ConfigurationClassPostProcessor 注解解析流程
1.Configuration是对哪些注解进行解析的？
1）@Component
2）@PropertySource
3）@ComponentScan、@ComponentScans
4）@import
5）@importResource
6）@Bean
2.ConfigurationClassPostProcessor是怎样被调用的？
1）我们先来看BeanFactoryPostProcessor 的执行，扫描所有的BeanDefinitionRegistryPostProcessor类型的BeanDefinition，查找到一个名为org.springframework.context.annotation.internalConfigurationAnnotationProcessor 的 BeanDefinition
但是这个名字对应的BeanDefinition到底是那个呢？
在下面的代码我们可以看到，在创建AnnotationConfigApplicationContext时候，构造方法中new了一个 AnnotatedBeanDefiniitonReader对象，里面调用了AnnotationConfigUtils方法，往BeanFactory中注册了一系列的内置BeanFactoryPostProcessor和BeanPostProcessor。
org.springframework.context.annotation.internalConfigurationAnnotationProcessor对应的类就是ConfigurationClassPostProcessor
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public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry, Environment environment) {
Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
Assert.notNull(environment, "Environment must not be null");
this.registry = registry;
this.conditionEvaluator = new ConditionEvaluator(registry, environment, null);
AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
}
public abstract class AnnotationConfigUtils {
/**
* The bean name of the internally managed Configuration annotation processor.
*/
public static final String CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME =
"org.springframework.context.annotation.internalConfigurationAnnotationProcessor";
/**
* The bean name of the internally managed BeanNameGenerator for use when processing
* {@link Configuration} classes. Set by {@link AnnotationConfigApplicationContext}
* and {@code AnnotationConfigWebApplicationContext} during bootstrap in order to make
* any custom name generation strategy available to the underlying
* {@link ConfigurationClassPostProcessor}.
* @since 3.1.1
*/
public static final String CONFIGURATION_BEAN_NAME_GENERATOR =
"org.springframework.context.annotation.internalConfigurationBeanNameGenerator";
/**
* The bean name of the internally managed Autowired annotation processor.
*/
public static final String AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME =
"org.springframework.context.annotation.internalAutowiredAnnotationProcessor";
/**
* The bean name of the internally managed Required annotation processor.
* @deprecated as of 5.1, since no Required processor is registered by default anymore
*/
@Deprecated
public static final String REQUIRED_ANNOTATION_PROCESSOR_BEAN_NAME =
"org.springframework.context.annotation.internalRequiredAnnotationProcessor";
/**
* The bean name of the internally managed JSR-250 annotation processor.
*/
public static final String COMMON_ANNOTATION_PROCESSOR_BEAN_NAME =
"org.springframework.context.annotation.internalCommonAnnotationProcessor";
/**
* The bean name of the internally managed JPA annotation processor.
*/
public static final String PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME =
"org.springframework.context.annotation.internalPersistenceAnnotationProcessor";
private static final String PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME =
"org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor";
/**
* The bean name of the internally managed @EventListener annotation processor.
*/
public static final String EVENT_LISTENER_PROCESSOR_BEAN_NAME =
"org.springframework.context.event.internalEventListenerProcessor";
/**
* The bean name of the internally managed EventListenerFactory.
*/
public static final String EVENT_LISTENER_FACTORY_BEAN_NAME =
"org.springframework.context.event.internalEventListenerFactory";
private static final boolean jsr250Present;
private static final boolean jpaPresent;
public static Set registerAnnotationConfigProcessors(
BeanDefinitionRegistry registry, @Nullable Object source) {
// 获取beanFactory
DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry);
if (beanFactory != null) {
if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) {
// //设置依赖比较器
beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
}
if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) {
// //设置自动装配解析器
beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());
}
}
// 创建BeanDefinitionHolder集合
Set beanDefs = new LinkedHashSet<>(8);
// 注册内部管理的用于处理@configuration注解的后置处理器的bean
if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class);
def.setSource(source);
// 注册BeanDefinition到注册表中
beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));
}
// 注册内部管理的用于处理@Autowired，@Value,@Inject以及@Lookup注解的后置处理器bean
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.
// 注册内部管理的用于处理JSR-250注解，例如@Resource,@PostConstruct,@PreDestroy的后置处理器bean
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.
// 注册内部管理的用于处理JPA注解的后置处理器bean
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));
}
// 注册内部管理的用于处理@EventListener注解的后置处理器的bean
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));
}
// 注册内部管理用于生产ApplicationListener对象的EventListenerFactory对象
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;
}
}
private static void invokeBeanDefinitionRegistryPostProcessors(
Collection postProcessors, BeanDefinitionRegistry registry) {
for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
postProcessor.postProcessBeanDefinitionRegistry(registry);
}
}
**3.ConfigurationClassPostProcessor怎样进行注解解析的？
1）processConfigBeanDefinitions方法
public class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPostProcessor,
PriorityOrdered, ResourceLoaderAware, BeanClassLoaderAware, EnvironmentAware {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
// 根据对应的registry对象生成hashcode值，此对象只会操作一次，如果之前处理过则抛出异常
int registryId = System.identityHashCode(registry);
if (this.registriesPostProcessed.contains(registryId)) {
throw new IllegalStateException(
"postProcessBeanDefinitionRegistry already called on this post-processor against " + registry);
}
if (this.factoriesPostProcessed.contains(registryId)) {
throw new IllegalStateException(
"postProcessBeanFactory already called on this post-processor against " + registry);
}
// 将马上要进行处理的registry对象的id值放到已经处理的集合对象中
this.registriesPostProcessed.add(registryId);
// 处理配置类的bean定义信息
processConfigBeanDefinitions(registry);
}
/**
* 构建和验证一个类是否被@Configuration修饰，并做相关的解析工作
*
* 如果你对此方法了解清楚了，那么springboot的自动装配原理就清楚了
*
* Build and validate a configuration model based on the registry of
* {@link Configuration} classes.
*/
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
// 创建存放BeanDefinitionHolder的对象集合
List configCandidates = new ArrayList<>();
// 当前registry就是DefaultListableBeanFactory，获取所有已经注册的BeanDefinition的beanName
String[] candidateNames = registry.getBeanDefinitionNames();
// 遍历所有要处理的beanDefinition的名称,筛选对应的beanDefinition（被注解修饰的）
for (String beanName : candidateNames) {
// 获取指定名称的BeanDefinition对象
BeanDefinition beanDef = registry.getBeanDefinition(beanName);
// 如果beanDefinition中的configurationClass属性不等于空，那么意味着已经处理过，输出日志信息
if (beanDef.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE) != null) {
if (logger.isDebugEnabled()) {
logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
}
}
// 判断当前BeanDefinition是否是一个配置类，并为BeanDefinition设置属性为lite或者full，此处设置属性值是为了后续进行调用
// 如果Configuration配置proxyBeanMethods代理为true则为full
// 如果加了@Bean、@Component、@ComponentScan、@Import、@ImportResource注解，则设置为lite
// 如果配置类上被@Order注解标注，则设置BeanDefinition的order属性值
else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
// 添加到对应的集合对象中
configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
}
}
// Return immediately if no @Configuration classes were found
// 如果没有发现任何配置类，则直接返回
if (configCandidates.isEmpty()) {
return;
}
// Sort by previously determined @Order value, if applicable
// 如果适用，则按照先前确定的@Order的值排序
configCandidates.sort((bd1, bd2) -> {
int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
return Integer.compare(i1, i2);
});
// Detect any custom bean name generation strategy supplied through the enclosing application context
// 判断当前类型是否是SingletonBeanRegistry类型
SingletonBeanRegistry sbr = null;
if (registry instanceof SingletonBeanRegistry) {
// 类型的强制转换
sbr = (SingletonBeanRegistry) registry;
// 判断是否有自定义的beanName生成器
if (!this.localBeanNameGeneratorSet) {
// 获取自定义的beanName生成器
BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(
AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR);
// 如果有自定义的命名生成策略
if (generator != null) {
//设置组件扫描的beanName生成策略
this.componentScanBeanNameGenerator = generator;
// 设置import bean name生成策略
this.importBeanNameGenerator = generator;
}
}
}
// 如果环境对象等于空，那么就重新创建新的环境对象
if (this.environment == null) {
this.environment = new StandardEnvironment();
}
// Parse each @Configuration class
// 实例化ConfigurationClassParser类，并初始化相关的参数，完成配置类的解析工作
ConfigurationClassParser parser = new ConfigurationClassParser(
this.metadataReaderFactory, this.problemReporter, this.environment,
this.resourceLoader, this.componentScanBeanNameGenerator, registry);
// 创建两个集合对象，
// 存放相关的BeanDefinitionHolder对象
Set candidates = new LinkedHashSet<>(configCandidates);
// 存放扫描包下的所有bean
Set alreadyParsed = new HashSet<>(configCandidates.size());
do {
// 解析带有@Controller、@Import、@ImportResource、@ComponentScan、@ComponentScans、@Bean的BeanDefinition
parser.parse(candidates);
// 将解析完的Configuration配置类进行校验，1、配置类不能是final，2、@Bean修饰的方法必须可以重写以支持CGLIB
parser.validate();
// 获取所有的bean,包括扫描的bean对象，@Import导入的bean对象
Set configClasses = new LinkedHashSet<>(parser.getConfigurationClasses());
// 清除掉已经解析处理过的配置类
configClasses.removeAll(alreadyParsed);
// Read the model and create bean definitions based on its content
// 判断读取器是否为空，如果为空的话，就创建完全填充好的ConfigurationClass实例的读取器
if (this.reader == null) {
this.reader = new ConfigurationClassBeanDefinitionReader(
registry, this.sourceExtractor, this.resourceLoader, this.environment,
this.importBeanNameGenerator, parser.getImportRegistry());
}
// 核心方法，将完全填充好的ConfigurationClass实例转化为BeanDefinition注册入IOC容器
this.reader.loadBeanDefinitions(configClasses);
// 添加到已经处理的集合中
alreadyParsed.addAll(configClasses);
candidates.clear();
// 这里判断registry.getBeanDefinitionCount() > candidateNames.length的目的是为了知道reader.loadBeanDefinitions(configClasses)这一步有没有向BeanDefinitionMap中添加新的BeanDefinition
// 实际上就是看配置类(例如AppConfig类会向BeanDefinitionMap中添加bean)
// 如果有，registry.getBeanDefinitionCount()就会大于candidateNames.length
// 这样就需要再次遍历新加入的BeanDefinition，并判断这些bean是否已经被解析过了，如果未解析，需要重新进行解析
// 这里的AppConfig类向容器中添加的bean，实际上在parser.parse()这一步已经全部被解析了
if (registry.getBeanDefinitionCount() > candidateNames.length) {
String[] newCandidateNames = registry.getBeanDefinitionNames();
Set oldCandidateNames = new HashSet<>(Arrays.asList(candidateNames));
Set alreadyParsedClasses = new HashSet<>();
for (ConfigurationClass configurationClass : alreadyParsed) {
alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
}
// 如果有未解析的类，则将其添加到candidates中，这样candidates不为空，就会进入到下一次的while的循环中
for (String candidateName : newCandidateNames) {
if (!oldCandidateNames.contains(candidateName)) {
BeanDefinition bd = registry.getBeanDefinition(candidateName);
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) &&
!alreadyParsedClasses.contains(bd.getBeanClassName())) {
candidates.add(new BeanDefinitionHolder(bd, candidateName));
}
}
}
candidateNames = newCandidateNames;
}
}
while (!candidates.isEmpty());
// Register the ImportRegistry as a bean in order to support ImportAware @Configuration classes
if (sbr != null && !sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {
sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
}
if (this.metadataReaderFactory instanceof CachingMetadataReaderFactory) {
// Clear cache in externally provided MetadataReaderFactory; this is a no-op
// for a shared cache since it'll be cleared by the ApplicationContext.
((CachingMetadataReaderFactory) this.metadataReaderFactory).clearCache();
}
}
}
调用processConfigBeanDefinitions方法
1）查找到BeanFactory中的所有BeanDefinition，进行循环遍历
查到是否有configurationClass属性，有的话证明已经被处理过
checkConfigurationClassCandidate：（
判断是否有@Configuration注解修饰，
如果被@Configuration修饰且需要被代理则设置属性为full，
如果被Component、@ComponentScan、@Import、@ImportResource标注 或者被有@Bean注解修饰的
方法则设置为lite
如果都没有就返回false
检测是否有order注解修饰，有的话就设置order属性）
将被注解修饰的添加到 configCandidates 集合中
对有order修饰的BeanDefinition进行排序
2）判断是否为SingletonBeanRegistry 类型，因为此时的BeanDefinitionRegistry为DefaultListableBeanFactory类型，而它实现了DefaultListableBeanFactory，ConfigurableListableBeanFactory继承ConfigurableBeanFactory 所以这个判断可以进来，然后强转为SingletonBeanRegistry 类型来判断是否有自定义的命名生成策略。
if (registry instanceof SingletonBeanRegistry) {
3）实例化一个ConfigurationClassParser 解析类，并初始化一系列的参数
进行解析！！！！
判断BeanDefintiion是什么类型的 （AnnotatedBeanDefinition类型，调用registry方法时已经设置过）
parser.parse(candidates);
public void parse(Set configCandidates) {
// 循环遍历configCandidates
for (BeanDefinitionHolder holder : configCandidates) {
// 获取BeanDefinition
BeanDefinition bd = holder.getBeanDefinition();
// 根据BeanDefinition类型的不同，调用parse不同的重载方法，实际上最终都是调用processConfigurationClass()方法
try {
// 注解类型
if (bd instanceof AnnotatedBeanDefinition) {
parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());
}
// 有class对象的
else if (bd instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) bd).hasBeanClass()) {
parse(((AbstractBeanDefinition) bd).getBeanClass(), holder.getBeanName());
}
else {
parse(bd.getBeanClassName(), holder.getBeanName());
}
}
catch (BeanDefinitionStoreException ex) {
throw ex;
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(
"Failed to parse configuration class [" + bd.getBeanClassName() + "]", ex);
}
}
// 执行找到的DeferredImportSelector
// DeferredImportSelector是ImportSelector的一个子类
// ImportSelector被设计成和@Import注解同样的效果，但是实现了ImportSelector的类可以条件性的决定导入某些配置
// DeferredImportSelector的设计魔都是在所有其他的配置类被处理后才进行处理
this.deferredImportSelectorHandler.process();
}
4）processConfigurationClass方法
shouldSkip方法：判断metadata为空或者存在@Conditional注解，如果都没有就直接返回false，否则直接跳过
判断是否已经被处理过
解析各个注解：
1.@Component注解解析（@Configuration、 @Controller、@Service、 都继承于@Component注解）
1)查找内部类是否有配置类，如果有的话则递归调用processConfigurationClass方法进行解析
private void processMemberClasses(ConfigurationClass configClass, SourceClass sourceClass,
Predicate filter) throws IOException {
// 找到内部类，内部类中也可能是一个配置类
Collection memberClasses = sourceClass.getMemberClasses();
// 如果不等于空的话
if (!memberClasses.isEmpty()) {
List candidates = new ArrayList<>(memberClasses.size());
// 循环判断内部类是不是配置类
for (SourceClass memberClass : memberClasses) {
if (ConfigurationClassUtils.isConfigurationCandidate(memberClass.getMetadata()) &&
!memberClass.getMetadata().getClassName().equals(configClass.getMetadata().getClassName())) {
candidates.add(memberClass);
}
}
// 对配置类进行排序操作
OrderComparator.sort(candidates);
// 遍历符合规则的类
for (SourceClass candidate : candidates) {
if (this.importStack.contains(configClass)) {
// 出现配置类循环导入，则直接报错
this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
}
else {
// 将配置类入栈
this.importStack.push(configClass);
try {
// 调用processConfigurationClass方法，因为内部类中还可能包含内部类，所以需要在做循环解析，实际工作中是不会有这中情况的
processConfigurationClass(candidate.asConfigClass(configClass), filter);
}
finally {
// 解析完出栈
this.importStack.pop();
}
}
}
}
}
2.@PropertySource 注解解析
1）获取注解上的属性，并转换为Resouce对象添加为属性资源
private void processPropertySource(AnnotationAttributes propertySource) throws IOException {
// 获取name属性
String name = propertySource.getString("name");
if (!StringUtils.hasLength(name)) {
name = null;
}
// 获取encoding属性
String encoding = propertySource.getString("encoding");
if (!StringUtils.hasLength(encoding)) {
encoding = null;
}
// 获取value属性
String[] locations = propertySource.getStringArray("value");
Assert.isTrue(locations.length > 0, "At least one @PropertySource(value) location is required");
boolean ignoreResourceNotFound = propertySource.getBoolean("ignoreResourceNotFound");
Class factoryClass = propertySource.getClass("factory");
PropertySourceFactory factory = (factoryClass == PropertySourceFactory.class ?
DEFAULT_PROPERTY_SOURCE_FACTORY : BeanUtils.instantiateClass(factoryClass));
for (String location : locations) {
try {
// 处理属性值的占位符
String resolvedLocation = this.environment.resolveRequiredPlaceholders(location);
// 讲指定位置的资源转换成resource对象
Resource resource = this.resourceLoader.getResource(resolvedLocation);
// 添加resource对象为属性资源
addPropertySource(factory.createPropertySource(name, new EncodedResource(resource, encoding)));
}
catch (IllegalArgumentException | FileNotFoundException | UnknownHostException | SocketException ex) {
// Placeholders not resolvable or resource not found when trying to open it
if (ignoreResourceNotFound) {
if (logger.isInfoEnabled()) {
logger.info("Properties location [" + location + "] not resolvable: " + ex.getMessage());
}
}
else {
throw ex;
}
}
}
}
3.@ComponentScan、@ComponentScans注解解析
1)扫描路径下所包含的所有类并进行解析this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());解析后的BeanDefinition放入到scannedBeanDefinitions集合中
2)循环遍历解析出来的BeanDefinition是否还有@ComponentScan注解，如果有则递归调用processConfigurationClass方法进行解析
Set componentScans = AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
if (!componentScans.isEmpty() &&
!this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
for (AnnotationAttributes componentScan : componentScans) {
// The config class is annotated with @ComponentScan -> perform the scan immediately
// 解析@ComponentScan和@ComponentScans配置的扫描的包所包含的类
// 比如 basePackages = com.my, 那么在这一步会扫描出这个包及子包下的class，然后将其解析成BeanDefinition
// (BeanDefinition可以理解为等价于BeanDefinitionHolder)
Set scannedBeanDefinitions =
this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
// Check the set of scanned definitions for any further config classes and parse recursively if needed
// 通过上一步扫描包com.my，有可能扫描出来的bean中可能也添加了ComponentScan或者ComponentScans注解.
//所以这里需要循环遍历一次，进行递归(parse)，继续解析，直到解析出的类上没有ComponentScan和ComponentScans
for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
if (bdCand == null) {
bdCand = holder.getBeanDefinition();
}
// 判断是否是一个配置类，并设置full或lite属性
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
// 通过递归方法进行解析
parse(bdCand.getBeanClassName(), holder.getBeanName());
}
}
}
}
public Set parse(AnnotationAttributes componentScan, final String declaringClass) {
// 创建对应的扫描类
ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry,
componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);
// 获取@ComponentScan的参数，并进行参数的设置工作
Class generatorClass = componentScan.getClass("nameGenerator");
boolean useInheritedGenerator = (BeanNameGenerator.class == generatorClass);
scanner.setBeanNameGenerator(useInheritedGenerator ? this.beanNameGenerator :
BeanUtils.instantiateClass(generatorClass));
// 获取scopedProxy属性
ScopedProxyMode scopedProxyMode = componentScan.getEnum("scopedProxy");
if (scopedProxyMode != ScopedProxyMode.DEFAULT) {
scanner.setScopedProxyMode(scopedProxyMode);
}
else {
Class resolverClass = componentScan.getClass("scopeResolver");
scanner.setScopeMetadataResolver(BeanUtils.instantiateClass(resolverClass));
}
// 获取resourcePattern属性
scanner.setResourcePattern(componentScan.getString("resourcePattern"));
// 获取includeFilters属性
for (AnnotationAttributes filter : componentScan.getAnnotationArray("includeFilters")) {
for (TypeFilter typeFilter : typeFiltersFor(filter)) {
scanner.addIncludeFilter(typeFilter);
}
}
// 获取excludeFilters属性
for (AnnotationAttributes filter : componentScan.getAnnotationArray("excludeFilters")) {
for (TypeFilter typeFilter : typeFiltersFor(filter)) {
scanner.addExcludeFilter(typeFilter);
}
}
// 获取lazyInit属性
boolean lazyInit = componentScan.getBoolean("lazyInit");
if (lazyInit) {
scanner.getBeanDefinitionDefaults().setLazyInit(true);
}
Set basePackages = new LinkedHashSet<>();
// 获取basePackages属性
String[] basePackagesArray = componentScan.getStringArray("basePackages");
for (String pkg : basePackagesArray) {
String[] tokenized = StringUtils.tokenizeToStringArray(this.environment.resolvePlaceholders(pkg),
ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
Collections.addAll(basePackages, tokenized);
}
// 获取basePackageClasses属性
for (Class clazz : componentScan.getClassArray("basePackageClasses")) {
basePackages.add(ClassUtils.getPackageName(clazz));
}
if (basePackages.isEmpty()) {
basePackages.add(ClassUtils.getPackageName(declaringClass));
}
scanner.addExcludeFilter(new AbstractTypeHierarchyTraversingFilter(false, false) {
@Override
protected boolean matchClassName(String className) {
return declaringClass.equals(className);
}
});
// 开始执行扫描，最终的扫描器是ClassPathBeanDefinitionScanner
return scanner.doScan(StringUtils.toStringArray(basePackages));
}
protected Set doScan(String... basePackages) {
Assert.notEmpty(basePackages, "At least one base package must be specified");
Set beanDefinitions = new LinkedHashSet<>();
// 遍历basePackages
for (String basePackage : basePackages) {
// 扫描basePackage,将符合要求的bean定义全部找出来
Set candidates = findCandidateComponents(basePackage);
// 遍历所有候选的bean定义
for (BeanDefinition candidate : candidates) {
// 解析@Scope注解，包括scopeName和proxyMode
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
// 使用beanName生成器来生成beanName
String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
if (candidate instanceof AbstractBeanDefinition) {
// 处理beanDefinition对象，例如，此bean是否可以自动装配到其他bean中
postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
}
if (candidate instanceof AnnotatedBeanDefinition) {
// 处理定义在目标类上的通用注解，包括@Lazy，@Primary，@DependsOn，@Role，@Description
AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
}
// 检查beanName是否已经注册过，如果注册过，检查是否兼容
if (checkCandidate(beanName, candidate)) {
// 将当前遍历bean的bean定义和beanName封装成BeanDefinitionHolder
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
// 根据proxyMode的值，选择是否创建作用域代理
definitionHolder =
AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
beanDefinitions.add(definitionHolder);
// 注册beanDefinition
registerBeanDefinition(definitionHolder, this.registry);
}
}
}
return beanDefinitions;
}
4.**@Import注解解析
1)递归获取所有有@Import注解的类
2）检验配置类Import引入的类是否是ImportSelector子类
- 获取导入的Class对象，通过反射来实例化ImportSelector对象，exclusionFilter来过滤掉不需要导入的
4）获取到引用的类，然后再递归调用processImports方法来处理引用类中包含的@Import注解**
private Set getImports(SourceClass sourceClass) throws IOException {
// 创建集合，存储包含@Import注解的类
Set imports = new LinkedHashSet<>();
// 创建集合，为了实现递归调用
Set visited = new LinkedHashSet<>();
// 收集@Import注解的类
collectImports(sourceClass, imports, visited);
return imports;
}
private void collectImports(SourceClass sourceClass, Set imports, Set visited)
throws IOException {
if (visited.add(sourceClass)) {
for (SourceClass annotation : sourceClass.getAnnotations()) {
String annName = annotation.getMetadata().getClassName();
// 递归处理其他可能包含@Import的注解类
if (!annName.equals(Import.class.getName())) {
collectImports(annotation, imports, visited);
}
}
// 获取Import注解的值
imports.addAll(sourceClass.getAnnotationAttributes(Import.class.getName(), "value"));
}
}
private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,
Collection importCandidates, Predicate exclusionFilter,
boolean checkForCircularImports) {
// 如果使用@Import注解修饰的类集合为空，那么直接返回
if (importCandidates.isEmpty()) {
return;
}
// 通过一个栈结构解决循环引入
if (checkForCircularImports && isChainedImportOnStack(configClass)) {
this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
}
else {
// 添加到栈中，用于处理循环引入的问题
this.importStack.push(configClass);
try {
// 遍历每一个@Import注解的类
for (SourceClass candidate : importCandidates) {
// 检验配置类Import引入的类是否是ImportSelector子类
if (candidate.isAssignable(ImportSelector.class)) {
// Candidate class is an ImportSelector -> delegate to it to determine imports
// 候选类是一个导入选择器->委托来确定是否进行导入
Class candidateClass = candidate.loadClass();
// 通过反射生成一个ImportSelect对象
ImportSelector selector = ParserStrategyUtils.instantiateClass(candidateClass, ImportSelector.class,
this.environment, this.resourceLoader, this.registry);
// 获取选择器的额外过滤器
Predicate selectorFilter = selector.getExclusionFilter();
if (selectorFilter != null) {
exclusionFilter = exclusionFilter.or(selectorFilter);
}
// 判断引用选择器是否是DeferredImportSelector接口的实例
// 如果是则应用选择器将会在所有的配置类都加载完毕后加载
if (selector instanceof DeferredImportSelector) {
// 将选择器添加到deferredImportSelectorHandler实例中，预留到所有的配置类加载完成后统一处理自动化配置类
this.deferredImportSelectorHandler.handle(configClass, (DeferredImportSelector) selector);
}
else {
// 获取引入的类，然后使用递归方式将这些类中同样添加了@Import注解引用的类
String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
Collection importSourceClasses = asSourceClasses(importClassNames, exclusionFilter);
// 递归处理，被Import进来的类也有可能@Import注解
processImports(configClass, currentSourceClass, importSourceClasses, exclusionFilter, false);
}
}
// 如果是实现了ImportBeanDefinitionRegistrar接口的bd
else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {
// Candidate class is an ImportBeanDefinitionRegistrar ->
// delegate to it to register additional bean definitions
// 候选类是ImportBeanDefinitionRegistrar -> 委托给当前注册器注册其他bean
Class candidateClass = candidate.loadClass();
ImportBeanDefinitionRegistrar registrar =
ParserStrategyUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class,
this.environment, this.resourceLoader, this.registry);
/**
* 放到当前configClass的importBeanDefinitionRegistrars中
* 在ConfigurationClassPostProcessor处理configClass时会随之一起处理
*/
configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());
}
else {
// Candidate class not an ImportSelector or ImportBeanDefinitionRegistrar ->
// process it as an @Configuration class
// 候选类既不是ImportSelector也不是ImportBeanDefinitionRegistrar-->将其作为@Configuration配置类处理
this.importStack.registerImport(
currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());
/**
* 如果Import的类型是普通类，则将其当作带有@Configuration的类一样处理
* 将candidate构造为ConfigurationClass，标注为importedBy，意味着它是通过被@Import进来的
* 后面处理会用到这个判断将这个普通类注册进DefaultListableBeanFactory
*/
processConfigurationClass(candidate.asConfigClass(configClass), exclusionFilter);
}
}
}
catch (BeanDefinitionStoreException ex) {
throw ex;
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(
"Failed to process import candidates for configuration class [" +
configClass.getMetadata().getClassName() + "]", ex);
}
finally {
this.importStack.pop();
}
}
}
5.@ImportResource注解解析
6.@Bean注解解析
1)获取有@Bean的方法，判断是否只有一个，只有一个的话直接返回，不是的话就一个一个添加到集合中
private Set retrieveBeanMethodMetadata(SourceClass sourceClass) {
AnnotationMetadata original = sourceClass.getMetadata();
Set beanMethods = original.getAnnotatedMethods(Bean.class.getName());
if (beanMethods.size() > 1 && original instanceof StandardAnnotationMetadata) {
// Try reading the class file via ASM for deterministic declaration order...
// Unfortunately, the JVM's standard reflection returns methods in arbitrary
// order, even between different runs of the same application on the same JVM.
try {
AnnotationMetadata asm =
this.metadataReaderFactory.getMetadataReader(original.getClassName()).getAnnotationMetadata();
Set asmMethods = asm.getAnnotatedMethods(Bean.class.getName());
if (asmMethods.size() >= beanMethods.size()) {
Set selectedMethods = new LinkedHashSet<>(asmMethods.size());
for (MethodMetadata asmMethod : asmMethods) {
for (MethodMetadata beanMethod : beanMethods) {
if (beanMethod.getMethodName().equals(asmMethod.getMethodName())) {
selectedMethods.add(beanMethod);
break;
}
}
}
if (selectedMethods.size() == beanMethods.size()) {
// All reflection-detected methods found in ASM method set -> proceed
beanMethods = selectedMethods;
}
}
}
catch (IOException ex) {
logger.debug("Failed to read class file via ASM for determining @Bean method order", ex);
// No worries, let's continue with the reflection metadata we started with...
}
}
return beanMethods;
}
SourceClass sourceClass = asSourceClass(configClass, filter);
do {
// 解析各种注解
sourceClass = doProcessConfigurationClass(configClass, sourceClass, filter);
}
while (sourceClass != null);
@Nullable
protected final SourceClass doProcessConfigurationClass(
ConfigurationClass configClass, SourceClass sourceClass, Predicate filter)
throws IOException {
// @Configuration继承了@Component
if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
// Recursively process any member (nested) classes first
// 递归处理内部类，因为内部类也是一个配置类，配置类上有@configuration注解，该注解继承@Component，if判断为true，调用processMemberClasses方法，递归解析配置类中的内部类
processMemberClasses(configClass, sourceClass, filter);
}
// Process any @PropertySource annotations
// 如果配置类上加了@PropertySource注解，那么就解析加载properties文件，并将属性添加到spring上下文中
for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), PropertySources.class,
org.springframework.context.annotation.PropertySource.class)) {
if (this.environment instanceof ConfigurableEnvironment) {
processPropertySource(propertySource);
}
else {
logger.info("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
"]. Reason: Environment must implement ConfigurableEnvironment");
}
}
// Process any @ComponentScan annotations
// 处理@ComponentScan或者@ComponentScans注解，并将扫描包下的所有bean转换成填充后的ConfigurationClass
// 此处就是将自定义的bean加载到IOC容器，因为扫描到的类可能也添加了@ComponentScan和@ComponentScans注解，因此需要进行递归解析
Set componentScans = AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
if (!componentScans.isEmpty() &&
!this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
for (AnnotationAttributes componentScan : componentScans) {
// The config class is annotated with @ComponentScan -> perform the scan immediately
// 解析@ComponentScan和@ComponentScans配置的扫描的包所包含的类
// 比如 basePackages = com.my, 那么在这一步会扫描出这个包及子包下的class，然后将其解析成BeanDefinition
// (BeanDefinition可以理解为等价于BeanDefinitionHolder)
Set scannedBeanDefinitions =
this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
// Check the set of scanned definitions for any further config classes and parse recursively if needed
// 通过上一步扫描包com.my，有可能扫描出来的bean中可能也添加了ComponentScan或者ComponentScans注解.
//所以这里需要循环遍历一次，进行递归(parse)，继续解析，直到解析出的类上没有ComponentScan和ComponentScans
for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
if (bdCand == null) {
bdCand = holder.getBeanDefinition();
}
// 判断是否是一个配置类，并设置full或lite属性
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
// 通过递归方法进行解析
parse(bdCand.getBeanClassName(), holder.getBeanName());
}
}
}
}
// Process any @Import annotations
// 处理@Import注解
processImports(configClass, sourceClass, getImports(sourceClass), filter, true);
// Process any @ImportResource annotations
// 处理@ImportResource注解，导入spring的配置文件
AnnotationAttributes importResource =
AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
if (importResource != null) {
String[] resources = importResource.getStringArray("locations");
Class readerClass = importResource.getClass("reader");
for (String resource : resources) {
String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);
configClass.addImportedResource(resolvedResource, readerClass);
}
}
// Process individual @Bean methods
// 处理加了@Bean注解的方法，将@Bean方法转化为BeanMethod对象，保存再集合中
Set beanMethods = retrieveBeanMethodMetadata(sourceClass);
for (MethodMetadata methodMetadata : beanMethods) {
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}
// Process default methods on interfaces
// 处理接口的默认方法实现，从jdk8开始，接口中的方法可以有自己的默认实现，因此如果这个接口的方法加了@Bean注解，也需要被解析
processInterfaces(configClass, sourceClass);
// Process superclass, if any
// 解析父类，如果被解析的配置类继承了某个类，那么配置类的父类也会被进行解析
if (sourceClass.getMetadata().hasSuperClass()) {
String superclass = sourceClass.getMetadata().getSuperClassName();
if (superclass != null && !superclass.startsWith("java") &&
!this.knownSuperclasses.containsKey(superclass)) {
this.knownSuperclasses.put(superclass, configClass);
// Superclass found, return its annotation metadata and recurse
return sourceClass.getSuperClass();
}
}
// No superclass -> processing is complete
return null;
}
将所有扫描到的BeanDefinition获取出来，放入集合中 其中包含@ComponentScan扫描的和@Import导入的，然后转换为BeanDefinition注册到BeanFactory中
// 获取所有的bean,包括扫描的bean对象，@Import导入的bean对象
Set configClasses = new LinkedHashSet<>(parser.getConfigurationClasses());
//将完全填充好的ConfigurationClass实例转化为BeanDefinition注册入IOC容器
this.reader.loadBeanDefinitions(configClasses);
loadBeanDefinitionsForBeanMethod 方法处理有@Bean注解标注的方法的BeanDefinition，
在此处设置@Bean 实例化 工厂方法名称以及工厂名称
设置解析的工厂方法，然后设置装配模式，默认是按构造器自动装配，
获取是否有自定义的装配模式，有的话重新设置，
检测是否有@PreDestroy或者@PostConstruct注解修饰，有的话设置initMethod，
设置destroy方法，
判断需不需要代理
注册Bean
// 设置工厂名
beanDef.setFactoryBeanName(configClass.getBeanName());
beanDef.setUniqueFactoryMethodName(methodName);
private void loadBeanDefinitionsForBeanMethod(BeanMethod beanMethod) {
ConfigurationClass configClass = beanMethod.getConfigurationClass();
// 获取方法元数据
MethodMetadata metadata = beanMethod.getMetadata();
// 获取方法名称
String methodName = metadata.getMethodName();
// Do we need to mark the bean as skipped by its condition?
if (this.conditionEvaluator.shouldSkip(metadata, ConfigurationPhase.REGISTER_BEAN)) {
configClass.skippedBeanMethods.add(methodName);
return;
}
if (configClass.skippedBeanMethods.contains(methodName)) {
return;
}
// 获取bean注解的属性
AnnotationAttributes bean = AnnotationConfigUtils.attributesFor(metadata, Bean.class);
Assert.state(bean != null, "No @Bean annotation attributes");
// Consider name and any aliases
// 获取别名
List names = new ArrayList<>(Arrays.asList(bean.getStringArray("name")));
String beanName = (!names.isEmpty() ? names.remove(0) : methodName);
// Register aliases even when overridden
for (String alias : names) {
// 注册剩下的别名
this.registry.registerAlias(beanName, alias);
}
// Has this effectively been overridden before (e.g. via XML)?
// 是否存在同名bean定义
if (isOverriddenByExistingDefinition(beanMethod, beanName)) {
if (beanName.equals(beanMethod.getConfigurationClass().getBeanName())) {
throw new BeanDefinitionStoreException(beanMethod.getConfigurationClass().getResource().getDescription(),
beanName, "Bean name derived from @Bean method '" + beanMethod.getMetadata().getMethodName() +
"' clashes with bean name for containing configuration class; please make those names unique!");
}
return;
}
// 封装为ConfigurationClassBeanDefinition,表示是来自配置类里的bean定义
ConfigurationClassBeanDefinition beanDef = new ConfigurationClassBeanDefinition(configClass, metadata, beanName);
// 设置来源的类
beanDef.setSource(this.sourceExtractor.extractSource(metadata, configClass.getResource()));
// 判断是否是静态的，设置BeanClass
if (metadata.isStatic()) {
// static @Bean method
if (configClass.getMetadata() instanceof StandardAnnotationMetadata) {
beanDef.setBeanClass(((StandardAnnotationMetadata) configClass.getMetadata()).getIntrospectedClass());
}
else {
beanDef.setBeanClassName(configClass.getMetadata().getClassName());
}
beanDef.setUniqueFactoryMethodName(methodName);
}
else {
// instance @Bean method
// 设置工厂名
beanDef.setFactoryBeanName(configClass.getBeanName());
beanDef.setUniqueFactoryMethodName(methodName);
}
// 如果方法元数据是标准方法元数据的话，就设置解析的工厂方法
if (metadata instanceof StandardMethodMetadata) {
beanDef.setResolvedFactoryMethod(((StandardMethodMetadata) metadata).getIntrospectedMethod());
}
// 设置自定义装配模式，默认是构造器
beanDef.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_CONSTRUCTOR);
// 设置略过属性检查
beanDef.setAttribute(org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor.
SKIP_REQUIRED_CHECK_ATTRIBUTE, Boolean.TRUE);
// 处理通用注解，注解里可能还有自动装配注解
AnnotationConfigUtils.processCommonDefinitionAnnotations(beanDef, metadata);
// 获取自动装配枚举信息
Autowire autowire = bean.getEnum("autowire");
if (autowire.isAutowire()) {
//如果是自动装配，也就是BY_NAME 或者 BY_TYPE，再设置了一次自动装配模式
beanDef.setAutowireMode(autowire.value());
}
// 自动装配候选，默认是true
boolean autowireCandidate = bean.getBoolean("autowireCandidate");
if (!autowireCandidate) {
beanDef.setAutowireCandidate(false);
}
// 初始化方法@PostConstruct和@PreDestory或者XML或者InitializingBean和DisposableBean接口
String initMethodName = bean.getString("initMethod");
if (StringUtils.hasText(initMethodName)) {
beanDef.setInitMethodName(initMethodName);
}
// 销毁方法
String destroyMethodName = bean.getString("destroyMethod");
beanDef.setDestroyMethodName(destroyMethodName);
// Consider scoping
// 处理作用域
ScopedProxyMode proxyMode = ScopedProxyMode.NO;
AnnotationAttributes attributes = AnnotationConfigUtils.attributesFor(metadata, Scope.class);
if (attributes != null) {
beanDef.setScope(attributes.getString("value"));
proxyMode = attributes.getEnum("proxyMode");
if (proxyMode == ScopedProxyMode.DEFAULT) {
proxyMode = ScopedProxyMode.NO;
}
}
// Replace the original bean definition with the target one, if necessary
BeanDefinition beanDefToRegister = beanDef;
// 如果作用域不是no的话就要使用代理
if (proxyMode != ScopedProxyMode.NO) {
BeanDefinitionHolder proxyDef = ScopedProxyCreator.createScopedProxy(
new BeanDefinitionHolder(beanDef, beanName), this.registry,
proxyMode == ScopedProxyMode.TARGET_CLASS);
beanDefToRegister = new ConfigurationClassBeanDefinition(
(RootBeanDefinition) proxyDef.getBeanDefinition(), configClass, metadata, beanName);
}
if (logger.isTraceEnabled()) {
logger.trace(String.format("Registering bean definition for @Bean method %s.%s()",
configClass.getMetadata().getClassName(), beanName));
}
this.registry.registerBeanDefinition(beanName, beanDefToRegister);
}
到此注解就已经解析完毕了，东西很多，还是需要自己下去DEBUG，自己看，注解解析这里，主要就是递归递归再递归，将所有内部包含的注解全部解析到