loadBeanDefinitions解析（三）
接上一篇loadBeanDefinitions解析（一）
parseCustomElement(ele)方法
該方法解析不是beans限制的xml節點
進入到NamespaceHandlerSupport類
@Nullable
public BeanDefinition parse(Element element, ParserContext parserContext) {
BeanDefinitionParser parser = findParserForElement(element, parserContext);
//掃描注冊 parser.parse(element, parserContext)
return (parser != null ? parser.parse(element, parserContext) : null);
}
進入到ComponentScanBeanDefinitionParser類
@Nullable
public BeanDefinition parse(Element element, ParserContext parserContext) {
//擷取base-package的
String basePackage = element.getAttribute(BASE_PACKAGE_ATTRIBUTE);
basePackage = parserContext.getReaderContext().getEnvironment().resolvePlaceholders(basePackage);
//切割
String[] basePackages = StringUtils.tokenizeToStringArray(basePackage,
ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
// Actually scan for bean definitions and register them.
//實際上，掃描bean定義并注冊它們。
ClassPathBeanDefinitionScanner scanner = configureScanner(parserContext, element);
//掃描注冊
Set<BeanDefinitionHolder> beanDefinitions = scanner.doScan(basePackages);
//注冊一些spring自帶的類
registerComponents(parserContext.getReaderContext(), beanDefinitions, element);
return null;
}
進入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<>();
for (String basePackage : basePackages) {
//掃描包下要注入spring容器的類
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
for (BeanDefinition candidate : candidates) {
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
//擷取類名
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)) {
//封裝成BeanDefinitionHolder
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
definitionHolder =
AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
//加入集合
beanDefinitions.add(definitionHolder);
//往beanfactroy注冊BeanDefinition
registerBeanDefinition(definitionHolder, this.registry);
}
}
}
return beanDefinitions;
}
進入findCandidateComponents方法的scanCandidateComponents方法
private Set<BeanDefinition> scanCandidateComponents(String basePackage) {
Set<BeanDefinition> candidates = new LinkedHashSet<>();
try {
String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
resolveBasePackage(basePackage) + '/' + this.resourcePattern;
//擷取該包下的是以類檔案源
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 {
//解析file并用類加載器加載類檔案擷取類的包名加類名放入MetadataReader
MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(resource);
//判斷AnnotationMetadataReadingVisitor.annotationSet中是否有Component注解，annotationSet是一個set集合
//AnnotationMetadataReadingVisitor在前面就已經通過類加載器解析過了裡面屬性都注入了
if (isCandidateComponent(metadataReader)) {
//把metadataReader部分屬性注入到BeanDefinition
ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
sbd.setResource(resource);
sbd.setSource(resource);
if (isCandidateComponent(sbd)) {
if (debugEnabled) {
logger.debug("Identified candidate component class: " + resource);
}
//加入集合
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;
}
getMetadataReader最後到SimpleMetadataReader類的SimpleMetadataReader構造方法
SimpleMetadataReader(Resource resource, @Nullable ClassLoader classLoader) throws IOException {
InputStream is = new BufferedInputStream(resource.getInputStream());
ClassReader classReader;
try {
classReader = new ClassReader(is);
}
catch (IllegalArgumentException ex) {
throw new NestedIOException("ASM ClassReader failed to parse class file - " +
"probably due to a new Java class file version that isn't supported yet: " + resource, ex);
}
finally {
is.close();
}
AnnotationMetadataReadingVisitor visitor = new AnnotationMetadataReadingVisitor(classLoader);
//擷取類的包名加類名放入visitor的className中,擷取類上的注解并注入annotationSet集合
classReader.accept(visitor, ClassReader.SKIP_DEBUG);
this.annotationMetadata = visitor;
// (since AnnotationMetadataReadingVisitor extends ClassMetadataReadingVisitor)
//由于AnnotationMetadatareadingVisitor擴充了ClassMetadatareadingVisitor
this.classMetadata = visitor;
this.resource = resource;
}
進入第2代碼塊的registerComponents方法中
protected void registerComponents(
XmlReaderContext readerContext, Set<BeanDefinitionHolder> beanDefinitions, Element element) {
Object source = readerContext.extractSource(element);
CompositeComponentDefinition compositeDef = new CompositeComponentDefinition(element.getTagName(), source);
for (BeanDefinitionHolder beanDefHolder : beanDefinitions) {
compositeDef.addNestedComponent(new BeanComponentDefinition(beanDefHolder));
}
// Register annotation config processors, if necessary.
//如有必要，注冊注釋配置處理器。
boolean annotationConfig = true;
if (element.hasAttribute(ANNOTATION_CONFIG_ATTRIBUTE)) {
annotationConfig = Boolean.valueOf(element.getAttribute(ANNOTATION_CONFIG_ATTRIBUTE));
}
if (annotationConfig) {
//注冊一些spring的類
Set<BeanDefinitionHolder> processorDefinitions =
AnnotationConfigUtils.registerAnnotationConfigProcessors(readerContext.getRegistry(), source);
for (BeanDefinitionHolder processorDefinition : processorDefinitions) {
compositeDef.addNestedComponent(new BeanComponentDefinition(processorDefinition));
}
}
// 激發元件注冊事件。
readerContext.fireComponentRegistered(compositeDef);
}
registerAnnotationConfigProcessors
public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors(
BeanDefinitionRegistry registry, @Nullable Object source) {
DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry);
if (beanFactory != null) {
if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) {
beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
}
if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) {
beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());
}
}
Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<>(8);
if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));
}
if (!registry.containsBeanDefinition(AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) {
//AutowiredAnnotationBeanPostProcessor是處理@Autowired的類
RootBeanDefinition def = new RootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME));
}
// Check for JSR-250 support, and if present add the CommonAnnotationBeanPostProcessor.
if (jsr250Present && !registry.containsBeanDefinition(COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)) {
//處理PostConstruct和PreDestroy的類
RootBeanDefinition def = new RootBeanDefinition(CommonAnnotationBeanPostProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, COMMON_ANNOTATION_PROCESSOR_BEAN_NAME));
}
// Check for JPA support, and if present add the PersistenceAnnotationBeanPostProcessor.
if (jpaPresent && !registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition();
try {
def.setBeanClass(ClassUtils.forName(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME,
AnnotationConfigUtils.class.getClassLoader()));
}
catch (ClassNotFoundException ex) {
throw new IllegalStateException(
"Cannot load optional framework class: " + PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, ex);
}
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME));
}
if (!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(EventListenerMethodProcessor.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME));
}
if (!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(DefaultEventListenerFactory.class);
def.setSource(source);
beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME));
}
return beanDefs;
}
進入到registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)
裡面是把該類注冊到beanfactory中
private static BeanDefinitionHolder registerPostProcessor(
BeanDefinitionRegistry registry, RootBeanDefinition definition, String beanName) {
definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
//注入到beanfactory中
registry.registerBeanDefinition(beanName, definition);
return new BeanDefinitionHolder(definition, beanName);
}
總結：該方法是解析不是beans限制的節點，掃描擷取源檔案，在用類加載器加載源檔案，擷取資訊該類上的注解注入到對應的容器中，在比對Component注解看類上是否有，有就注入到beanfactory中，在注冊一些spring内置的類如處理@Autowired的AutowiredAnnotationBeanPostProcessor等
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