标签：isp 流程图 ignore ini eating 为我 callback 属性 guarantee
首先说一点，因为Spring中的对象默认为单例，想要获取它默认init_lazy默认为false。
下面的图是整个流程的流程图，下面跟的源码解析就是按照这个流程来的。
至于基于XML依赖注入的过程，首先要找一个比较合适的入口，那就是getBean。那么具体是怎么实现的呢？首先写个测试方法：
ClassPathXmlApplicationContext app = new ClassPathXmlApplicationContext("application-common.xml","application-beans.xml","application_jdbc.xml"); Object obj = app.getBean("member");
第一句在我上篇文章---Spring-BeanFactory基本工作流程中就用到了，主要是作为一个初始化IOC容器的入口，那么我们现在的场景是：IOC容器已经创建好，我们在XML文件中配置的信息已经加载到BeanDefinition中了，那么我们现在的目的就是去获得它。第二句就是我们本篇文章的入口：getBean。
@Override public Object getBean(String name) throws BeansException { assertBeanFactoryActive(); return getBeanFactory().getBean(name); }
首先执行的是assertBeanFactoryActive方法，本人在上一篇分析Spring源码的时候就已经赞誉过Spring方法的命名，我们可以通过这个名字来判断它到底有什么意思，首先说明它是一个断言方法，然后判断的事BeanFactory是不是Active的，如果不是就直接抛异常了。
protected void assertBeanFactoryActive() { if (!this.active.get()) { if (this.closed.get()) { throw new IllegalStateException(getDisplayName() + " has been closed already"); } else { throw new IllegalStateException(getDisplayName() + " has not been refreshed yet"); } } }
然后我们接着看getBean方法，可以看到，它会调getBeanFactory方法，他返回的是一个BeanFactory，然后调BeanFactory中的getBean方法：
在之前的文章中提到过，Spring中做实事的方法都是以do开头的，我们可以看到，在getBean方法中调用了一个doGetBean方法，看名字可以了解到是真正拿到Bean的方法，在doGetBean方法中，首先先将我们传进来的指定的名字转化为管理Bean的名字，然后再创建一个名为bean的Object对象，作为我们要返回的实例。由于我们依赖注入的对象为单例，所以我们要做的就是首先在cache中检查有没有已经创建好的实例。（Spring中从BeanDefinition创建的Bean不是存放在IOC中，而是存放在Cache容器中，IOC只是存放Bean关系），如果有Bean存在，就直接返回，如果Cache中没有这个Bean，那么就要创建它。
在我们要自己创建Bean的时候，首先先检查这个Bean有没有相关的BeanDefinition，首先要解析出Bean的原始名称，然后现在当前BeanFactory里检查，如果没有，就去父BeanFactory里面找，如果还是找不到则沿着容器的继承体系向父级容器查找。当当前容器的父亲容器存在而且在当前容器中找不到这个bean时，就开始在父容器里找，会找父级BeanFactory的getBean方法。
如果在当前的Bean里面有，则首先向容器中标记这个Bean已经被创建了，然后根据指定Bean名称获取其父级的Bean定义，主要解决Bean继承时子类合并父类公共属性问题。接着获取该Bean所有依赖Bean的名称，如果有依赖Bean存在，那么就递归获取依赖Bean，并将依赖Bean注册给当前的Bean。
针对于Bean的类型（单例还是原型），Spring在创建Bean的过程都不一样，先看如果创建单例Bean的方法，首先看一下Spring在这是怎么处理的，它先使用一个内部匿名类，就是一个SingletonFactory类，然后将Bean实际名、Bean的BeanDefinition和Bean参数传入createBean方法（在下面会分析细节分析这个方法，这边只是大致过一下doGetBean方法）。并返回创建出的Bean实例。同样的，如果是一个原型Bean，因为每次都会建立一个新的实例，然后将获得的实例返回给之前创建的bean。如果Bean既不是单例，也不是原型的话，那么就要根据Bean定义资源中配置的生命周期范围来选择合适的实例化Bean方法（这种情况出现在web那块比较多，如session，reques等）。
最后要对创建好的Bean进行检查，如果符合规范，就认为创建好了并且返回。
//AbstractBeanFactory.class //获取IOC容器中指定名称的Bean @Override public Object getBean(String name) throws BeansException { //doGetBean才是真正向IoC容器获取被管理Bean的过程 return doGetBean(name, null, null, false); }
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2 //真正实现向IOC容器获取Bean的功能，也是触发依赖注入功能的地方 3 protected <T> T doGetBean(final String name, @Nullable final Class<T> requiredType, 4 @Nullable final Object[] args, boolean typeCheckOnly) throws BeansException { 5 6 //根据指定的名称获取被管理Bean的名称，剥离指定名称中对容器的相关依赖 7 //如果指定的是别名，将别名转换为规范的Bean名称 8 final String beanName = transformedBeanName(name); 9 Object bean; 10 11 // Eagerly check singleton cache for manually registered singletons. 12 //先从缓存中取是否已经有被创建过的单态类型的Bean 13 //对于单例模式的Bean整个IOC容器中只创建一次，不需要重复创建 14 Object sharedInstance = getSingleton(beanName); 15 //IOC容器创建单例模式Bean实例对象 16 if (sharedInstance != null && args == null) { 17 if (logger.isDebugEnabled()) { 18 //如果指定名称的Bean在容器中已有单例模式的Bean被创建 19 //直接返回已经创建的Bean 20 if (isSingletonCurrentlyInCreation(beanName)) { 21 logger.debug("Returning eagerly cached instance of singleton bean ‘" + beanName + 22 "‘ that is not fully initialized yet - a consequence of a circular reference"); 23 } 24 else { 25 logger.debug("Returning cached instance of singleton bean ‘" + beanName + "‘"); 26 } 27 } 28 //获取给定Bean的实例对象，主要是完成FactoryBean的相关处理 29 //注意：BeanFactory是管理容器中Bean的工厂，而FactoryBean是 30 //创建创建对象的工厂Bean，两者之间有区别 31 bean = getObjectForBeanInstance(sharedInstance, name, beanName, null); 32 } 33 34 else { 35 // Fail if we‘re already creating this bean instance: 36 // We‘re assumably within a circular reference. 37 //缓存没有正在创建的单例模式Bean 38 //缓存中已经有已经创建的原型模式Bean 39 //但是由于循环引用的问题导致实例化对象失败 40 if (isPrototypeCurrentlyInCreation(beanName)) { 41 throw new BeanCurrentlyInCreationException(beanName); 42 } 43 44 // Check if bean definition exists in this factory. 45 //对IOC容器中是否存在指定名称的BeanDefinition进行检查，首先检查是否 46 //能在当前的BeanFactory中获取的所需要的Bean，如果不能则委托当前容器 47 //的父级容器去查找，如果还是找不到则沿着容器的继承体系向父级容器查找 48 BeanFactory parentBeanFactory = getParentBeanFactory(); 49 //当前容器的父级容器存在，且当前容器中不存在指定名称的Bean 50 if (parentBeanFactory != null && !containsBeanDefinition(beanName)) { 51 // Not found -> check parent. 52 //解析指定Bean名称的原始名称 53 String nameToLookup = originalBeanName(name); 54 if (parentBeanFactory instanceof AbstractBeanFactory) { 55 return ((AbstractBeanFactory) parentBeanFactory).doGetBean( 56 nameToLookup, requiredType, args, typeCheckOnly); 57 } 58 else if (args != null) { 59 // Delegation to parent with explicit args. 60 //委派父级容器根据指定名称和显式的参数查找 61 return (T) parentBeanFactory.getBean(nameToLookup, args); 62 } 63 else { 64 // No args -> delegate to standard getBean method. 65 //委派父级容器根据指定名称和类型查找 66 return parentBeanFactory.getBean(nameToLookup, requiredType); 67 } 68 } 69 70 //创建的Bean是否需要进行类型验证，一般不需要 71 if (!typeCheckOnly) { 72 //向容器标记指定的Bean已经被创建 73 markBeanAsCreated(beanName); 74 } 75 76 try { 77 //根据指定Bean名称获取其父级的Bean定义 78 //主要解决Bean继承时子类合并父类公共属性问题 79 final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName); 80 checkMergedBeanDefinition(mbd, beanName, args); 81 82 // Guarantee initialization of beans that the current bean depends on. 83 //获取当前Bean所有依赖Bean的名称 84 String[] dependsOn = mbd.getDependsOn(); 85 //如果当前Bean有依赖Bean 86 if (dependsOn != null) { 87 for (String dep : dependsOn) { 88 if (isDependent(beanName, dep)) { 89 throw new BeanCreationException(mbd.getResourceDescription(), beanName, 90 "Circular depends-on relationship between ‘" + beanName + "‘ and ‘" + dep + "‘"); 91 } 92 //递归调用getBean方法，获取当前Bean的依赖Bean 93 registerDependentBean(dep, beanName); 94 //把被依赖Bean注册给当前依赖的Bean 95 getBean(dep); 96 } 97 } 98 99 // Create bean instance. 100 //创建单例模式Bean的实例对象 101 if (mbd.isSingleton()) { 102 //这里使用了一个匿名内部类，创建Bean实例对象，并且注册给所依赖的对象 103 sharedInstance = getSingleton(beanName, () -> { 104 try { 105 //创建一个指定Bean实例对象，如果有父级继承，则合并子类和父类的定义 106 return createBean(beanName, mbd, args); 107 } 108 catch (BeansException ex) { 109 // Explicitly remove instance from singleton cache: It might have been put there 110 // eagerly by the creation process, to allow for circular reference resolution. 111 // Also remove any beans that received a temporary reference to the bean. 112 //显式地从容器单例模式Bean缓存中清除实例对象 113 destroySingleton(beanName); 114 throw ex; 115 } 116 }); 117 //获取给定Bean的实例对象 118 bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd); 119 } 120 121 //IOC容器创建原型模式Bean实例对象 122 else if (mbd.isPrototype()) { 123 // It‘s a prototype -> create a new instance. 124 //原型模式(Prototype)是每次都会创建一个新的对象 125 Object prototypeInstance = null; 126 try { 127 //回调beforePrototypeCreation方法，默认的功能是注册当前创建的原型对象 128 beforePrototypeCreation(beanName); 129 //创建指定Bean对象实例 130 prototypeInstance = createBean(beanName, mbd, args); 131 } 132 finally { 133 //回调afterPrototypeCreation方法，默认的功能告诉IOC容器指定Bean的原型对象不再创建 134 afterPrototypeCreation(beanName); 135 } 136 //获取给定Bean的实例对象 137 bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd); 138 } 139 140 //要创建的Bean既不是单例模式，也不是原型模式，则根据Bean定义资源中 141 //配置的生命周期范围，选择实例化Bean的合适方法，这种在Web应用程序中 142 //比较常用，如：request、session、application等生命周期 143 else { 144 String scopeName = mbd.getScope(); 145 final Scope scope = this.scopes.get(scopeName); 146 //Bean定义资源中没有配置生命周期范围，则Bean定义不合法 147 if (scope == null) { 148 throw new IllegalStateException("No Scope registered for scope name ‘" + scopeName + "‘"); 149 } 150 try { 151 //这里又使用了一个匿名内部类，获取一个指定生命周期范围的实例 152 Object scopedInstance = scope.get(beanName, () -> { 153 beforePrototypeCreation(beanName); 154 try { 155 return createBean(beanName, mbd, args); 156 } 157 finally { 158 afterPrototypeCreation(beanName); 159 } 160 }); 161 //获取给定Bean的实例对象 162 bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd); 163 } 164 catch (IllegalStateException ex) { 165 throw new BeanCreationException(beanName, 166 "Scope ‘" + scopeName + "‘ is not active for the current thread; consider " + 167 "defining a scoped proxy for this bean if you intend to refer to it from a singleton", 168 ex); 169 } 170 } 171 } 172 catch (BeansException ex) { 173 cleanupAfterBeanCreationFailure(beanName); 174 throw ex; 175 } 176 } 177 178 // Check if required type matches the type of the actual bean instance. 179 //对创建的Bean实例对象进行类型检查 180 if (requiredType != null && !requiredType.isInstance(bean)) { 181 try { 182 T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType); 183 if (convertedBean == null) { 184 throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass()); 185 } 186 return convertedBean; 187 } 188 catch (TypeMismatchException ex) { 189 if (logger.isDebugEnabled()) { 190 logger.debug("Failed to convert bean ‘" + name + "‘ to required type ‘" + 191 ClassUtils.getQualifiedName(requiredType) + "‘", ex); 192 } 193 throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass()); 194 } 195 } 196 return (T) bean; 197 }
上面比较详细的介绍了Bean实例是如何创建的，那么接下来主要是重点分析一下几个比较重要的方法的细节。先说一下如果Cache容器中有之前已经创建过的该Bean的实例，在31行，我们进入getObjectForBeanInstance方法。
我们已经拿到了在Cache中拿到了该Bean的FactoryBean,在这说一下FactoryBean和BeanFactory的区别，FactoryBean是用来创建生产Bean的工厂的Bean（有点绕）而BeanFactory是管理Bean的工厂。然后进入getObjectForBeanInstance方法，首先我们会去判断这个Bean是不是一个工厂Bean，如果不是工厂Bean，或者说我们想要得到的就是一个工厂，那么就直接返回它。如果是工厂Bean并且我们要得到的是一个Bean实例，那么首先看一下工厂Bean的缓存中有木有实例，如果有就返回，如果没有，就会调用getObjectFromFactoryBean方法来获得Bean实例。
protected Object getObjectForBeanInstance( Object beanInstance, String name, String beanName, @Nullable RootBeanDefinition mbd) { // Don‘t let calling code try to dereference the factory if the bean isn‘t a factory. //容器已经得到了Bean实例对象，这个实例对象可能是一个普通的Bean， //也可能是一个工厂Bean，如果是一个工厂Bean，则使用它创建一个Bean实例对象， //如果调用本身就想获得一个容器的引用，则指定返回这个工厂Bean实例对象 //如果指定的名称是容器的解引用(dereference，即是对象本身而非内存地址)， //且Bean实例也不是创建Bean实例对象的工厂Bean if (BeanFactoryUtils.isFactoryDereference(name) && !(beanInstance instanceof FactoryBean)) { throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass()); } // Now we have the bean instance, which may be a normal bean or a FactoryBean. // If it‘s a FactoryBean, we use it to create a bean instance, unless the // caller actually wants a reference to the factory. //如果Bean实例不是工厂Bean，或者指定名称是容器的解引用， //调用者向获取对容器的引用，则直接返回当前的Bean实例 if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) { return beanInstance; } //处理指定名称不是容器的解引用，或者根据名称获取的Bean实例对象是一个工厂Bean //使用工厂Bean创建一个Bean的实例对象 Object object = null; if (mbd == null) { //从Bean工厂缓存中获取给定名称的Bean实例对象 object = getCachedObjectForFactoryBean(beanName); } //让Bean工厂生产给定名称的Bean对象实例 if (object == null) { // Return bean instance from factory. FactoryBean<?> factory = (FactoryBean<?>) beanInstance; // Caches object obtained from FactoryBean if it is a singleton. //如果从Bean工厂生产的Bean是单态模式的，则缓存 if (mbd == null && containsBeanDefinition(beanName)) { //从容器中获取指定名称的Bean定义，如果继承基类，则合并基类相关属性 mbd = getMergedLocalBeanDefinition(beanName); } //如果从容器得到Bean定义信息，并且Bean定义信息不是虚构的， //则让工厂Bean生产Bean实例对象 boolean synthetic = (mbd != null && mbd.isSynthetic()); //调用FactoryBeanRegistrySupport类的getObjectFromFactoryBean方法， //实现工厂Bean生产Bean对象实例的过程 object = getObjectFromFactoryBean(factory, beanName, !synthetic); } return object; }
接下来我们看一看是怎么从FactoryBean里拿到Bean实例的，先进入getObjectFromFactoryBean方法。
//Bean工厂生产Bean实例对象 protected Object getObjectFromFactoryBean(FactoryBean<?> factory, String beanName, boolean shouldPostProcess) { //Bean工厂是单态模式，并且Bean工厂缓存中存在指定名称的Bean实例对象 if (factory.isSingleton() && containsSingleton(beanName)) { //多线程同步，以防止数据不一致 synchronized (getSingletonMutex()) { //直接从Bean工厂缓存中获取指定名称的Bean实例对象 Object object = this.factoryBeanObjectCache.get(beanName); //Bean工厂缓存中没有指定名称的实例对象，则生产该实例对象 if (object == null) { //调用Bean工厂的getObject方法生产指定Bean的实例对象 object = doGetObjectFromFactoryBean(factory, beanName); // Only post-process and store if not put there already during getObject() call above // (e.g. because of circular reference processing triggered by custom getBean calls) Object alreadyThere = this.factoryBeanObjectCache.get(beanName); if (alreadyThere != null) { object = alreadyThere; } else { if (shouldPostProcess) { try { object = postProcessObjectFromFactoryBean(object, beanName); } catch (Throwable ex) { throw new BeanCreationException(beanName, "Post-processing of FactoryBean‘s singleton object failed", ex); } } //将生产的实例对象添加到Bean工厂缓存中 this.factoryBeanObjectCache.put(beanName, object); } } return object; } } //调用Bean工厂的getObject方法生产指定Bean的实例对象 else { Object object = doGetObjectFromFactoryBean(factory, beanName); if (shouldPostProcess) { try { object = postProcessObjectFromFactoryBean(object, beanName); } catch (Throwable ex) { throw new BeanCreationException(beanName, "Post-processing of FactoryBean‘s object failed", ex); } } return object; } }
由于我们现在创建的Bean为单例模式，所以要保证线程安全，首先先判断在FactoryBean里有没有该Bean的缓存，如果没有就自己创建，方法为doGetBeanFromFactoryBean，并且将创建好的Bean存到Cache里。那么我们到现在又看到了一个做实事的方法，看名字这个方法应该是生产Bean的方法。
//调用Bean工厂的getObject方法生产指定Bean的实例对象 private Object doGetObjectFromFactoryBean(final FactoryBean<?> factory, final String beanName) throws BeanCreationException { Object object; try { if (System.getSecurityManager() != null) { AccessControlContext acc = getAccessControlContext(); try { //实现PrivilegedExceptionAction接口的匿名内置类 //根据JVM检查权限，然后决定BeanFactory创建实例对象 object = AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> factory.getObject(), acc); } catch (PrivilegedActionException pae) { throw pae.getException(); } } else { //调用BeanFactory接口实现类的创建对象方法 object = factory.getObject(); } } catch (FactoryBeanNotInitializedException ex) { throw new BeanCurrentlyInCreationException(beanName, ex.toString()); } catch (Throwable ex) { throw new BeanCreationException(beanName, "FactoryBean threw exception on object creation", ex); } // Do not accept a null value for a FactoryBean that‘s not fully // initialized yet: Many FactoryBeans just return null then. //创建出来的实例对象为null，或者因为单态对象正在创建而返回null if (object == null) { if (isSingletonCurrentlyInCreation(beanName)) { throw new BeanCurrentlyInCreationException( beanName, "FactoryBean which is currently in creation returned null from getObject"); } object = new NullBean(); } return object; }
通过这个方法，我们就得到了单例Bean的实例（不管它有没有在Cache里存在）。
同样，如果缓存中没有被创建的Bean，那么在之前那段代码中（doGetBean），就不会走31行那一块，而是接着往下走，到101行，执行到createBean方法，这里用到了lamda表达式，new了一个内部类objectFactory。
//AbstractAutowireCapableBeanFactory.class //创建Bean实例对象 @Override protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) throws BeanCreationException { if (logger.isDebugEnabled()) { logger.debug("Creating instance of bean ‘" + beanName + "‘"); } RootBeanDefinition mbdToUse = mbd; // Make sure bean class is actually resolved at this point, and // clone the bean definition in case of a dynamically resolved Class // which cannot be stored in the shared merged bean definition. //判断需要创建的Bean是否可以实例化，即是否可以通过当前的类加载器加载 Class<?> resolvedClass = resolveBeanClass(mbd, beanName); if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) { mbdToUse = new RootBeanDefinition(mbd); mbdToUse.setBeanClass(resolvedClass); } // Prepare method overrides. //校验和准备Bean中的方法覆盖 try { mbdToUse.prepareMethodOverrides(); } catch (BeanDefinitionValidationException ex) { throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(), beanName, "Validation of method overrides failed", ex); } try { // Give BeanPostProcessors a chance to return a proxy instead of the target bean instance. //如果Bean配置了初始化前和初始化后的处理器，则试图返回一个需要创建Bean的代理对象 Object bean = resolveBeforeInstantiation(beanName, mbdToUse); if (bean != null) { return bean; } } catch (Throwable ex) { throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName, "BeanPostProcessor before instantiation of bean failed", ex); } try { //创建Bean的入口 Object beanInstance = doCreateBean(beanName, mbdToUse, args); if (logger.isDebugEnabled()) { logger.debug("Finished creating instance of bean ‘" + beanName + "‘"); } return beanInstance; } catch (BeanCreationException ex) { // A previously detected exception with proper bean creation context already... throw ex; } catch (ImplicitlyAppearedSingletonException ex) { // An IllegalStateException to be communicated up to DefaultSingletonBeanRegistry... throw ex; } catch (Throwable ex) { throw new BeanCreationException( mbdToUse.getResourceDescription(), beanName, "Unexpected exception during bean creation", ex); } }
在这里，会调用doCreateBean方法
//AbstractAutowireCapableBeanFactory.class //真正创建Bean的方法 protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args) throws BeanCreationException { // Instantiate the bean. //封装被创建的Bean对象 BeanWrapper instanceWrapper = null; if (mbd.isSingleton()) { instanceWrapper = this.factoryBeanInstanceCache.remove(beanName); } if (instanceWrapper == null) { instanceWrapper = createBeanInstance(beanName, mbd, args); } final Object bean = instanceWrapper.getWrappedInstance(); //获取实例化对象的类型 Class<?> beanType = instanceWrapper.getWrappedClass(); if (beanType != NullBean.class) { mbd.resolvedTargetType = beanType; } // Allow post-processors to modify the merged bean definition. //调用PostProcessor后置处理器 synchronized (mbd.postProcessingLock) { if (!mbd.postProcessed) { try { applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName); } catch (Throwable ex) { throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Post-processing of merged bean definition failed", ex); } mbd.postProcessed = true; } } // Eagerly cache singletons to be able to resolve circular references // even when triggered by lifecycle interfaces like BeanFactoryAware. //向容器中缓存单例模式的Bean对象，以防循环引用 boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences && isSingletonCurrentlyInCreation(beanName)); if (earlySingletonExposure) { if (logger.isDebugEnabled()) { logger.debug("Eagerly caching bean ‘" + beanName + "‘ to allow for resolving potential circular references"); } //这里是一个匿名内部类，为了防止循环引用，尽早持有对象的引用 addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean)); } // Initialize the bean instance. //Bean对象的初始化，依赖注入在此触发 //这个exposedObject在初始化完成之后返回作为依赖注入完成后的Bean Object exposedObject = bean; try { //将Bean实例对象封装，并且Bean定义中配置的属性值赋值给实例对象 populateBean(beanName, mbd, instanceWrapper); //初始化Bean对象 exposedObject = initializeBean(beanName, exposedObject, mbd); } catch (Throwable ex) { if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) { throw (BeanCreationException) ex; } else { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex); } } if (earlySingletonExposure) { //获取指定名称的已注册的单例模式Bean对象 Object earlySingletonReference = getSingleton(beanName, false); if (earlySingletonReference != null) { //根据名称获取的已注册的Bean和正在实例化的Bean是同一个 if (exposedObject == bean) { //当前实例化的Bean初始化完成 exposedObject = earlySingletonReference; } //当前Bean依赖其他Bean，并且当发生循环引用时不允许新创建实例对象 else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) { String[] dependentBeans = getDependentBeans(beanName); Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length); //获取当前Bean所依赖的其他Bean for (String dependentBean : dependentBeans) { //对依赖Bean进行类型检查 if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) { actualDependentBeans.add(dependentBean); } } if (!actualDependentBeans.isEmpty()) { throw new BeanCurrentlyInCreationException(beanName, "Bean with name ‘" + beanName + "‘ has been injected into other beans [" + StringUtils.collectionToCommaDelimitedString(actualDependentBeans) + "] in its raw version as part of a circular reference, but has eventually been " + "wrapped. This means that said other beans do not use the final version of the " + "bean. This is often the result of over-eager type matching - consider using " + "‘getBeanNamesOfType‘ with the ‘allowEagerInit‘ flag turned off, for example."); } } } } // Register bean as disposable. //注册完成依赖注入的Bean try { registerDisposableBeanIfNecessary(beanName, bean, mbd); } catch (BeanDefinitionValidationException ex) { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex); } return exposedObject; }
这里首先创建一个包装类，用到了BeanWrapper来包装Bean，然后到createBeanInstance方法使得生成一个Bean的Wrapper类。并保证容器缓存中有此Bean对象的单例模式。然后调用populateBean方法，将BeanDefinition的属性赋值给实例对象，并调用initializeBean方法初始化Bean对象。并对Bean对象进行一系列的检查，然后返回生成的Bean。
首先我们先看一下createBeanInstance方法，这个方法返回的是一个BeanWrapper对象，首先确定Bean是可以实例化的，然后就对Bean进行实例化。实例化的方法有三种：（1）工厂方法 （2）容器自动装配 （3）Bean的构造方法
protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) { // Make sure bean class is actually resolved at this point. //检查确认Bean是可实例化的 Class<?> beanClass = resolveBeanClass(mbd, beanName); //使用工厂方法对Bean进行实例化 if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) { throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Bean class isn‘t public, and non-public access not allowed: " + beanClass.getName()); } Supplier<?> instanceSupplier = mbd.getInstanceSupplier(); if (instanceSupplier != null) { return obtainFromSupplier(instanceSupplier, beanName); } if (mbd.getFactoryMethodName() != null) { //调用工厂方法实例化 return instantiateUsingFactoryMethod(beanName, mbd, args); } // Shortcut when re-creating the same bean... //使用容器的自动装配方法进行实例化 boolean resolved = false; boolean autowireNecessary = false; if (args == null) { synchronized (mbd.constructorArgumentLock) { if (mbd.resolvedConstructorOrFactoryMethod != null) { resolved = true; autowireNecessary = mbd.constructorArgumentsResolved; } } } if (resolved) { if (autowireNecessary) { //配置了自动装配属性，使用容器的自动装配实例化 //容器的自动装配是根据参数类型匹配Bean的构造方法 return autowireConstructor(beanName, mbd, null, null); } else { //使用默认的无参构造方法实例化 return instantiateBean(beanName, mbd); } } // Need to determine the constructor... //使用Bean的构造方法进行实例化 Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName); if (ctors != null || mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR || mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args)) { //使用容器的自动装配特性，调用匹配的构造方法实例化 return autowireConstructor(beanName, mbd, ctors, args); } // No special handling: simply use no-arg constructor. //使用默认的无参构造方法实例化 return instantiateBean(beanName, mbd); }
首先是工厂方法实例化Bean，调用的是instantiateUsingFactoryMethod方法，这边不详细分析了。
之后是使用容器自动装配来进行实例化，如果匹配了自动装配属性，那么久使用容器自动装配实例化，如果没有，则用构造方法进行实例化，这里说一下用构造方法进行实例化的过程
无参构造方法instantiateBean方法，这里就是实例Bean的方法。
//使用默认的无参构造方法实例化Bean对象 protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) { try { Object beanInstance; final BeanFactory parent = this; //获取系统的安全管理接口，JDK标准的安全管理API if (System.getSecurityManager() != null) { //这里是一个匿名内置类，根据实例化策略创建实例对象 beanInstance = AccessController.doPrivileged((PrivilegedAction<Object>) () -> getInstantiationStrategy().instantiate(mbd, beanName, parent), getAccessControlContext()); } else { //将实例化的对象封装起来 beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent); } BeanWrapper bw = new BeanWrapperImpl(beanInstance); initBeanWrapper(bw); return bw; } catch (Throwable ex) { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Instantiation of bean failed", ex); } }
首先实例对象，用到的是instantiate方法，然后再将其包装成BeanWrapper
然后到instantiate方法。
//使用初始化策略实例化Bean对象 @Override public Object instantiate(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner) { // Don‘t override the class with CGLIB if no overrides. //如果Bean定义中没有方法覆盖，则就不需要CGLIB父类类的方法 if (!bd.hasMethodOverrides()) { Constructor<?> constructorToUse; synchronized (bd.constructorArgumentLock) { //获取对象的构造方法或工厂方法 constructorToUse = (Constructor<?>) bd.resolvedConstructorOrFactoryMethod; //如果没有构造方法且没有工厂方法 if (constructorToUse == null) { //使用JDK的反射机制，判断要实例化的Bean是否是接口 final Class<?> clazz = bd.getBeanClass(); if (clazz.isInterface()) { throw new BeanInstantiationException(clazz, "Specified class is an interface"); } try { if (System.getSecurityManager() != null) { //这里是一个匿名内置类，使用反射机制获取Bean的构造方法 constructorToUse = AccessController.doPrivileged( (PrivilegedExceptionAction<Constructor<?>>) () -> clazz.getDeclaredConstructor()); } else { constructorToUse = clazz.getDeclaredConstructor(); } bd.resolvedConstructorOrFactoryMethod = constructorToUse; } catch (Throwable ex) { throw new BeanInstantiationException(clazz, "No default constructor found", ex); } } } //使用BeanUtils实例化，通过反射机制调用”构造方法.newInstance(arg)”来进行实例化 return BeanUtils.instantiateClass(constructorToUse); } else { // Must generate CGLIB subclass. //使用CGLIB来实例化对象 return instantiateWithMethodInjection(bd, beanName, owner); } }
首先检查Bean中有没有覆盖父类方法，如果没有的话，就不用CGLIB父类类的方法，然后通过反射获得Bean的构造方法，之后通过BeanUtils使用构造方法进行实例化。如果有覆盖方法，那么就要使用CGLIB来进行实例化
然后调用instantiateWithMethodInjection方法
@Override protected Object instantiateWithMethodInjection(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner) { return instantiateWithMethodInjection(bd, beanName, owner, null); }
@Override protected Object instantiateWithMethodInjection(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner, @Nullable Constructor<?> ctor, @Nullable Object... args) { // Must generate CGLIB subclass... return new CglibSubclassCreator(bd, owner).instantiate(ctor, args); }
到这里可以看到调用使用CGLIB的instantiate方法。
public Object instantiate(@Nullable Constructor<?> ctor, @Nullable Object... args) { //创建代理子类 Class<?> subclass = createEnhancedSubclass(this.beanDefinition); Object instance; if (ctor == null) { instance = BeanUtils.instantiateClass(subclass); } else { try { Constructor<?> enhancedSubclassConstructor = subclass.getConstructor(ctor.getParameterTypes()); instance = enhancedSubclassConstructor.newInstance(args); } catch (Exception ex) { throw new BeanInstantiationException(this.beanDefinition.getBeanClass(), "Failed to invoke constructor for CGLIB enhanced subclass [" + subclass.getName() + "]", ex); } } // SPR-10785: set callbacks directly on the instance instead of in the // enhanced class (via the Enhancer) in order to avoid memory leaks. Factory factory = (Factory) instance; factory.setCallbacks(new Callback[] {NoOp.INSTANCE, new LookupOverrideMethodInterceptor(this.beanDefinition, this.owner), new ReplaceOverrideMethodInterceptor(this.beanDefinition, this.owner)}); return instance; }
然后调用instantiateClass方法
public static <T> T instantiateClass(Class<T> clazz) throws BeanInstantiationException { Assert.notNull(clazz, "Class must not be null"); if (clazz.isInterface()) { throw new BeanInstantiationException(clazz, "Specified class is an interface"); } try { Constructor<T> ctor = (KotlinDetector.isKotlinType(clazz) ? KotlinDelegate.findPrimaryConstructor(clazz) : clazz.getDeclaredConstructor()); if (ctor == null) { throw new BeanInstantiationException(clazz, "No default constructor found"); } return instantiateClass(ctor); } catch (NoSuchMethodException ex) { throw new BeanInstantiationException(clazz, "No default constructor found", ex); } }
public static <T> T instantiateClass(Constructor<T> ctor, Object... args) throws BeanInstantiationException { Assert.notNull(ctor, "Constructor must not be null"); try { ReflectionUtils.makeAccessible(ctor); return (KotlinDetector.isKotlinType(ctor.getDeclaringClass()) ? KotlinDelegate.instantiateClass(ctor, args) : ctor.newInstance(args)); } catch (InstantiationException ex) { throw new BeanInstantiationException(ctor, "Is it an abstract class?", ex); } catch (IllegalAccessException ex) { throw new BeanInstantiationException(ctor, "Is the constructor accessible?", ex); } catch (IllegalArgumentException ex) { throw new BeanInstantiationException(ctor, "Illegal arguments for constructor", ex); } catch (InvocationTargetException ex) { throw new BeanInstantiationException(ctor, "Constructor threw exception", ex.getTargetException()); } }
回到instantiateBean方法，我们得到了实例化的Bean对象，那么接下来就是将他封装起来。调用了BeanWrapperImpl的构造方法，并初始化这个BeanWrapper然后将其返回。
之后回到createBeanInstance方法，刚才介绍的是用无参构造函数方法将其进行实例化封装，接下来如果有参数，那么就会使用容器的自动装配特性，调用匹配的构造方法进行实例化。
再回到之前调用createBeanInstance方法的时候，也就是在AbstractAutowireCapableBeanFactory这个类里的doCreateBean方法中，会调用populateBean方法，这里就是真正的依赖注入。
1 //将Bean属性设置到生成的实例对象上 2 protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) { 3 if (bw == null) { 4 if (mbd.hasPropertyValues()) { 5 throw new BeanCreationException( 6 mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance"); 7 } 8 else { 9 // Skip property population phase for null instance. 10 return; 11 } 12 } 13 14 // Give any InstantiationAwareBeanPostProcessors the opportunity to modify the 15 // state of the bean before properties are set. This can be used, for example, 16 // to support styles of field injection. 17 boolean continueWithPropertyPopulation = true; 18 19 if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) { 20 for (BeanPostProcessor bp : getBeanPostProcessors()) { 21 if (bp instanceof InstantiationAwareBeanPostProcessor) { 22 InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; 23 if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) { 24 continueWithPropertyPopulation = false; 25 break; 26 } 27 } 28 } 29 } 30 31 if (!continueWithPropertyPopulation) { 32 return; 33 } 34 //获取容器在解析Bean定义资源时为BeanDefiniton中设置的属性值 35 PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null); 36 37 //对依赖注入处理，首先处理autowiring自动装配的依赖注入 38 if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME || 39 mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) { 40 MutablePropertyValues newPvs = new MutablePropertyValues(pvs); 41 42 // Add property values based on autowire by name if applicable. 43 //根据Bean名称进行autowiring自动装配处理 44 if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) { 45 autowireByName(beanName, mbd, bw, newPvs); 46 } 47 48 // Add property values based on autowire by type if applicable. 49 //根据Bean类型进行autowiring自动装配处理 50 if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) { 51 autowireByType(beanName, mbd, bw, newPvs); 52 } 53 54 pvs = newPvs; 55 } 56 57 //对非autowiring的属性进行依赖注入处理 58 59 boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors(); 60 boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE); 61 62 if (hasInstAwareBpps || needsDepCheck) { 63 if (pvs == null) { 64 pvs = mbd.getPropertyValues(); 65 } 66 PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching); 67 if (hasInstAwareBpps) { 68 for (BeanPostProcessor bp : getBeanPostProcessors()) { 69 if (bp instanceof InstantiationAwareBeanPostProcessor) { 70 InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; 71 pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName); 72 if (pvs == null) { 73 return; 74 } 75 } 76 } 77 } 78 if (needsDepCheck) { 79 checkDependencies(beanName, mbd, filteredPds, pvs); 80 } 81 } 82 83 if (pvs != null) { 84 //对属性进行注入 85 applyPropertyValues(beanName, mbd, bw, pvs); 86 } 87 }
首先会检查这个包装类是否为空，在保证不为空的前提下，首先获取BeanDefinition中的资源属性值，然后对其进行自动装配处理，最后对属性进行注入。
在populateBean方法的最后，会对属性进行注入，调用applyPropertyValues方法
//解析并注入依赖属性的过程 protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) { if (pvs.isEmpty()) { return; } //封装属性值 MutablePropertyValues mpvs = null; List<PropertyValue> original; if (System.getSecurityManager() != null) { if (bw instanceof BeanWrapperImpl) { //设置安全上下文，JDK安全机制 ((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext()); } } if (pvs instanceof MutablePropertyValues) { mpvs = (MutablePropertyValues) pvs; //属性值已经转换 if (mpvs.isConverted()) { // Shortcut: use the pre-converted values as-is. try { //为实例化对象设置属性值 bw.setPropertyValues(mpvs); return; } catch (BeansException ex) { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Error setting property values", ex); } } //获取属性值对象的原始类型值 original = mpvs.getPropertyValueList(); } else { original = Arrays.asList(pvs.getPropertyValues()); } //获取用户自定义的类型转换 TypeConverter converter = getCustomTypeConverter(); if (converter == null) { converter = bw; } //创建一个Bean定义属性值解析器，将Bean定义中的属性值解析为Bean实例对象的实际值 BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter); // Create a deep copy, resolving any references for values. //为属性的解析值创建一个拷贝，将拷贝的数据注入到实例对象中 List<PropertyValue> deepCopy = new ArrayList<>(original.size()); boolean resolveNecessary = false; for (PropertyValue pv : original) { //属性值不需要转换 if (pv.isConverted()) { deepCopy.add(pv); } //属性值需要转换 else { String propertyName = pv.getName(); //原始的属性值，即转换之前的属性值 Object originalValue = pv.getValue(); //转换属性值，例如将引用转换为IOC容器中实例化对象引用 Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue); //转换之后的属性值 Object convertedValue = resolvedValue; //属性值是否可以转换 boolean convertible = bw.isWritableProperty(propertyName) && !PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName); if (convertible) { //使用用户自定义的类型转换器转换属性值 convertedValue = convertForProperty(resolvedValue, propertyName, bw, converter); } // Possibly store converted value in merged bean definition, // in order to avoid re-conversion for every created bean instance. //存储转换后的属性值，避免每次属性注入时的转换工作 if (resolvedValue == originalValue) { if (convertible) { //设置属性转换之后的值 pv.setConvertedValue(convertedValue); } deepCopy.add(pv); } //属性是可转换的，且属性原始值是字符串类型，且属性的原始类型值不是 //动态生成的字符串，且属性的原始值不是集合或者数组类型 else if (convertible && originalValue instanceof TypedStringValue && !((TypedStringValue) originalValue).isDynamic() && !(convertedValue instanceof Collection || ObjectUtils.isArray(convertedValue))) { pv.setConvertedValue(convertedValue); //重新封装属性的值 deepCopy.add(pv); } else { resolveNecessary = true; deepCopy.add(new PropertyValue(pv, convertedValue)); } } } if (mpvs != null && !resolveNecessary) { //标记属性值已经转换过 mpvs.setConverted(); } // Set our (possibly massaged) deep copy. //进行属性依赖注入 try { bw.setPropertyValues(new MutablePropertyValues(deepCopy)); } catch (BeansException ex) { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Error setting property values", ex); } }
在这里核心调用的是resolveValueIfNecessary方法，将BeanDefinition里的一些属性解析出来，通过反射new出来一个对象。BeanDefinition相当于保存在内存中的配置文件，保存着所有跟这个类属性相关的信息，依赖注入就是把BeanDefinition这个信息读出来，通过反射机制或者代理等机制创建对象。一个Bean对应着一个BeanDefinition
新创建的对象不会放在IOC容器里，而是会存入到另外一个cache容器。IOC容器存放的是一个关系。
//BeanDefinitionValueResolver.class
//解析属性值，对注入类型进行转换 @Nullable public Object resolveValueIfNecessary(Object argName, @Nullable Object value) { // We must check each value to see whether it requires a runtime reference // to another bean to be resolved. //对引用类型的属性进行解析 if (value instanceof RuntimeBeanReference) { RuntimeBeanReference ref = (RuntimeBeanReference) value; //调用引用类型属性的解析方法 return resolveReference(argName, ref); } //对属性值是引用容器中另一个Bean名称的解析 else if (value instanceof RuntimeBeanNameReference) { String refName = ((RuntimeBeanNameReference) value).getBeanName(); refName = String.valueOf(doEvaluate(refName)); //从容器中获取指定名称的Bean if (!this.beanFactory.containsBean(refName)) { throw new BeanDefinitionStoreException( "Invalid bean name ‘" + refName + "‘ in bean reference for " + argName); } return refName; } //对Bean类型属性的解析，主要是Bean中的内部类 else if (value instanceof BeanDefinitionHolder) { // Resolve BeanDefinitionHolder: contains BeanDefinition with name and aliases. BeanDefinitionHolder bdHolder = (BeanDefinitionHolder) value; return resolveInnerBean(argName, bdHolder.getBeanName(), bdHolder.getBeanDefinition()); } else if (value instanceof BeanDefinition) { // Resolve plain BeanDefinition, without contained name: use dummy name. BeanDefinition bd = (BeanDefinition) value; String innerBeanName = "(inner bean)" + BeanFactoryUtils.GENERATED_BEAN_NAME_SEPARATOR + ObjectUtils.getIdentityHexString(bd); return resolveInnerBean(argName, innerBeanName, bd); } //对集合数组类型的属性解析 else if (value instanceof ManagedArray) { // May need to resolve contained runtime references. ManagedArray array = (ManagedArray) value; //获取数组的类型 Class<?> elementType = array.resolvedElementType; if (elementType == null) { //获取数组元素的类型 String elementTypeName = array.getElementTypeName(); if (StringUtils.hasText(elementTypeName)) { try { //使用反射机制创建指定类型的对象 elementType = ClassUtils.forName(elementTypeName, this.beanFactory.getBeanClassLoader()); array.resolvedElementType = elementType; } catch (Throwable ex) { // Improve the message by showing the context. throw new BeanCreationException( this.beanDefinition.getResourceDescription(), this.beanName, "Error resolving array type for " + argName, ex); } } //没有获取到数组的类型，也没有获取到数组元素的类型 //则直接设置数组的类型为Object else { elementType = Object.class; } } //创建指定类型的数组 return resolveManagedArray(argName, (List<?>) value, elementType); } //解析list类型的属性值 else if (value instanceof ManagedList) { // May need to resolve contained runtime references. return resolveManagedList(argName, (List<?>) value); } //解析set类型的属性值 else if (value instanceof ManagedSet) { // May need to resolve contained runtime references. return resolveManagedSet(argName, (Set<?>) value); } //解析map类型的属性值 else if (value instanceof ManagedMap) { // May need to resolve contained runtime references. return resolveManagedMap(argName, (Map<?, ?>) value); } //解析props类型的属性值，props其实就是key和value均为字符串的map else if (value instanceof ManagedProperties) { Properties original = (Properties) value; //创建一个拷贝，用于作为解析后的返回值 Properties copy = new Properties(); original.forEach((propKey, propValue) -> { if (propKey instanceof TypedStringValue) { propKey = evaluate((TypedStringValue) propKey); } if (propValue instanceof TypedStringValue) { propValue = evaluate((TypedStringValue) propValue); } if (propKey == null || propValue == null) { throw new BeanCreationException( this.beanDefinition.getResourceDescription(), this.beanName, "Error converting Properties key/value pair for " + argName + ": resolved to null"); } copy.put(propKey, propValue); }); return copy; } //解析字符串类型的属性值 else if (value instanceof TypedStringValue) { // Convert value to target type here. TypedStringValue typedStringValue = (TypedStringValue) value; Object valueObject = evaluate(typedStringValue); try { //获取属性的目标类型 Class<?> resolvedTargetType = resolveTargetType(typedStringValue); if (resolvedTargetType != null) { //对目标类型的属性进行解析，递归调用 return this.typeConverter.convertIfNecessary(valueObject, resolvedTargetType); } //没有获取到属性的目标对象，则按Object类型返回 else { return valueObject; } } catch (Throwable ex) { // Improve the message by showing the context. throw new BeanCreationException( this.beanDefinition.getResourceDescription(), this.beanName, "Error converting typed String value for " + argName, ex); } } else if (value instanceof NullBean) { return null; } else { return evaluate(value); } }
同时，在上个方法中（applyPropertyValues），会调用到bw.setPropertyValues方法，他的作用是为实例化的对象设置属性
@Override public void setPropertyValues(PropertyValues pvs, boolean ignoreUnknown, boolean ignoreInvalid) throws BeansException { List<PropertyAccessException> propertyAccessExceptions = null; List<PropertyValue> propertyValues = (pvs instanceof MutablePropertyValues ? ((MutablePropertyValues) pvs).getPropertyValueList() : Arrays.asList(pvs.getPropertyValues())); for (PropertyValue pv : propertyValues) { try { // This method may throw any BeansException, which won‘t be caught // here, if there is a critical failure such as no matching field. // We can attempt to deal only with less serious exceptions. setPropertyValue(pv); } catch (NotWritablePropertyException ex) { if (!ignoreUnknown) { throw ex; } // Otherwise, just ignore it and continue... } catch (NullValueInNestedPathException ex) { if (!ignoreInvalid) { throw ex; } // Otherwise, just ignore it and continue... } catch (PropertyAccessException ex) { if (propertyAccessExceptions == null) { propertyAccessExceptions = new LinkedList<>(); } propertyAccessExceptions.add(ex); } } // If we encountered individual exceptions, throw the composite exception. if (propertyAccessExceptions != null) { PropertyAccessException[] paeArray = propertyAccessExceptions.toArray(new PropertyAccessException[propertyAccessExceptions.size()]); throw new PropertyBatchUpdateException(paeArray); } }
主要一点是弄清楚wrapper是怎么来的。Wrapper对原生对象进行包装，通过构造方法存储原始对象，然后放入cache的是Wrapper。
考虑一下为什么要用到包装模式：减少代码侵入，能够在原生的基础之上再进行扩展，他可以覆盖、调用方法，甚至可以在原来的方法之上增加监听器、回调函数等。包装模式相当于静态代理的一种额外模式。
到这儿，Bean的依赖注入就搞定了。总结一下，在我们之前操作的IOC容器初始化后，将XML上的内容转化为BeanDefinition中的内容，然后通过传入指定Bean的名字，首先判断Chache中有没有，也要查看其父级BeanFactory，如果有，就通过限定名字得到实例，如果没有，就去创建，创建的方式也分单例和原型两种。
标签：isp 流程图 ignore ini eating 为我 callback 属性 guarantee
原文地址：https://www.cnblogs.com/Jolivan/p/9226289.html
