目录：Springboot源码学习目录上文：06、SpringBoot 启动 准备运行环境(prepareEnvironment)流程(三)前言：
一、创建应用上下文
debug进入createApplicationContext方法
protected ConfigurableApplicationContext createApplicationContext() {
// 一个创建应用上下文的工厂方法
return this.applicationContextFactory.create(this.webApplicationType);
}工厂方法的默认实现，通过之前获取到的容器类型来决定创建什么样的工厂，此时我们的webApplicationType是SERVLET
ApplicationContextFactory DEFAULT = (webApplicationType) -> {
try {
switch (webApplicationType) {
case SERVLET:
return new AnnotationConfigServletWebServerApplicationContext();
case REACTIVE:
return new AnnotationConfigReactiveWebServerApplicationContext();
default:
return new AnnotationConfigApplicationContext();
}
}
catch (Exception ex) {
throw new IllegalStateException("Unable create a default ApplicationContext instance, "+ "you may need a custom ApplicationContextFactory", ex);
}
};创建AnnotationConfigServletWebServerApplicationContext会初始化AnnotatedBeanDefinitionReader，ClassPathBeanDefinitionScanner
看名字我们也大概知道，这两个类都和BeanDefinition的读取有关
public AnnotationConfigServletWebServerApplicationContext() {
// AnnotatedBeanDefinitionReader 实例化过程见 标题二
this.reader = new AnnotatedBeanDefinitionReader(this);
// ClassPathBeanDefinitionScanner 实例化过程见 标题三
this.scanner = new ClassPathBeanDefinitionScanner(this);
}父类中会初始化一个bean工厂DefaultListableBeanFactory
public GenericApplicationContext() {
this.beanFactory = new DefaultListableBeanFactory();
}父类中还会初始化一个资源解析器getResourcePatternResolver
public AbstractApplicationContext() {
this.resourcePatternResolver = getResourcePatternResolver();
}二、创建AnnotatedBeanDefinitionReader
AnnotatedBeanDefinitionReader在实例化的过程中会向上下文的工厂中注册很多重要的beanDefinition
// debug进入AnnotatedBeanDefinitionReader的构造方法
public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry) {
// 调用重载构造方法
this(registry, getOrCreateEnvironment(registry));
}
// 重载构造方法
public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry, Environment environment) {
Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
Assert.notNull(environment, "Environment must not be null");
// 将当前上下文赋值给registry
this.registry = registry;
this.conditionEvaluator = new ConditionEvaluator(registry, environment, null);
// 工具类，向上下文注入beanDefinition
AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
}下面的逻辑都是AnnotationConfigUtils这个工具类的
通过此工具类的 registerAnnotationConfigProcessors方法注入的BeanDefinition的角色都是基础设施bean(ROLE_INFRASTRUCTURE)
注入的 BeanDefinition 有如下ConfigurationClassPostProcessor：是一个BeanFactoryPostProcessor,用于解析@Component，@PropertySources，@ComponentScans，@Import，@ImportResource，@BeanAutowiredAnnotationBeanPostProcessor：是一个BeanPostProcessor,用于解析 @Autowired，@ValueCommonAnnotationBeanPostProcessor：是一个BeanPostProcessor,用于解析@Resource，@WebServiceRef，@EJBPersistenceAnnotationBeanPostProcessor：是一个BeanPostProcessor,和jpa相关，没有这个类的依赖不会注入这个类的BeanDefinitionEventListenerMethodProcessor：实现了BeanFactoryPostProcessor，和SmartInitializingSingleton，和DefaultEventListenerFactory配合将有@EventListener注解的方法封装为监听器DefaultEventListenerFactory：主要功能是将有@EventListener注解的方法封装为监听器
public static void registerAnnotationConfigProcessors(BeanDefinitionRegistry registry) {
// 调用重载
registerAnnotationConfigProcessors(registry, null);
}
// 继续debug进入重载方法，就是真正的注入beanDefinition
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);
// 如果上下文中没有ConfigurationClassPostProcessor就注入
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));
}
// 如果上下文中没有AutowiredAnnotationBeanPostProcessor就注入
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));
}
// 如果上下文中没有CommonAnnotationBeanPostProcessor就注入
// 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));
}
// 如果上下文中没有PersistenceAnnotationBeanPostProcessor，并且没有引入依赖就注入
// 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));
}
// 如果上下文中没有EventListenerMethodProcessor就注入
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));
}
// 如果上下文中没有DefaultEventListenerFactory就注入
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;
}三、创建ClassPathBeanDefinitionScanner
主要是将@Component,@ManagedBean,@Named,放在过滤器中作为基础注解，使其和其子类，都可以被扫描注入spring上下文
其实在应用上下文创建时初始化的这个扫描器，在后续中并没有用到他的过滤器，只是在后续 @ComponentScan注解解析过程中又会创建一个，过程和本次一样
这里看到这里先给大家展示一下
// 调用构造方法，后续会多次调用重载的构造方法
public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry) {
this(registry, true);
}
public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters) {
this(registry, useDefaultFilters, getOrCreateEnvironment(registry));
}
public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters,
Environment environment) {
this(registry, useDefaultFilters, environment,
(registry instanceof ResourceLoader ? (ResourceLoader) registry : null));
}
// 调用构造方法
public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters,
Environment environment, @Nullable ResourceLoader resourceLoader) {
Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
this.registry = registry;
if (useDefaultFilters) {
// 我们要看的重要的逻辑
registerDefaultFilters();
}
setEnvironment(environment);
setResourceLoader(resourceLoader);
}这个方法中会将 @Component，@ManagedBean，@Named 都加入包含的过滤器中，在后面 解析 @ComponentScan 时告知要讲那类注入到容器中
protected void registerDefaultFilters() {
this.includeFilters.add(new AnnotationTypeFilter(Component.class));
ClassLoader cl = ClassPathScanningCandidateComponentProvider.class.getClassLoader();
try {
this.includeFilters.add(new AnnotationTypeFilter(
((Class<? extends Annotation>) ClassUtils.forName("javax.annotation.ManagedBean", cl)), false));
logger.trace("JSR-250 'javax.annotation.ManagedBean' found and supported for component scanning");
}
catch (ClassNotFoundException ex) {
// JSR-250 1.1 API (as included in Java EE 6) not available - simply skip.
}
try {
this.includeFilters.add(new AnnotationTypeFilter(
((Class<? extends Annotation>) ClassUtils.forName("javax.inject.Named", cl)), false));
logger.trace("JSR-330 'javax.inject.Named' annotation found and supported for component scanning");
}
catch (ClassNotFoundException ex) {
// JSR-330 API not available - simply skip.
}
}
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