写在前
前面对SpringIOC的源码进行了分析，主要是针对SpringIOC的整体源码流程进行分析，并没有涉及到太多细节部分。接下来，会对SpringIOC的内置后置处理器的源码进行分析总结。Spring中的内置处理器有两类，即Bean的后置处理器和BeanFactory的后置处理器，本篇将会对这两类的后置处理器进行一个总结分析。
invokeBeanFactoryPostProcessors
这里会获取两处存储BeanFactoryPostProcessor的对象，传入供接下来的调用，1.当前Bean工厂，2.和我们自己调用addBeanFactoryPostProcessor的自定义BeanFactoryPostProcessor。
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
//调用BeanDefinitionRegistryPostProcessor的后置处理器 Begin
// 定义已处理的后置处理器
Set<String> processedBeans = new HashSet<>();
//判断我们的beanFactory实现了BeanDefinitionRegistry(实现了该结构就有注册和获取Bean定义的能力）
if (beanFactory instanceof BeanDefinitionRegistry) {
//强行把我们的bean工厂转为BeanDefinitionRegistry，因为待会需要注册Bean定义
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
//保存BeanFactoryPostProcessor类型的后置 BeanFactoryPostProcessor 提供修改
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
//保存BeanDefinitionRegistryPostProcessor类型的后置处理器 BeanDefinitionRegistryPostProcessor 提供注册
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
//循环我们传递进来的beanFactoryPostProcessors
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
//判断我们的后置处理器是不是BeanDefinitionRegistryPostProcessor
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
//进行强制转化
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
//调用他作为BeanDefinitionRegistryPostProcessor的处理器的后置方法
registryProcessor.postProcessBeanDefinitionRegistry(registry);
//添加到我们用于保存的BeanDefinitionRegistryPostProcessor的集合中
registryProcessors.add(registryProcessor);
}
else {//若没有实现BeanDefinitionRegistryPostProcessor 接口，那么他就是BeanFactoryPostProcessor
//把当前的后置处理器加入到regularPostProcessors中
regularPostProcessors.add(postProcessor);
}
}
//定义一个集合用户保存当前准备创建的BeanDefinitionRegistryPostProcessor
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
//第一步:去容器中获取BeanDefinitionRegistryPostProcessor的bean的处理器名称
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
//循环筛选出来的匹配BeanDefinitionRegistryPostProcessor的类型名称
for (String ppName : postProcessorNames) {
//判断是否实现了PriorityOrdered接口的
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
//显示的调用getBean()的方式获取出该对象然后加入到currentRegistryProcessors集合中去
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
//同时也加入到processedBeans集合中去
processedBeans.add(ppName);
}
}
//对currentRegistryProcessors集合中BeanDefinitionRegistryPostProcessor进行排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
// 把当前的加入到总的里面去
registryProcessors.addAll(currentRegistryProcessors);
/**
* 在这里典型的BeanDefinitionRegistryPostProcessor就是ConfigurationClassPostProcessor
* 用于进行bean定义的加载 比如我们的包扫描，@import 等等。。。。。。。。。
* 详细往下查看invokeBeanDefinitionRegistryPostProcessors方法源码
*/
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
//调用完之后，马上clea掉
currentRegistryProcessors.clear();
//---------------------------------------调用内置实现PriorityOrdered接口ConfigurationClassPostProcessor完毕--优先级No1-End----------------------------------------------------------------------------------------------------------------------------
//去容器中获取BeanDefinitionRegistryPostProcessor的bean的处理器名称（内置的和上面注册的）
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
//循环上一步获取的BeanDefinitionRegistryPostProcessor的类型名称
for (String ppName : postProcessorNames) {
//表示没有被处理过,且实现了Ordered接口的
if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
//显示的调用getBean()的方式获取出该对象然后加入到currentRegistryProcessors集合中去
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
//同时也加入到processedBeans集合中去
processedBeans.add(ppName);
}
}
//对currentRegistryProcessors集合中BeanDefinitionRegistryPostProcessor进行排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
//把他加入到用于保存到registryProcessors中
registryProcessors.addAll(currentRegistryProcessors);
//调用他的后置处理方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
//调用完之后，马上clea掉
currentRegistryProcessors.clear();
//-----------------------------------------调用自定义Order接口BeanDefinitionRegistryPostProcessor完毕-优先级No2-End-----------------------------------------------------------------------------------------------------------------------------
//调用没有实现任何优先级接口的BeanDefinitionRegistryPostProcessor
//定义一个重复处理的开关变量 默认值为true
boolean reiterate = true;
//第一次就可以进来
while (reiterate) {
//进入循环马上把开关变量给改为false
reiterate = false;
//去容器中获取BeanDefinitionRegistryPostProcessor的bean的处理器名称
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
//循环上一步获取的BeanDefinitionRegistryPostProcessor的类型名称
for (String ppName : postProcessorNames) {
//没有被处理过的
if (!processedBeans.contains(ppName)) {
//显示的调用getBean()的方式获取出该对象然后加入到currentRegistryProcessors集合中去
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
//同时也加入到processedBeans集合中去
processedBeans.add(ppName);
//再次设置为true
reiterate = true;
}
}
//对currentRegistryProcessors集合中BeanDefinitionRegistryPostProcessor进行排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
//把他加入到用于保存到registryProcessors中
registryProcessors.addAll(currentRegistryProcessors);
//调用他的后置处理方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
//进行clear
currentRegistryProcessors.clear();
}
//-----------------------------------------调用没有实现任何优先级接口自定义BeanDefinitionRegistryPostProcessor完毕--End-----------------------------------------------------------------------------------------------------------------------------
//调用 BeanDefinitionRegistryPostProcessor.postProcessBeanFactory方法
//详情源码往下看invokeBeanFactoryPostProcessors
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
//调用BeanFactoryPostProcessor 自设的（没有）
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
else {
//若当前的beanFactory没有实现了BeanDefinitionRegistry 说明没有注册Bean定义的能力
// 那么就直接调用BeanDefinitionRegistryPostProcessor.postProcessBeanFactory方法
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
//-----------------------------------------所有BeanDefinitionRegistryPostProcessor调用完毕--End-----------------------------------------------------------------------------------------------------------------------------
//-----------------------------------------处理BeanFactoryPostProcessor --Begin-----------------------------------------------------------------------------------------------------------------------------
//获取容器中所有的 BeanFactoryPostProcessor
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
//保存BeanFactoryPostProcessor类型实现了priorityOrdered
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
//保存BeanFactoryPostProcessor类型实现了Ordered接口的
List<String> orderedPostProcessorNames = new ArrayList<>();
//保存BeanFactoryPostProcessor没有实现任何优先级接口的
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
for (String ppName : postProcessorNames) {
//processedBeans包含的话，表示在上面处理BeanDefinitionRegistryPostProcessor的时候处理过了
if (processedBeans.contains(ppName)) {
// skip - already processed in first phase above
}
//判断是否实现了PriorityOrdered 优先级最高
else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
}
//判断是否实现了Ordered 优先级 其次
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
//没有实现任何的优先级接口的 最后调用
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// 排序
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
// 先调用BeanFactoryPostProcessor实现了 PriorityOrdered接口的
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
//再调用BeanFactoryPostProcessor实现了 Ordered.
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>();
for (String postProcessorName : orderedPostProcessorNames) {
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
sortPostProcessors(orderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
//调用没有实现任何方法接口的
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
for (String postProcessorName : nonOrderedPostProcessorNames) {
nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
//-----------------------------------------处理BeanFactoryPostProcessor --End-----------------------------------------------------------------------------------------------------------------------------
// Clear cached merged bean definitions since the post-processors might have
// modified the original metadata, e.g. replacing placeholders in values...
beanFactory.clearMetadataCache();
//------------------------- BeanFactoryPostProcessor和BeanDefinitionRegistryPostProcessor调用完毕 --End-----------------------------------------------------------------------------------------------------------------------------
}
这个方法分为两部分，第一部分先调用所有实现了BeanDefinitionRegistry接口的后置处理器，第二部分处理BeanFactoryPostProcessor后置处理器。
实现了BeanDefinitionRegistry接口的后置处理器，也有先后的调用顺序：
首先：调用内置实现PriorityOrdered接口ConfigurationClassPostProcessor；
其次：调用自定义Order接口BeanDefinitionRegistryPostProcessor；
接着：调用没有实现任何优先级接口自定义BeanDefinitionRegistryPostProcessor；
最后：调用BeanFactoryPostProcessor 自定义的后置处理器；
invokeBeanDefinitionRegistryPostProcessors
进入到ConfigurationClassPostProcessor的postProcessBeanDefinitionRegistry方法，前面说过ConfigurationClassPostProcessor也实现了BeanDefinitionRegistryPostProcessor的接口。
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
//获取IOC 容器中目前所有bean定义的名称
String[] candidateNames = registry.getBeanDefinitionNames();
//循环我们的上一步获取的所有的bean定义信息
for (String beanName : candidateNames) {
//通过bean的名称来获取我们的bean定义对象
BeanDefinition beanDef = registry.getBeanDefinition(beanName);
//判断是否有没有解析过
if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||
ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) {
if (logger.isDebugEnabled()) {
logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
}
}
//进行正在的解析判断是不是完全的配置类 还是一个非正式的配置类
else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
//满足添加 就加入到候选的配置类集合中
configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
}
}
// 若没有找到配置类 直接返回
if (configCandidates.isEmpty()) {
return;
}
//对我们的配置类进行Order排序
configCandidates.sort((bd1, bd2) -> {
int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
return Integer.compare(i1, i2);
});
// 创建我们通过@CompentScan导入进来的bean name的生成器
// 创建我们通过@Import导入进来的bean的名称
SingletonBeanRegistry sbr = null;
if (registry instanceof SingletonBeanRegistry) {
sbr = (SingletonBeanRegistry) registry;
if (!this.localBeanNameGeneratorSet) {
BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR);
if (generator != null) {
//设置@CompentScan导入进来的bean的名称生成器(默认类首字母小写）也可以自己定义，一般不会
this.componentScanBeanNameGenerator = generator;
//设置@Import导入进来的bean的名称生成器(默认类首字母小写）也可以自己定义，一般不会
this.importBeanNameGenerator = generator;
}
}
}
if (this.environment == null) {
this.environment = new StandardEnvironment();
}
//创建一个配置类解析器对象
ConfigurationClassParser parser = new ConfigurationClassParser(
this.metadataReaderFactory, this.problemReporter, this.environment,
this.resourceLoader, this.componentScanBeanNameGenerator, registry);
//用于保存我们的配置类BeanDefinitionHolder放入上面筛选出来的配置类
Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);
//用于保存我们的已经解析的配置类，长度默认为解析出来默认的配置类的集合长度
Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());
//do while 会进行第一次解析
do {
//真正的解析我们的配置类
//详细源码往下看parse方法
parser.parse(candidates);
parser.validate();
//解析出来的配置类
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());
}
// 此处才把@Bean的方法和@Import 注册到BeanDefinitionMap中
this.reader.loadBeanDefinitions(configClasses);
//加入到已经解析的集合中
alreadyParsed.addAll(configClasses);
candidates.clear();
//判断我们ioc容器中的是不是>候选原始的bean定义的个数
if (registry.getBeanDefinitionCount() > candidateNames.length) {
//获取所有的bean定义
String[] newCandidateNames = registry.getBeanDefinitionNames();
//原始的老的候选的bean定义
Set<String> oldCandidateNames = new HashSet<>(Arrays.asList(candidateNames));
Set<String> alreadyParsedClasses = new HashSet<>();
//赋值已经解析的
for (ConfigurationClass configurationClass : alreadyParsed) {
alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
}
for (String candidateName : newCandidateNames) {
//表示当前循环的还没有被解析过
if (!oldCandidateNames.contains(candidateName)) {
BeanDefinition bd = registry.getBeanDefinition(candidateName);
//判断有没有被解析过
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) &&
!alreadyParsedClasses.contains(bd.getBeanClassName())) {
candidates.add(new BeanDefinitionHolder(bd, candidateName));
}
}
}
candidateNames = newCandidateNames;
}
}
//存在没有解析过的 需要循环解析
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();
}
}
ConfigurationClassParser的parse方法
好深~~ 现在才到了真正解析配置类。
doProcessConfigurationClass
这里只看一个解析@ComponentScan 注解的实现。
@Nullable
protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
throws IOException {
// Recursively process any member (nested) classes first
processMemberClasses(configClass, sourceClass);
//处理我们的@propertySource注解的
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");
}
}
//解析我们的 @ComponentScan 注解
//从我们的配置类上解析处ComponentScans的对象集合属性
Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
if (!componentScans.isEmpty() &&
!this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
//循环解析 我们解析出来的AnnotationAttributes
for (AnnotationAttributes componentScan : componentScans) {
//把我们扫描出来的类变为bean定义的集合 真正的解析
//详细往下看componentScanParser.parse源码
Set<BeanDefinitionHolder> scannedBeanDefinitions =
this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
//循环处理我们包扫描出来的bean定义
for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
if (bdCand == null) {
bdCand = holder.getBeanDefinition();
}
//判断当前扫描出来的bean定义是不是一个配置类,若是的话 直接进行递归解析
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
//递归解析 因为@Component算是lite配置类
parse(bdCand.getBeanClassName(), holder.getBeanName());
}
}
}
}
// 处理 @Import annotations
processImports(configClass, sourceClass, getImports(sourceClass), true);
// 处理 @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);
}
}
// 处理 @Bean methods 获取到我们配置类中所有标注了@Bean的方法
Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
for (MethodMetadata methodMetadata : beanMethods) {
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}
// 处理配置类接口 默认方法的@Bean
processInterfaces(configClass, sourceClass);
// 处理配置类的父类的 ，循环再解析
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();
}
}
// 没有父类解析完成
return null;
}
componentScanParser.parse方法
public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {
// 这里的scanner是新创建的，与最前面开始的构造函数中初始化的scanner不是同一个。
ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry,
componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);
//为我们的扫描器设置beanName的生成器对象
Class<? extends BeanNameGenerator> generatorClass = componentScan.getClass("nameGenerator");
boolean useInheritedGenerator = (BeanNameGenerator.class == generatorClass);
scanner.setBeanNameGenerator(useInheritedGenerator ? this.beanNameGenerator :
BeanUtils.instantiateClass(generatorClass));
/**
* 解析@Scope的ProxyMode属性， 该属性可以将Bean创建问jdk代理或cglib代理
*/
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"));
//设置CompentScan对象的includeFilters 包含的属性
for (AnnotationAttributes filter : componentScan.getAnnotationArray("includeFilters")) {
for (TypeFilter typeFilter : typeFiltersFor(filter)) {
scanner.addIncludeFilter(typeFilter);
}
}
//设置CompentScan对象的excludeFilters 包含的属性
for (AnnotationAttributes filter : componentScan.getAnnotationArray("excludeFilters")) {
for (TypeFilter typeFilter : typeFiltersFor(filter)) {
scanner.addExcludeFilter(typeFilter);
}
}
/**
* 是否懒加载，此懒加载为componentScan延迟加载所有类
*/
boolean lazyInit = componentScan.getBoolean("lazyInit");
if (lazyInit) {
scanner.getBeanDefinitionDefaults().setLazyInit(true);
}
//包路径com.tuling.iocbeanlifecicle
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);
}
});
//真正的进行扫描解析
//往下看scanner.doScan源码
return scanner.doScan(StringUtils.toStringArray(basePackages));
}
scanner.doScan
protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
Assert.notEmpty(basePackages, "At least one base package must be specified");
//创建bean定义的holder对象用于保存扫描后生成的bean定义对象
Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();
//循环我们的包路径集合
//即@ComponentScan(basePackages = {"com.xxx.xxx"})
//和@ComponentScans()
for (String basePackage : basePackages) {
//找到候选的Components
//详细往下看findCandidateComponents方法源码
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
for (BeanDefinition candidate : candidates) {
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
//设置我们的beanName
String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
//这是默认配置 autowire-candidate
if (candidate instanceof AbstractBeanDefinition) {
postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
}
//获取@Lazy @DependsOn等注解的数据设置到BeanDefinition中
if (candidate instanceof AnnotatedBeanDefinition) {
AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
}
//把我们解析出来的组件bean定义注册到我们的IOC容器中（容器中没有才注册）
if (checkCandidate(beanName, candidate)) {
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
definitionHolder =
AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
beanDefinitions.add(definitionHolder);
//注册到IOC容器中DefaultListableBeanFactory.registerBeanDefinition方法
registerBeanDefinition(definitionHolder, this.registry);
}
}
}
return beanDefinitions;
}
findCandidateComponents
private Set<BeanDefinition> scanCandidateComponents(String basePackage) {
Set<BeanDefinition> candidates = new LinkedHashSet<>();
try {
//把我们的包路径转为资源路径 cn/xxx/MainConfig
String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
resolveBasePackage(basePackage) + '/' + this.resourcePattern;
//扫描指定包路径下面的所有.class文件
Resource[] resources = getResourcePatternResolver().getResources(packageSearchPath);
boolean traceEnabled = logger.isTraceEnabled();
boolean debugEnabled = logger.isDebugEnabled();
//需要我们的resources集合
for (Resource resource : resources) {
if (traceEnabled) {
logger.trace("Scanning " + resource);
}
//判断当的是不是可读的
if (resource.isReadable()) {
try {
MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(resource);
//是不是候选的组件
if (isCandidateComponent(metadataReader)) {
//包装成为一个ScannedGenericBeanDefinition
ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
//并且设置class资源
sbd.setResource(resource);
sbd.setSource(resource);
//这里面会判断是不是接口、顶级类、抽象类等不会加入集合，排除掉
//跟mybatis集成要重写这个方法
if (isCandidateComponent(sbd)) {
if (debugEnabled) {
logger.debug("Identified candidate component class: " + resource);
}
//加入到集合中
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
return candidates;
}
invokeBeanFactoryPostProcessors
会去for循环调用所有后置处理器，这里没有自定义的实现后置处理器，因此只有一个内置的后置处理器也就是ConfigurationClassPostProcessor后置处理器，主要用来解析配置类。进入到postProcessBeanFactory方法。
在enhanceConfigurationClasses方法中使用cglib对配置类进行代理，因为@Bean方法到时候要进行创建Bean实例。
插入个问题：这边为什么要使用动态代理？举个例子：
配置类加与不加@Configuration的区别。
@Configuration
@ComponentScan(basePackages = {"com.xxx.xxxx"})
public class MainConfig {
@Bean("car")
public Car car(){
Car car = new Car();
car.setName("xxxx");
car.setTank(tank());
// 如果不去ioc 容器中拿 是不是每次都会创建新的
// 因此这边会使用动态代理来进行增强
// 都会先根据方法名 getBean("car")
return car;
}
@Bean
public Tank tank(){
return new Tank();
}
}
如果去掉@Configuration注解，会每次的创建一个新的tank对象。
接着看源码：
enhanceConfigurationClasses
public void enhanceConfigurationClasses(ConfigurableListableBeanFactory beanFactory) {
Map<String, AbstractBeanDefinition> configBeanDefs = new LinkedHashMap<>();
for (String beanName : beanFactory.getBeanDefinitionNames()) {
BeanDefinition beanDef = beanFactory.getBeanDefinition(beanName);
/*
只有full版配置类才会创建cglib代理(只有加@Configuration会给类标记为full)
虽然我们在指定配置的时候不标注@Configuration也行，所以加不加注解的区别就在这里
那么加了@Configuration和不加有本质上有什么区别的？
当在配置类中一个@Bean 使用方法的方式引用另一个Bean如果不加注解就会重复加载Bean
如果加了@Configuration 则会在这里创建cglib代理，当调用@Bean方法时会先检测容器中是否存在*/
if (ConfigurationClassUtils.isFullConfigurationClass(beanDef)) {
if (!(beanDef instanceof AbstractBeanDefinition)) {
throw new BeanDefinitionStoreException("Cannot enhance @Configuration bean definition '" +
beanName + "' since it is not stored in an AbstractBeanDefinition subclass");
}
else if (logger.isWarnEnabled() && beanFactory.containsSingleton(beanName)) {
logger.warn("Cannot enhance @Configuration bean definition '" + beanName +
"' since its singleton instance has been created too early. The typical cause " +
"is a non-static @Bean method with a BeanDefinitionRegistryPostProcessor " +
"return type: Consider declaring such methods as 'static'.");
}
configBeanDefs.put(beanName, (AbstractBeanDefinition) beanDef);
}
}
if (configBeanDefs.isEmpty()) {
// nothing to enhance -> return immediately
return;
}
ConfigurationClassEnhancer enhancer = new ConfigurationClassEnhancer();
for (Map.Entry<String, AbstractBeanDefinition> entry : configBeanDefs.entrySet()) {
AbstractBeanDefinition beanDef = entry.getValue();
// If a @Configuration class gets proxied, always proxy the target class
beanDef.setAttribute(AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE, Boolean.TRUE);
try {
// Set enhanced subclass of the user-specified bean class
Class<?> configClass = beanDef.resolveBeanClass(this.beanClassLoader);
if (configClass != null) {
Class<?> enhancedClass = enhancer.enhance(configClass, this.beanClassLoader);
if (configClass != enhancedClass) {
if (logger.isDebugEnabled()) {
logger.debug(String.format("Replacing bean definition '%s' existing class '%s' with " +
"enhanced class '%s'", entry.getKey(), configClass.getName(), enhancedClass.getName()));
}
// 重新修改Bean定义的Class，在创建Bean的实例时将会实例cglib的类
beanDef.setBeanClass(enhancedClass);
}
}
}
catch (Throwable ex) {
throw new IllegalStateException("Cannot load configuration class: " + beanDef.getBeanClassName(), ex);
}
}
}
插入：判断是否是full配置类。
public static boolean checkConfigurationClassCandidate(BeanDefinition beanDef, MetadataReaderFactory metadataReaderFactory) {
String className = beanDef.getBeanClassName();
if (className == null || beanDef.getFactoryMethodName() != null) {
return false;
}
AnnotationMetadata metadata;
if (beanDef instanceof AnnotatedBeanDefinition &&
className.equals(((AnnotatedBeanDefinition) beanDef).getMetadata().getClassName())) {
// Can reuse the pre-parsed metadata from the given BeanDefinition...
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.
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;
}
}
/**
* 判断是不是真正的配置类 就是判断当前的bean的class上有没有标注了@Configuration注解
*/
if (isFullConfigurationCandidate(metadata)) {
//设置了标记
beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_FULL);
}
//这里判断该配置类是一个非正式的配置类(Component ComponentScan Import ImportResource)
else if (isLiteConfigurationCandidate(metadata)) {
beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_LITE);
}
else {
return false;
}
//解析配置类上是否标注了@Order注解
Integer order = getOrder(metadata);
if (order != null) {
beanDef.setAttribute(ORDER_ATTRIBUTE, order);
}
return true;
}
