spring源码解析01---component-scan

╰半夏微凉° 2022-02-19 04:15 174阅读 0赞

# 1、ContextNamespaceHandler #

public class ContextNamespaceHandler extends NamespaceHandlerSupport { 
        public ContextNamespaceHandler() { 
        }
    
        public void init() { 
            this.registerBeanDefinitionParser("property-placeholder", new PropertyPlaceholderBeanDefinitionParser());
            this.registerBeanDefinitionParser("property-override", new PropertyOverrideBeanDefinitionParser());
            this.registerBeanDefinitionParser("annotation-config", new AnnotationConfigBeanDefinitionParser());
            //扫描<context:component-scan/>
            this.registerBeanDefinitionParser("component-scan", new ComponentScanBeanDefinitionParser());
            this.registerBeanDefinitionParser("load-time-weaver", new LoadTimeWeaverBeanDefinitionParser());
            this.registerBeanDefinitionParser("spring-configured", new SpringConfiguredBeanDefinitionParser());
            this.registerBeanDefinitionParser("mbean-export", new MBeanExportBeanDefinitionParser());
            this.registerBeanDefinitionParser("mbean-server", new MBeanServerBeanDefinitionParser());
        }
    }

# 2、ComponentScanBeanDefinitionParser #

@Nullable
        public BeanDefinition parse(Element element, ParserContext parserContext) { 
        	//获取扫描包
            String basePackage = element.getAttribute("base-package");
            basePackage = parserContext.getReaderContext().getEnvironment().resolvePlaceholders(basePackage);
            String[] basePackages = StringUtils.tokenizeToStringArray(basePackage, ",; \t\n");
            ClassPathBeanDefinitionScanner scanner = this.configureScanner(parserContext, element);
            //扫描包
            Set<BeanDefinitionHolder> beanDefinitions = scanner.doScan(basePackages);
            //注册component
            this.registerComponents(parserContext.getReaderContext(), beanDefinitions, element);
            return null;
        }

# 3、ClassPathBeanDefinitionScanner #

/** * Perform a scan within the specified base packages, * returning the registered bean definitions. * <p>This method does <i>not</i> register an annotation config processor * but rather leaves this up to the caller. * @param basePackages the packages to check for annotated classes * @return set of beans registered if any for tooling registration purposes (never {@code null}) */
    	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) { 
    			//浏览包中的候选类
    			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;
    	}