聊聊spring tx的EnableTransactionManagement

2023年9月26日 233次阅读来源: 后端开发

序

本文主要研究一下spring tx的EnableTransactionManagement

EnableTransactionManagement

spring-tx-5.1.6.RELEASE-sources.jar!/org/springframework/transaction/annotation/EnableTransactionManagement.java

@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.
     * <p><b>The default is {@link AdviceMode#PROXY}.</b>
     * Please note that proxy mode allows for interception of calls through the proxy
     * only. Local calls within the same class cannot get intercepted that way; an
     * {@link Transactional} annotation on such a method within a local call will be
     * ignored since Spring's interceptor does not even kick in for such a runtime
     * scenario. For a more advanced mode of interception, consider switching this to
     * {@link AdviceMode#ASPECTJ}.
     */
    AdviceMode mode() default AdviceMode.PROXY;

    /**
     * Indicate the ordering of the execution of the transaction advisor
     * when multiple advices are applied at a specific joinpoint.
     * <p>The default is {@link Ordered#LOWEST_PRECEDENCE}.
     */
    int order() default Ordered.LOWEST_PRECEDENCE;

}

EnableTransactionManagement有三个属性，分别是proxyTargetClass、AdviceMode、order；它import了TransactionManagementConfigurationSelector
proxyTargetClass设置为true表示使用基于子类实现的代理(CGLIB)，设置为false表示使用基于接口实现的代理，默认为false
AdviceMode表示是使用哪种transactional advice，有PROXY及ASPECTJ两种，默认是AdviceMode.PROXY

TransactionManagementConfigurationSelector

spring-tx-5.1.6.RELEASE-sources.jar!/org/springframework/transaction/annotation/TransactionManagementConfigurationSelector.java

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);
    }

}

TransactionManagementConfigurationSelector继承了抽象类AdviceModeImportSelector，它覆盖了selectImports，该方法根据adviceMode返回要创建的类名；如果是PROXY模式，则返回AutoProxyRegistrar.class.getName()，ProxyTransactionManagementConfiguration.class.getName()；如果是ASPECTJ模式，则返回TransactionManagementConfigUtils.JTA_TRANSACTION_ASPECT_CONFIGURATION_CLASS_NAME或者是TransactionManagementConfigUtils.TRANSACTION_ASPECT_CONFIGURATION_CLASS_NAME

AbstractTransactionManagementConfiguration

spring-tx-5.1.6.RELEASE-sources.jar!/org/springframework/transaction/annotation/AbstractTransactionManagementConfiguration.java

@Configuration
public abstract class AbstractTransactionManagementConfiguration implements ImportAware {

    @Nullable
    protected AnnotationAttributes enableTx;

    /**
     * Default transaction manager, as configured through a {@link TransactionManagementConfigurer}.
     */
    @Nullable
    protected PlatformTransactionManager txManager;


    @Override
    public void setImportMetadata(AnnotationMetadata importMetadata) {
        this.enableTx = AnnotationAttributes.fromMap(
                importMetadata.getAnnotationAttributes(EnableTransactionManagement.class.getName(), false));
        if (this.enableTx == null) {
            throw new IllegalArgumentException(
                    "@EnableTransactionManagement is not present on importing class " + importMetadata.getClassName());
        }
    }

    @Autowired(required = false)
    void setConfigurers(Collection<TransactionManagementConfigurer> configurers) {
        if (CollectionUtils.isEmpty(configurers)) {
            return;
        }
        if (configurers.size() > 1) {
            throw new IllegalStateException("Only one TransactionManagementConfigurer may exist");
        }
        TransactionManagementConfigurer configurer = configurers.iterator().next();
        this.txManager = configurer.annotationDrivenTransactionManager();
    }


    @Bean(name = TransactionManagementConfigUtils.TRANSACTIONAL_EVENT_LISTENER_FACTORY_BEAN_NAME)
    @Role(BeanDefinition.ROLE_INFRASTRUCTURE)
    public static TransactionalEventListenerFactory transactionalEventListenerFactory() {
        return new TransactionalEventListenerFactory();
    }

}

AbstractTransactionManagementConfiguration为EnableTransactionManagement注解提供了通用的结构，这里主要是初始化了txManager，以及创建了TransactionalEventListenerFactory；它有三个子类，分别是ProxyTransactionManagementConfiguration、AspectJTransactionManagementConfiguration、AspectJJtaTransactionManagementConfiguration

ProxyTransactionManagementConfiguration

spring-tx-5.1.6.RELEASE-sources.jar!/org/springframework/transaction/annotation/ProxyTransactionManagementConfiguration.java

@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;
    }

}

ProxyTransactionManagementConfiguration继承了AbstractTransactionManagementConfiguration，这里它注册了BeanFactoryTransactionAttributeSourceAdvisor、TransactionAttributeSource(AnnotationTransactionAttributeSource)、TransactionInterceptor

AnnotationTransactionAttributeSource

spring-tx-5.1.6.RELEASE-sources.jar!/org/springframework/transaction/annotation/AnnotationTransactionAttributeSource.java

public class AnnotationTransactionAttributeSource extends AbstractFallbackTransactionAttributeSource
        implements Serializable {

    private static final boolean jta12Present;

    private static final boolean ejb3Present;

    static {
        ClassLoader classLoader = AnnotationTransactionAttributeSource.class.getClassLoader();
        jta12Present = ClassUtils.isPresent("javax.transaction.Transactional", classLoader);
        ejb3Present = ClassUtils.isPresent("javax.ejb.TransactionAttribute", classLoader);
    }

    private final boolean publicMethodsOnly;

    private final Set<TransactionAnnotationParser> annotationParsers;


    /**
     * Create a default AnnotationTransactionAttributeSource, supporting
     * public methods that carry the {@code Transactional} annotation
     * or the EJB3 {@link javax.ejb.TransactionAttribute} annotation.
     */
    public AnnotationTransactionAttributeSource() {
        this(true);
    }

    /**
     * Create a custom AnnotationTransactionAttributeSource, supporting
     * public methods that carry the {@code Transactional} annotation
     * or the EJB3 {@link javax.ejb.TransactionAttribute} annotation.
     * @param publicMethodsOnly whether to support public methods that carry
     * the {@code Transactional} annotation only (typically for use
     * with proxy-based AOP), or protected/private methods as well
     * (typically used with AspectJ class weaving)
     */
    public AnnotationTransactionAttributeSource(boolean publicMethodsOnly) {
        this.publicMethodsOnly = publicMethodsOnly;
        if (jta12Present || ejb3Present) {
            this.annotationParsers = new LinkedHashSet<>(4);
            this.annotationParsers.add(new SpringTransactionAnnotationParser());
            if (jta12Present) {
                this.annotationParsers.add(new JtaTransactionAnnotationParser());
            }
            if (ejb3Present) {
                this.annotationParsers.add(new Ejb3TransactionAnnotationParser());
            }
        }
        else {
            this.annotationParsers = Collections.singleton(new SpringTransactionAnnotationParser());
        }
    }

    //......

}

AnnotationTransactionAttributeSource的无参构造器，设置了publicMethodsOnly为true，同时创建了SpringTransactionAnnotationParser

TransactionInterceptor

spring-tx-5.1.6.RELEASE-sources.jar!/org/springframework/transaction/interceptor/TransactionInterceptor.java

public class TransactionInterceptor extends TransactionAspectSupport implements MethodInterceptor, Serializable {

    /**
     * Create a new TransactionInterceptor.
     * <p>Transaction manager and transaction attributes still need to be set.
     * @see #setTransactionManager
     * @see #setTransactionAttributes(java.util.Properties)
     * @see #setTransactionAttributeSource(TransactionAttributeSource)
     */
    public TransactionInterceptor() {
    }

    /**
     * Create a new TransactionInterceptor.
     * @param ptm the default transaction manager to perform the actual transaction management
     * @param attributes the transaction attributes in properties format
     * @see #setTransactionManager
     * @see #setTransactionAttributes(java.util.Properties)
     */
    public TransactionInterceptor(PlatformTransactionManager ptm, Properties attributes) {
        setTransactionManager(ptm);
        setTransactionAttributes(attributes);
    }

    /**
     * Create a new TransactionInterceptor.
     * @param ptm the default transaction manager to perform the actual transaction management
     * @param tas the attribute source to be used to find transaction attributes
     * @see #setTransactionManager
     * @see #setTransactionAttributeSource(TransactionAttributeSource)
     */
    public TransactionInterceptor(PlatformTransactionManager ptm, TransactionAttributeSource tas) {
        setTransactionManager(ptm);
        setTransactionAttributeSource(tas);
    }


    @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);
    }


    //---------------------------------------------------------------------
    // Serialization support
    //---------------------------------------------------------------------

    private void writeObject(ObjectOutputStream oos) throws IOException {
        // Rely on default serialization, although this class itself doesn't carry state anyway...
        oos.defaultWriteObject();

        // Deserialize superclass fields.
        oos.writeObject(getTransactionManagerBeanName());
        oos.writeObject(getTransactionManager());
        oos.writeObject(getTransactionAttributeSource());
        oos.writeObject(getBeanFactory());
    }

    private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException {
        // Rely on default serialization, although this class itself doesn't carry state anyway...
        ois.defaultReadObject();

        // Serialize all relevant superclass fields.
        // Superclass can't implement Serializable because it also serves as base class
        // for AspectJ aspects (which are not allowed to implement Serializable)!
        setTransactionManagerBeanName((String) ois.readObject());
        setTransactionManager((PlatformTransactionManager) ois.readObject());
        setTransactionAttributeSource((TransactionAttributeSource) ois.readObject());
        setBeanFactory((BeanFactory) ois.readObject());
    }

}

TransactionInterceptor继承了抽象类TransactionAspectSupport，同时实现了MethodInterceptor, Serializable接口；其invoke方法首先读取targetClass，然后调用了抽象类TransactionAspectSupport的invokeWithinTransaction方法