背景

上篇我们说明了事务实现基本要素aop等等Spring的事务实现一

继续描述一下事务引入的几种方式

方式

注解

spring3.1之后引入了新的注解EnableTransactionManagement

为了不维护太多的xml Spring从3.1版本组件增加java的配置类

而EnableTransactionManagement就是其中一个开启事务的注解

SpringBoot是注解的集大成者

@Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Import(TransactionManagementConfigurationSelector.class) public @interface EnableTransactionManagement {      /**     * Indicate whether subclass-based (CGLIB) proxies are to be created ({@code true}) as     * opposed to standard Java interface-based proxies ({@code false}). The default is     * {@code false}. <strong>Applicable only if {@link #mode()} is set to     * {@link AdviceMode#PROXY}</strong>.     * <p>Note that setting this attribute to {@code true} will affect <em>all</em>     * Spring-managed beans requiring proxying, not just those marked with     * {@code @Transactional}. For example, other beans marked with Spring's     * {@code @Async} annotation will be upgraded to subclass proxying at the same     * time. This approach has no negative impact in practice unless one is explicitly     * expecting one type of proxy vs another, e.g. in tests.     */    boolean proxyTargetClass() default false;      /**     * Indicate how transactional advice should be applied. The default is     * {@link AdviceMode#PROXY}.     * @see AdviceMode     */    AdviceMode mode() default AdviceMode.PROXY;      /**     * Indicate the ordering of the execution of the transaction advisor     * when multiple advices are applied at a specific joinpoint.     * The default is {@link Ordered#LOWEST_PRECEDENCE}.     */    int order() default Ordered.LOWEST_PRECEDENCE;   }

一旦使用了该注解很明显会引入TransactionManagementConfigurationSelector

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:             return new String[] {AutoProxyRegistrar.class.getName(), ProxyTransactionManagementConfiguration.class.getName()};          case ASPECTJ:             return new String[] {TransactionManagementConfigUtils.TRANSACTION_ASPECT_CONFIGURATION_CLASS_NAME};          default:             return null;       }    }   }

通常来说我们都是使用proxy 而使用aspectj相对来说比较麻烦需要在编译期支持

那么就会引入ProxyTransactionManagementConfiguration

@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());       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;    }   }

从这边可以知道advisor使用的是BeanFactoryTransactionAttributeSourceAdvisor===》this.enableTx.<Integer>getNumber("order") 这个enableTX是从EnableTransactionManagement读取的order 默认为最低顺序？【思考是为什么】

默认情况下使用的是注解支持的attributeSource 事务注解与tx:attributes共存

同时我们使用真正的业务实现在此【事务切面】TransactionInterceptor

advisor可以告诉我们是如何进行拦截的

public class BeanFactoryTransactionAttributeSourceAdvisor extends AbstractBeanFactoryPointcutAdvisor {      private TransactionAttributeSource transactionAttributeSource;      private final TransactionAttributeSourcePointcut pointcut = new TransactionAttributeSourcePointcut() {       @Override       protected TransactionAttributeSource getTransactionAttributeSource() {          return transactionAttributeSource;       }    };        /**     * Set the transaction attribute source which is used to find transaction     * attributes. This should usually be identical to the source reference     * set on the transaction interceptor itself.     * @see TransactionInterceptor#setTransactionAttributeSource     */    public void setTransactionAttributeSource(TransactionAttributeSource transactionAttributeSource) {       this.transactionAttributeSource = transactionAttributeSource;    }      /**     * Set the {@link ClassFilter} to use for this pointcut.     * Default is {@link ClassFilter#TRUE}.     */    public void setClassFilter(ClassFilter classFilter) {       this.pointcut.setClassFilter(classFilter);    }      public Pointcut getPointcut() {       return this.pointcut;    }   }

这就是我们使用的pointCut可以看到这边的attributeSource是从传入的===》此处是AnnotationTransactionAttributeSource

XML

虽然Spring提供了注解形式开启事务的方式，但是还有好多小伙伴会使用xml方式

<aop:config proxy-target-class="true">     <aop:pointcut id="serviceMethod"                   expression=" execution(public *  com.air.tqb.service..*(..)) and !execution(public * com.air.tqb.service.report..*(..)) and !execution(public * com.air.tqb.service.saiku..*(..))"/>     <aop:advisor order="1" pointcut-ref="serviceMethod" advice-ref="txAdvice"/> </aop:config> <tx:advice id="txAdvice" transaction-manager="transactionManager">     <tx:attributes>         <tx:method name="addBranch" read-only="false" rollback-for="java.lang.Exception"                    timeout="100"/>         <tx:method name="load*" read-only="true" propagation="SUPPORTS"                    timeout="20"/>         <tx:method name="find*" read-only="true" propagation="SUPPORTS"                    timeout="20"/>         <tx:method name="is*" read-only="true" propagation="SUPPORTS"                    timeout="20"/>         <tx:method name="has*" read-only="true" propagation="SUPPORTS"                    timeout="20"/>         <tx:method name="check*" read-only="true" propagation="SUPPORTS"                    timeout="20"/>         <tx:method name="get*" read-only="true" propagation="SUPPORTS"                    timeout="20"/>         <tx:method name="select*" read-only="true" propagation="SUPPORTS"                    timeout="20"/>         <tx:method name="list*" read-only="true" propagation="SUPPORTS"                    timeout="50"/>         <tx:method name="loginCheck" read-only="true" propagation="SUPPORTS"                    timeout="20"/>         <tx:method name="selectDiff*" read-only="true" propagation="SUPPORTS"                    timeout="120"/>         <tx:method name="*" propagation="REQUIRED" rollback-for="java.lang.Exception"                    timeout="50"/>     </tx:attributes> </tx:advice>

这是一种方式用来提供NameMatch

还有一种注解形式的事务注解与tx:attributes共存【这个注解是指具体使用什么事务】

通常来说我们使用

tx:advice

但是使用advice是远远不够的 这个advice需要和pointCut集合起来组成advisor

/**  * Create a {@link RootBeanDefinition} for the advisor described in the supplied. Does <strong>not</strong>  * parse any associated '{@code pointcut}' or '{@code pointcut-ref}' attributes.  */ private AbstractBeanDefinition createAdvisorBeanDefinition(Element advisorElement, ParserContext parserContext) {    RootBeanDefinition advisorDefinition = new RootBeanDefinition(DefaultBeanFactoryPointcutAdvisor.class);    advisorDefinition.setSource(parserContext.extractSource(advisorElement));      String adviceRef = advisorElement.getAttribute(ADVICE_REF);    if (!StringUtils.hasText(adviceRef)) {       parserContext.getReaderContext().error(             "'advice-ref' attribute contains empty value.", advisorElement, this.parseState.snapshot());    }    else {       advisorDefinition.getPropertyValues().add(             ADVICE_BEAN_NAME, new RuntimeBeanNameReference(adviceRef));    }      if (advisorElement.hasAttribute(ORDER_PROPERTY)) {       advisorDefinition.getPropertyValues().add(             ORDER_PROPERTY, advisorElement.getAttribute(ORDER_PROPERTY));    }      return advisorDefinition; } 

很明显 我们使用的就是DefaultBeanFactoryPointcutAdvisor

public class DefaultBeanFactoryPointcutAdvisor extends AbstractBeanFactoryPointcutAdvisor {      private Pointcut pointcut = Pointcut.TRUE;        /**     * Specify the pointcut targeting the advice.     * <p>Default is {@code Pointcut.TRUE}.     * @see #setAdviceBeanName     */    public void setPointcut(Pointcut pointcut) {       this.pointcut = (pointcut != null ? pointcut : Pointcut.TRUE);    }      public Pointcut getPointcut() {       return this.pointcut;    }        @Override    public String toString() {       return getClass().getName() + ": pointcut [" + getPointcut() + "]; advice bean '" + getAdviceBeanName() + "'";    }   }

此处可以看到如果不设置PointCut那么使用的就是PointCut.True

class TruePointcut implements Pointcut, Serializable {      public static final TruePointcut INSTANCE = new TruePointcut();      /**     * Enforce Singleton pattern.     */    private TruePointcut() {    }      public ClassFilter getClassFilter() {       return ClassFilter.TRUE;    }      public MethodMatcher getMethodMatcher() {       return MethodMatcher.TRUE;    }      /**     * Required to support serialization. Replaces with canonical     * instance on deserialization, protecting Singleton pattern.     * Alternative to overriding {@code equals()}.     */    private Object readResolve() {       return INSTANCE;    }      @Override    public String toString() {       return "Pointcut.TRUE";    }   }

换言之将所有情况下都会proxy