Spring声明式事务注解之@EnableTransactionManagement解析

@Target (ElementType.TYPE)

@Retention (RetentionPolicy.RUNTIME)

@Documented

// 通过@Import导入TransactionManagementConfigurationSelector组件

@Import (TransactionManagementConfigurationSelector. class )

public @interface EnableTransactionManagement {

  boolean proxyTargetClass() default false ;

  AdviceMode mode() default AdviceMode.PROXY;

  int order() default Ordered.LOWEST_PRECEDENCE;

}

public class TransactionManagementConfigurationSelector extends AdviceModeImportSelector<EnableTransactionManagement> {

  /**

   * {@inheritDoc}

   * @return {@link ProxyTransactionManagementConfiguration} or

   * {@code AspectJTransactionManagementConfiguration} for {@code PROXY} and

   * {@code ASPECTJ} values of {@link EnableTransactionManagement#mode()}, respectively

   */

  @Override

  protected String[] selectImports(AdviceMode adviceMode) {

   switch (adviceMode) {

    case PROXY:

     // 根据@EnableTransactionManagement的固定值PROXY，这里会导入AutoProxyRegistrar组件和ProxyTransactionManagementConfiguration组件

     return new String[] {AutoProxyRegistrar. class .getName(), ProxyTransactionManagementConfiguration. class .getName()};

    case ASPECTJ:

     return new String[] {TransactionManagementConfigUtils.TRANSACTION_ASPECT_CONFIGURATION_CLASS_NAME};

    default :

     return null ;

   }

  }

}

InfrastructureAdvisorAutoProxyCreator

     --AbstractAdvisorAutoProxyCreator

         --AbstractAdvisorAutoProxyCreator

             --ProxyProcessorSupport

             --SmartInstantiationAwareBeanPostProcessor  // 跟AOP是原理是一样的

                 --InstantiationAwareBeanPostProcessor

                     --BeanPostProcessor

             --BeanFactoryAware

package org.springframework.transaction.annotation;

import org.springframework.beans.factory.config.BeanDefinition;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import org.springframework.context.annotation.Role;

import org.springframework.transaction.config.TransactionManagementConfigUtils;

import org.springframework.transaction.interceptor.BeanFactoryTransactionAttributeSourceAdvisor;

import org.springframework.transaction.interceptor.TransactionAttributeSource;

import org.springframework.transaction.interceptor.TransactionInterceptor;

@Configuration

public class ProxyTransactionManagementConfiguration extends AbstractTransactionManagementConfiguration {

     /**

         事务增强器(Advisor)，在事务类创建的时候，被AutoProxyRegistrar导入的组件InfrastructureAdvisorAutoProxyCreator拦截，

         InfrastructureAdvisorAutoProxyCreator拦截的逻就是增强事务类的事务方法，  而BeanFactoryTransactionAttributeSourceAdvisor作为增强器，

         与需要增强的方法(这里是指被@Transactional标记的方法)进行匹配，匹配成功的增强器，最后转成拦截器(MethodInterceptor,

         就是下面的TransactionInterceptor)，然后与目标方法一起在拦截器链中被执行，达到方法增强的效果；

         BeanFactoryTransactionAttributeSourceAdvisor的继承关系如下：

         BeanFactoryTransactionAttributeSourceAdvisor

             --AbstractBeanFactoryPointcutAdvisor

                 --AbstractPointcutAdvisor

                     --PointcutAdvisor

                         --Advisor

         AOP中AspectJPointcutAdvisor的继承关系如下，与AbstractPointcutAdvisor一样，都实现PointcutAdvisor

                 --AspectJPointcutAdvisor

                     --PointcutAdvisor

                         --Advisor

     */

     @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;

     }

     /**

         @Transactional注解的解析类；负责解析事务方法上@Transactional中的各个参数配置，解析的时机是在创建事务类之后被增强的时候，

         匹配事务方法的时候一起被解析了

         AnnotationTransactionAttributeSource的继承关系如下：

         AnnotationTransactionAttributeSource

             --AbstractFallbackTransactionAttributeSource

                 --TransactionAttributeSource

         通过方法org.springframework.transaction.interceptor.AbstractFallbackTransactionAttributeSource.getTransactionAttribute(Method, Class<?>)

         解析出事务信息TransactionAttribute；

         AnnotationTransactionAttributeSource在方法findTransactionAttribute(Class<?>)中依赖于SpringTransactionAnnotationParser在解析事务类时，

         绑定事务方法与增强器的时候进行@Transactional注解解析；

     */

     @Bean

     @Role (BeanDefinition.ROLE_INFRASTRUCTURE)

     public TransactionAttributeSource transactionAttributeSource() {

         return new AnnotationTransactionAttributeSource();

     }

     /**

         被@Transactional标记的事务方法的拦截器，实际是一个MethodInterceptor

         保存了事务属性信息，事务管理器；

         在目标方法执行的时候；执行拦截器链；

     */

     @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;

     }

}

protected TransactionAttribute parseTransactionAnnotation(AnnotationAttributes attributes) {

     RuleBasedTransactionAttribute rbta = new RuleBasedTransactionAttribute();

     Propagation propagation = attributes.getEnum( "propagation" );

     rbta.setPropagationBehavior(propagation.value());

     Isolation isolation = attributes.getEnum( "isolation" );

     rbta.setIsolationLevel(isolation.value());

     rbta.setTimeout(attributes.getNumber( "timeout" ).intValue());

     rbta.setReadOnly(attributes.getBoolean( "readOnly" ));

     rbta.setQualifier(attributes.getString( "value" ));

     ArrayList<RollbackRuleAttribute> rollBackRules = new ArrayList<RollbackRuleAttribute>();

     Class<?>[] rbf = attributes.getClassArray( "rollbackFor" );

     for (Class<?> rbRule : rbf) {

         RollbackRuleAttribute rule = new RollbackRuleAttribute(rbRule);

         rollBackRules.add(rule);

     }

     String[] rbfc = attributes.getStringArray( "rollbackForClassName" );

     for (String rbRule : rbfc) {

         RollbackRuleAttribute rule = new RollbackRuleAttribute(rbRule);

         rollBackRules.add(rule);

     }

     Class<?>[] nrbf = attributes.getClassArray( "noRollbackFor" );

     for (Class<?> rbRule : nrbf) {

         NoRollbackRuleAttribute rule = new NoRollbackRuleAttribute(rbRule);

         rollBackRules.add(rule);

     }

     String[] nrbfc = attributes.getStringArray( "noRollbackForClassName" );

     for (String rbRule : nrbfc) {

         NoRollbackRuleAttribute rule = new NoRollbackRuleAttribute(rbRule);

         rollBackRules.add(rule);

     }

     rbta.getRollbackRules().addAll(rollBackRules);

     return rbta;

}

AutoProxyRegistrar

ProxyTransactionManagementConfiguration