spring boot默认扫描的路径

一般来说spring boot默认的扫描路径是启动类当前的包和子包

@SpringBootApplication
@EnableTransactionManagement(proxyTargetClass = true)
@MapperScan(basePackages = {"com.frame.springboot.dao", "com.frame.springboot.base"})
public class SpringbootApplication {public static void main(String[] args) {SpringApplication app = new SpringApplication(SpringbootApplication.class);app.addListeners(new MyApplicationStartedEventListener());app.run(args);}static class MyApplicationStartedEventListener implements ApplicationListener<ApplicationStartedEvent> {private Logger logger = LoggerFactory.getLogger(MyApplicationStartedEventListener.class);@Overridepublic void onApplicationEvent(ApplicationStartedEvent event) {SpringApplication app = event.getSpringApplication();app.setBannerMode(Banner.Mode.OFF);// 不显示banner信息logger.info("==MyApplicationStartedEventListener==");}}}

例如这个类的包和子类。

接下来就从源码角度来分析这是为什么

首先这个加载过程肯定是从 refreshcontext 中的操作，因此进入。

  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();}}}

这个操作实在初始化factorypostprocessors中进行的。

接下来进入方法

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, this.getBeanFactoryPostProcessors());if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean("loadTimeWeaver")) {beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));}}

在这里很明显是把任务委托给了PostProcessorRegistrationDelegate。接下来我们继续点击进入

invokeBeanFactoryPostProcessors的方法很长我只截取我们关心的代码

public static void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {Set<String> processedBeans = new HashSet();int var9;ArrayList currentRegistryProcessors;String[] postProcessorNames;if (beanFactory instanceof BeanDefinitionRegistry) {BeanDefinitionRegistry registry = (BeanDefinitionRegistry)beanFactory;List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList();List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList();Iterator var6 = beanFactoryPostProcessors.iterator();while(var6.hasNext()) {BeanFactoryPostProcessor postProcessor = (BeanFactoryPostProcessor)var6.next();if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor)postProcessor;registryProcessor.postProcessBeanDefinitionRegistry(registry);registryProcessors.add(registryProcessor);} else {regularPostProcessors.add(postProcessor);}}
}

这里先来简单的说一下，首先会调用传入的beanFactoryPostProcessors的postProcessBeanDefinitionRegistry。处理一般会调用

ConfigurationClassPostProcessor类，接下来进去看一下postProcessBeanDefinitionRegistry方法

public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {int registryId = System.identityHashCode(registry);if (this.registriesPostProcessed.contains(registryId)) {throw new IllegalStateException("postProcessBeanDefinitionRegistry already called on this post-processor against " + registry);} else if (this.factoriesPostProcessed.contains(registryId)) {throw new IllegalStateException("postProcessBeanFactory already called on this post-processor against " + registry);} else {this.registriesPostProcessed.add(registryId);this.processConfigBeanDefinitions(registry);}
}

在这里最重要的还是processConfigBeanDefinitions方法，但是这个方法实在是太长了截取重要的步骤

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {//省略parser.parse(candidates);
}

这个方法主要是用来解析beandefinitions。进入看一下

   public void parse(Set<BeanDefinitionHolder> configCandidates) {this.deferredImportSelectors = new LinkedList();Iterator var2 = configCandidates.iterator();while(var2.hasNext()) {BeanDefinitionHolder holder = (BeanDefinitionHolder)var2.next();BeanDefinition bd = holder.getBeanDefinition();try {if (bd instanceof AnnotatedBeanDefinition) {this.parse(((AnnotatedBeanDefinition)bd).getMetadata(), holder.getBeanName());} else if (bd instanceof AbstractBeanDefinition && ((AbstractBeanDefinition)bd).hasBeanClass()) {this.parse(((AbstractBeanDefinition)bd).getBeanClass(), holder.getBeanName());} else {this.parse(bd.getBeanClassName(), holder.getBeanName());}} catch (BeanDefinitionStoreException var6) {throw var6;} catch (Throwable var7) {throw new BeanDefinitionStoreException("Failed to parse configuration class [" + bd.getBeanClassName() + "]", var7);}}this.processDeferredImportSelectors();}

这由于我们使用的是注解来进行那么进入第一个parse，主要调用了processConfigurationClass 的方法

protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {if (!this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {ConfigurationClass existingClass = (ConfigurationClass)this.configurationClasses.get(configClass);if (existingClass != null) {if (configClass.isImported()) {if (existingClass.isImported()) {existingClass.mergeImportedBy(configClass);}return;}this.configurationClasses.remove(configClass);Iterator it = this.knownSuperclasses.values().iterator();while(it.hasNext()) {if (configClass.equals(it.next())) {it.remove();}}}ConfigurationClassParser.SourceClass sourceClass = this.asSourceClass(configClass);do {sourceClass = this.doProcessConfigurationClass(configClass, sourceClass);} while(sourceClass != null);this.configurationClasses.put(configClass, configClass);}}

这个方法获取config的class和解析，其中主要方法是doProcessConfigurationClass

    protected final ConfigurationClassParser.SourceClass doProcessConfigurationClass(ConfigurationClass configClass, ConfigurationClassParser.SourceClass sourceClass) throws IOException {Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);if (!componentScans.isEmpty() && !this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {Iterator var13 = componentScans.iterator();while(var13.hasNext()) {AnnotationAttributes componentScan = (AnnotationAttributes)var13.next();Set<BeanDefinitionHolder> scannedBeanDefinitions = this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());Iterator var7 = scannedBeanDefinitions.iterator();while(var7.hasNext()) {BeanDefinitionHolder holder = (BeanDefinitionHolder)var7.next();if (ConfigurationClassUtils.checkConfigurationClassCandidate(holder.getBeanDefinition(), this.metadataReaderFactory)) {this.parse(holder.getBeanDefinition().getBeanClassName(), holder.getBeanName());}}}}}

只截取了其中的重要部分，看到componentScanParser.parse了，那么基本就想到是要去获取Component组件了，为什么config会和component关系呢，请看一下注解内部里面有一个@component。接下来进去看一下。

    public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {Set<String> basePackages = new LinkedHashSet();String[] basePackagesArray = componentScan.getStringArray("basePackages");String[] var19 = basePackagesArray;int var21 = basePackagesArray.length;int var22;for(var22 = 0; var22 < var21; ++var22) {String pkg = var19[var22];String[] tokenized = StringUtils.tokenizeToStringArray(this.environment.resolvePlaceholders(pkg), ",; \t\n");basePackages.addAll(Arrays.asList(tokenized));}Class[] var20 = componentScan.getClassArray("basePackageClasses");var21 = var20.length;for(var22 = 0; var22 < var21; ++var22) {Class<?> clazz = var20[var22];basePackages.add(ClassUtils.getPackageName(clazz));}if (basePackages.isEmpty()) {basePackages.add(ClassUtils.getPackageName(declaringClass));}
}

这个代码是为了寻找可以扫描的基础包，但是在创建启动类的时候我们并没有设置也就是 basePackages.isEmpty()==true 。接下来的操作是添加 declaringClass 路径，那么这个类是什么呢。这个类就是你的启动类。所以真正设置扫描路径的代码在这。

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