Spring源码------IOC容器初始化过程
前言
IOC容器的初始化过程,我这边分为两大步
1.容器的初始化
AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(MyConfig.class); 
2.Bean的创建
Food food = annotationConfigApplicationContext.getBean("food", Food.class);
1.容器的初始化
1.1初始化DefaultListableBeanFactory
AnnotationConfigApplicationContext继承GenericApplicationContext,所以在初始化AnnotationConfigApplicationContext的时候,会先调用父类GenericApplicationContext的构造函数,而 DefaultListableBeanFactory实现了BeanDefinitionRegistry,所以最终AnnotationConfigApplicationContext既是一个BeanFactory,也是一个BeanDefinitionRegistry
public GenericApplicationContext() {
this.beanFactory = new DefaultListableBeanFactory();
}1.2初始化reader
this.reader = new AnnotatedBeanDefinitionReader(this);该方法最主要的作用就是注册内置的五个BeanDefinition到BeanDefinitionMap中,重点关注前两个
ConfigurationClassPostProcessor[实现BeanDefinitionRegistryPostProcessor]AutowiredAnnotationBeanPostProcessor[实现BeanPostProcessor]CommonAnnotationBeanPostProcessor[实现BeanPostProcessor]EventListenerMethodProcessor[实现BeanFactoryPostProcessor]DefaultEventListenerFactory
public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors(
BeanDefinitionRegistry registry, @Nullable Object source) {
DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry);
if (beanFactory != null) {
if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) {
beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
}
if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) {
beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());
}
}
Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<>(8);
if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));
}
if (!registry.containsBeanDefinition(AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME));
}
// Check for JSR-250 support, and if present add the CommonAnnotationBeanPostProcessor.
if (jsr250Present && !registry.containsBeanDefinition(COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(CommonAnnotationBeanPostProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, COMMON_ANNOTATION_PROCESSOR_BEAN_NAME));
}
// Check for JPA support, and if present add the PersistenceAnnotationBeanPostProcessor.
if (jpaPresent && !registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition();
try {
def.setBeanClass(ClassUtils.forName(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME,
AnnotationConfigUtils.class.getClassLoader()));
}
catch (ClassNotFoundException ex) {
throw new IllegalStateException(
"Cannot load optional framework class: " + PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, ex);
}
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME));
}
if (!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(EventListenerMethodProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME));
}
if (!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(DefaultEventListenerFactory.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME));
}
return beanDefs;
}1.3初始化scanner
该scanner只有显式调用才会用到,不重要
annotationConfigApplicationContext.scan("com.lyf.study");1.4注册传入的配置类MyConfig
public void register(Class<?>... componentClasses) {
for (Class<?> componentClass : componentClasses) {
registerBean(componentClass);
}
}最终会到AnnotatedBeanDefinitionReader中的doRegisterBean方法中
关键步骤如下:
1.4.1解析@Conditional注解,判断配置类是否满足加载条件,不满足则直接跳过
if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) {
return;
}1.4.2将配置类注册到BeanDefinitionMap中
BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);1.5执行refresh的invokeBeanFactoryPostProcessor
1.5.1执行手动添加的BeanDefinitionRegistryPostProcessor
若手动注册为BeanDefinitionRegistryPostProcessor,则先执行其postProcessBeanDefinitionRegistry方法
注:BeanFactoryPostProcessor是BeanDefinitionRegistryPostProcessor的父类
BeanFactoryPostProcessor
有postProcessBeanFactory方法,主要用于修改BeanDefinitionMap中的BeanDefinition
BeanDefinitionRegistryPostProcessor
有postProcessBeanDefinitionRegistry方法,主要用于添加BeanDefinition到BeanDefinitionMap中
//beanFactoryPostProcessors中的所有postProcessor都是显式调用annotationConfigApplicationContext.addBeanFactoryPostProcessor(null);来的
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
registryProcessor.postProcessBeanDefinitionRegistry(registry);
registryProcessors.add(registryProcessor);
}
else {
regularPostProcessors.add(postProcessor);
}
}
1.5.2 执行实现PriorityOrdered接口的BeanDefinitionRegistryPostProcessor(关键)
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();这里默认情况下只会获取到reader中注册的5个内置的BeanFactoryPostProcessor中的ConfigurationClassPostProcessor,然后执行ConfigurationClassPostProcessor的postProcessBeanDefinitionRegistry方法
ConfigurationClassPostProcessor的postProcessBeanDefinitionRegistry非常的关键,它主要做了一下几件事:
(1)从beanFactory中获取所有已经注册到BeanDefinitionMap中的BeanDefinitionNames
(2)给使用了@Configuration注解的BeanDefinition打上full的标识[后续会使用cglib增强],给使用了@Order注解的BeanDefinition打上优先等级
(3)将符合(2)的所有BeanDefinition放入configCandidates列表中
(4)对configCandidates列表中的BeanDefinition,依据order属性值排序,值越小,优先级越高
(5)构建ConfigurationClassParser,解析每一个使用@Configuration的类,内部会对@Component、@PropertySource、@ComponentScan、@Import、@ImportResource、@Bean注解做处理
(6)将解析出来的对象转成BeanDefintion注册到BeanDefinitionMap中
1.5.3 执行实现PriorityOrdered接口的BeanDefinitionRegistryPostProcessor
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();1.5.4执行剩下的BeanDefinitionRegistryPostProcessor
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
boolean reiterate = true;
while (reiterate) {
reiterate = false;
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
reiterate = true;
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
}1.5.5执行所有BeanDefinitionRegistryPostProcessor的postProcessBeanFactory
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);1.5.6执行所有BeanFactoryPostProcessor的postProcessBeanFactory
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
for (String ppName : postProcessorNames) {
if (processedBeans.contains(ppName)) {
// skip - already processed in first phase above
}
else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
for (String postProcessorName : orderedPostProcessorNames) {
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
sortPostProcessors(orderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
// Finally, invoke all other BeanFactoryPostProcessors.
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
for (String postProcessorName : nonOrderedPostProcessorNames) {
nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
// Clear cached merged bean definitions since the post-processors might have
// modified the original metadata, e.g. replacing placeholders in values...
beanFactory.clearMetadataCache();1.6执行refresh的registerBeanPostProcessors方法
依据内置的AutowiredAnnotationBeanPostProcessor和CommonAnnotationBeanPostProcessor对应的BeanDefinition,生成相对应的Bean,并添加到容器中
- BeanDefinitionRegistryPostProcessor
最先执行,主要用于添加BeanDefinition
- BeanFactoryPostProcessor
次要执行,主要用于修改BeanDefinition
- BeanPostProcessor
最后执行,在Bean初始化前会调用postProcessBeforeInitialization,在Bean初始化之后会 调用postProcessAfterInitialization
至此,容器大致的初始化过程结束.