Spring事务如何实现
1.Spring事务底层是基于数据库事务和AOP机制的
2.首先对于使用了@Transactional注解的Bean,Spring会创建一个代理对象作为Bean
3.当调用代理对象的方法时,会先判断该方法上是否加了@Transactional注解
4.如果加了,那么则利用事务管理器创建一个数据库连接
5.并且修改数据库连接的autocommit属性为false,禁止此连接的自动提交,这是实现Spring事务非常重要的一步
6.然后执行当前方法,方法中会执行sql
7.执行完当前方法后,如果没有出现异常就直接提交事务
8.如果出现了异常,并且这个异常是需要回滚的就会回滚事务,否则仍然提交事务
注:
1.Spring事务的隔离级别对应的就是数据库的隔离级别
2.Spring事务的传播机制是Spring事务自己实现的,也是Spring事务中最复杂的
3.Spring事务的传播机制是基于数据库连接来做的,一个数据库连接就是一个事务,如果传播机制配置为需要新开一个事务,那么实际上就是先新建一个数据库连接,在此新数据库连接上执行sql
Spring事务实现的几种方式
事务几种实现方式
(1)编程式事务管理对基于 POJO 的应用来说是唯一选择。我们需要在代码中调用beginTransaction()、commit()、rollback()等事务管理相关的方法,这就是编程式事务管理。
(2)基于 TransactionProxyFactoryBean的声明式事务管理
(3)基于 @Transactional 的声明式事务管理
(4)基于Aspectj AOP配置事务
编程式事务管理
1、transactionTemplate
此种方式是自动的事务管理,无需手动开启、提交、回滚。
配置事务管理器
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<!-- 配置事务管理器 ,封装了所有的事务操作,依赖于连接池 --> < bean id = "transactionManager" class = "org.springframework.jdbc.datasource.DataSourceTransactionManager" > < property name = "dataSource" ref = "dataSource" ></ property > </ bean > |
配置事务模板对象
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<!-- 配置事务模板对象 --> < bean id = "transactionTemplate" class = "org.springframework.transaction.support.TransactionTemplate" > < property name = "transactionManager" ref = "transactionManager" ></ property > </ bean > |
测试
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@Controller @RequestMapping ( "/tx" ) @RunWith (SpringJUnit4ClassRunner. class ) @ContextConfiguration (locations = { "classpath:applicationContext.xml" }) public class TransactionController { @Resource public TransactionTemplate transactionTemplate; @Resource public DataSource dataSource; private static JdbcTemplate jdbcTemplate; private static final String INSERT_SQL = "insert into cc(id) values(?)" ; private static final String COUNT_SQL = "select count(*) from cc" ; @Test public void TransactionTemplateTest(){ //获取jdbc核心类对象,进而操作数据库 jdbcTemplate = new JdbcTemplate(dataSource); //通过注解 获取xml中配置的 事务模板对象 transactionTemplate.setIsolationLevel(TransactionDefinition.ISOLATION_READ_COMMITTED); //重写execute方法实现事务管理 transactionTemplate.execute( new TransactionCallbackWithoutResult() { @Override protected void doInTransactionWithoutResult(TransactionStatus status) { jdbcTemplate.update(INSERT_SQL, "33" ); //字段sd为int型,所以插入肯定失败报异常,自动回滚,代表TransactionTemplate自动管理事务 } }); int i = jdbcTemplate.queryForInt(COUNT_SQL); System.out.println( "表中记录总数:" +i); } } |
2、PlatformTransactionManager
使用 事务管理器 PlatformTransactionManager 对象,PlatformTransactionManager是DataSourceTransactionManager实现的接口类
此方式,可手动开启、提交、回滚事务。
只需要:配置事务管理
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<!-- 配置事务管理 ,封装了所有的事务操作,依赖于连接池 --> < bean id = "transactionManager" class = "org.springframework.jdbc.datasource.DataSourceTransactionManager" > < property name = "dataSource" ref = "dataSource" ></ property > </ bean > |
测试
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@Controller @RequestMapping ( "/tx" ) @RunWith (SpringJUnit4ClassRunner. class ) @ContextConfiguration (locations = { "classpath:applicationContext.xml" }) public class TransactionController { @Resource public PlatformTransactionManager transactionManager; //这里就是将配置数据管理对象注入进来, @Resource public DataSource dataSource; private static JdbcTemplate jdbcTemplate; private static final String INSERT_SQL = "insert into cc(id) values(?)" ; private static final String COUNT_SQL = "select count(*) from cc" ; @Test public void showTransaction(){ //定义使用隔离级别,传播行为 DefaultTransactionDefinition def = new DefaultTransactionDefinition(); def.setIsolationLevel(TransactionDefinition.ISOLATION_READ_COMMITTED); def.setPropagationBehavior(TransactionDefinition.PROPAGATION_REQUIRED); //事务状态类,通过PlatformTransactionManager的getTransaction方法根据事务定义获取;获取事务状态后,Spring根据传播行为来决定如何开启事务 TransactionStatus transaction = transactionManager.getTransaction(def); jdbcTemplate = new JdbcTemplate(dataSource); int i = jdbcTemplate.queryForInt(COUNT_SQL); System.out.println( "表中记录总数:" +i); try { jdbcTemplate.update(INSERT_SQL, "2" ); jdbcTemplate.update(INSERT_SQL, "是否" ); //出现异常,因为字段为int类型,会报异常,自动回滚 transactionManager.commit(transaction); } catch (Exception e){ e.printStackTrace(); transactionManager.rollback(transaction); } int i1 = jdbcTemplate.queryForInt(COUNT_SQL); System.out.println( "表中记录总数:" +i1); } } |
声明式事务管理
1、基于Aspectj AOP开启事务
配置事务通知
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<!-- 配置事务增强 --> < tx:advice id = "txAdvice" transaction-manager = "transactionManager" > < tx:attributes > < tx:method name = "*" propagation = "REQUIRED" rollback-for = "Exception" /> </ tx:attributes > </ tx:advice > |
配置织入
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<!-- aop代理事务。扫描 cn.sys.service 路径下所有的方法 --> < aop:config > <!-- 扫描 cn.sys.service 路径下所有的方法,并加入事务处理 --> < aop:pointcut id = "tx" expression = "execution(* cn.sys.service.*.*(..))" /> < aop:advisor advice-ref = "txAdvice" pointcut-ref = "tx" /> </ aop:config > |
一个完整的例子
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<? 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:context = "http://www.springframework.org/schema/context" xmlns:tx = "http://www.springframework.org/schema/tx" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd"> <!-- 创建加载外部Properties文件对象 --> < bean class = "org.springframework.beans.factory.config.PropertyPlaceholderConfigurer" > < property name = "location" value = "classpath:dataBase.properties" ></ property > </ bean > <!-- 引入redis属性配置文件 --> < import resource = "classpath:redis-context.xml" /> <!-- 配置数据库连接资源 --> < bean id = "dataSource" class = "org.apache.commons.dbcp.BasicDataSource" scope = "singleton" > < property name = "driverClassName" value = "${driver}" ></ property > < property name = "url" value = "${url}" ></ property > < property name = "username" value = "${username}" ></ property > < property name = "password" value = "${password}" ></ property > < property name = "maxActive" value = "${maxActive}" ></ property > < property name = "maxIdle" value = "${maxIdle}" ></ property > < property name = "minIdle" value = "${minIdle}" ></ property > < property name = "initialSize" value = "${initialSize}" ></ property > < property name = "maxWait" value = "${maxWait}" ></ property > < property name = "removeAbandonedTimeout" value = "${removeAbandonedTimeout}" ></ property > < property name = "removeAbandoned" value = "${removeAbandoned}" ></ property > <!-- 配置sql心跳包 --> < property name = "testWhileIdle" value = "true" /> < property name = "testOnBorrow" value = "false" /> < property name = "testOnReturn" value = "false" /> < property name = "validationQuery" value = "select 1" /> < property name = "timeBetweenEvictionRunsMillis" value = "60000" /> < property name = "numTestsPerEvictionRun" value = "${maxActive}" /> </ bean > <!--创建SQLSessionFactory对象 --> < bean id = "sqlSessionFactory" class = "org.mybatis.spring.SqlSessionFactoryBean" > < property name = "dataSource" ref = "dataSource" ></ property > < property name = "configLocation" value = "classpath:MyBatis_config.xml" ></ property > </ bean > <!-- 创建MapperScannerConfigurer对象 --> < bean class = "org.mybatis.spring.mapper.MapperScannerConfigurer" > < property name = "basePackage" value = "cn.sys.dao" ></ property > </ bean > <!-- 配置扫描器 IOC 注解 --> < context:component-scan base-package = "cn.sys" /> <!-- 配置事务管理 ,封装了所有的事务操作,依赖于连接池 --> < bean id = "transactionManager" class = "org.springframework.jdbc.datasource.DataSourceTransactionManager" > < property name = "dataSource" ref = "dataSource" ></ property > </ bean > <!-- 配置事务模板对象 --> < bean id = "transactionTemplate" class = "org.springframework.transaction.support.TransactionTemplate" > < property name = "transactionManager" ref = "transactionManager" ></ property > </ bean > <!-- 配置事务增强 --> < tx:advice id = "txAdvice" transaction-manager = "transactionManager" > < tx:attributes > < tx:method name = "*" propagation = "REQUIRED" rollback-for = "Exception" /> </ tx:attributes > </ tx:advice > <!-- aop代理事务 --> < aop:config > < aop:pointcut id = "tx" expression = "execution(* cn.sys.service.*.*(..))" /> < aop:advisor advice-ref = "txAdvice" pointcut-ref = "tx" /> </ aop:config > </ beans > |
这样就算是给 cn.sys.service下所有的方法加入了事务
也可以用springboot的配置类方式:
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package com.junjie.test; @Configurationpublic class TxAnoConfig { /*事务拦截类型*/ @Bean ( "txSource" ) public TransactionAttributeSource transactionAttributeSource() { NameMatchTransactionAttributeSource source = new NameMatchTransactionAttributeSource(); /*只读事务,不做更新操作*/ RuleBasedTransactionAttribute requiredTx = new RuleBasedTransactionAttribute(TransactionDefinition.PROPAGATION_REQUIRED, Collections.singletonList( new RollbackRuleAttribute(Exception. class ))); requiredTx.setTimeout( 60 ); Map<String, TransactionAttribute> txMap = new HashMap<>(); txMap.put( "*" , requiredTx); source.setNameMap(txMap); return source; } /** * 切面拦截规则 参数会自动从容器中注入 */ @Bean public AspectJExpressionPointcutAdvisor pointcutAdvisor(TransactionInterceptor txInterceptor) { AspectJExpressionPointcutAdvisor pointcutAdvisor = new AspectJExpressionPointcutAdvisor(); pointcutAdvisor.setAdvice(txInterceptor); pointcutAdvisor.setExpression( "execution (* com.cmb..*Controller.*(..))" ); return pointcutAdvisor; } /*事务拦截器*/ @Bean ( "txInterceptor" ) TransactionInterceptor getTransactionInterceptor(PlatformTransactionManager tx) { return new TransactionInterceptor(tx, transactionAttributeSource()); } } |
2、基于注解的 @Transactional 的声明式事务管理
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@Transactional public int saveRwHist(List list) { return rwDao.saveRwHist(list); } |
这个注解的开启需要在spring.xml里加上一个开启注解事务的配置
以上的开启事务方式,仅需要了解即可,如今在工作中,一般不会用到这几种方式,过于繁琐。一般都是直接用springboot自带的@Transactional 注解,就可以完成这些事务管理操作。但是如果想知道事务底层的实现原理,以上的几种原始方式,还是可以参考的。
总结
这些仅为个人经验,希望能给大家一个参考,也希望大家多多支持服务器之家。
原文链接:https://blog.csdn.net/dayuiicghaid/article/details/125262298