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);
@Override
public 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。
