Spring 注解 事物开发
一、声明式事务：
环境搭建： 1、导入相关依赖 数据源、数据库驱动、Spring-jdbc模块
<dependency> <groupId>org.springframework</groupId> <artifactId>spring-jdbc</artifactId> <version>4.3.13.RELEASE</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.44</version> </dependency>
2、配置数据源、JdbcTemplate（Spring提供的简化数据库操作的工具）操作数据
3、给方法上标注 @Transactional 表示当前方法是一个事务方法；
@Transactional public void add() { deptDao.insert(); int i=10/0; }
4、 @EnableTransactionManagement 开启基于注解的事务管理功能； @EnableXXX 5、配置事务管理器来控制事务; @Bean public PlatformTransactionManager transactionManager()
代码：
package com.willow.tx; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.jdbc.core.JdbcTemplate; import org.springframework.jdbc.datasource.DataSourceTransactionManager; import org.springframework.jdbc.datasource.DriverManagerDataSource; import org.springframework.transaction.PlatformTransactionManager; import org.springframework.transaction.annotation.EnableTransactionManagement; import javax.sql.DataSource; @Configuration @EnableTransactionManagement @ComponentScan("com.willow.tx") public class TxConfig { @Bean public DataSource dataSource(){ DriverManagerDataSource ds = new DriverManagerDataSource (); ds.setDriverClassName("com.mysql.jdbc.Driver"); ds.setUrl("jdbc:mysql://192.168.7.108/willow"); ds.setUsername("root"); ds.setPassword("123456"); return ds; } @Bean public JdbcTemplate jdbcTemplate(){ return new JdbcTemplate(dataSource()); } @Bean public PlatformTransactionManager transactionManager(){ return new DataSourceTransactionManager(dataSource()); } }
二、事物原理部分
1）、@EnableTransactionManagement注解
@Import(TransactionManagementConfigurationSelector.class)利用TransactionManagementConfigurationSelector给容器中会导入下面两个组件
AutoProxyRegistrar
ProxyTransactionManagementConfiguration
public class TransactionManagementConfigurationSelector extends AdviceModeImportSelector<EnableTransactionManagement> { @Override protected String[] selectImports(AdviceMode adviceMode) { //AdviceMode在 EnableTransactionManagement注解中 默认为AdviceMode mode() default AdviceMode.PROXY; switch (adviceMode) { case PROXY: return new String[] {AutoProxyRegistrar.class.getName(), ProxyTransactionManagementConfiguration.class.getName()}; case ASPECTJ: return new String[] {TransactionManagementConfigUtils.TRANSACTION_ASPECT_CONFIGURATION_CLASS_NAME}; default: return null; } } }
2）、AutoProxyRegistrar：
给容器中注册一个 InfrastructureAdvisorAutoProxyCreator 组件
1. AutoProxyRegistrar.registerBeanDefinitions() --> 2. AopConfigUtils.registerAutoProxyCreatorIfNecessary(registry); --> 3. public static BeanDefinition registerAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry) { return registerAutoProxyCreatorIfNecessary(registry, null); } 4.public static BeanDefinition registerAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry, Object source) { return registerOrEscalateApcAsRequired(InfrastructureAdvisorAutoProxyCreator.class, registry, source); //注册了一个InfrastructureAdvisorAutoProxyCreator组件 }
InfrastructureAdvisorAutoProxyCreator：？原理和AOP部分的AnnotationAwareAspectJAutoProxyCreator一样，利用后置处理器机制在对象创建以后，包装对象，返回一个代理对象（增强器），代理对象执行方法利用拦截器链进行调用；
3）、ProxyTransactionManagementConfiguration 做了什么？
3.1 、给容器中注册事务增强器；
3.1.1）、事务增强器要用事务注解的信息，AnnotationTransactionAttributeSource解析事务注解
@Configuration public class ProxyTransactionManagementConfiguration extends AbstractTransactionManagementConfiguration { //事物增强器 @Bean(name = TransactionManagementConfigUtils.TRANSACTION_ADVISOR_BEAN_NAME) @Role(BeanDefinition.ROLE_INFRASTRUCTURE) public BeanFactoryTransactionAttributeSourceAdvisor transactionAdvisor() { BeanFactoryTransactionAttributeSourceAdvisor advisor = new BeanFactoryTransactionAttributeSourceAdvisor(); advisor.setTransactionAttributeSource(transactionAttributeSource()); advisor.setAdvice(transactionInterceptor()); advisor.setOrder(this.enableTx.<Integer>getNumber("order")); return advisor; } @Bean @Role(BeanDefinition.ROLE_INFRASTRUCTURE) public TransactionAttributeSource transactionAttributeSource() { return new AnnotationTransactionAttributeSource(); } // 2）、事务拦截器： // TransactionInterceptor；保存了事务属性信息，事务管理器；他是一个 MethodInterceptor； @Bean @Role(BeanDefinition.ROLE_INFRASTRUCTURE) public TransactionInterceptor transactionInterceptor() { TransactionInterceptor interceptor = new TransactionInterceptor(); interceptor.setTransactionAttributeSource(transactionAttributeSource()); if (this.txManager != null) { interceptor.setTransactionManager(this.txManager); } return interceptor; } }
3.1.2）、事务拦截器：
MethodInterceptor在目标方法执行的时候；
执行拦截器链；
事务拦截器：
1）、先获取事务相关的属性
2）、再获取PlatformTransactionManager，如果事先没有添加指定任何transactionmanger最终会从容器中按照类型获取一个PlatformTransactionManager；
3）、执行目标方法
如果异常，获取到事务管理器，利用事务管理回滚操作；
如果正常，利用事务管理器，提交事务
3.1.2.1 MethodInterceptor在目标方法执行的时候；
TransactionInterceptor.invoke() 方法
@Override public Object invoke(final MethodInvocation invocation) throws Throwable { Class<?> targetClass = (invocation.getThis() != null ? AopUtils.getTargetClass(invocation.getThis()) : null); return invokeWithinTransaction(invocation.getMethod(), targetClass, new InvocationCallback() { @Override public Object proceedWithInvocation() throws Throwable { return invocation.proceed(); } }); }
3.1.2.2 TransactionAspectSupport.invokeWithinTransaction()方法
protected Object invokeWithinTransaction(Method method, Class<?> targetClass, final InvocationCallback invocation) throws Throwable { // 1）、先获取事务相关的属性 final TransactionAttribute txAttr = getTransactionAttributeSource().getTransactionAttribute(method, targetClass); // 2）、再获取PlatformTransactionManager，如果事先没有添加指定任何transactionmanger final PlatformTransactionManager tm = determineTransactionManager(txAttr); //获取要执行的事物方法 final String joinpointIdentification = methodIdentification(method, targetClass, txAttr); if (txAttr == null || !(tm instanceof CallbackPreferringPlatformTransactionManager)) { // 创建一个事物 TransactionInfo txInfo = createTransactionIfNecessary(tm, txAttr, joinpointIdentification); Object retVal = null; try { //事物方法的执行 retVal = invocation.proceedWithInvocation(); } catch (Throwable ex) { // 有异常回滚事物 completeTransactionAfterThrowing(txInfo, ex); throw ex; } finally { cleanupTransactionInfo(txInfo); } //得到事物管理器，提交事物 commitTransactionAfterReturning(txInfo); return retVal; } else { final ThrowableHolder throwableHolder = new ThrowableHolder(); // It's a CallbackPreferringPlatformTransactionManager: pass a TransactionCallback in. try { Object result = ((CallbackPreferringPlatformTransactionManager) tm).execute(txAttr, new TransactionCallback<Object>() { @Override public Object doInTransaction(TransactionStatus status) { TransactionInfo txInfo = prepareTransactionInfo(tm, txAttr, joinpointIdentification, status); try { return invocation.proceedWithInvocation(); } catch (Throwable ex) { if (txAttr.rollbackOn(ex)) { // A RuntimeException: will lead to a rollback. if (ex instanceof RuntimeException) { throw (RuntimeException) ex; } else { throw new ThrowableHolderException(ex); } } else { // A normal return value: will lead to a commit. throwableHolder.throwable = ex; return null; } } finally { cleanupTransactionInfo(txInfo); } } }); // Check result state: It might indicate a Throwable to rethrow. if (throwableHolder.throwable != null) { throw throwableHolder.throwable; } return result; } catch (ThrowableHolderException ex) { throw ex.getCause(); } catch (TransactionSystemException ex2) { if (throwableHolder.throwable != null) { logger.error("Application exception overridden by commit exception", throwableHolder.throwable); ex2.initApplicationException(throwableHolder.throwable); } throw ex2; } catch (Throwable ex2) { if (throwableHolder.throwable != null) { logger.error("Application exception overridden by commit exception", throwableHolder.throwable); } throw ex2; } } }
3.1.2.2.1）、获取PlatformTransactionManager
如果事先没有添加指定任何transactionmanger最终会从容器中按照类型获取一个PlatformTransactionManager
protected PlatformTransactionManager determineTransactionManager(TransactionAttribute txAttr) { // Do not attempt to lookup tx manager if no tx attributes are set if (txAttr == null || this.beanFactory == null) { return getTransactionManager(); } //判断是否@Transactional(transactionManager = "")指定了transactionManager String qualifier = txAttr.getQualifier(); if (StringUtils.hasText(qualifier)) { return determineQualifiedTransactionManager(qualifier); } else if (StringUtils.hasText(this.transactionManagerBeanName)) { return determineQualifiedTransactionManager(this.transactionManagerBeanName); } else { PlatformTransactionManager defaultTransactionManager = getTransactionManager(); if (defaultTransactionManager == null) { defaultTransactionManager = this.transactionManagerCache.get(DEFAULT_TRANSACTION_MANAGER_KEY); if (defaultTransactionManager == null) { defaultTransactionManager = this.beanFactory.getBean(PlatformTransactionManager.class); //在IOC容器中获取PlatformTransactionManager this.transactionManagerCache.putIfAbsent( DEFAULT_TRANSACTION_MANAGER_KEY, defaultTransactionManager); } } return defaultTransactionManager; } }
