我们直接上code：
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) { /** * 1：基于前面的include/exclude filter等，筛选出满足条件的beanDefinition集合 * 但这时候的beanDefinition还不是完整的，还有些属性没设置 */ 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); // 一些处理，根据autowireCandidatePatterns field，判断当前bean是否够格，作为自动注入的候选者 if (candidate instanceof AbstractBeanDefinition) { postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName); } // 调用setPrimary/setLazyInit/setDependsOn/setTole来设置beanDefiniiton属性 if (candidate instanceof AnnotatedBeanDefinition) { AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate); } // 这里，注册到beanDefinitionRegistry if (checkCandidate(beanName, candidate)) { BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName); definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry); beanDefinitions.add(definitionHolder); // 注册到beanDefinitionRegistry registerBeanDefinition(definitionHolder, this.registry); } } } return beanDefinitions; }大体流程，就这样结束了。
里面有意思的细节，主要是，查找指定包下，满足条件的beanDefiniiton这块。
/** * Scan the class path for candidate components. * @param basePackage the package to check for annotated classes * @return a corresponding Set of autodetected bean definitions */ public Set<BeanDefinition> findCandidateComponents(String basePackage) { Set<BeanDefinition> candidates = new LinkedHashSet<BeanDefinition>(); try { String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX + resolveBasePackage(basePackage) + "http://www.likecs.com/" + 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; }注意哈，这里获取的beanDefinition的类型是什么？
是ScannedGenericBeanDefinition。
学了这么多讲，是时候回头看看曾经走过的路了：
根据include/exclude filter来判断的过程也很有意思：
/** * Determine whether the given class does not match any exclude filter * and does match at least one include filter. * @param metadataReader the ASM ClassReader for the class * @return whether the class qualifies as a candidate component */ protected boolean isCandidateComponent(MetadataReader metadataReader) throws IOException { for (TypeFilter tf : this.excludeFilters) { if (tf.match(metadataReader, this.metadataReaderFactory)) { return false; } } for (TypeFilter tf : this.includeFilters) { if (tf.match(metadataReader, this.metadataReaderFactory)) { AnnotationMetadata metadata = metadataReader.getAnnotationMetadata(); if (!metadata.isAnnotated(Profile.class.getName())) { return true; } AnnotationAttributes profile = MetadataUtils.attributesFor(metadata, Profile.class); return this.environment.acceptsProfiles(profile.getStringArray("value")); } } return false; } 总结component-scan的探索之旅就这么结束了。欢迎大家留言，觉得有帮助的话，请关注我，后续会输出更多内容。