Spring更多分析--spring源码分析系列
主要分析内容：
一、BeanPostProcessor简述与demo示例
二、BeanPostProcessor源码分析：注册时机和触发点
(源码基于spring 5.1.3.RELEASE分析)
一、BeanPostProcessor简述与demo示例
BeanPostProcessor是spring非常重要的拓展接口，例如aop通过拓展接口生产代理bean等。接口有两个方法：
/**
* Factory hook that allows for custom modification of new bean instances,
* e.g. checking for marker interfaces or wrapping them with proxies.
*
* <p>ApplicationContexts can autodetect BeanPostProcessor beans in their
* bean definitions and apply them to any beans subsequently created.
* Plain bean factories allow for programmatic registration of post-processors,
* applying to all beans created through this factory.
*
* <p>Typically, post-processors that populate beans via marker interfaces
* or the like will implement {@link #postProcessBeforeInitialization},
* while post-processors that wrap beans with proxies will normally
* implement {@link #postProcessAfterInitialization}.
*
* @author Juergen Hoeller
* @since 10.10.2003
* @see InstantiationAwareBeanPostProcessor
* @see DestructionAwareBeanPostProcessor
* @see ConfigurableBeanFactory#addBeanPostProcessor
* @see BeanFactoryPostProcessor
*/
public interface BeanPostProcessor {
/**
* Apply this BeanPostProcessor to the given new bean instance <i>before</i> any bean
* initialization callbacks (like InitializingBean's {@code afterPropertiesSet}
* or a custom init-method). The bean will already be populated with property values.
* The returned bean instance may be a wrapper around the original.
* <p>The default implementation returns the given {@code bean} as-is.
* @param bean the new bean instance
* @param beanName the name of the bean
* @return the bean instance to use, either the original or a wrapped one;
* if {@code null}, no subsequent BeanPostProcessors will be invoked
* @throws org.springframework.beans.BeansException in case of errors
* @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet
*/
@Nullable
default Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
return bean;
}
/**
* Apply this BeanPostProcessor to the given new bean instance <i>after</i> any bean
* initialization callbacks (like InitializingBean's {@code afterPropertiesSet}
* or a custom init-method). The bean will already be populated with property values.
* The returned bean instance may be a wrapper around the original.
* <p>In case of a FactoryBean, this callback will be invoked for both the FactoryBean
* instance and the objects created by the FactoryBean (as of Spring 2.0). The
* post-processor can decide whether to apply to either the FactoryBean or created
* objects or both through corresponding {@code bean instanceof FactoryBean} checks.
* <p>This callback will also be invoked after a short-circuiting triggered by a
* {@link InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation} method,
* in contrast to all other BeanPostProcessor callbacks.
* <p>The default implementation returns the given {@code bean} as-is.
* @param bean the new bean instance
* @param beanName the name of the bean
* @return the bean instance to use, either the original or a wrapped one;
* if {@code null}, no subsequent BeanPostProcessors will be invoked
* @throws org.springframework.beans.BeansException in case of errors
* @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet
* @see org.springframework.beans.factory.FactoryBean
*/
@Nullable
default Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
return bean;
}
}
View Code
以上为spring原始接口，这里说明一下：
- ApplicationContext类型的容器会自动发现和注册该类型的bean，通过BeanPostProcessor可以对bean进行定制化，接口作用域是所有bean创建。
- postProcessBeforeInitialization触发时机在bean实例化(Instantiation)之后，所有初始化(Initialization)动作(包括 InitializingBean#afterPrpertiesSet() 和 定制化init-method())以前。
- postProcessAfterInitialization触发时机在bean实例化(Instantiation)之后，所有初始化(Initialization)动作(包括 InitializingBean#afterPrpertiesSet() 和 定制化init-method())以后。同时还会在InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation 和 FactoryBean(bean工厂)获得bean时候调用。这个也是重要的点，放在往后的博客中阐述。
由于ApplicationContext可以自动发现并注册BeanPostProcessor，如下使用ApplicationContext类型容器实现一个简单demo。 对应的demo代码可参考： https://gitee.com/zhouxiaoxing91/learning-src/tree/master
1 public class BeanPostProcessorTest {
2
3 private ApplicationContext applicationContext ;
4
5 @Before
6 public void beforeApplicationContext(){
7 /**
8 * ApplicationContext 自动注册 BeanPostProcessor
9 * 不需要手动注册
10 * */
11 applicationContext = new ClassPathXmlApplicationContext("ioc-beanPostProcessor.xml") ;
12 }
13
14 @Test
15 public void test(){
16 Bean bean = applicationContext.getBean("bean", Bean.class) ;
17 System.out.println(bean);
18 }
19
20 @After
21 public void after(){
22 ((ClassPathXmlApplicationContext)applicationContext).close();
23 }
24 }
BeanPostProcessorTest.java
1 public class Bean {
2
3 public Bean(){
4
5 }
6
7 public Bean(String name){
8 System.out.println("构造函数被调用啦");
9 this.name = name ;
10 }
11
12 private String name ;
13
14
15 public String getName() {
16 return name;
17 }
18
19 public void setName(String name) {
20 this.name = name;
21 }
22
23 @Override
24 public String toString() {
25 return "Bean{" +
26 "name='" + name + '\'' +
27 '}';
28 }
29 }
Bean.java
1 public class LogicBeanPostProcessor implements BeanPostProcessor {
2
3 @Nullable
4 @Override
5 public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
6 System.out.println("LogicBeanPostProcessor.postProcessAfterInitialization 执行啦 beanName = " + beanName);
7 return bean;
8 }
9
10 @Nullable
11 @Override
12 public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
13 System.out.println("LogicBeanPostProcessor.postProcessBeforeInitialization 执行啦 beanName = " + beanName);
14 return bean;
15 }
16 }
LogicBeanPostProcessor.java
1 <?xml version="1.0" encoding="utf-8"?>
2 <beans xmlns="http://www.springframework.org/schema/beans"
3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
4 xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
5
6 <bean id="bean" class="com.nancy.ioc.Bean">
7 <constructor-arg name="name" value="zhouxiaoxing"/>
8 </bean>
9
10 <bean id="logicBeanPostProcessor" class="com.nancy.ioc.BeanPostProcessor.LogicBeanPostProcessor"/>
11 </beans>
ioc-beanPostProcessor.xml
运行结果符合以上的结论：
构造函数被调用啦
LogicBeanPostProcessor.postProcessBeforeInitialization 执行啦 beanName = bean
LogicBeanPostProcessor.postProcessAfterInitialization 执行啦 beanName = bean
Bean{name='zhouxiaoxing'}
提出两个疑问：
1、在ApplicationContext容器中何时注册BeanPostProcessor接口 ？
2、何时apply对应的回调方法呢 ？
二、BeanPostProcessor源码分析：注册时机和触发点
1、注册BeanPostProcessor
在AbstractApplicationContext容器启动的refresh()会注册BeanPostProcessor，源码如下：
1 @Override
2 public void refresh() throws BeansException, IllegalStateException {
3 synchronized (this.startupShutdownMonitor) {
4 // Prepare this context for refreshing.
5 prepareRefresh();
6
7 // Tell the subclass to refresh the internal bean factory.
8 ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
9
10 // Prepare the bean factory for use in this context.
11 prepareBeanFactory(beanFactory);
12
13 try {
14 // Allows post-processing of the bean factory in context subclasses.
15 postProcessBeanFactory(beanFactory);
16
17 // Invoke factory processors registered as beans in the context.
18 invokeBeanFactoryPostProcessors(beanFactory);
19
20 // Register bean processors that intercept bean creation.
21 // 注册BeanPostProcessor 在bean创建的时候进行拦截
22 registerBeanPostProcessors(beanFactory);
23
24 // Initialize message source for this context.
25 initMessageSource();
26
27 // Initialize event multicaster for this context.
28 initApplicationEventMulticaster();
29
30 // Initialize other special beans in specific context subclasses.
31 onRefresh();
32
33 // Check for listener beans and register them.
34 registerListeners();
35
36 // Instantiate all remaining (non-lazy-init) singletons.
37 finishBeanFactoryInitialization(beanFactory);
38
39 // Last step: publish corresponding event.
40 finishRefresh();
41 }
42
43 catch (BeansException ex) {
44 if (logger.isWarnEnabled()) {
45 logger.warn("Exception encountered during context initialization - " +
46 "cancelling refresh attempt: " + ex);
47 }
48
49 // Destroy already created singletons to avoid dangling resources.
50 destroyBeans();
51
52 // Reset 'active' flag.
53 cancelRefresh(ex);
54
55 // Propagate exception to caller.
56 throw ex;
57 }
58
59 finally {
60 // Reset common introspection caches in Spring's core, since we
61 // might not ever need metadata for singleton beans anymore...
62 resetCommonCaches();
63 }
64 }
65 }
66
67 ......
68
69 /**
70 * Instantiate and invoke all registered BeanPostProcessor beans,
71 * respecting explicit order if given.
72 * <p>Must be called before any instantiation of application beans.
73 */
74 protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
75 PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
76 }
跟进PostProcessorRegistrationDelegate.registerBeanPostProcessors
1 public static void registerBeanPostProcessors(
2 ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
3
4 /**
5 * 此时bean的定义加载已经完成，但是还没有实例化。 获得所有BeanPostProcessor bean对应的beanName
6 */
7 String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
8
9 /**
10 * 注册日志BeanPostProcessor， 检测注册的bean是否为spring基础服务类并打印日志
11 */
12 // Register BeanPostProcessorChecker that logs an info message when
13 // a bean is created during BeanPostProcessor instantiation, i.e. when
14 // a bean is not eligible for getting processed by all BeanPostProcessors.
15 int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
16 beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
17
18 /**
19 * 当有注册多个BeanPostProcessor接口时会按顺序进行，即 实现PriorityOrdered->实现Ordered->普通类型接口->内部系统MergedBeanDefinitionPostProcessor
20 */
21 // Separate between BeanPostProcessors that implement PriorityOrdered,
22 // Ordered, and the rest.
23 List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
24 List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
25 List<String> orderedPostProcessorNames = new ArrayList<>();
26 List<String> nonOrderedPostProcessorNames = new ArrayList<>();
27 for (String ppName : postProcessorNames) {
28 if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
29
30 /**
31 * 通过beanFactory.getBean(), 将会提前初始化BeanPostProcessor类型实例
32 */
33 BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
34 priorityOrderedPostProcessors.add(pp);
35 if (pp instanceof MergedBeanDefinitionPostProcessor) {
36 internalPostProcessors.add(pp);
37 }
38 }
39 else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
40 orderedPostProcessorNames.add(ppName);
41 }
42 else {
43 nonOrderedPostProcessorNames.add(ppName);
44 }
45 }
46
47 // First, register the BeanPostProcessors that implement PriorityOrdered.
48 sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
49 registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
50
51 // Next, register the BeanPostProcessors that implement Ordered.
52 List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>();
53 for (String ppName : orderedPostProcessorNames) {
54 BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
55 orderedPostProcessors.add(pp);
56 if (pp instanceof MergedBeanDefinitionPostProcessor) {
57 internalPostProcessors.add(pp);
58 }
59 }
60 sortPostProcessors(orderedPostProcessors, beanFactory);
61 registerBeanPostProcessors(beanFactory, orderedPostProcessors);
62
63 // Now, register all regular BeanPostProcessors.
64 List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
65 for (String ppName : nonOrderedPostProcessorNames) {
66 BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
67 nonOrderedPostProcessors.add(pp);
68 if (pp instanceof MergedBeanDefinitionPostProcessor) {
69 internalPostProcessors.add(pp);
70 }
71 }
72 registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
73
74 // Finally, re-register all internal BeanPostProcessors.
75 sortPostProcessors(internalPostProcessors, beanFactory);
76 registerBeanPostProcessors(beanFactory, internalPostProcessors);
77
78 /**
79 * ApplicationListener探测器，当bean实现ApplicationListener接口时自动注册监听
80 */
81 // Re-register post-processor for detecting inner beans as ApplicationListeners,
82 // moving it to the end of the processor chain (for picking up proxies etc).
83 beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
84 }
85
86 /**
87 * 按照给定Ordered的顺序排序
88 */
89 private static void sortPostProcessors(List<?> postProcessors, ConfigurableListableBeanFactory beanFactory) {
90 Comparator<Object> comparatorToUse = null;
91 if (beanFactory instanceof DefaultListableBeanFactory) {
92 comparatorToUse = ((DefaultListableBeanFactory) beanFactory).getDependencyComparator();
93 }
94 if (comparatorToUse == null) {
95 comparatorToUse = OrderComparator.INSTANCE;
96 }
97 postProcessors.sort(comparatorToUse);
98 }
99
100 /**
101 * Register the given BeanPostProcessor beans.
102 */
103 private static void registerBeanPostProcessors(
104 ConfigurableListableBeanFactory beanFactory, List<BeanPostProcessor> postProcessors) {
105
106 for (BeanPostProcessor postProcessor : postProcessors) {
107 beanFactory.addBeanPostProcessor(postProcessor);
108 }
109 }
跟进AbstractBeanFactory#addBeanPostProcessor
1 /** BeanPostProcessors to apply in createBean. */
2 private final List<BeanPostProcessor> beanPostProcessors = new CopyOnWriteArrayList<>();
3
4 /** Indicates whether any InstantiationAwareBeanPostProcessors have been registered. */
5 private volatile boolean hasInstantiationAwareBeanPostProcessors;
6
7 /** Indicates whether any DestructionAwareBeanPostProcessors have been registered. */
8 private volatile boolean hasDestructionAwareBeanPostProcessors;
9
10
11 /**
12 * 所有的BeanPostProcessor接口实例保存于CopyOnWriteArrayList中
13 * 1、一个实例只注册一次
14 * 2、通过hasInstantiationAwareBeanPostProcessors设置，判定是否存在InstantiationAwareBeanPostProcessor接口实例，为后续执行做判断
15 * 3、通过hasDestructionAwareBeanPostProcessors设置，判定是否存在DestructionAwareBeanPostProcessor接口实例，为后续执行做判断
16 */
17 @Override
18 public void addBeanPostProcessor(BeanPostProcessor beanPostProcessor) {
19 Assert.notNull(beanPostProcessor, "BeanPostProcessor must not be null");
20 // Remove from old position, if any
21 this.beanPostProcessors.remove(beanPostProcessor);
22 // Track whether it is instantiation/destruction aware
23 if (beanPostProcessor instanceof InstantiationAwareBeanPostProcessor) {
24 this.hasInstantiationAwareBeanPostProcessors = true;
25 }
26 if (beanPostProcessor instanceof DestructionAwareBeanPostProcessor) {
27 this.hasDestructionAwareBeanPostProcessors = true;
28 }
29 // Add to end of list
30 this.beanPostProcessors.add(beanPostProcessor);
31 }
修改上述demo中LogicBeanPostProcessor.java文件，并debug模式查看：
1 public class LogicBeanPostProcessor implements BeanPostProcessor {
2
3 public LogicBeanPostProcessor(){
4 System.out.println("LogicBeanPostProcessor 被 beanFactory.getBean() 提前初始化");
5 }
6
7 @Nullable
8 @Override
9 public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
10 System.out.println("LogicBeanPostProcessor.postProcessAfterInitialization 执行啦 beanName = " + beanName);
11 return bean;
12 }
13
14 @Nullable
15 @Override
16 public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
17 System.out.println("LogicBeanPostProcessor.postProcessBeforeInitialization 执行啦 beanName = " + beanName);
18 return bean;
19 }
20 }
查看PostProcessorRegistrationDelegate#registerBeanPostProcessors，注册一个普通BeanPostProcessor -> logicBeanPostProcessor
最后运行结果：
LogicBeanPostProcessor 被 beanFactory.getBean() 提前初始化
构造函数被调用啦
LogicBeanPostProcessor.postProcessBeforeInitialization 执行啦 beanName = bean
LogicBeanPostProcessor.postProcessAfterInitialization 执行啦 beanName = bean
Bean{name='zhouxiaoxing'}
总结如下：
(1)、BeanPostProcessor注册的入口在AbstractApplicationContext容器启动的refresh()的AbstractApplicationContext#registerBeanPostProcessors。
(2)、AbstractApplicationContext进而委派PostProcessorRegistrationDelegate#registerBeanPostProcessors实现注册。
(3)、当有注册多个BeanPostProcessor接口时会按顺序进行，即 实现PriorityOrdered->实现Ordered->普通类型接口->内部系统MergedBeanDefinitionPostProcessor。而同种类型也会进行排序，按顺序注册。
(4)、BeanPostProcessor类型实例会通过BeanFactory#getBean()提前初始化。
2、触发BeanPostProcessor方法
触发BeanPostProcessor有很多入口，首先分析几个入口后续的再补上。
触发（1）****AbstractAutowireCapableBeanFactory#createBean 中：
1 /**
2 * Central method of this class: creates a bean instance,
3 * populates the bean instance, applies post-processors, etc.
4 * @see #doCreateBean
5 */
6 @Override
7 protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
8 throws BeanCreationException {
9
10 if (logger.isTraceEnabled()) {
11 logger.trace("Creating instance of bean '" + beanName + "'");
12 }
13 RootBeanDefinition mbdToUse = mbd;
14
15 // Make sure bean class is actually resolved at this point, and
16 // clone the bean definition in case of a dynamically resolved Class
17 // which cannot be stored in the shared merged bean definition.
18 Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
19 if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
20 mbdToUse = new RootBeanDefinition(mbd);
21 mbdToUse.setBeanClass(resolvedClass);
22 }
23
24 // Prepare method overrides.
25 try {
26 mbdToUse.prepareMethodOverrides();
27 }
28 catch (BeanDefinitionValidationException ex) {
29 throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
30 beanName, "Validation of method overrides failed", ex);
31 }
32
33 try {
34 // Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
35 Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
36 if (bean != null) {
37 return bean;
38 }
39 }
40 catch (Throwable ex) {
41 throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,
42 "BeanPostProcessor before instantiation of bean failed", ex);
43 }
44
45 try {
46 // bean 创建
47 Object beanInstance = doCreateBean(beanName, mbdToUse, args);
48 if (logger.isTraceEnabled()) {
49 logger.trace("Finished creating instance of bean '" + beanName + "'");
50 }
51 return beanInstance;
52 }
53 catch (BeanCreationException | ImplicitlyAppearedSingletonException ex) {
54 // A previously detected exception with proper bean creation context already,
55 // or illegal singleton state to be communicated up to DefaultSingletonBeanRegistry.
56 throw ex;
57 }
58 catch (Throwable ex) {
59 throw new BeanCreationException(
60 mbdToUse.getResourceDescription(), beanName, "Unexpected exception during bean creation", ex);
61 }
62 }
63
64 /**
65 * Actually create the specified bean. Pre-creation processing has already happened
66 * at this point, e.g. checking {@code postProcessBeforeInstantiation} callbacks.
67 * <p>Differentiates between default bean instantiation, use of a
68 * factory method, and autowiring a constructor.
69 * @param beanName the name of the bean
70 * @param mbd the merged bean definition for the bean
71 * @param args explicit arguments to use for constructor or factory method invocation
72 * @return a new instance of the bean
73 * @throws BeanCreationException if the bean could not be created
74 * @see #instantiateBean
75 * @see #instantiateUsingFactoryMethod
76 * @see #autowireConstructor
77 */
78 protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args)
79 throws BeanCreationException {
80
81 // Instantiate the bean.
82 BeanWrapper instanceWrapper = null;
83 if (mbd.isSingleton()) {
84 instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
85 }
86 if (instanceWrapper == null) {
87 instanceWrapper = createBeanInstance(beanName, mbd, args);
88 }
89
90 // 省略......
91
92 // Initialize the bean instance.
93 Object exposedObject = bean;
94 try {
95 // 根据加载到的bean definition给 bean赋值
96 populateBean(beanName, mbd, instanceWrapper);
97 // 调用bean初始化方法
98 exposedObject = initializeBean(beanName, exposedObject, mbd);
99 }
100 catch (Throwable ex) {
101 if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
102 throw (BeanCreationException) ex;
103 }
104 else {
105 throw new BeanCreationException(
106 mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
107 }
108 }
109
110 // 省略......
111
112 return exposedObject;
113 }
跟进AbstractAutowireCapableBeanFactory#initializeBean方法：
1 /**
2 * Initialize the given bean instance, applying factory callbacks
3 * as well as init methods and bean post processors.
4 * <p>Called from {@link #createBean} for traditionally defined beans,
5 * and from {@link #initializeBean} for existing bean instances.
6 * @param beanName the bean name in the factory (for debugging purposes)
7 * @param bean the new bean instance we may need to initialize
8 * @param mbd the bean definition that the bean was created with
9 * (can also be {@code null}, if given an existing bean instance)
10 * @return the initialized bean instance (potentially wrapped)
11 * @see BeanNameAware
12 * @see BeanClassLoaderAware
13 * @see BeanFactoryAware
14 * @see #applyBeanPostProcessorsBeforeInitialization
15 * @see #invokeInitMethods
16 * @see #applyBeanPostProcessorsAfterInitialization
17 */
18 protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {
19 // 1、工厂factory类 接口回调
20 if (System.getSecurityManager() != null) {
21 AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
22 invokeAwareMethods(beanName, bean);
23 return null;
24 }, getAccessControlContext());
25 }
26 else {
27 invokeAwareMethods(beanName, bean);
28 }
29
30 Object wrappedBean = bean;
31 if (mbd == null || !mbd.isSynthetic()) {
32 // 2、BeanPostProcessor前置执行
33 wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
34 }
35
36 try {
37 // 3、InitializingBean接口方法 or 自定义 init method 执行
38 invokeInitMethods(beanName, wrappedBean, mbd);
39 }
40 catch (Throwable ex) {
41 throw new BeanCreationException(
42 (mbd != null ? mbd.getResourceDescription() : null),
43 beanName, "Invocation of init method failed", ex);
44 }
45 if (mbd == null || !mbd.isSynthetic()) {
46 // 4、BeanPostProcessor后置执行
47 wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
48 }
49
50 return wrappedBean;
51 }
对应回调方法：
1 private void invokeAwareMethods(final String beanName, final Object bean) {
2 if (bean instanceof Aware) {
3 if (bean instanceof BeanNameAware) {
4 ((BeanNameAware) bean).setBeanName(beanName);
5 }
6 if (bean instanceof BeanClassLoaderAware) {
7 ClassLoader bcl = getBeanClassLoader();
8 if (bcl != null) {
9 ((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);
10 }
11 }
12 if (bean instanceof BeanFactoryAware) {
13 ((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
14 }
15 }
16 }
17
18 /**
19 * Give a bean a chance to react now all its properties are set,
20 * and a chance to know about its owning bean factory (this object).
21 * This means checking whether the bean implements InitializingBean or defines
22 * a custom init method, and invoking the necessary callback(s) if it does.
23 * @param beanName the bean name in the factory (for debugging purposes)
24 * @param bean the new bean instance we may need to initialize
25 * @param mbd the merged bean definition that the bean was created with
26 * (can also be {@code null}, if given an existing bean instance)
27 * @throws Throwable if thrown by init methods or by the invocation process
28 * @see #invokeCustomInitMethod
29 */
30 protected void invokeInitMethods(String beanName, final Object bean, @Nullable RootBeanDefinition mbd)
31 throws Throwable {
32
33 boolean isInitializingBean = (bean instanceof InitializingBean);
34 if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
35 if (logger.isTraceEnabled()) {
36 logger.trace("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
37 }
38 if (System.getSecurityManager() != null) {
39 try {
40 AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> {
41 ((InitializingBean) bean).afterPropertiesSet();
42 return null;
43 }, getAccessControlContext());
44 }
45 catch (PrivilegedActionException pae) {
46 throw pae.getException();
47 }
48 }
49 else {
50 ((InitializingBean) bean).afterPropertiesSet();
51 }
52 }
53
54 if (mbd != null && bean.getClass() != NullBean.class) {
55 String initMethodName = mbd.getInitMethodName();
56 if (StringUtils.hasLength(initMethodName) &&
57 !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
58 !mbd.isExternallyManagedInitMethod(initMethodName)) {
59 invokeCustomInitMethod(beanName, bean, mbd);
60 }
61 }
62 }
63
64 @Override
65 public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
66 throws BeansException {
67
68 Object result = existingBean;
69 for (BeanPostProcessor processor : getBeanPostProcessors()) {
70 Object current = processor.postProcessBeforeInitialization(result, beanName);
71 if (current == null) {
72 return result;
73 }
74 result = current;
75 }
76 return result;
77 }
78
79 @Override
80 public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
81 throws BeansException {
82
83 Object result = existingBean;
84 for (BeanPostProcessor processor : getBeanPostProcessors()) {
85 Object current = processor.postProcessAfterInitialization(result, beanName);
86 if (current == null) {
87 return result;
88 }
89 result = current;
90 }
91 return result;
92 }
initializeBean对应的方法
总结如下：
(1.1)、由此可见BeanPostProcessor的一个触发入口在AbstractAutowireCapableBeanFactory#createBean，最终至AbstractAutowireCapableBeanFactory#initializeBean。
(1.2)、AbstractAutowireCapableBeanFactory#initializeBean不但会触发BeanPostProcessor回掉方法，并且还会按顺序执行bean生命周期：
- factory类型接口(BeanNameAware#setBeanName)
- factory类型接口(BeanClassLoaderAware#setBeanClassLoader)
- factory类型接口(BeanFactoryAware#setBeanFactory)
- BeanPostProcessor#postProcessBeforeInitialization
- InitializingBean和自定义的init-method
- BeanPostProcessor#postProcessAfterInitialization
触发（2）FactoryBeanRegistrySupport（后续补上）
