spring bean的加载
2015-12-23 20:22
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一般调用方式是
首先获取BeanFactory(DefaultListableBeanFactory类),然后调用AbstractBeanFactory类中的getBean方法
真正的调用在doGetBean中
[code]MyJavaBean bean = (MyJavaBean) bf.getBean("myJavaBean");
首先获取BeanFactory(DefaultListableBeanFactory类),然后调用AbstractBeanFactory类中的getBean方法
[code]@Override public Object getBean(String name) throws BeansException { assertBeanFactoryActive(); return getBeanFactory().getBean(name); }
[code]@Override public Object getBean(String name) throws BeansException { return doGetBean(name, null, null, false); }
真正的调用在doGetBean中
[code]protected <T> T doGetBean( final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly) throws BeansException { //获取beanName 主要为处理别名和&beanName这两种形式 final String beanName = transformedBeanName(name); Object bean; /** 分别从singletonObjects(beanName->beanName instance),earlySingletonObjects(beanName->beanName instance)主要用于检测循环引用,可以在bean还在创建的过程中提前获取bean,singletonFactories(beanName->objectFactory)三个缓存中获取bean */ Object sharedInstance = getSingleton(beanName); if (sharedInstance != null && args == null) { if (logger.isDebugEnabled()) { if (isSingletonCurrentlyInCreation(beanName)) { logger.debug("Returning eagerly cached instance of singleton bean '" + beanName + "' that is not fully initialized yet - a consequence of a circular reference"); } else { logger.debug("Returning cached instance of singleton bean '" + beanName + "'"); } } /** 如果通过缓存获取到了bean的实例,还需要对该实例进行验证 因为不管是从缓存中获取到的bean还是我们通过不同的scope策略加载的bean,都是bean的原始形式,不一定是我们最终需要的bean 例如我们定义一个工厂bean,那么此时获取的是工厂bean本身,但实际上我们需要的是bean中定义的factory-bean方法返回的bean */ bean = getObjectForBeanInstance(sharedInstance, name, beanName, null); } else { //如果没有从缓存中获取bean实例,首先检查是否存在循环引用,只有在单例情况下才尝试解决循环引用 if (isPrototypeCurrentlyInCreation(beanName)) { throw new BeanCurrentlyInCreationException(beanName); } //若已经加载的BeanDefinition中不包含该beanName,则从(父容器)parentBeanFactory中检测,若存在,则调用parentBeanFactory加载该bean BeanFactory parentBeanFactory = getParentBeanFactory(); if (parentBeanFactory != null && !containsBeanDefinition(beanName)) { // Not found -> check parent. String nameToLookup = originalBeanName(name); if (args != null) { // Delegation to parent with explicit args. return (T) parentBeanFactory.getBean(nameToLookup, args); } else { // No args -> delegate to standard getBean method. return parentBeanFactory.getBean(nameToLookup, requiredType); } } //如果不仅仅做类型检测则是要创建bean,在这里做记录,并清除mergedBeanDefinitions中的缓存 if (!typeCheckOnly) { markBeanAsCreated(beanName); } try { /** (1)验证beanName对应的BeanDefinition是否存在 若不存在直接抛异常 (2)若该bean是子bean则要合并父类的相关属性 (3)合并后要验证mergedBeanDefinition,该bean不能为抽象bean */ final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName); checkMergedBeanDefinition(mbd, beanName, args); //若存在依赖则递归实例化依赖的bean,该依赖由depends-on属性引入 String[] dependsOn = mbd.getDependsOn(); if (dependsOn != null) { for (String dependsOnBean : dependsOn) { if (isDependent(beanName, dependsOnBean)) { throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Circular depends-on relationship between '" + beanName + "' and '" + dependsOnBean + "'"); } registerDependentBean(dependsOnBean, beanName); getBean(dependsOnBean); } } //根据不同的scope创建bean的实例 if (mbd.isSingleton()) { sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() { @Override public Object getObject() throws BeansException { try { return createBean(beanName, mbd, args); } catch (BeansException ex) { // Explicitly remove instance from singleton cache: It might have been put there // eagerly by the creation process, to allow for circular reference resolution. // Also remove any beans that received a temporary reference to the bean. destroySingleton(beanName); throw ex; } } }); bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd); } else if (mbd.isPrototype()) { // It's a prototype -> create a new instance. Object prototypeInstance = null; try { beforePrototypeCreation(beanName); prototypeInstance = createBean(beanName, mbd, args); } finally { afterPrototypeCreation(beanName); } bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd); } else { String scopeName = mbd.getScope(); final Scope scope = this.scopes.get(scopeName); if (scope == null) { throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'"); } try { Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() { @Override public Object getObject() throws BeansException { beforePrototypeCreation(beanName); try { return createBean(beanName, mbd, args); } finally { afterPrototypeCreation(beanName); } } }); bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd); } catch (IllegalStateException ex) { throw new BeanCreationException(beanName, "Scope '" + scopeName + "' is not active for the current thread; consider " + "defining a scoped proxy for this bean if you intend to refer to it from a singleton", ex); } } } catch (BeansException ex) { cleanupAfterBeanCreationFailure(beanName); throw ex; } } //检查获取的bean实例是否符合bean的实际类型 if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) { try { return getTypeConverter().convertIfNecessary(bean, requiredType); } catch (TypeMismatchException ex) { if (logger.isDebugEnabled()) { logger.debug("Failed to convert bean '" + name + "' to required type [" + ClassUtils.getQualifiedName(requiredType) + "]", ex); } throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass()); } } return (T) bean; }
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