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This article mainly introduces "how to parse the @ Configuration/@Import annotation of SpringFramework". In the daily operation, I believe many people have doubts about how to parse the @ Configuration/@Import annotation of SpringFramework. The editor has consulted all kinds of materials and sorted out a simple and easy-to-use operation method. I hope it will be helpful for you to answer the doubt of "how to parse the @ Configuration/@Import annotation of SpringFramework"! Next, please follow the editor to study!

The version of Spring is 5.0.9.The release version of Spring boot is 2.0.3.release.

In Springboot, the Servlet web application uses AnnotationConfigServletWebServerApplicationContext. AnnotatedBeanDefinitionReader is instantiated in its constructor, such as List-1, and AnnotationConfigUtils.registerAnnotationConfigProcessors (this.registry) is called, as shown in List-2:

List-1

Public AnnotatedBeanDefinitionReader (BeanDefinitionRegistry registry, Environment environment) {Assert.notNull (registry, "BeanDefinitionRegistry must not be null"); Assert.notNull (environment, "Environment must not be null"); this.registry = registry; this.conditionEvaluator = new ConditionEvaluator (registry, environment, null); AnnotationConfigUtils.registerAnnotationConfigProcessors (this.registry);}

List-2

Public static Set registerAnnotationConfigProcessors (BeanDefinitionRegistry registry, @ Nullable Object source) {... 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));}

As shown in List-2, ConfigurationClassPostProcessor is converted to BeanDefinition and registered with registry. ConfigurationClassPostProcessor implements the BeanFacotryPostProcessor interface, and if you are familiar with SpringIOC, you should know what this does.

Figure 1

AnnotationConfigServletWebServerApplicationContext inherits AbstractApplicationContext,AbstractApplicationContext 's refresh () as shown in List-3 below, calling this.invokeBeanFactoryPostProcessors (beanFactory) in refresh (), then calling PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors (beanFactory, this.getBeanFactoryPostProcessors ()) to get all the BeanFactoryPostProcessor from the BeanFactory method, and then calling BeanFactoryPostProcessor's postProcessBeanFactory ().

List-3

Public void refresh () throws BeansException, IllegalStateException {synchronized (this.startupShutdownMonitor) {this.prepareRefresh (); ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory (); this.prepareBeanFactory (beanFactory); try {this.postProcessBeanFactory (beanFactory); this.invokeBeanFactoryPostProcessors (beanFactory); this.registerBeanPostProcessors (beanFactory); this.initMessageSource (); this.initApplicationEventMulticaster () This.onRefresh (); this.registerListeners (); this.finishBeanFactoryInitialization (beanFactory); this.finishRefresh ();} catch (BeansException var9) {if (this.logger.isWarnEnabled ()) {this.logger.warn ("Exception encountered during context initialization-cancelling refresh attempt:" + var9);} this.destroyBeans () This.cancelRefresh (var9); throw var9;} finally {this.resetCommonCaches ();}

Back to ConfigurationClassPostProcessor, look at its postProcessBeanFactory (), called processConfigBeanDefinitions (), the following List-4, a lot of code, but look at the key parts, 1 ConfigurationClassUtils.checkConfigurationClassCandidate to focus on, this method to determine whether there are Configuration/ComponentScan/Import/ImportResource comments on the class, if there are these comments, then will be added to the configCandidates, loop processing configCandidates, to ConfigurationClassParser.pase () for parsing.

List-4

Public void processConfigBeanDefinitions (BeanDefinitionRegistry registry) {List configCandidates = new ArrayList (); 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) }} / / 1 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 } / / 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; if (registry instanceof SingletonBeanRegistry) {sbr = (SingletonBeanRegistry) registry If (! this.localBeanNameGeneratorSet) {BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton (CONFIGURATION_BEAN_NAME_GENERATOR); if (generator! = null) {this.componentScanBeanNameGenerator = generator; this.importBeanNameGenerator = generator;} if (this.environment = = null) {this.environment = new StandardEnvironment () } / / Parse each @ Configuration class ConfigurationClassParser parser = new ConfigurationClassParser (this.metadataReaderFactory, this.problemReporter, this.environment, this.resourceLoader, this.componentScanBeanNameGenerator, registry); Set candidates = new LinkedHashSet (configCandidates); Set alreadyParsed = new HashSet (configCandidates.size ()); do {parser.parse (candidates); parser.validate (); Set 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 ());} this.reader.loadBeanDefinitions (configClasses); alreadyParsed.addAll (configClasses) Candidates.clear (); if (registry.getBeanDefinitionCount () > candidateNames.length) {String [] newCandidateNames = registry.getBeanDefinitionNames (); Set oldCandidateNames = new HashSet (Arrays.asList (candidateNames)); Set alreadyParsedClasses = new HashSet (); for (ConfigurationClass configurationClass: alreadyParsed) {alreadyParsedClasses.add (configurationClass.getMetadata (). GetClassName ()) } 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 ();}}

The processing of Selector introduced by Import on the EnableXX annotation in autoassembly is handled here, and it is interesting to note that the value in the String [] returned by Selector needs to be the full path cumulative name of the class, because the beanName of type String is converted to the corresponding Class type using Class.forName ().

At this point, the study on "how to parse SpringFramework's @ Configuration/@Import comments" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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