spring boot实战(第十篇)Spring boot Bean加载源码分析
2015-10-13 23:30
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前言
前面的文章描述了Application对应Bean的创建,本篇将阐述spring boot中bean的创建过程refresh
首先来看SpringApplication#run方法中refresh()方法// Refresh the context refresh(context);调用的是AbstractApplicationContext中的refresh方法
protected void refresh(ApplicationContext applicationContext) { Assert.isInstanceOf(AbstractApplicationContext.class, applicationContext); ((AbstractApplicationContext) applicationContext).refresh(); }方法定义如下:
public void refresh() throws BeansException, IllegalStateException { synchronized (this.startupShutdownMonitor) { // Prepare this context for refreshing. prepareRefresh(); // Tell the subclass to refresh the internal bean factory. ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); // Prepare the bean factory for use in this context. prepareBeanFactory(beanFactory); try { // Allows post-processing of the bean factory in context subclasses. postProcessBeanFactory(beanFactory); // Invoke factory processors registered as beans in the context. invokeBeanFactoryPostProcessors(beanFactory); // Register bean processors that intercept bean creation. registerBeanPostProcessors(beanFactory); // Initialize message source for this context. initMessageSource(); // Initialize event multicaster for this context. initApplicationEventMulticaster(); // Initialize other special beans in specific context subclasses. onRefresh(); // Check for listener beans and register them. registerListeners(); // Instantiate all remaining (non-lazy-init) singletons. finishBeanFactoryInitialization(beanFactory); // Last step: publish corresponding event. finishRefresh(); } catch (BeansException ex) { logger.warn("Exception encountered during context initialization - cancelling refresh attempt", ex); // Destroy already created singletons to avoid dangling resources. destroyBeans(); // Reset 'active' flag. cancelRefresh(ex); // Propagate exception to caller. throw ex; } } }该方法中涉及的过程非常多,需要一步步来分析获取BeanFactory
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();通过前面的文章应该知道对应的BeanFactory为DefaultListableBeanFactory直奔主题来看如下方法
invokeBeanFactoryPostProcessors(beanFactory);
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) { PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors()); }首先来看getBeanFactoryPostProcessors(),其对应值为:ConfigurationWarningsApplicationContextInitializer$ConfigurationWarningsPostProcessor、PropertySourceOrderingPostProcessorConfigurationWarningsApplicationContextInitializer是在ConfigurationWarningsApplicationContextInitializer中执行
public void initialize(ConfigurableApplicationContext context) { context.addBeanFactoryPostProcessor(new ConfigurationWarningsPostProcessor( getChecks())); }添加PropertySourceOrderingPostProcessor是在ConfigFileApplicationListener执行
protected void addPostProcessors(ConfigurableApplicationContext context) { context.addBeanFactoryPostProcessor(new PropertySourceOrderingPostProcessor( context)); }添加来看invokeBeanFactoryPostProcessors方法
public static void invokeBeanFactoryPostProcessors( ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) { // Invoke BeanDefinitionRegistryPostProcessors first, if any. Set<String> processedBeans = new HashSet<String>(); if (beanFactory instanceof BeanDefinitionRegistry) { ...//处理后处理器 String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered. List<BeanDefinitionRegistryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>(); for (String ppName : postProcessorNames) { if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); processedBeans.add(ppName); } } OrderComparator.sort(priorityOrderedPostProcessors); registryPostProcessors.addAll(priorityOrderedPostProcessors); invokeBeanDefinitionRegistryPostProcessors(priorityOrderedPostProcessors, registry); // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered. postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); List<BeanDefinitionRegistryPostProcessor> orderedPostProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>(); for (String ppName : postProcessorNames) { if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) { orderedPostProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); processedBeans.add(ppName); } } OrderComparator.sort(orderedPostProcessors); registryPostProcessors.addAll(orderedPostProcessors); invokeBeanDefinitionRegistryPostProcessors(orderedPostProcessors, registry); // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear. boolean reiterate = true; while (reiterate) { reiterate = false; postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); for (String ppName : postProcessorNames) { if (!processedBeans.contains(ppName)) { BeanDefinitionRegistryPostProcessor pp = beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class); registryPostProcessors.add(pp); processedBeans.add(ppName); pp.postProcessBeanDefinitionRegistry(registry); reiterate = true; } } } // Now, invoke the postProcessBeanFactory callback of all processors handled so far 执行后处理器 invokeBeanFactoryPostProcessors(registryPostProcessors, beanFactory); invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory); }
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);按照bean的类型获取类型为BeanDefinitionRegistryPostProcessor的bean,这里获取到的bean名称为:org.springframework.context.annotation.internalConfigurationAnnotationProcessor;对应的Class为ConfigurationClassPostProcessor在前面文章中创建上下文的时候beanfactory创建了该bean。经过排序后执行如下方法
invokeBeanDefinitionRegistryPostProcessors(priorityOrderedPostProcessors, registry);
private static void invokeBeanDefinitionRegistryPostProcessors( Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) { for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) { postProcessor.postProcessBeanDefinitionRegistry(registry); } }实际调用ConfigurationClassPostProcessor#postProcessBeanDefinitionRegistry
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) { ...//注册若干bean processConfigBeanDefinitions(registry); }processConfigBeanDefinitions(registry)如下:
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) { Set<BeanDefinitionHolder> configCandidates = new LinkedHashSet<BeanDefinitionHolder>(); String[] candidateNames = registry.getBeanDefinitionNames(); for (String beanName : candidateNames) { BeanDefinition beanDef = registry.getBeanDefinition(beanName); if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) || ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) { if (logger.isDebugEnabled()) { logger.debug("Bean definition has already been processed as a configuration class: " + beanDef); } } else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) { configCandidates.add(new BeanDefinitionHolder(beanDef, beanName)); } } // Return immediately if no @Configuration classes were found if (configCandidates.isEmpty()) { return; } // Detect any custom bean name generation strategy supplied through the enclosing application context SingletonBeanRegistry singletonRegistry = null; if (registry instanceof SingletonBeanRegistry) { singletonRegistry = (SingletonBeanRegistry) registry; if (!this.localBeanNameGeneratorSet && singletonRegistry.containsSingleton(CONFIGURATION_BEAN_NAME_GENERATOR)) { BeanNameGenerator generator = (BeanNameGenerator) singletonRegistry.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR); this.componentScanBeanNameGenerator = generator; this.importBeanNameGenerator = generator; } } // Parse each @Configuration class ConfigurationClassParser parser = new ConfigurationClassParser( this.metadataReaderFactory, this.problemReporter, this.environment, this.resourceLoader, this.componentScanBeanNameGenerator, registry); Set<ConfigurationClass> alreadyParsed = new HashSet<ConfigurationClass>(configCandidates.size()); do { parser.parse(configCandidates); parser.validate(); Set<ConfigurationClass> configClasses = new LinkedHashSet<ConfigurationClass>(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.problemReporter, this.metadataReaderFactory, this.resourceLoader, this.environment, this.importBeanNameGenerator, parser.getImportRegistry()); } this.reader.loadBeanDefinitions(configClasses); alreadyParsed.addAll(configClasses); configCandidates.clear(); if (registry.getBeanDefinitionCount() > candidateNames.length) { String[] newCandidateNames = registry.getBeanDefinitionNames(); Set<String> oldCandidateNames = new HashSet<String>(Arrays.asList(candidateNames)); Set<String> alreadyParsedClasses = new HashSet<String>(); for (ConfigurationClass configurationClass : alreadyParsed) { alreadyParsedClasses.add(configurationClass.getMetadata().getClassName()); } for (String candidateName : newCandidateNames) { if (!oldCandidateNames.contains(candidateName)) { BeanDefinition beanDef = registry.getBeanDefinition(candidateName); if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory) && !alreadyParsedClasses.contains(beanDef.getBeanClassName())) { configCandidates.add(new BeanDefinitionHolder(beanDef, candidateName)); } } } candidateNames = newCandidateNames; } } while (!configCandidates.isEmpty()); // Register the ImportRegistry as a bean in order to support ImportAware @Configuration classes if (singletonRegistry != null) { if (!singletonRegistry.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) { singletonRegistry.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry()); } } if (this.metadataReaderFactory instanceof CachingMetadataReaderFactory) { ((CachingMetadataReaderFactory) this.metadataReaderFactory).clearCache(); } }又是一段很长的代码
String[] candidateNames = registry.getBeanDefinitionNames();获取已经注册的bean名称,其信息为:这里看到上一篇中创建的Application对应bean
for (String beanName : candidateNames) { BeanDefinition beanDef = registry.getBeanDefinition(beanName); if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) || ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) { if (logger.isDebugEnabled()) { logger.debug("Bean definition has already been processed as a configuration class: " + beanDef); } } else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) { configCandidates.add(new BeanDefinitionHolder(beanDef, beanName)); } }判断对应bean是否为配置文件bean(包含Configuration注解),经过筛选只有Application对应bean满足条件
ConfigurationClassParser parser = new ConfigurationClassParser( this.metadataReaderFactory, this.problemReporter, this.environment, this.resourceLoader, this.componentScanBeanNameGenerator, registry);该代码构造了Configuration类解析器执行
parser.parse(configCandidates);
public void parse(Set<BeanDefinitionHolder> configCandidates) { this.deferredImportSelectors = new LinkedList<DeferredImportSelectorHolder>(); for (BeanDefinitionHolder holder : configCandidates) { BeanDefinition bd = holder.getBeanDefinition(); try { if (bd instanceof AnnotatedBeanDefinition) { //执行该部分代码 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 (Exception ex) { throw new BeanDefinitionStoreException( "Failed to parse configuration class [" + bd.getBeanClassName() + "]", ex); } } processDeferredImportSelectors(); }调用
parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());最终调用
protected void processConfigurationClass(ConfigurationClass configClass) throws IOException { if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) { return; } 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 import. // Let's remove the old one and go with the new one. this.configurationClasses.remove(configClass); for (Iterator<ConfigurationClass> it = this.knownSuperclasses.values().iterator(); it.hasNext(); ) { if (configClass.equals(it.next())) { it.remove(); } } } } // Recursively process the configuration class and its superclass hierarchy. SourceClass sourceClass = asSourceClass(configClass); do { sourceClass = doProcessConfigurationClass(configClass, sourceClass); } while (sourceClass != null); this.configurationClasses.put(configClass, configClass); }首先判断该bean是否被跳过(该部分代码上一篇已说明),然后对Class进行包装,调用sourceClass = doProcessConfigurationClass(configClass,sourceClass)处理Application类
解析Configuration注解
protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass) throws IOException { // Recursively process any member (nested) classes first 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 AnnotationAttributes componentScan = AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ComponentScan.class); if (componentScan != null && !this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) { // The config class is annotated with @ComponentScan -> perform the scan immediately 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 necessary for (BeanDefinitionHolder holder : scannedBeanDefinitions) { if (ConfigurationClassUtils.checkConfigurationClassCandidate(holder.getBeanDefinition(), this.metadataReaderFactory)) { parse(holder.getBeanDefinition().getBeanClassName(), holder.getBeanName()); } } } // Process any @Import annotations processImports(configClass, sourceClass, getImports(sourceClass), true); // Process any @ImportResource annotations if (sourceClass.getMetadata().isAnnotated(ImportResource.class.getName())) { AnnotationAttributes importResource = AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class); String[] resources = importResource.getStringArray("value"); 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 = sourceClass.getMetadata().getAnnotatedMethods(Bean.class.getName()); for (MethodMetadata methodMetadata : beanMethods) { configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass)); } // Process superclass, if any if (sourceClass.getMetadata().hasSuperClass()) { String superclass = sourceClass.getMetadata().getSuperClassName(); if (!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; }到这里就看到了如何去解析Application类
processMemberClasses(configClass, sourceClass);处理其中内部类,解析内部类的过程和外部类相似,因此继续看下面的代码
处理PropertySource注解
// 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"); } }<pre name="code" class="html">其核心操作:
private void processPropertySource(AnnotationAttributes propertySource) throws IOException {String name = propertySource.getString("name");String[] locations = propertySource.getStringArray("value");boolean ignoreResourceNotFound = propertySource.getBoolean("ignoreResourceNotFound");Assert.isTrue(locations.length > 0, "At least one @PropertySource(value) location is required");for (String location : locations) {try {String resolvedLocation = this.environment.resolveRequiredPlaceholders(location);Resource resource = this.resourceLoader.getResource(resolvedLocation);ResourcePropertySource rps = (StringUtils.hasText(name) ?new ResourcePropertySource(name, resource) : new ResourcePropertySource(resource));addPropertySource(rps);}catch (IllegalArgumentException ex) {// from resolveRequiredPlaceholdersif (!ignoreResourceNotFound) {throw ex;}}catch (FileNotFoundException ex) {// from ResourcePropertySource constructorif (!ignoreResourceNotFound) {throw ex;}}}}通过注解中的信息获取资源信息,然后添加到MutablePropertySourcespropertySources = ((ConfigurableEnvironment)this.environment).getPropertySources()中,该内容前面已有讲述
解析ComponentScan注解
// Process any @ComponentScan annotationsAnnotationAttributes componentScan = AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ComponentScan.class);if (componentScan != null && !this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {// The config class is annotated with @ComponentScan -> perform the scan immediatelySet<BeanDefinitionHolder> scannedBeanDefinitions =this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());// Check the set of scanned definitions for any further config classes and parse recursively if necessaryfor (BeanDefinitionHolder holder : scannedBeanDefinitions) {if (ConfigurationClassUtils.checkConfigurationClassCandidate(holder.getBeanDefinition(), this.metadataReaderFactory)) {parse(holder.getBeanDefinition().getBeanClassName(), holder.getBeanName());}}}ComponentScan注解的作用大家都明白,扫描执行路径下bean信息,那么具体是如何实现的?需要跟进去看代码,调用
Set<BeanDefinitionHolder> scannedBeanDefinitions =this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {...//通过注解中的信息设置扫描器的参数信息return scanner.doScan(StringUtils.toStringArray(basePackages));}代码中忽略了扫描器对应的参数信息,直接看doScan方法
protected Set<BeanDefinitionHolder> doScan(String... basePackages) {Assert.notEmpty(basePackages, "At least one base package must be specified");Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<BeanDefinitionHolder>();for (String basePackage : basePackages) {Set<BeanDefinition> candidates = findCandidateComponents(basePackage);for (BeanDefinition candidate : candidates) {ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);candidate.setScope(scopeMetadata.getScopeName());String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);if (candidate instanceof AbstractBeanDefinition) {postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);}if (candidate instanceof AnnotatedBeanDefinition) {AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);}if (checkCandidate(beanName, candidate)) {BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);beanDefinitions.add(definitionHolder);registerBeanDefinition(definitionHolder, this.registry);}}}return beanDefinitions;}遍历basePackages信息,
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);查询类路径下申明的组件信息,
public Set<BeanDefinition> findCandidateComponents(String basePackage) {Set<BeanDefinition> candidates = new LinkedHashSet<BeanDefinition>();try {String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +resolveBasePackage(basePackage) + "/" + this.resourcePattern;Resource[] resources = this.resourcePatternResolver.getResources(packageSearchPath);boolean traceEnabled = logger.isTraceEnabled();boolean debugEnabled = logger.isDebugEnabled();for (Resource resource : resources) {if (traceEnabled) {logger.trace("Scanning " + resource);}if (resource.isReadable()) {try {MetadataReader metadataReader = this.metadataReaderFactory.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);}return candidates;}看
Resource[] resources = this.resourcePatternResolver.getResources(packageSearchPath);
public Resource[] getResources(String locationPattern) throws IOException {Assert.notNull(locationPattern, "Location pattern must not be null");if (locationPattern.startsWith(CLASSPATH_ALL_URL_PREFIX)) {// a class path resource (multiple resources for same name possible)if (getPathMatcher().isPattern(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()))) {// a class path resource patternreturn findPathMatchingResources(locationPattern);}else {// all class path resources with the given namereturn findAllClassPathResources(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()));}}else {// Only look for a pattern after a prefix here// (to not get fooled by a pattern symbol in a strange prefix).int prefixEnd = locationPattern.indexOf(":") + 1;if (getPathMatcher().isPattern(locationPattern.substring(prefixEnd))) {// a file patternreturn findPathMatchingResources(locationPattern);}else {// a single resource with the given namereturn new Resource[] {getResourceLoader().getResource(locationPattern)};}}}解析路径信息,这里spring有自己的一套继续规则,通过findPathMatchingResources()检索到指定类路径下所有的*.class文件,然后调用findAllClassPathResources解析Class文件
protected Resource[] findAllClassPathResources(String location) throws IOException {String path = location;if (path.startsWith("/")) {path = path.substring(1);}Set<Resource> result = doFindAllClassPathResources(path);return result.toArray(new Resource[result.size()]);}
protected Set<Resource> doFindAllClassPathResources(String path) throws IOException {Set<Resource> result = new LinkedHashSet<Resource>(16);ClassLoader cl = getClassLoader();Enumeration<URL> resourceUrls = (cl != null ? cl.getResources(path) : ClassLoader.getSystemResources(path));while (resourceUrls.hasMoreElements()) {URL url = resourceUrls.nextElement();result.add(convertClassLoaderURL(url));}if ("".equals(path)) {// The above result is likely to be incomplete, i.e. only containing file system references.// We need to have pointers to each of the jar files on the classpath as well...addAllClassLoaderJarRoots(cl, result);}return result;}通过上面的代码可以发现,在获取到path路径以后spring采用类加载器获取指定Class文件对应的资源信息获取完资源信息后调用
MetadataReader metadataReader = this.metadataReaderFactory.getMetadataReader(resource);解析资源信息对应的元数据
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);}}如果存在Componment注解修饰的Class文件则加入到BeanDefinition集合中返回。回到调用扫描bean处
for (BeanDefinitionHolder holder : scannedBeanDefinitions) {if (ConfigurationClassUtils.checkConfigurationClassCandidate(holder.getBeanDefinition(), this.metadataReaderFactory)) {parse(holder.getBeanDefinition().getBeanClassName(), holder.getBeanName());}}遍历扫描到的bean信息,如果为配置bean,则执行parse方法,该方法调用processConfigurationClass,形成一个递归的操作。
解析Import注解
<span style="font-family:Arial, Helvetica, sans-serif;"> </span><span style="font-family: Arial, Helvetica, sans-serif;">processImports(</span><span class="s1" style="font-family: Arial, Helvetica, sans-serif;">configClass</span><span style="font-family: Arial, Helvetica, sans-serif;">, </span><span class="s1" style="font-family: Arial, Helvetica, sans-serif;">sourceClass</span><span style="font-family: Arial, Helvetica, sans-serif;">, getImports(</span><span class="s1" style="font-family: Arial, Helvetica, sans-serif;">sourceClass</span><span style="font-family: Arial, Helvetica, sans-serif;">), </span><span class="s2" style="font-family: Arial, Helvetica, sans-serif;">true</span><span style="font-family: Arial, Helvetica, sans-serif;">);</span>处理import注解,该注解在spring boot中使用非常频繁
private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,Collection<SourceClass> importCandidates, boolean checkForCircularImports) throws IOException {...this.importStack.push(configClass);try {for (SourceClass candidate : importCandidates) {if (candidate.isAssignable(ImportSelector.class)) {// Candidate class is an ImportSelector -> delegate to it to determine importsClass<?> candidateClass = candidate.loadClass();ImportSelector selector = BeanUtils.instantiateClass(candidateClass, ImportSelector.class);invokeAwareMethods(selector);if (this.deferredImportSelectors != null && selector instanceof DeferredImportSelector) {this.deferredImportSelectors.add(new DeferredImportSelectorHolder(configClass, (DeferredImportSelector) selector));}else {String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());Collection<SourceClass> importSourceClasses = asSourceClasses(importClassNames);processImports(configClass, currentSourceClass, importSourceClasses, false);}}else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {// Candidate class is an ImportBeanDefinitionRegistrar ->// delegate to it to register additional bean definitionsClass<?> candidateClass = candidate.loadClass();ImportBeanDefinitionRegistrar registrar =BeanUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class);invokeAwareMethods(registrar);configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());}else {// Candidate class not an ImportSelector or ImportBeanDefinitionRegistrar ->// process it as an @Configuration classthis.importStack.registerImport(currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());processConfigurationClass(candidate.asConfigClass(configClass));}}}catch (BeanDefinitionStoreException ex) {throw ex;}catch (Exception ex) {throw new BeanDefinitionStoreException("Failed to process import candidates for configuration class [" +configClass.getMetadata().getClassName() + "]", ex);}finally {this.importStack.pop();}}}如果Import注解中Class为ImportSelector子类,通过invokeAwareMethods(selector)设置aware值,如果类型为DeferredImportSelector则添加到deferredImportSelectors集合中,待前面的parser.parse(configCandidates)方法中processDeferredImportSelectors()处理;如果不是,则执行selectImports方法,将获取到的结果递归调用processImports,解析selectImports得到的结果如果Import注解中Class为ImportBeanDefinitionRegistrar子类,则添加到importBeanDefinitionRegistrars中,注意该部分的数据在执行完parser.parse(configCandidates)后调用this.reader.loadBeanDefinitions(configClasses)解析否则执行配置信息的解析操作。
解析ImportResource注解
// Process any @ImportResource annotationsif (sourceClass.getMetadata().isAnnotated(ImportResource.class.getName())) {AnnotationAttributes importResource = AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);String[] resources = importResource.getStringArray("value");Class<? extends BeanDefinitionReader> readerClass = importResource.getClass("reader");for (String resource : resources) {String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);configClass.addImportedResource(resolvedResource, readerClass);}}
解析Bean注解
Set<MethodMetadata> beanMethods = sourceClass.getMetadata().getAnnotatedMethods(Bean.class.getName());for (MethodMetadata methodMetadata : beanMethods) {configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));}上面这两个注解相对来讲要简单一些,至此bean的解析完成,这里面涉及到多重递归,首先理清楚一条线才能把代码看明白。
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