Spring源码分析(三) -- Spring中的BeanFactoryPostProcessor
@FunctionalInterface
public interface BeanFactoryPostProcessor {
void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;
}
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- 从定义中可以看出BeanFactoryPostProcessor是一个函数式接口
- BeanFactoryPostProcessor只有一个方法，这个方法返回了一个BeanFactory对象，这个对象可以理解为Spring中的容器。
- postProcessBeanFactory是在注册完BeanDefinition后回调，这个回调中可以修改BeanDefinition的属性从而达到修改实例化的Bean
BeanFactoryPostProcessor的拓展类---BeanDefinitionRegistryPostProcessor
public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor {
void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException;
}
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- BeanDefinitionRegistryPostProcessor继承了BeanFactoryPostProcessor，表示BeanDefinitionRegistryPostProcessor也是一个BeanFactoryPostProcessor
- BeanDefinitionRegistryPostProcessor是一个接口，新增了一个方法
- BeanDefinitionRegistryPostProcessor有一个重要的实现类ConfigurationClassPostProcessor
ConfigurationClassPostProcessor 定义
public class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPostProcessor, PriorityOrdered, ResourceLoaderAware, BeanClassLoaderAware, EnvironmentAware 复制代码
- 主要关心实现BeanDefinitionRegistryPostProcessor接口的方法postProcessBeanDefinitionRegistry
postProcessBeanDefinitionRegistry 方法
//这个是一个空壳方法
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
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);
}
this.registriesPostProcessed.add(registryId);
//核心在这，跟进去
processConfigBeanDefinitions(registry);
}
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processConfigBeanDefinitions 方法
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
//定义一个list存放app 提供的bd（项目当中提供了@Compent）
List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
//获取容器中注册的所有bd名字
//7个,系统六个加上一个自己的配置类一共七个
String[] candidateNames = registry.getBeanDefinitionNames();
/**
* Full的配置类会被代理
* Lite的配置类不会被代理
*/
for (String beanName : candidateNames) {
BeanDefinition beanDef = registry.getBeanDefinition(beanName);
if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||
ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) {
//如果BeanDefinition中的configurationClass属性为full或者lite,则意味着已经处理过了,直接跳过
//这里需要结合下面的代码才能理解
if (logger.isDebugEnabled()) {
logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
}
}
//判断是否是Configuration类，如果加了Configuration下面的这几个注解就不再判断了
// 还有 add(Component.class.getName());
// candidateIndicators.add(ComponentScan.class.getName());
// candidateIndicators.add(Import.class.getName());
// candidateIndicators.add(ImportResource.class.getName());
//beanDef == appconfig
else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
//BeanDefinitionHolder 也可以看成一个数据结构
configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
}
}
// Return immediately if no @Configuration classes were found
if (configCandidates.isEmpty()) {
return;
}
// 排序，根据order,不重要
// Sort by previously determined @Order value, if applicable
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
SingletonBeanRegistry sbr = null;
//如果BeanDefinitionRegistry是SingletonBeanRegistry子类的话,
// 由于我们当前传入的是DefaultListableBeanFactory,是SingletonBeanRegistry 的子类
// 因此会将registry强转为SingletonBeanRegistry
if (registry instanceof SingletonBeanRegistry) {
sbr = (SingletonBeanRegistry) registry;
if (!this.localBeanNameGeneratorSet) {//是否有自定义的
BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR);
//SingletonBeanRegistry中有id为 org.springframework.context.annotation.internalConfigurationBeanNameGenerator
//如果有则利用他的，否则则是spring默认的
if (generator != null) {
this.componentScanBeanNameGenerator = generator;
this.importBeanNameGenerator = generator;
}
}
}
if (this.environment == null) {
this.environment = new StandardEnvironment();
}
// Parse each @Configuration class
//实例化ConfigurationClassParser 为了解析各个配置类
ConfigurationClassParser parser = new ConfigurationClassParser(
this.metadataReaderFactory, this.problemReporter, this.environment,
this.resourceLoader, this.componentScanBeanNameGenerator, registry);
//实例化2个set,candidates用于将之前加入的configCandidates进行去重
//因为可能有多个配置类重复了
//alreadyParsed用于判断是否处理过
Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);
Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());
do {
//candidates中存放的是配置类，这里解析配置类
//这里很重要
parser.parse(candidates);
parser.validate();
//map.keyset
Set<ConfigurationClass> configClasses = new LinkedHashSet<>(parser.getConfigurationClasses());
configClasses.removeAll(alreadyParsed);
// Read the model and create bean definitions based on its content
if (this.reader == null) {
this.reader = new ConfigurationClassBeanDefinitionReader(
registry, this.sourceExtractor, this.resourceLoader, this.environment,
this.importBeanNameGenerator, parser.getImportRegistry());
}
/**
* 这里值得注意的是扫描出来的bean当中可能包含了特殊类
* 比如ImportBeanDefinitionRegistrar那么也在这个方法里面处理
* 但是并不是包含在configClasses当中
* configClasses当中主要包含的是importSelector
* 因为ImportBeanDefinitionRegistrar在扫描出来的时候已经被添加到一个list当中去了
* 上面解析出来的@Bean和@Import（三种）都会放入configClasses中
*/
//bd 到 map 除却普通
//跟进去
this.reader.loadBeanDefinitions(configClasses);
alreadyParsed.addAll(configClasses);
candidates.clear();
//由于我们这里进行了扫描，把扫描出来的BeanDefinition注册给了factory
if (registry.getBeanDefinitionCount() > candidateNames.length) {
String[] newCandidateNames = registry.getBeanDefinitionNames();
Set<String> oldCandidateNames = new HashSet<>(Arrays.asList(candidateNames));
Set<String> alreadyParsedClasses = new HashSet<>();
for (ConfigurationClass configurationClass : alreadyParsed) {
alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
}
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();
}
}
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checkConfigurationClassCandidate 方法
//如果传入的BeanDefinition有Configuration注解，把BeanDefinition的CONFIGURATION_CLASS_ATTRIBUTE属性设置为full，这个属性在实例化的时候会生成代理对象
//如果传入的BeanDefinition有Component、ComponentScan、Import、ImportResource注解，把BeanDefinition的CONFIGURATION_CLASS_ATTRIBUTE属性设置为lite
public static boolean checkConfigurationClassCandidate(BeanDefinition beanDef, MetadataReaderFactory metadataReaderFactory) {
String className = beanDef.getBeanClassName();
if (className == null || beanDef.getFactoryMethodName() != null) {
return false;
}
AnnotationMetadata metadata;
// 配置类默认为AnnotatedGenericBeanDefinition对象
if (beanDef instanceof AnnotatedBeanDefinition &&
className.equals(((AnnotatedBeanDefinition) beanDef).getMetadata().getClassName())) {
// Can reuse the pre-parsed metadata from the given BeanDefinition...
//如果BeanDefinition 是 AnnotatedBeanDefinition的实例,并且className 和 BeanDefinition中 的元数据 的类名相同
// 则直接从BeanDefinition 获得Metadata
metadata = ((AnnotatedBeanDefinition) beanDef).getMetadata();
}
else if (beanDef instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) beanDef).hasBeanClass()) {
// Check already loaded Class if present...
// since we possibly can't even load the class file for this Class.
//如果BeanDefinition 是 AbstractBeanDefinition的实例,并且beanDef 有 beanClass 属性存在
//则实例化StandardAnnotationMetadata
Class<?> beanClass = ((AbstractBeanDefinition) beanDef).getBeanClass();
metadata = new StandardAnnotationMetadata(beanClass, true);
}
else {
try {
MetadataReader metadataReader = metadataReaderFactory.getMetadataReader(className);
metadata = metadataReader.getAnnotationMetadata();
}
catch (IOException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Could not find class file for introspecting configuration annotations: " + className, ex);
}
return false;
}
}
//判断当前这个bd中存在的类是不是加了@Configruation注解
//如果存在则spring认为他是一个全注解的类
if (isFullConfigurationCandidate(metadata)) {
//如果存在 Configuration 注解,则为BeanDefinition 设置configurationClass属性为full
beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_FULL);
}
//判断是否加了以下注解，摘录isLiteConfigurationCandidate的源码
// candidateIndicators.add(Component.class.getName());
// candidateIndicators.add(ComponentScan.class.getName());
// candidateIndicators.add(Import.class.getName());
// candidateIndicators.add(ImportResource.class.getName());
//如果不存在Configuration注解，spring则认为是一个部分注解类
else if (isLiteConfigurationCandidate(metadata)) {
beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_LITE);
}
else {
return false;
}
// It's a full or lite configuration candidate... Let's determine the order value, if any.
Integer order = getOrder(metadata);
if (order != null) {
beanDef.setAttribute(ORDER_ATTRIBUTE, order);
}
return true;
}
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parse 方法
//解析配置类，主要是把Configuration注解类里面导入的类解析为对应的BeanDefinition并注册到容器中去
//注意这个configCandidates里面只有自己的配置类
public void parse(Set<BeanDefinitionHolder> configCandidates) {
this.deferredImportSelectors = new LinkedList<>();
//根据BeanDefinition 的类型 做不同的处理,一般都会调用ConfigurationClassParser#parse 进行解析
for (BeanDefinitionHolder holder : configCandidates) {
BeanDefinition bd = holder.getBeanDefinition();
try {
if (bd instanceof AnnotatedBeanDefinition) {
//解析注解对象，并且把解析出来的bd放到map，但是这里的bd指的是普通的
//何谓不普通的呢？比如@Bean 和各种beanFactoryPostProcessor得到的bean不在这里put
//但是是这里解析，只是不put而已
parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());
}
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);
}
}
//处理延迟加载的importSelect？跳过
processDeferredImportSelectors();
}
//这个是空壳方法，接着跟进去
protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {
processConfigurationClass(new ConfigurationClass(metadata, beanName));
}
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processConfigurationClass 方法
//处理配置类
protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
//判断是否应该跳过解析
if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
return;
}
// 处理Imported 的情况
//就是当前这个注解类有没有被别的类import
ConfigurationClass existingClass = this.configurationClasses.get(configClass);
if (existingClass != null) {
if (configClass.isImported()) {
if (existingClass.isImported()) {
existingClass.mergeImportedBy(configClass);
}
// Otherwise ignore new imported config class; existing non-imported class overrides it.
return;
}
else {
// Explicit bean definition found, probably replacing an imports.
// Let's remove the old one and go with the new one.
this.configurationClasses.remove(configClass);
this.knownSuperclasses.values().removeIf(configClass::equals);
}
}
// Recursively process the configuration class and its superclass hierarchy.
SourceClass sourceClass = asSourceClass(configClass);
do {
//这个里面会注册BeanDefinition，重点看这步
sourceClass = doProcessConfigurationClass(configClass, sourceClass);
}
while (sourceClass != null);
//一个map，用来存放扫描出来的bean（注意这里的bean不是对象，仅仅bean的信息，因为还没到实例化这一步）
this.configurationClasses.put(configClass, configClass);
}
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doProcessConfigurationClass 方法
//真正解析配置类的方法
//注意这个ConfigurationClass对象是从ConfigurationClassPostProcessor中传过来的
//@Bean、@Import（三种）解析出来的类都放入ConfigurationClass对象中
//ConfigurationClassPostProcessor会调用this.reader.loadBeanDefinitions(configClasses)方法来统一解析
protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
throws IOException {
// Recursively process any member (nested) classes first
//处理内部类，跳过
processMemberClasses(configClass, sourceClass);
// Process any @PropertySource annotations
for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), PropertySources.class,
org.springframework.context.annotation.PropertySource.class)) {
if (this.environment instanceof ConfigurableEnvironment) {
processPropertySource(propertySource);
}
else {
logger.warn("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
"]. Reason: Environment must implement ConfigurableEnvironment");
}
}
// Process any @ComponentScan annotations
//处理所有@ComponentScan注解
Set<AnnotationAttributes> 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
//扫描普通类=componentScan=com.test
//这里扫描出来所有@@Component
//并且把扫描的出来的普通bean放到map当中
//在这注册普通的BeanDefinition,跟进去
Set<BeanDefinitionHolder> scannedBeanDefinitions =
this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
// Check the set of scanned definitions for any further config classes and parse recursively if needed
//检查扫描出来的类当中是否还有configuration
for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
if (bdCand == null) {
bdCand = holder.getBeanDefinition();
}
//检查 todo
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
//如果扫描@ComponentScan里面还有配置类，进行递归，回到上面的parse方法
parse(bdCand.getBeanClassName(), holder.getBeanName());
}
}
}
}
/**
* 上面的代码就是扫描普通类----@Component
* 并且放到了map当中
*/
// Process any @Import annotations
//处理@Import imports 3种情况
//ImportSelector
//普通类
//ImportBeanDefinitionRegistrar
//这里和内部地柜调用时候的情况不同
/**
* 这里处理的import是需要判断我们的类当中时候有@Import注解
* 如果有这把@Import当中的值拿出来，是一个类
* 比如@Import(xxxxx.class)，那么这里便把xxxxx传进去进行解析
* 在解析的过程中如果发觉是一个importSelector那么就回调selector的方法
* 返回一个字符串（类名），通过这个字符串得到一个类
* 继而在递归调用本方法来处理这个类
*
* 判断一组类是不是imports（3种import）
*
*
*/
//跟进去
processImports(configClass, sourceClass, getImports(sourceClass), true);
// Process any @ImportResource annotations
AnnotationAttributes importResource =
AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
if (importResource != null) {
String[] resources = importResource.getStringArray("locations");
Class<? extends BeanDefinitionReader> readerClass = importResource.getClass("reader");
for (String resource : resources) {
String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);
configClass.addImportedResource(resolvedResource, readerClass);
}
}
// Process individual @Bean methods
Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
for (MethodMetadata methodMetadata : beanMethods) {
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}
// Process default methods on interfaces
processInterfaces(configClass, sourceClass);
// Process superclass, if any
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;
}
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parse 方法
public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {
//这里的scanner是重新创建的，不是初始化AnnotationConfigApplicationContext时创建的对象
ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry,
componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);
//BeanNameGenerator
Class<? extends BeanNameGenerator> generatorClass = componentScan.getClass("nameGenerator");
boolean useInheritedGenerator = (BeanNameGenerator.class == generatorClass);
scanner.setBeanNameGenerator(useInheritedGenerator ? this.beanNameGenerator :
BeanUtils.instantiateClass(generatorClass));
//web应用的，跳过
ScopedProxyMode scopedProxyMode = componentScan.getEnum("scopedProxy");
if (scopedProxyMode != ScopedProxyMode.DEFAULT) {
scanner.setScopedProxyMode(scopedProxyMode);
}
else {
Class<? extends ScopeMetadataResolver> resolverClass = componentScan.getClass("scopeResolver");
scanner.setScopeMetadataResolver(BeanUtils.instantiateClass(resolverClass));
}
scanner.setResourcePattern(componentScan.getString("resourcePattern"));
//遍历当中的过滤
for (AnnotationAttributes filter : componentScan.getAnnotationArray("includeFilters")) {
for (TypeFilter typeFilter : typeFiltersFor(filter)) {
scanner.addIncludeFilter(typeFilter);
}
}
for (AnnotationAttributes filter : componentScan.getAnnotationArray("excludeFilters")) {
for (TypeFilter typeFilter : typeFiltersFor(filter)) {
scanner.addExcludeFilter(typeFilter);
}
}
//默认false
boolean lazyInit = componentScan.getBoolean("lazyInit");
if (lazyInit) {
scanner.getBeanDefinitionDefaults().setLazyInit(true);
}
//获取@ComponentScan注解的值
Set<String> basePackages = new LinkedHashSet<>();
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);
}
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);
}
});
//这个是核心，扫描路径并把符合条件的类转换为BeanDefinition对象
return scanner.doScan(StringUtils.toStringArray(basePackages));
}
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doScan 方法
//扫描路径
//把符合条件的类转换为对应的BeanDefinition对象
//为BeanDefinition对象赋值
//把BeanDefinition对象注册到容器中
protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
Assert.notEmpty(basePackages, "At least one base package must be specified");
Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();
for (String basePackage : basePackages) {
//扫描basePackage路径下的java文件
//符合条件的并把它转成BeanDefinition类型，跟进去
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
for (BeanDefinition candidate : candidates) {
//解析scope属性
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
if (candidate instanceof AbstractBeanDefinition) {
//如果这个类是AbstractBeanDefinition的子类
//则为他设置默认值，比如lazy，init destory
postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
}
if (candidate instanceof AnnotatedBeanDefinition) {
//检查并且处理常用的注解
//这里的处理主要是指把常用注解的值设置到AnnotatedBeanDefinition当中
//当前前提是这个类必须是AnnotatedBeanDefinition类型的，说白了就是加了注解的类
AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
}
if (checkCandidate(beanName, candidate)) {
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
definitionHolder =
AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
beanDefinitions.add(definitionHolder);
//加入到map当中，这里是注册功能把BeanDefinition注册到容器中
registerBeanDefinition(definitionHolder, this.registry);
}
}
}
return beanDefinitions;
}
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findCandidateComponents 方法
//扫描包，空壳方法
public Set<BeanDefinition> findCandidateComponents(String basePackage) {
if (this.componentsIndex != null && indexSupportsIncludeFilters()) {
return addCandidateComponentsFromIndex(this.componentsIndex, basePackage);
}
else {
//看这个
return scanCandidateComponents(basePackage);
}
}
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scanCandidateComponents 方法
private Set<BeanDefinition> scanCandidateComponents(String basePackage) {
Set<BeanDefinition> candidates = new LinkedHashSet<>();
try {
//这一步会把packageSearchPath的值修改为 classpath*:com/ktcatv/**/*.class
String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
resolveBasePackage(basePackage) + '/' + this.resourcePattern;
//asm 读取class文件生成Resource对象，跳过吧，内容太多了不是重点
Resource[] resources = getResourcePatternResolver().getResources(packageSearchPath);
boolean traceEnabled = logger.isTraceEnabled();
boolean debugEnabled = logger.isDebugEnabled();
for (Resource resource : resources) {
if (traceEnabled) {
logger.trace("Scanning " + resource);
}
if (resource.isReadable()) {
try {
//这里可以把Resource对象转换为ScannedGenericBeanDefinition对象，只记住这点就行了
MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(resource);
if (isCandidateComponent(metadataReader)) {
ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
sbd.setResource(resource);
sbd.setSource(resource);
if (isCandidateComponent(sbd)) {
if (debugEnabled) {
logger.debug("Identified candidate component class: " + resource);
}
candidates.add(sbd);
}
else {
if (debugEnabled) {
logger.debug("Ignored because not a concrete top-level class: " + resource);
}
}
}
else {
if (traceEnabled) {
logger.trace("Ignored because not matching any filter: " + resource);
}
}
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(
"Failed to read candidate component class: " + resource, ex);
}
}
else {
if (traceEnabled) {
logger.trace("Ignored because not readable: " + resource);
}
}
}
}
catch (IOException ex) {
throw new BeanDefinitionStoreException("I/O failure during classpath scanning", ex);
}
//返回解析后的BeanDefinition集合
return candidates;
}
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- 回到doScan方法接着看
registerBeanDefinition 方法
//注册BeanDefinition，空壳方法
protected void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) {
//跟进去
BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, registry);
}
//这个才是真实的注册BeanDefinition对象的方法
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// Register bean definition under primary name.
String beanName = definitionHolder.getBeanName();
//这里注册BeanDefinition，这个跟进去
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
// 注册别名，如果有的话
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String alias : aliases) {
registry.registerAlias(beanName, alias);
}
}
}
//DefaultListabaleBeanFactory中的方法
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {
Assert.hasText(beanName, "Bean name must not be empty");
Assert.notNull(beanDefinition, "BeanDefinition must not be null");
if (beanDefinition instanceof AbstractBeanDefinition) {
try {
((AbstractBeanDefinition) beanDefinition).validate();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Validation of bean definition failed", ex);
}
}
BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
if (existingDefinition != null) {
if (!isAllowBeanDefinitionOverriding()) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
"': There is already [" + existingDefinition + "] bound.");
}
else if (existingDefinition.getRole() < beanDefinition.getRole()) {
// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
if (logger.isWarnEnabled()) {
logger.warn("Overriding user-defined bean definition for bean '" + beanName +
"' with a framework-generated bean definition: replacing [" +
existingDefinition + "] with [" + beanDefinition + "]");
}
}
else if (!beanDefinition.equals(existingDefinition)) {
if (logger.isInfoEnabled()) {
logger.info("Overriding bean definition for bean '" + beanName +
"' with a different definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
else {
if (logger.isDebugEnabled()) {
logger.debug("Overriding bean definition for bean '" + beanName +
"' with an equivalent definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
this.beanDefinitionMap.put(beanName, beanDefinition);
}
else {
if (hasBeanCreationStarted()) {
//这里是处理已经被注册的逻辑，应该是被其他的BeanFactoryPostProcessor修改后进入这里
// Cannot modify startup-time collection elements anymore (for stable iteration)
synchronized (this.beanDefinitionMap) {
this.beanDefinitionMap.put(beanName, beanDefinition);
List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
updatedDefinitions.addAll(this.beanDefinitionNames);
updatedDefinitions.add(beanName);
this.beanDefinitionNames = updatedDefinitions;
if (this.manualSingletonNames.contains(beanName)) {
Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
updatedSingletons.remove(beanName);
this.manualSingletonNames = updatedSingletons;
}
}
}
else {
// 这里是正常的逻辑，注册BeanDefinition就是放进beanDefinitionMap对象中
this.beanDefinitionMap.put(beanName, beanDefinition);
this.beanDefinitionNames.add(beanName);
this.manualSingletonNames.remove(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (existingDefinition != null || containsSingleton(beanName)) {
resetBeanDefinition(beanName);
}
}
复制代码
- 回到 doProcessConfigurationClass 方法继续看
processImports 方法
//处理@Import注解，这个后面会重新开一篇来讲解
private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,
Collection<SourceClass> importCandidates, boolean checkForCircularImports) {
if (importCandidates.isEmpty()) {
return;
}
if (checkForCircularImports && isChainedImportOnStack(configClass)) {
this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
}
else {
this.importStack.push(configClass);
try {
for (SourceClass candidate : importCandidates) {
//处理ImportSelector类
if (candidate.isAssignable(ImportSelector.class)) {
// Candidate class is an ImportSelector -> delegate to it to determine imports
Class<?> candidateClass = candidate.loadClass();
//反射实现一个对象
ImportSelector selector = BeanUtils.instantiateClass(candidateClass, ImportSelector.class);
ParserStrategyUtils.invokeAwareMethods(
selector, this.environment, this.resourceLoader, this.registry);
if (this.deferredImportSelectors != null && selector instanceof DeferredImportSelector) {
this.deferredImportSelectors.add(
new DeferredImportSelectorHolder(configClass, (DeferredImportSelector) selector));
}
else {
//回调
String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
Collection<SourceClass> importSourceClasses = asSourceClasses(importClassNames);
//递归，这里第二次调用processImports
//如果是一个普通类，会进else
processImports(configClass, currentSourceClass, importSourceClasses, false);
}
}
//处理ImportBeanDefinitionRegistrar类
else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {
// Candidate class is an ImportBeanDefinitionRegistrar ->
// delegate to it to register additional bean definitions
Class<?> candidateClass = candidate.loadClass();
ImportBeanDefinitionRegistrar registrar =
BeanUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class);
ParserStrategyUtils.invokeAwareMethods(
registrar, this.environment, this.resourceLoader, this.registry);
//添加到一个list当中和importselector不同
configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());
}
else {
// Candidate class not an ImportSelector or ImportBeanDefinitionRegistrar ->
// process it as an @Configuration class
// 否则，加入到importStack后调用processConfigurationClass 进行处理
//processConfigurationClass里面主要就是把类放到configurationClasses
//configurationClasses是一个集合，会在后面拿出来解析成bd继而注册
//可以看到普通类在扫描出来的时候就被注册了
//如果是importSelector，会先放到configurationClasses后面进行出来注册
this.importStack.registerImport(
currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());
processConfigurationClass(candidate.asConfigClass(configClass));
}
}
}
catch (BeanDefinitionStoreException ex) {
throw ex;
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(
"Failed to process imports candidates for configuration class [" +
configClass.getMetadata().getClassName() + "]", ex);
}
finally {
this.importStack.pop();
}
}
}
复制代码
- 回到 processConfigBeanDefinitions 方法继续
loadBeanDefinitions 方法
//空壳方法
public void loadBeanDefinitions(Set<ConfigurationClass> configurationModel) {
TrackedConditionEvaluator trackedConditionEvaluator = new TrackedConditionEvaluator();
for (ConfigurationClass configClass : configurationModel) {
//跟进去
loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);
}
}
复制代码
loadBeanDefinitionsForConfigurationClass 方法
private void loadBeanDefinitionsForConfigurationClass(
ConfigurationClass configClass, TrackedConditionEvaluator trackedConditionEvaluator) {
if (trackedConditionEvaluator.shouldSkip(configClass)) {
String beanName = configClass.getBeanName();
if (StringUtils.hasLength(beanName) && this.registry.containsBeanDefinition(beanName)) {
this.registry.removeBeanDefinition(beanName);
}
this.importRegistry.removeImportingClass(configClass.getMetadata().getClassName());
return;
}
//如果一个类是被import的，会被spring标记
//在这里完成注册
if (configClass.isImported()) {
registerBeanDefinitionForImportedConfigurationClass(configClass);
}
//@Bean
for (BeanMethod beanMethod : configClass.getBeanMethods()) {
loadBeanDefinitionsForBeanMethod(beanMethod);
}
//xml
loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
//注册Registrar
loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
}
复制代码
- 到这就把配置文件解析完成了
ConfigurationClassPostProcessor 小结
- ConfigurationClassPostProcessor 是Spring内部最重要的一个BeanDefinitionRegistryPostProcesso的实现类，它的主要工作就是解析配置文件
-
ConfigurationClassPostProcessor 工作流程
-
- 从容器中获取所有的BeanDefinition对象
- 筛选出需要解析的配置类的BeanDefinition对象
- 遍历筛选出来的BeanDefinition对象，进行解析
- 解析@ComponentScan获取路径
- 扫描路径下符合条件的类，把符合条件的类转换为对应的BeanDefinition，这里不会处理@Bean和@Import只会添加到ConfigurationClass对象中
- 注册转换的BeanDefinition对象
- 使用 ConfigurationClassBeanDefinitionReader 加载上面扫描出来的其他类（@Bean和@Import）转换为BeanDefinition并注册到容器中
-
BeanFactoryPostProcessor 的自定义使用
Dao类
public interface IDao {
void query();
}
@Repository("indexDao")
public class IndexDao implements IDao {
@Override
public void query() {
System.out.println("index dao");
}
}
复制代码
Service类
public interface IService {
void service();
}
//注意这里没有注解，不能被Spring扫描到
public class IndexService implements IService {
@Override
public void service() {
System.out.println("service");
}
}
复制代码
Appconfig类
@Configuration
@ComponentScan("com.ktcatv")
public class Appconfig {
}
复制代码
BeanFactoryPostPorcessor类
@Component
public class BeanFactoryPostPorcessorTest implements BeanFactoryPostProcessor {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
//这里获取了IndexDao的BeanDefinition对象，修改了它的beanCalss属性
BeanDefinition indexDao = beanFactory.getBeanDefinition("indexDao");
indexDao.setBeanClassName(IndexService.class.getName());
}
}
复制代码
Test类
public class Test {
public static void main(String[] args) {
AnnotationConfigApplicationContext configApplicationContext = new AnnotationConfigApplicationContext(Appconfig.class);
//可以正常执行，说明上面的BeanFactoryPostPorcessorTest类成功修改了 IndexDao 类的实例化过程
IService service = configApplicationContext.getBean(IService.class);
service.service();
}
}
复制代码
正文到此结束
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文章和留言都翻到11页了 没有OOM
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朋友，翻页到11页，及以后，会出现OOM，无法访问
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搞个gitee的项目
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版本号是多少，你可以下载哪个代码仓库，jdk选1.8 直接跑就行
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