1、事务处理实现
实现步骤:
* 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 * 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; * 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()
代码实现:
@EnableTransactionManagement @ComponentScan("com.atguigu.tx") @Configuration public class TxConfig { //数据源 @Bean public DataSource dataSource() throws Exception{ ComboPooledDataSource dataSource = new ComboPooledDataSource(); dataSource.setUser("root"); dataSource.setPassword("123456"); dataSource.setDriverClass("com.mysql.jdbc.Driver"); dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/test"); return dataSource; } @Bean public JdbcTemplate jdbcTemplate() throws Exception{ //Spring对@Configuration类会特殊处理;给容器中加组件的方法,多次调用都只是从容器中找组件 JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource()); return jdbcTemplate; } //注册事务管理器在容器中 @Bean public PlatformTransactionManager transactionManager() throws Exception{ return new DataSourceTransactionManager(dataSource()); } }
2、事务处理原理
原理分析:
* 原理:
* 1)、@EnableTransactionManagement * 利用TransactionManagementConfigurationSelector给容器中会导入组件 * 导入两个组件 * AutoProxyRegistrar * ProxyTransactionManagementConfiguration * 2)、AutoProxyRegistrar: * 给容器中注册一个 InfrastructureAdvisorAutoProxyCreator 组件; * InfrastructureAdvisorAutoProxyCreator:? * 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? * 1、给容器中注册事务增强器; * 1)、事务增强器要用事务注解的信息,AnnotationTransactionAttributeSource解析事务注解 * 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; * 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 * */
核心代码
1、EnableTransactionManagement注解,注入TransactionManagementConfigurationSelector类
@Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Import(TransactionManagementConfigurationSelector.class) public @interface EnableTransactionManagement {
2、TransactionManagementConfigurationSelector类,最终会导入AutoProxyRegistrar.class和ProxyTransactionManagementConfiguration.class两个组件。
public class TransactionManagementConfigurationSelector extends AdviceModeImportSelector<EnableTransactionManagement> { /** * Returns {@link ProxyTransactionManagementConfiguration} or * {@code AspectJ(Jta)TransactionManagementConfiguration} for {@code PROXY} * and {@code ASPECTJ} values of {@link EnableTransactionManagement#mode()}, * respectively. */ @Override protected String[] selectImports(AdviceMode adviceMode) { switch (adviceMode) { case PROXY: return new String[] {AutoProxyRegistrar.class.getName(), ProxyTransactionManagementConfiguration.class.getName()}; case ASPECTJ: return new String[] {determineTransactionAspectClass()}; default: return null; } } private String determineTransactionAspectClass() { return (ClassUtils.isPresent("javax.transaction.Transactional", getClass().getClassLoader()) ? TransactionManagementConfigUtils.JTA_TRANSACTION_ASPECT_CONFIGURATION_CLASS_NAME : TransactionManagementConfigUtils.TRANSACTION_ASPECT_CONFIGURATION_CLASS_NAME); } }
3、AutoProxyRegistrar类的作用为:
给容器中注册一个 InfrastructureAdvisorAutoProxyCreator 组件;
最终的目的是: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;
@Override public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) { boolean candidateFound = false; Set<String> annTypes = importingClassMetadata.getAnnotationTypes(); for (String annType : annTypes) { AnnotationAttributes candidate = AnnotationConfigUtils.attributesFor(importingClassMetadata, annType); if (candidate == null) { continue; } Object mode = candidate.get("mode"); Object proxyTargetClass = candidate.get("proxyTargetClass"); if (mode != null && proxyTargetClass != null && AdviceMode.class == mode.getClass() && Boolean.class == proxyTargetClass.getClass()) { candidateFound = true; if (mode == AdviceMode.PROXY) { AopConfigUtils.registerAutoProxyCreatorIfNecessary(registry); if ((Boolean) proxyTargetClass) { AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry); return; } } } } if (!candidateFound && logger.isInfoEnabled()) { String name = getClass().getSimpleName(); logger.info(String.format("%s was imported but no annotations were found " + "having both 'mode' and 'proxyTargetClass' attributes of type " + "AdviceMode and boolean respectively. This means that auto proxy " + "creator registration and configuration may not have occurred as " + "intended, and components may not be proxied as expected. Check to " + "ensure that %s has been @Import'ed on the same class where these " + "annotations are declared; otherwise remove the import of %s " + "altogether.", name, name, name)); } }
InfrastructureAdvisorAutoProxyCreator类的作用与AnnotationAwareAspectJAutoProxyCreator类的作用类似。
@SuppressWarnings("serial") public abstract class AbstractAutoProxyCreator extends ProxyProcessorSupport implements SmartInstantiationAwareBeanPostProcessor, BeanFactoryAware {
4、ProxyTransactionManagementConfiguration类
代理事务管理配置类
@Configuration public class ProxyTransactionManagementConfiguration extends AbstractTransactionManagementConfiguration { @Bean(name = TransactionManagementConfigUtils.TRANSACTION_ADVISOR_BEAN_NAME) @Role(BeanDefinition.ROLE_INFRASTRUCTURE) public BeanFactoryTransactionAttributeSourceAdvisor transactionAdvisor() { BeanFactoryTransactionAttributeSourceAdvisor advisor = new BeanFactoryTransactionAttributeSourceAdvisor(); advisor.setTransactionAttributeSource(transactionAttributeSource()); advisor.setAdvice(transactionInterceptor()); if (this.enableTx != null) { advisor.setOrder(this.enableTx.<Integer>getNumber("order")); } return advisor; } @Bean @Role(BeanDefinition.ROLE_INFRASTRUCTURE) public TransactionAttributeSource transactionAttributeSource() { return new AnnotationTransactionAttributeSource(); } @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; } }
TransactionInterceptor类,事务调用:invokeWithinTransaction()方法为最终执行的方法
@Override @Nullable public Object invoke(MethodInvocation invocation) throws Throwable { // Work out the target class: may be {@code null}. // The TransactionAttributeSource should be passed the target class // as well as the method, which may be from an interface. Class<?> targetClass = (invocation.getThis() != null ? AopUtils.getTargetClass(invocation.getThis()) : null); // Adapt to TransactionAspectSupport's invokeWithinTransaction... return invokeWithinTransaction(invocation.getMethod(), targetClass, invocation::proceed); }
TransactionAspectSupport类的最终事务方法执行:
@Nullable protected Object invokeWithinTransaction(Method method, @Nullable Class<?> targetClass, final InvocationCallback invocation) throws Throwable { // If the transaction attribute is null, the method is non-transactional. TransactionAttributeSource tas = getTransactionAttributeSource(); final TransactionAttribute txAttr = (tas != null ? tas.getTransactionAttribute(method, targetClass) : null); final PlatformTransactionManager tm = determineTransactionManager(txAttr); final String joinpointIdentification = methodIdentification(method, targetClass, txAttr); if (txAttr == null || !(tm instanceof CallbackPreferringPlatformTransactionManager)) { // Standard transaction demarcation with getTransaction and commit/rollback calls. TransactionInfo txInfo = createTransactionIfNecessary(tm, txAttr, joinpointIdentification); Object retVal; try { // This is an around advice: Invoke the next interceptor in the chain. // This will normally result in a target object being invoked. retVal = invocation.proceedWithInvocation(); } catch (Throwable ex) { // target invocation exception completeTransactionAfterThrowing(txInfo, ex); throw ex; } finally { cleanupTransactionInfo(txInfo); } 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, 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; } } }
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