Spring源代码解析（八）：Spring驱动Hibernate的实现

O/R工具出现之后，简化了许多复杂的信息持久化的开发。Spring应用开发者可以通过Spring提供的O/R方案更方便的使用各种持久化工具，比如Hibernate；下面我们就Spring+Hibernate中的Spring实现做一个简单的剖析。
Spring对Hinberanate的配置是通过LocalSessionFactoryBean来完成的，这是一个工厂Bean的实现，在基类AbstractSessionFactoryBean中：

/**
 * 这是FactoryBean需要实现的接口方法，直接取得当前的sessionFactory的值
 */
public Object getObject() {
    return this.sessionFactory;
}

    /**
     * 这是FactoryBean需要实现的接口方法，直接取得当前的sessionFactory的值
     */
    public Object getObject() {
        return this.sessionFactory;
    }

这个值在afterPropertySet中定义：

public void afterPropertiesSet() throws Exception {
    //这个buildSessionFactory是通过配置信息得到SessionFactory的地方
    SessionFactory rawSf = buildSessionFactory();
    //这里使用了Proxy方法插入对getCurrentSession的拦截，得到和事务相关的session
    this.sessionFactory = wrapSessionFactoryIfNecessary(rawSf);
}

    public void afterPropertiesSet() throws Exception {
        //这个buildSessionFactory是通过配置信息得到SessionFactory的地方
        SessionFactory rawSf = buildSessionFactory();
        //这里使用了Proxy方法插入对getCurrentSession的拦截，得到和事务相关的session
        this.sessionFactory = wrapSessionFactoryIfNecessary(rawSf);
    }

我们先看看SessionFactory是怎样创建的，这个方法很长，包含了创建Hibernate的SessionFactory的详尽步骤：

protected SessionFactory buildSessionFactory() throws Exception {
    SessionFactory sf = null;

    // Create Configuration instance.
    Configuration config = newConfiguration();

    //这里配置数据源，事务管理器，LobHander到Holder中，这个Holder是一个ThreadLocal变量,这样这些资源就和线程绑定了
    if (this.dataSource != null) {
        // Make given DataSource available for SessionFactory configuration.
        configTimeDataSourceHolder.set(this.dataSource);
    }

    if (this.jtaTransactionManager != null) {
        // Make Spring-provided JTA TransactionManager available.
        configTimeTransactionManagerHolder.set(this.jtaTransactionManager);
    }

    if (this.lobHandler != null) {
        // Make given LobHandler available for SessionFactory configuration.
        // Do early because because mapping resource might refer to custom types.
        configTimeLobHandlerHolder.set(this.lobHandler);
    }

    //这里是使用Hibernate的各个属性的配置，这里使用了Configuration类来抽象这些数据
    try {
        // Set connection release mode "on_close" as default.
        // This was the case for Hibernate 3.0; Hibernate 3.1 changed
        // it to "auto" (i.e. "after_statement" or "after_transaction").
        // However, for Spring's resource management (in particular for
        // HibernateTransactionManager), "on_close" is the better default.
        config.setProperty(Environment.RELEASE_CONNECTIONS, ConnectionReleaseMode.ON_CLOSE.toString());

        if (!isExposeTransactionAwareSessionFactory()) {
            // Not exposing a SessionFactory proxy with transaction-aware
            // getCurrentSession() method -> set Hibernate 3.1 CurrentSessionContext
            // implementation instead, providing the Spring-managed Session that way.
            // Can be overridden by a custom value for corresponding Hibernate property.
            config.setProperty(Environment.CURRENT_SESSION_CONTEXT_CLASS,
                    "org.springframework.orm.hibernate3.SpringSessionContext");
        }

        if (this.entityInterceptor != null) {
            // Set given entity interceptor at SessionFactory level.
            config.setInterceptor(this.entityInterceptor);
        }

        if (this.namingStrategy != null) {
            // Pass given naming strategy to Hibernate Configuration.
            config.setNamingStrategy(this.namingStrategy);
        }

        if (this.typeDefinitions != null) {
            // Register specified Hibernate type definitions.
            Mappings mappings = config.createMappings();
            for (int i = 0; i < this.typeDefinitions.length; i++) {
                TypeDefinitionBean typeDef = this.typeDefinitions[i];
                mappings.addTypeDef(typeDef.getTypeName(), typeDef.getTypeClass(), typeDef.getParameters());
            }
        }

        if (this.filterDefinitions != null) {
            // Register specified Hibernate FilterDefinitions.
            for (int i = 0; i < this.filterDefinitions.length; i++) {
                config.addFilterDefinition(this.filterDefinitions[i]);
            }
        }

        if (this.configLocations != null) {
            for (int i = 0; i < this.configLocations.length; i++) {
                // Load Hibernate configuration from given location.
                config.configure(this.configLocations[i].getURL());
            }
        }

        if (this.hibernateProperties != null) {
            // Add given Hibernate properties to Configuration.
            config.addProperties(this.hibernateProperties);
        }

        if (this.dataSource != null) {
            boolean actuallyTransactionAware =
                    (this.useTransactionAwareDataSource || this.dataSource instanceof TransactionAwareDataSourceProxy);
            // Set Spring-provided DataSource as Hibernate ConnectionProvider.
            config.setProperty(Environment.CONNECTION_PROVIDER,
                    actuallyTransactionAware ?
                    TransactionAwareDataSourceConnectionProvider.class.getName() :
                    LocalDataSourceConnectionProvider.class.getName());
        }

        if (this.jtaTransactionManager != null) {
            // Set Spring-provided JTA TransactionManager as Hibernate property.
            config.setProperty(
                    Environment.TRANSACTION_MANAGER_STRATEGY, LocalTransactionManagerLookup.class.getName());
        }

        if (this.mappingLocations != null) {
            // Register given Hibernate mapping definitions, contained in resource files.
            for (int i = 0; i < this.mappingLocations.length; i++) {
                config.addInputStream(this.mappingLocations[i].getInputStream());
            }
        }

        if (this.cacheableMappingLocations != null) {
            // Register given cacheable Hibernate mapping definitions, read from the file system.
            for (int i = 0; i < this.cacheableMappingLocations.length; i++) {
                config.addCacheableFile(this.cacheableMappingLocations[i].getFile());
            }
        }

        if (this.mappingJarLocations != null) {
            // Register given Hibernate mapping definitions, contained in jar files.
            for (int i = 0; i < this.mappingJarLocations.length; i++) {
                Resource resource = this.mappingJarLocations[i];
                config.addJar(resource.getFile());
            }
        }

        if (this.mappingDirectoryLocations != null) {
            // Register all Hibernate mapping definitions in the given directories.
            for (int i = 0; i < this.mappingDirectoryLocations.length; i++) {
                File file = this.mappingDirectoryLocations[i].getFile();
                if (!file.isDirectory()) {
                    throw new IllegalArgumentException(
                            "Mapping directory location [" + this.mappingDirectoryLocations[i] +
                            "] does not denote a directory");
                }
                config.addDirectory(file);
            }
        }

        if (this.entityCacheStrategies != null) {
            // Register cache strategies for mapped entities.
            for (Enumeration classNames = this.entityCacheStrategies.propertyNames(); classNames.hasMoreElements();) {
                String className = (String) classNames.nextElement();
                String[] strategyAndRegion =
                        StringUtils.commaDelimitedListToStringArray(this.entityCacheStrategies.getProperty(className));
                if (strategyAndRegion.length > 1) {
                    config.setCacheConcurrencyStrategy(className, strategyAndRegion[0], strategyAndRegion[1]);
                }
                else if (strategyAndRegion.length > 0) {
                    config.setCacheConcurrencyStrategy(className, strategyAndRegion[0]);
                }
            }
        }

        if (this.collectionCacheStrategies != null) {
            // Register cache strategies for mapped collections.
            for (Enumeration collRoles = this.collectionCacheStrategies.propertyNames(); collRoles.hasMoreElements();) {
                String collRole = (String) collRoles.nextElement();
                String[] strategyAndRegion =
                        StringUtils.commaDelimitedListToStringArray(this.collectionCacheStrategies.getProperty(collRole));
                if (strategyAndRegion.length > 1) {
                    config.setCollectionCacheConcurrencyStrategy(collRole, strategyAndRegion[0], strategyAndRegion[1]);
                }
                else if (strategyAndRegion.length > 0) {
                    config.setCollectionCacheConcurrencyStrategy(collRole, strategyAndRegion[0]);
                }
            }
        }

        if (this.eventListeners != null) {
            // Register specified Hibernate event listeners.
            for (Iterator it = this.eventListeners.entrySet().iterator(); it.hasNext();) {
                Map.Entry entry = (Map.Entry) it.next();
                Assert.isTrue(entry.getKey() instanceof String, "Event listener key needs to be of type String");
                String listenerType = (String) entry.getKey();
                Object listenerObject = entry.getValue();
                if (listenerObject instanceof Collection) {
                    Collection listeners = (Collection) listenerObject;
                    EventListeners listenerRegistry = config.getEventListeners();
                    Object[] listenerArray =
                            (Object[]) Array.newInstance(listenerRegistry.getListenerClassFor(listenerType), listeners.size());
                    listenerArray = listeners.toArray(listenerArray);
                    config.setListeners(listenerType, listenerArray);
                }
                else {
                    config.setListener(listenerType, listenerObject);
                }
            }
        }

        // Perform custom post-processing in subclasses.
        postProcessConfiguration(config);

        // 这里是根据Configuration配置创建SessionFactory的地方
        logger.info("Building new Hibernate SessionFactory");
        this.configuration = config;
        sf = newSessionFactory(config);
    }
    //最后把和线程绑定的资源清空
    finally {
        if (this.dataSource != null) {
            // Reset DataSource holder.
            configTimeDataSourceHolder.set(null);
        }

        if (this.jtaTransactionManager != null) {
            // Reset TransactionManager holder.
            configTimeTransactionManagerHolder.set(null);
        }

        if (this.lobHandler != null) {
            // Reset LobHandler holder.
            configTimeLobHandlerHolder.set(null);
        }
    }

    // Execute schema update if requested.
    if (this.schemaUpdate) {
        updateDatabaseSchema();
    }

    return sf;
}

    protected SessionFactory buildSessionFactory() throws Exception {
        SessionFactory sf = null;

        // Create Configuration instance.
        Configuration config = newConfiguration();

        //这里配置数据源，事务管理器，LobHander到Holder中，这个Holder是一个ThreadLocal变量,这样这些资源就和线程绑定了
        if (this.dataSource != null) {
            // Make given DataSource available for SessionFactory configuration.
            configTimeDataSourceHolder.set(this.dataSource);
        }

        if (this.jtaTransactionManager != null) {
            // Make Spring-provided JTA TransactionManager available.
            configTimeTransactionManagerHolder.set(this.jtaTransactionManager);
        }

        if (this.lobHandler != null) {
            // Make given LobHandler available for SessionFactory configuration.
            // Do early because because mapping resource might refer to custom types.
            configTimeLobHandlerHolder.set(this.lobHandler);
        }

        //这里是使用Hibernate的各个属性的配置，这里使用了Configuration类来抽象这些数据
        try {
            // Set connection release mode "on_close" as default.
            // This was the case for Hibernate 3.0; Hibernate 3.1 changed
            // it to "auto" (i.e. "after_statement" or "after_transaction").
            // However, for Spring's resource management (in particular for
            // HibernateTransactionManager), "on_close" is the better default.
            config.setProperty(Environment.RELEASE_CONNECTIONS, ConnectionReleaseMode.ON_CLOSE.toString());

            if (!isExposeTransactionAwareSessionFactory()) {
                // Not exposing a SessionFactory proxy with transaction-aware
                // getCurrentSession() method -> set Hibernate 3.1 CurrentSessionContext
                // implementation instead, providing the Spring-managed Session that way.
                // Can be overridden by a custom value for corresponding Hibernate property.
                config.setProperty(Environment.CURRENT_SESSION_CONTEXT_CLASS,
                        "org.springframework.orm.hibernate3.SpringSessionContext");
            }

            if (this.entityInterceptor != null) {
                // Set given entity interceptor at SessionFactory level.
                config.setInterceptor(this.entityInterceptor);
            }

            if (this.namingStrategy != null) {
                // Pass given naming strategy to Hibernate Configuration.
                config.setNamingStrategy(this.namingStrategy);
            }

            if (this.typeDefinitions != null) {
                // Register specified Hibernate type definitions.
                Mappings mappings = config.createMappings();
                for (int i = 0; i < this.typeDefinitions.length; i++) {
                    TypeDefinitionBean typeDef = this.typeDefinitions[i];
                    mappings.addTypeDef(typeDef.getTypeName(), typeDef.getTypeClass(), typeDef.getParameters());
                }
            }

            if (this.filterDefinitions != null) {
                // Register specified Hibernate FilterDefinitions.
                for (int i = 0; i < this.filterDefinitions.length; i++) {
                    config.addFilterDefinition(this.filterDefinitions[i]);
                }
            }

            if (this.configLocations != null) {
                for (int i = 0; i < this.configLocations.length; i++) {
                    // Load Hibernate configuration from given location.
                    config.configure(this.configLocations[i].getURL());
                }
            }

            if (this.hibernateProperties != null) {
                // Add given Hibernate properties to Configuration.
                config.addProperties(this.hibernateProperties);
            }

            if (this.dataSource != null) {
                boolean actuallyTransactionAware =
                        (this.useTransactionAwareDataSource || this.dataSource instanceof TransactionAwareDataSourceProxy);
                // Set Spring-provided DataSource as Hibernate ConnectionProvider.
                config.setProperty(Environment.CONNECTION_PROVIDER,
                        actuallyTransactionAware ?
                        TransactionAwareDataSourceConnectionProvider.class.getName() :
                        LocalDataSourceConnectionProvider.class.getName());
            }

            if (this.jtaTransactionManager != null) {
                // Set Spring-provided JTA TransactionManager as Hibernate property.
                config.setProperty(
                        Environment.TRANSACTION_MANAGER_STRATEGY, LocalTransactionManagerLookup.class.getName());
            }

            if (this.mappingLocations != null) {
                // Register given Hibernate mapping definitions, contained in resource files.
                for (int i = 0; i < this.mappingLocations.length; i++) {
                    config.addInputStream(this.mappingLocations[i].getInputStream());
                }
            }

            if (this.cacheableMappingLocations != null) {
                // Register given cacheable Hibernate mapping definitions, read from the file system.
                for (int i = 0; i < this.cacheableMappingLocations.length; i++) {
                    config.addCacheableFile(this.cacheableMappingLocations[i].getFile());
                }
            }

            if (this.mappingJarLocations != null) {
                // Register given Hibernate mapping definitions, contained in jar files.
                for (int i = 0; i < this.mappingJarLocations.length; i++) {
                    Resource resource = this.mappingJarLocations[i];
                    config.addJar(resource.getFile());
                }
            }

            if (this.mappingDirectoryLocations != null) {
                // Register all Hibernate mapping definitions in the given directories.
                for (int i = 0; i < this.mappingDirectoryLocations.length; i++) {
                    File file = this.mappingDirectoryLocations[i].getFile();
                    if (!file.isDirectory()) {
                        throw new IllegalArgumentException(
                                "Mapping directory location [" + this.mappingDirectoryLocations[i] +
                                "] does not denote a directory");
                    }
                    config.addDirectory(file);
                }
            }

            if (this.entityCacheStrategies != null) {
                // Register cache strategies for mapped entities.
                for (Enumeration classNames = this.entityCacheStrategies.propertyNames(); classNames.hasMoreElements();) {
                    String className = (String) classNames.nextElement();
                    String[] strategyAndRegion =
                            StringUtils.commaDelimitedListToStringArray(this.entityCacheStrategies.getProperty(className));
                    if (strategyAndRegion.length > 1) {
                        config.setCacheConcurrencyStrategy(className, strategyAndRegion[0], strategyAndRegion[1]);
                    }
                    else if (strategyAndRegion.length > 0) {
                        config.setCacheConcurrencyStrategy(className, strategyAndRegion[0]);
                    }
                }
            }

            if (this.collectionCacheStrategies != null) {
                // Register cache strategies for mapped collections.
                for (Enumeration collRoles = this.collectionCacheStrategies.propertyNames(); collRoles.hasMoreElements();) {
                    String collRole = (String) collRoles.nextElement();
                    String[] strategyAndRegion =
                            StringUtils.commaDelimitedListToStringArray(this.collectionCacheStrategies.getProperty(collRole));
                    if (strategyAndRegion.length > 1) {
                        config.setCollectionCacheConcurrencyStrategy(collRole, strategyAndRegion[0], strategyAndRegion[1]);
                    }
                    else if (strategyAndRegion.length > 0) {
                        config.setCollectionCacheConcurrencyStrategy(collRole, strategyAndRegion[0]);
                    }
                }
            }

            if (this.eventListeners != null) {
                // Register specified Hibernate event listeners.
                for (Iterator it = this.eventListeners.entrySet().iterator(); it.hasNext();) {
                    Map.Entry entry = (Map.Entry) it.next();
                    Assert.isTrue(entry.getKey() instanceof String, "Event listener key needs to be of type String");
                    String listenerType = (String) entry.getKey();
                    Object listenerObject = entry.getValue();
                    if (listenerObject instanceof Collection) {
                        Collection listeners = (Collection) listenerObject;
                        EventListeners listenerRegistry = config.getEventListeners();
                        Object[] listenerArray =
                                (Object[]) Array.newInstance(listenerRegistry.getListenerClassFor(listenerType), listeners.size());
                        listenerArray = listeners.toArray(listenerArray);
                        config.setListeners(listenerType, listenerArray);
                    }
                    else {
                        config.setListener(listenerType, listenerObject);
                    }
                }
            }

            // Perform custom post-processing in subclasses.
            postProcessConfiguration(config);

            // 这里是根据Configuration配置创建SessionFactory的地方
            logger.info("Building new Hibernate SessionFactory");
            this.configuration = config;
            sf = newSessionFactory(config);
        }
        //最后把和线程绑定的资源清空
        finally {
            if (this.dataSource != null) {
                // Reset DataSource holder.
                configTimeDataSourceHolder.set(null);
            }

            if (this.jtaTransactionManager != null) {
                // Reset TransactionManager holder.
                configTimeTransactionManagerHolder.set(null);
            }

            if (this.lobHandler != null) {
                // Reset LobHandler holder.
                configTimeLobHandlerHolder.set(null);
            }
        }

        // Execute schema update if requested.
        if (this.schemaUpdate) {
            updateDatabaseSchema();
        }

        return sf;
    }

而直接调用org.hibernate.cfg.Configuration来得到需要的SessionFactory:

protected SessionFactory newSessionFactory(Configuration config) throws HibernateException {
    return config.buildSessionFactory();
}

    protected SessionFactory newSessionFactory(Configuration config) throws HibernateException {
        return config.buildSessionFactory();
    }

所以我们这里看到LocalSessionFactory大致起到的一个读取资源配置然后生成SessionFactory的作用；当然这里在得到 SessionFactory之后，还需要对session的事务管理作一些处理 - 使用了一个Proxy模式对getCurrentSession方法进行了拦截；

//这里先根据当前的SessionFactory的类型得到Proxy，然后插入Spring定义好的getCurrentSession拦截器
    protected SessionFactory getTransactionAwareSessionFactoryProxy(SessionFactory target) {
        Class sfInterface = SessionFactory.class;
        if (target instanceof SessionFactoryImplementor) {
            sfInterface = SessionFactoryImplementor.class;
        }
        return (SessionFactory) Proxy.newProxyInstance(sfInterface.getClassLoader(),
                new Class[] {sfInterface}, new TransactionAwareInvocationHandler(target));
    }

//这里先根据当前的SessionFactory的类型得到Proxy，然后插入Spring定义好的getCurrentSession拦截器
    protected SessionFactory getTransactionAwareSessionFactoryProxy(SessionFactory target) {
        Class sfInterface = SessionFactory.class;
        if (target instanceof SessionFactoryImplementor) {
            sfInterface = SessionFactoryImplementor.class;
        }
        return (SessionFactory) Proxy.newProxyInstance(sfInterface.getClassLoader(),
                new Class[] {sfInterface}, new TransactionAwareInvocationHandler(target));
    }

拦截器的实现如下：

private static class TransactionAwareInvocationHandler implements InvocationHandler {

    private final SessionFactory target;

    public TransactionAwareInvocationHandler(SessionFactory target) {
        this.target = target;
    }

    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        // Invocation on SessionFactory/SessionFactoryImplementor interface coming in...
        // 这里对getCurrentSession方法进行拦截，得到一个和当前事务绑定的session交给用户
        if (method.getName().equals("getCurrentSession")) {
            // Handle getCurrentSession method: return transactional Session, if any.
            try {
                return SessionFactoryUtils.doGetSession((SessionFactory) proxy, false);
            }
            catch (IllegalStateException ex) {
                throw new HibernateException(ex.getMessage());
            }
        }
        else if (method.getName().equals("equals")) {
            // Only consider equal when proxies are identical.
            return (proxy == args[0] ? Boolean.TRUE : Boolean.FALSE);
        }
        else if (method.getName().equals("hashCode")) {
            // Use hashCode of SessionFactory proxy.
            return new Integer(hashCode());
        }

        // 这里是需要运行的SessionFactory的目标方法
        try {
            return method.invoke(this.target, args);
        }
        catch (InvocationTargetException ex) {
            throw ex.getTargetException();
        }
    }
}

    private static class TransactionAwareInvocationHandler implements InvocationHandler {

        private final SessionFactory target;

        public TransactionAwareInvocationHandler(SessionFactory target) {
            this.target = target;
        }

        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            // Invocation on SessionFactory/SessionFactoryImplementor interface coming in...
            // 这里对getCurrentSession方法进行拦截，得到一个和当前事务绑定的session交给用户
            if (method.getName().equals("getCurrentSession")) {
                // Handle getCurrentSession method: return transactional Session, if any.
                try {
                    return SessionFactoryUtils.doGetSession((SessionFactory) proxy, false);
                }
                catch (IllegalStateException ex) {
                    throw new HibernateException(ex.getMessage());
                }
            }
            else if (method.getName().equals("equals")) {
                // Only consider equal when proxies are identical.
                return (proxy == args[0] ? Boolean.TRUE : Boolean.FALSE);
            }
            else if (method.getName().equals("hashCode")) {
                // Use hashCode of SessionFactory proxy.
                return new Integer(hashCode());
            }

            // 这里是需要运行的SessionFactory的目标方法
            try {
                return method.invoke(this.target, args);
            }
            catch (InvocationTargetException ex) {
                throw ex.getTargetException();


  


  

    
    
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