【Spring原始碼分析】非懶載入的單例Bean初始化過程（下篇）

五月的倉頡發表於2017-02-04
Spring原始碼單例Bean

doCreateBean方法

上文【Spring原始碼分析】非懶載入的單例Bean初始化過程（上篇），分析了單例的Bean初始化流程，並跟蹤程式碼進入了主流程，看到了Bean是如何被例項化出來的。先貼一下AbstractAutowireCapableBeanFactory的doCreateBean方法程式碼：

 1 protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args) {
 2     // Instantiate the bean.
 3     BeanWrapper instanceWrapper = null;
 4     if (mbd.isSingleton()) {
 5         instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
 6     }
 7     if (instanceWrapper == null) {
 8         instanceWrapper = createBeanInstance(beanName, mbd, args);
 9     }
10     final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
11     Class beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
12 
13     // Allow post-processors to modify the merged bean definition.
14     synchronized (mbd.postProcessingLock) {
15         if (!mbd.postProcessed) {
16             applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
17             mbd.postProcessed = true;
18         }
19     }
20 
21     // Eagerly cache singletons to be able to resolve circular references
22     // even when triggered by lifecycle interfaces like BeanFactoryAware.
23     boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
24             isSingletonCurrentlyInCreation(beanName));
25     if (earlySingletonExposure) {
26         if (logger.isDebugEnabled()) {
27             logger.debug("Eagerly caching bean '" + beanName +
28                     "' to allow for resolving potential circular references");
29         }
30         addSingletonFactory(beanName, new ObjectFactory() {
31             public Object getObject() throws BeansException {
32                 return getEarlyBeanReference(beanName, mbd, bean);
33             }
34         });
35     }
36 
37     // Initialize the bean instance.
38     Object exposedObject = bean;
39     try {
40         populateBean(beanName, mbd, instanceWrapper);
41         if (exposedObject != null) {
42             exposedObject = initializeBean(beanName, exposedObject, mbd);
43         }
44     }
45     catch (Throwable ex) {
46         if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
47             throw (BeanCreationException) ex;
48         }
49         else {
50             throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
51         }
52     }
53 
54     if (earlySingletonExposure) {
55         Object earlySingletonReference = getSingleton(beanName, false);
56         if (earlySingletonReference != null) {
57             if (exposedObject == bean) {
58                 exposedObject = earlySingletonReference;
59             }
60             else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
61                 String[] dependentBeans = getDependentBeans(beanName);
62                 Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length);
63                 for (String dependentBean : dependentBeans) {
64                     if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
65                         actualDependentBeans.add(dependentBean);
66                     }
67                 }
68                 if (!actualDependentBeans.isEmpty()) {
69                     throw new BeanCurrentlyInCreationException(beanName,
70                             "Bean with name '" + beanName + "' has been injected into other beans [" +
71                             StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
72                             "] in its raw version as part of a circular reference, but has eventually been " +
73                             "wrapped. This means that said other beans do not use the final version of the " +
74                             "bean. This is often the result of over-eager type matching - consider using " +
75                             "'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.");
76                 }
77             }
78         }
79     }
80 
81     // Register bean as disposable.
82     try {
83         registerDisposableBeanIfNecessary(beanName, bean, mbd);
84     }
85     catch (BeanDefinitionValidationException ex) {
86         throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
87     }
88 
89     return exposedObject;
90 }

下面繼續分析初始化一個Bean的流程，不太重要的流程就跳過了。

 

屬性注入

屬性注入的程式碼比較好找，可以看一下40行，取名為populateBean，即填充Bean的意思，看一下程式碼實現：

 1 protected void populateBean(String beanName, AbstractBeanDefinition mbd, BeanWrapper bw) {
 2     PropertyValues pvs = mbd.getPropertyValues();
 3 
 4     if (bw == null) {
 5         if (!pvs.isEmpty()) {
 6             throw new BeanCreationException(
 7                     mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
 8         }
 9         else {
10             // Skip property population phase for null instance.
11             return;
12         }
13     }
14 
15     // Give any InstantiationAwareBeanPostProcessors the opportunity to modify the
16     // state of the bean before properties are set. This can be used, for example,
17     // to support styles of field injection.
18     boolean continueWithPropertyPopulation = true;
19 
20     if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
21         for (BeanPostProcessor bp : getBeanPostProcessors()) {
22             if (bp instanceof InstantiationAwareBeanPostProcessor) {
23                 InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
24                 if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
25                     continueWithPropertyPopulation = false;
26                     break;
27                 }
28             }
29         }
30     }
31 
32     if (!continueWithPropertyPopulation) {
33         return;
34     }
35 
36     if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||
37             mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
38         MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
39 
40         // Add property values based on autowire by name if applicable.
41         if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
42             autowireByName(beanName, mbd, bw, newPvs);
43         }
44 
45         // Add property values based on autowire by type if applicable.
46         if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
47             autowireByType(beanName, mbd, bw, newPvs);
48         }
49 
50         pvs = newPvs;
51     }
52 
53     boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
54     boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);
55 
56     if (hasInstAwareBpps || needsDepCheck) {
57         PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw);
58         if (hasInstAwareBpps) {
59             for (BeanPostProcessor bp : getBeanPostProcessors()) {
60                 if (bp instanceof InstantiationAwareBeanPostProcessor) {
61                     InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
62                     pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
63                     if (pvs == null) {
64                         return;
65                     }
66                 }
67             }
68         }
69         if (needsDepCheck) {
70             checkDependencies(beanName, mbd, filteredPds, pvs);
71         }
72     }
73 
74     applyPropertyValues(beanName, mbd, bw, pvs);
75 }

這段程式碼層次有點深，跟一下74行的applyPropertyValues方法，最後那個pvs的實現類為MutablePropertyValues，裡面持有一個List<PropertyValue>，每一個PropertyValue包含了此Bean屬性的屬性名與屬性值。74行的程式碼實現為：

 1 protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
 2     if (pvs == null || pvs.isEmpty()) {
 3         return;
 4     }
 5 
 6     MutablePropertyValues mpvs = null;
 7     List<PropertyValue> original;
 8         
 9     if (System.getSecurityManager()!= null) {
10         if (bw instanceof BeanWrapperImpl) {
11             ((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext());
12         }
13     }
14 
15     if (pvs instanceof MutablePropertyValues) {
16         mpvs = (MutablePropertyValues) pvs;
17         if (mpvs.isConverted()) {
18             // Shortcut: use the pre-converted values as-is.
19             try {
20                 bw.setPropertyValues(mpvs);
21                 return;
22             }
23             catch (BeansException ex) {
24                 throw new BeanCreationException(
25                         mbd.getResourceDescription(), beanName, "Error setting property values", ex);
26             }
27         }
28         original = mpvs.getPropertyValueList();
29     }
30     else {
31         original = Arrays.asList(pvs.getPropertyValues());
32     }
33 
34     TypeConverter converter = getCustomTypeConverter();
35     if (converter == null) {
36         converter = bw;
37     }
38     BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter);
39 
40     // Create a deep copy, resolving any references for values.
41     List<PropertyValue> deepCopy = new ArrayList<PropertyValue>(original.size());
42     boolean resolveNecessary = false;
43     for (PropertyValue pv : original) {
44         if (pv.isConverted()) {
45             deepCopy.add(pv);
46         }
47         else {
48             String propertyName = pv.getName();
49             Object originalValue = pv.getValue();
50             Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);
51             Object convertedValue = resolvedValue;
52             boolean convertible = bw.isWritableProperty(propertyName) &&
53                         !PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName);
54             if (convertible) {
55                 convertedValue = convertForProperty(resolvedValue, propertyName, bw, converter);
56             }
57             // Possibly store converted value in merged bean definition,
58             // in order to avoid re-conversion for every created bean instance.
59             if (resolvedValue == originalValue) {
60                 if (convertible) {
61                     pv.setConvertedValue(convertedValue);
62                 }
63                 deepCopy.add(pv);
64             }
65             else if (convertible && originalValue instanceof TypedStringValue &&
66                     !((TypedStringValue) originalValue).isDynamic() &&
67                     !(convertedValue instanceof Collection || ObjectUtils.isArray(convertedValue))) {
68                 pv.setConvertedValue(convertedValue);
69                 deepCopy.add(pv);
70             }
71             else {
72                 resolveNecessary = true;
73                 deepCopy.add(new PropertyValue(pv, convertedValue));
74             }
75         }
76     }
77     if (mpvs != null && !resolveNecessary) {
78         mpvs.setConverted();
79     }
80 
81     // Set our (possibly massaged) deep copy.
82     try {
83         bw.setPropertyValues(new MutablePropertyValues(deepCopy));
84     }
85     catch (BeansException ex) {
86         throw new BeanCreationException(
87                 mbd.getResourceDescription(), beanName, "Error setting property values", ex);
88     }
89 }

之後在第41行~第76行做了一次深拷貝（只是名字叫做深拷貝而已，其實就是遍歷PropertyValue然後一個一個賦值到一個新的List而不是Java語義上的Clone，這裡使用深拷貝是為了解析Values值中的所有引用），將PropertyValue一個一個賦值到一個新的List裡面去，起名為deepCopy。最後執行83行進行復制，bw即BeanWrapper，持有Bean例項的一個Bean包裝類，看一下程式碼實現：

 1 public void setPropertyValues(PropertyValues pvs, boolean ignoreUnknown, boolean ignoreInvalid)
 2         throws BeansException {
 3 
 4     List<PropertyAccessException> propertyAccessExceptions = null;
 5     List<PropertyValue> propertyValues = (pvs instanceof MutablePropertyValues ?
 6             ((MutablePropertyValues) pvs).getPropertyValueList() : Arrays.asList(pvs.getPropertyValues()));
 7     for (PropertyValue pv : propertyValues) {
 8         try {
 9             // This method may throw any BeansException, which won't be caught
10             // here, if there is a critical failure such as no matching field.
11             // We can attempt to deal only with less serious exceptions.
12             setPropertyValue(pv);
13         }
14         catch (NotWritablePropertyException ex) {
15             if (!ignoreUnknown) {
16                 throw ex;
17             }
18             // Otherwise, just ignore it and continue...
19         }
20         catch (NullValueInNestedPathException ex) {
21             if (!ignoreInvalid) {
22                 throw ex;
23             }
24             // Otherwise, just ignore it and continue...
25         }
26         catch (PropertyAccessException ex) {
27             if (propertyAccessExceptions == null) {
28                 propertyAccessExceptions = new LinkedList<PropertyAccessException>();
29             }
30             propertyAccessExceptions.add(ex);
31         }
32     }
33 
34     // If we encountered individual exceptions, throw the composite exception.
35     if (propertyAccessExceptions != null) {
36         PropertyAccessException[] paeArray =
37                 propertyAccessExceptions.toArray(new PropertyAccessException[propertyAccessExceptions.size()]);
38         throw new PropertyBatchUpdateException(paeArray);
39     }
40 }

這段程式碼沒什麼特別的，遍歷前面的deepCopy，拿每一個PropertyValue，執行第12行的setPropertyValue：

 1 public void setPropertyValue(PropertyValue pv) throws BeansException {
 2     PropertyTokenHolder tokens = (PropertyTokenHolder) pv.resolvedTokens;
 3     if (tokens == null) {
 4         String propertyName = pv.getName();
 5         BeanWrapperImpl nestedBw;
 6         try {
 7             nestedBw = getBeanWrapperForPropertyPath(propertyName);
 8         }
 9         catch (NotReadablePropertyException ex) {
10             throw new NotWritablePropertyException(getRootClass(), this.nestedPath + propertyName,
11                     "Nested property in path '" + propertyName + "' does not exist", ex);
12         }
13         tokens = getPropertyNameTokens(getFinalPath(nestedBw, propertyName));
14         if (nestedBw == this) {
15             pv.getOriginalPropertyValue().resolvedTokens = tokens;
16         }
17         nestedBw.setPropertyValue(tokens, pv);
18     }
19     else {
20         setPropertyValue(tokens, pv);
21     }
22 }

找一個合適的BeanWrapper，這裡就是自身，然後執行17行的setPropertyValue方法進入最後一步，方法非常長，擷取核心的一段：

 1 final Method writeMethod = (pd instanceof GenericTypeAwarePropertyDescriptor ?
 2     ((GenericTypeAwarePropertyDescriptor) pd).getWriteMethodForActualAccess() :
 3     pd.getWriteMethod());
 4     if (!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers()) && !writeMethod.isAccessible()) {
 5     if (System.getSecurityManager()!= null) {
 6         AccessController.doPrivileged(new PrivilegedAction<Object>() {
 7                 public Object run() {
 8                     writeMethod.setAccessible(true);
 9                     return null;
10                 }
11             });
12         }
13         else {
14             writeMethod.setAccessible(true);
15         }
16     }
17     final Object value = valueToApply;
18     if (System.getSecurityManager() != null) {
19     try {
20         AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
21             public Object run() throws Exception {
22                 writeMethod.invoke(object, value);
23                 return null;
24             }
25         }, acc);
26     }
27     catch (PrivilegedActionException ex) {
28         throw ex.getException();
29     }
30 }
31 else {
32     writeMethod.invoke(this.object, value);
33 }

大致流程就是兩步：

（1）拿到寫方法並將方法的可見性設定為true

（2）拿到Value值，對Bean通過反射呼叫寫方法

這樣完成了對於Bean屬性值的設定。

 

Aware注入

接下來是Aware注入。在使用Spring的時候我們將自己的Bean實現BeanNameAware介面、BeanFactoryAware介面等，依賴容器幫我們注入當前Bean的名稱或者Bean工廠，其程式碼實現先追溯到上面doCreateBean方法的42行initializeBean方法：

 1 protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
 2     if (System.getSecurityManager() != null) {
 3         AccessController.doPrivileged(new PrivilegedAction<Object>() {
 4             public Object run() {
 5                 invokeAwareMethods(beanName, bean);
 6                 return null;
 7             }
 8         }, getAccessControlContext());
 9     }
10     else {
11         invokeAwareMethods(beanName, bean);
12     }
13         
14     Object wrappedBean = bean;
15     if (mbd == null || !mbd.isSynthetic()) {
16         wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
17     }
18 
19     try {
20         invokeInitMethods(beanName, wrappedBean, mbd);
21     }
22     catch (Throwable ex) {
23         throw new BeanCreationException(
24                 (mbd != null ? mbd.getResourceDescription() : null),
25                 beanName, "Invocation of init method failed", ex);
26     }
27 
28     if (mbd == null || !mbd.isSynthetic()) {
29         wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
30     }
31     return wrappedBean;
32 }

看一下上面第5行的實現：

 1 private void invokeAwareMethods(final String beanName, final Object bean) {
 2     if (bean instanceof BeanNameAware) {
 3         ((BeanNameAware) bean).setBeanName(beanName);
 4     }
 5     if (bean instanceof BeanClassLoaderAware) {
 6         ((BeanClassLoaderAware) bean).setBeanClassLoader(getBeanClassLoader());
 7     }
 8     if (bean instanceof BeanFactoryAware) {
 9         ((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
10     }
11 }

看到這裡判斷，如果bean是BeanNameAware介面的實現類會呼叫setBeanName方法、如果bean是BeanClassLoaderAware介面的實現類會呼叫setBeanClassLoader方法、如果是BeanFactoryAware介面的實現類會呼叫setBeanFactory方法，注入對應的屬性值。

 

呼叫BeanPostProcessor的postProcessBeforeInitialization方法

上面initializeBean方法再看16行其實現：

 1 public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
 2         throws BeansException {
 3 
 4     Object result = existingBean;
 5     for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
 6         result = beanProcessor.postProcessBeforeInitialization(result, beanName);
 7         if (result == null) {
 8             return result;
 9         }
10     }
11     return result;
12 }

遍歷每個BeanPostProcessor介面實現，呼叫postProcessBeforeInitialization方法，這個介面的呼叫時機之後會總結，這裡就程式碼先簡單提一下。

 

呼叫初始化方法

initializeBean方法的20行，呼叫Bean的初始化方法，看一下實現：

 1 protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)
 2         throws Throwable {
 3 
 4     boolean isInitializingBean = (bean instanceof InitializingBean);
 5     if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
 6         if (logger.isDebugEnabled()) {
 7             logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
 8         }
 9         if (System.getSecurityManager() != null) {
10             try {
11                 AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
12                     public Object run() throws Exception {
13                         ((InitializingBean) bean).afterPropertiesSet();
14                         return null;
15                     }
16                 }, getAccessControlContext());
17             }
18             catch (PrivilegedActionException pae) {
19                 throw pae.getException();
20             }
21         }                
22         else {
23             ((InitializingBean) bean).afterPropertiesSet();
24         }
25     }
26 
27     if (mbd != null) {
28         String initMethodName = mbd.getInitMethodName();
29         if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
30                     !mbd.isExternallyManagedInitMethod(initMethodName)) {
31             invokeCustomInitMethod(beanName, bean, mbd);
32         }
33     }
34 }

看到，程式碼做了兩件事情：

1、先判斷Bean是否InitializingBean的實現類，是的話，將Bean強轉為InitializingBean，直接呼叫afterPropertiesSet()方法

2、嘗試去拿init-method，假如有的話，通過反射，呼叫initMethod

因此，兩種方法各有優劣：使用實現InitializingBean介面的方式效率更高一點，因為init-method方法是通過反射進行呼叫的；從另外一個角度講，使用init-method方法之後和Spring的耦合度會更低一點。具體使用哪種方式呼叫初始化方法，看個人喜好。

 

呼叫BeanPostProcessor的postProcessAfterInitialization方法

最後一步，initializeBean方法的29行：

 1 public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
 2         throws BeansException {
 3 
 4     Object result = existingBean;
 5     for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
 6         result = beanProcessor.postProcessAfterInitialization(result, beanName);
 7         if (result == null) {
 8             return result;
 9         }
10     }
11     return result;
12 }

同樣遍歷BeanPostProcessor，呼叫postProcessAfterInitialization方法。因此對於BeanPostProcessor方法總結一下：

1、在初始化每一個Bean的時候都會呼叫每一個配置的BeanPostProcessor的方法

2、在Bean屬性設定、Aware設定後呼叫postProcessBeforeInitialization方法

3、在初始化方法呼叫後呼叫postProcessAfterInitialization方法

 

註冊需要執行銷燬方法的Bean

接下來看一下最上面doCreateBean方法的第83行registerDisposableBeanIfNecessary(beanName, bean, mbd)這一句，完成了建立Bean的最後一件事情：註冊需要執行銷燬方法的Bean。

看一下方法的實現：

 1 protected void registerDisposableBeanIfNecessary(String beanName, Object bean, RootBeanDefinition mbd) {
 2     AccessControlContext acc = (System.getSecurityManager() != null ? getAccessControlContext() : null);
 3     if (!mbd.isPrototype() && requiresDestruction(bean, mbd)) {
 4         if (mbd.isSingleton()) {
 5             // Register a DisposableBean implementation that performs all destruction
 6             // work for the given bean: DestructionAwareBeanPostProcessors,
 7             // DisposableBean interface, custom destroy method.
 8             registerDisposableBean(beanName,
 9                     new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), acc));
10         }
11         else {
12             // A bean with a custom scope...
13             Scope scope = this.scopes.get(mbd.getScope());
14             if (scope == null) {
15                 throw new IllegalStateException("No Scope registered for scope '" + mbd.getScope() + "'");
16             }
17             scope.registerDestructionCallback(beanName,
18                     new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), acc));
19         }
20     }
21 }

其中第3行第一個判斷為必須不是prototype（原型）的，第二個判斷requiresDestruction方法的實現為：

1 protected boolean requiresDestruction(Object bean, RootBeanDefinition mbd) {
2     return (bean != null &&
3             (bean instanceof DisposableBean || mbd.getDestroyMethodName() != null ||
4                     hasDestructionAwareBeanPostProcessors()));
5 }

要註冊銷燬方法，Bean需要至少滿足以下三個條件之一：

（1）Bean是DisposableBean的實現類，此時執行DisposableBean的介面方法destroy()

（2）Bean標籤中有配置destroy-method屬性，此時執行destroy-method配置指定的方法

（3）當前Bean對應的BeanFactory中持有DestructionAwareBeanPostProcessor介面的實現類，此時執行DestructionAwareBeanPostProcessor的介面方法postProcessBeforeDestruction

在滿足上面三個條件之一的情況下，容器便會註冊銷燬該Bean，註冊Bean的方法很簡單，見registerDisposableBean方法實現：

1 public void registerDisposableBean(String beanName, DisposableBean bean) {
2     synchronized (this.disposableBeans) {
3         this.disposableBeans.put(beanName, bean);
4     }
5 }

容器銷燬的時候，會遍歷disposableBeans，逐一執行銷燬方法。

 

流程總結

本文和上篇文章分析了Spring Bean初始化的步驟，最後用一幅圖總結一下Spring Bean初始化的流程：

圖只是起梳理流程作用，拋磚引玉，具體程式碼實現還需要網友朋友們照著程式碼自己去一步一步分析。

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