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3468) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1957) .................. at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:53) at com.sun.proxy.$Proxy35.updateWithErrTest(Unknown Source) at com.shop.manager.service.impl.ContentServiceImpl.deleteContentGroup(ContentServiceImpl.java:94) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:302) at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190) .......
2. 捕获异常，但不处理，不抛出
代码
/** * 删除多条记录 */ @Override public ShopResult deleteContentGroup(String[] ids) { if (null == ids || ids.length == 0) { return ShopResult.error(); } for (String idStr : ids) { Long id = new Long(idStr); contentMappger.deleteByPrimaryKey(id); } try { contentMappger.updateWithErrTest(31L); //错误代码，SQL语句错误。用来测试事务，看是否回滚 } catch (Exception e) { //捕获异常，但不处理 System.out.println("-----nothing to do-------"); } return ShopResult.ok(); }
运行结果：事务提交，未回滚。
### The error occurred while setting parameters ### SQL: delete form tb_content where kid = ? ### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'tb_content where kid = 31' at line 1 ] -----nothing to do------- 2017-06-18 14:27:59,493 [http-bio-8080-exec-4] [org.mybatis.spring.SqlSessionUtils]-[DEBUG] Transaction synchronization committing SqlSession //(事务提交) [org.apache.ibatis.session.defaults.DefaultSqlSession@616a85a9]
3. 捕获异常，并抛出RuntimeException异常
Spring碰到Unchecked Exceptions都会回滚，不仅是RuntimeException，也包括Error。
代码
/** * 删除多条记录 */ @Override public ShopResult deleteContentGroup(String[] ids) { if (null == ids || ids.length == 0) { return ShopResult.error(); } for (String idStr : ids) { Long id = new Long(idStr); contentMappger.deleteByPrimaryKey(id); } try { contentMappger.updateWithErrTest(31L); //错误代码，SQL语句错误。用来测试事务，看是否回滚 } catch (Exception e) { System.out.println("----throw Exception-----"); throw new RuntimeException(); } return ShopResult.ok(); }
运行结果：如预期的一样，抛出RuntimeException，事务发生回滚。
### SQL: delete form tb_content where kid = ? ### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'tb_content where kid = 31' at line 1 ] ----throw Exception----- 2017-06-18 14:21:27,928 [http-bio-8080-exec-1] [org.mybatis.spring.SqlSessionUtils]-[DEBUG] Transaction synchronization deregistering SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3ef56e3a] ............... 2017-06-18 14:21:27,941 [http-bio-8080-exec-1] [org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver]-[DEBUG] Resolving exception from handler [public com.shop.common.pojo.ShopResult com.shop.manager.controller.ContentController.deleteContentGroup(java.lang.String)]: java.lang.RuntimeException 2017-06-18 14:21:27,941 [http-bio-8080-exec-1] [org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver]-[DEBUG] Resolving exception from handler [public com.shop.common.pojo.ShopResult com.shop.manager.controller.ContentController.deleteContentGroup(java.lang.String)]: java.lang.RuntimeException 2017-06-18 14:21:27,942 [http-bio-8080-exec-1] [org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver]-[DEBUG] Resolving exception from handler [public com.shop.common.pojo.ShopResult com.shop.manager.controller.ContentController.deleteContentGroup(java.lang.String)]: java.lang.RuntimeException 2017-06-18 14:21:27,942 [http-bio-8080-exec-1] [org.springframework.web.servlet.DispatcherServlet]-[DEBUG] Could not complete request java.lang.RuntimeException at com.shop.manager.service.impl.ContentServiceImpl.deleteContentGroup(ContentServiceImpl.java:98) //异常 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
4.捕获异常，并继续抛出原捕获的异常
代码：
/** * 删除多条记录 */ @Override public ShopResult deleteContentGroup(String[] ids) { if (null == ids || ids.length == 0) { return ShopResult.error(); } for (String idStr : ids) { Long id = new Long(idStr); contentMappger.deleteByPrimaryKey(id); } try { contentMappger.updateWithErrTest(31L); //错误代码，SQL语句错误。用来测试事务，看是否回滚 } catch (Exception e) { //捕获异常，继续抛出 System.out.println("-----throw Exception-------"); throw e; } return ShopResult.ok(); }
运行结果：抛出异常，事务发生回滚
### The error occurred while setting parameters ### SQL: delete form tb_content where kid = ? ### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'tb_content where kid = 31' at line 1 ] -----throw Exception------- 2017-06-18 14:36:25,308 [http-bio-8080-exec-9] [org.mybatis.spring.SqlSessionUtils]-[DEBUG] Transaction synchronization deregistering SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@45fe0f70] 2017-06-18 14:36:25,308 [http-bio-8080-exec-9] [org.mybatis.spring.SqlSessionUtils]-[DEBUG] Transaction synchronization closing SqlSession //事务回滚 [org.apache.ibatis.session.defaults.DefaultSqlSession@45fe0f70]
5. 捕获异常，并抛出新new的异常(或自定义Exception异常) new Exception
代码：
/** * 删除多条记录 * @throws Exception */ @Override public ShopResult deleteContentGroup(String[] ids) throws Exception { if (null == ids || ids.length == 0) { return ShopResult.error(); } for (String idStr : ids) { Long id = new Long(idStr); contentMappger.deleteByPrimaryKey(id); } try { contentMappger.updateWithErrTest(31L); //错误代码，SQL语句错误。用来测试事务，看是否回滚 } catch (Exception e) { //捕获异常，抛出新异常 System.out.println("-----throw new Exception(e)-------"); throw new Exception(e); } return ShopResult.ok(); }
运行结果：事务提交，未回滚。（Spring的默认回滚异常类型不包括Exception）
### The error occurred while setting parameters ### SQL: delete form tb_content where kid = ? ### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'tb_content where kid = 31' at line 1 ] -----throw new Exception(e) ------- 2017-06-18 14:43:16,098 [http-bio-8080-exec-10] [org.mybatis.spring.SqlSessionUtils]-[DEBUG] Transaction synchronization committing SqlSession //事务提交 [org.apache.ibatis.session.defaults.DefaultSqlSession@32c4821] 2017-06-18 14:43:16,098 [http-bio-8080-exec-10] [org.mybatis.spring.SqlSessionUtils]-[DEBUG] Transaction synchronization deregistering SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@32c4821]
6. 在事务配置中没有设置rollback-for异常类型为Exception
<!-- 事务管理器 --> <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager"> <property name="dataSource" ref="dataSource"/> </bean> <!-- 通知 --> <tx:advice id="txAdvice" transaction-manager="transactionManager"> <!-- 事务行为控制 --> <tx:attributes> <tx:method name="save" propagation="REQUIRED" rollback-for="Exception"/> <tx:method name="insert*" propagation="REQUIRED" rollback-for="Exception"/> <tx:method name="add*" propagation="REQUIRED" rollback-for="Exception"/> <tx:method name="create*" propagation="REQUIRED" rollback-for="Exception"/> <tx:method name="delete*" propagation="REQUIRED" rollback-for="Exception"/> <tx:method name="update*" propagation="REQUIRED" rollback-for="Exception"/> <tx:method name="find*" propagation="SUPPORTS" read-only="true" /> <tx:method name="select*" propagation="SUPPORTS" read-only="true" /> <tx:method name="get*" propagation="SUPPORTS" read-only="true" /> </tx:attributes> </tx:advice> <!-- 配置切面 --> <aop:config> <aop:advisor advice-ref="txAdvice" pointcut="execution(* com.shop.manager.service.*.*(..))" /> </aop:config>
/** * 删除多条记录 * @throws Exception */ @Override public ShopResult deleteContentGroup(String[] ids) throws Exception { if (null == ids || ids.length == 0) { return ShopResult.error(); } for (String idStr : ids) { Long id = new Long(idStr); contentMappger.deleteByPrimaryKey(id); } try { contentMappger.updateWithErrTest(31L); //错误代码，SQL语句错误。用来测试事务，看是否回滚 } catch (Exception e) { //捕获异常，继续抛出 System.out.println("-----throw new Exception-------"); throw new Exception("---自定义Exception，事务中已配置rollback-for---"); } return ShopResult.ok(); }
运行结果：如预期一样发生回滚
### The error may involve com.shop.manager.mapper.TbContentMapper.updateWithErrTest-Inline ### The error occurred while setting parameters ### SQL: delete form tb_content where kid = ? ### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'tb_content where kid = 31' at line 1 ] -----throw new Exception------- 2017-06-18 15:07:02,273 [http-bio-8080-exec-8] [org.mybatis.spring.SqlSessionUtils]-[DEBUG] Transaction synchronization deregistering SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@f177061] 2017-06-18 15:07:02,273 [http-bio-8080-exec-8] [org.mybatis.spring.SqlSessionUtils]-[DEBUG] Transaction synchronization closing SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@f177061]
总结：
- Spring事务管理是根据异常来进行回滚操作；
- Spring与Mybatis整合时，虽然在Service方法中并没有check异常，但是如果数据库有异常发生，默认会进行事务回滚。
- Spring 如果不添加rollbackFor等属性，Spring碰到Unchecked Exceptions都会回滚，不仅是RuntimeException，也包括Error。
- 如果在事务方法中捕获异常并进行处理，一定要继续抛出异常并在Spring事务管理中进行rollbak-for配置。
原文出处：
[1] zeng1994, 浅谈Spring中的事务回滚, https://www.cnblogs.com/zeng1994/p/8257763.html
[2] JeangLee, Spring事务管理——回滚(rollback-for)控制, https://blog.csdn.net/ljyhust/article/details/73431968?locationNum=5&fps=1