Spring 扫描原理（核心重点）

this.scanner = new ClassPathBeanDefinitionScanner(this);//扫描器1 

//扫描器2 
ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry, componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);

/**
 * @author: wangyj
 * @create: 2022-03-08
 * @version: 1.0.0
 * @link https://fangshixiang.blog.csdn.net/article/details/88765470
 **/
@Repository("repositoryName")
@Service("serviceName")
@EnableAsync
class MetaDemo extends HashMap<String, String> implements Serializable {

	private static class InnerClass {
	}

	@Autowired
	private String getName() {
		return "demo";
	}

	public static void main(String[] args) throws IOException {
		StandardAnnotationMetadata metadata = new StandardAnnotationMetadata(MetaDemo.class, true);
		// 演示ClassMetadata的效果
		System.out.println("==============ClassMetadata==============");
		ClassMetadata classMetadata = metadata;
		System.out.println(classMetadata.getClassName()); //com.fsx.maintest.MetaDemo
		System.out.println(classMetadata.getEnclosingClassName()); //null  如果自己是内部类此处就有值了
		System.out.println(StringUtils.arrayToCommaDelimitedString(classMetadata.getMemberClassNames())); //com.fsx.maintest.MetaDemo$InnerClass 若木有内部类返回空数组[]
		System.out.println(StringUtils.arrayToCommaDelimitedString(classMetadata.getInterfaceNames())); // java.io.Serializable
		System.out.println(classMetadata.hasSuperClass()); // true(只有Object这里是false)
		System.out.println(classMetadata.getSuperClassName()); // java.util.HashMap

		System.out.println(classMetadata.isAnnotation()); // false（是否是注解类型的Class，这里显然是false）
		System.out.println(classMetadata.isFinal()); // false
		System.out.println(classMetadata.isIndependent()); // true(top class或者static inner class，就是独立可new的)
		// 演示AnnotatedTypeMetadata的效果
		System.out.println("==============AnnotatedTypeMetadata==============");
		AnnotatedTypeMetadata annotatedTypeMetadata = metadata;
		System.out.println(annotatedTypeMetadata.isAnnotated(Service.class.getName())); // true（依赖的AnnotatedElementUtils.isAnnotated这个方法）
		System.out.println(annotatedTypeMetadata.isAnnotated(Component.class.getName())); // true

		System.out.println(annotatedTypeMetadata.getAnnotationAttributes(Service.class.getName())); //{value=serviceName}
		System.out.println(annotatedTypeMetadata.getAnnotationAttributes(Component.class.getName())); // {value=repositoryName}（@Repository的value值覆盖了@Service的）
		System.out.println(annotatedTypeMetadata.getAnnotationAttributes(EnableAsync.class.getName())); // {order=2147483647, annotation=interface java.lang.annotation.Annotation, proxyTargetClass=false, mode=PROXY}

		// 看看getAll的区别：value都是数组的形式
		System.out.println(annotatedTypeMetadata.getAllAnnotationAttributes(Service.class.getName())); // {value=[serviceName]}
		System.out.println(annotatedTypeMetadata.getAllAnnotationAttributes(Component.class.getName())); // {value=[, ]} --> 两个Component的value值都拿到了，只是都是空串而已
		System.out.println(annotatedTypeMetadata.getAllAnnotationAttributes(EnableAsync.class.getName())); //{order=[2147483647], annotation=[interface java.lang.annotation.Annotation], proxyTargetClass=[false], mode=[PROXY]}

		// 演示AnnotationMetadata子接口的效果（重要）
		System.out.println("==============AnnotationMetadata==============");
		AnnotationMetadata annotationMetadata = metadata;
		System.out.println(annotationMetadata.getAnnotationTypes()); // [org.springframework.stereotype.Repository, org.springframework.stereotype.Service, org.springframework.scheduling.annotation.EnableAsync]
		System.out.println(annotationMetadata.getMetaAnnotationTypes(Service.class.getName())); // [org.springframework.stereotype.Component, org.springframework.stereotype.Indexed]
		System.out.println(annotationMetadata.getMetaAnnotationTypes(Component.class.getName())); // []（meta就是获取注解上面的注解,会排除掉java.lang这些注解们）

		System.out.println(annotationMetadata.hasAnnotation(Service.class.getName())); // true
		System.out.println(annotationMetadata.hasAnnotation(Component.class.getName())); // false（注意这里返回的是false）

		System.out.println(annotationMetadata.hasMetaAnnotation(Service.class.getName())); // false（注意这一组的结果和上面相反，因为它看的是meta）
		System.out.println(annotationMetadata.hasMetaAnnotation(Component.class.getName())); // true

		System.out.println(annotationMetadata.hasAnnotatedMethods(Autowired.class.getName())); // true
		annotationMetadata.getAnnotatedMethods(Autowired.class.getName()).forEach(methodMetadata -> {
			System.out.println(methodMetadata.getClass()); // class org.springframework.core.type.StandardMethodMetadata
			System.out.println(methodMetadata.getMethodName()); // getName
			System.out.println(methodMetadata.getReturnTypeName()); // java.lang.String
		});

		// ********** 像这些元数据，在框架设计时候很多时候我们都希望从File(Resource)里得到，而不是从Class文件里获取，所以就是MetadataReader和MetadataReaderFactory **********
		CachingMetadataReaderFactory readerFactory = new CachingMetadataReaderFactory();
		// 下面两种初始化方式都可，效果一样
		//MetadataReader metadataReader = readerFactory.getMetadataReader(MetaDemo.class.getName());
		MetadataReader metadataReader = readerFactory.getMetadataReader(new ClassPathResource("jinggo/spring/example/batMan/spring/MetaDemo.class"));

		ClassMetadata classMetadata2 = metadataReader.getClassMetadata();
		AnnotationMetadata annotationMetadata2 = metadataReader.getAnnotationMetadata();
		Resource resource = metadataReader.getResource();

		System.out.println(classMetadata2); // org.springframework.core.type.classreading.AnnotationMetadataReadingVisitor@79079097
		System.out.println(annotationMetadata2); // org.springframework.core.type.classreading.AnnotationMetadataReadingVisitor@79079097
		System.out.println(resource); // class path resource [com/fsx/maintest/MetaDemo.class]
	}
}