(转)Spring对注解(Annotation)处理源码分析1——扫描和读取Bean定义

public class AnnotationConfigApplicationContext extends GenericApplicationContext {
	//创建一个读取注解的Bean定义读取器，并将其设置到容器中
	private final AnnotatedBeanDefinitionReader reader = new AnnotatedBeanDefinitionReader(this);
	//创建一个扫描指定类路径中注解Bean定义的扫描器，并将其设置到容器中
	private final ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this);
//默认构造函数，初始化一个空容器，容器不包含任何 Bean 信息，需要在稍后通过调用其register() //方法注册配置类，并调用refresh()方法刷新容器，触发容器对注解Bean的载入、解析和注册过程
	public AnnotationConfigApplicationContext() {
	}
	//最常用的构造函数，通过将涉及到的配置类传递给该构造函数，以实现将相应配置类中的Bean
//自动注册到容器中
	public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) {
		register(annotatedClasses);
		refresh();
	}
//该构造函数会自动扫描以给定的包及其子包下的所有类，并自动识别所有的Spring Bean，将其
//注册到容器中
	public AnnotationConfigApplicationContext(String... basePackages) {
		scan(basePackages);
		refresh();
	}
	//为容器的注解Bean读取器和注解Bean扫描器设置Bean名称产生器
	public void setBeanNameGenerator(BeanNameGenerator beanNameGenerator) {
		this.reader.setBeanNameGenerator(beanNameGenerator);
		this.scanner.setBeanNameGenerator(beanNameGenerator);
	}
	//为容器的注解Bean读取器和注解Bean扫描器设置作用范围元信息解析器
	public void setScopeMetadataResolver(ScopeMetadataResolver scopeMetadataResolver) {
		this.reader.setScopeMetadataResolver(scopeMetadataResolver);
		this.scanner.setScopeMetadataResolver(scopeMetadataResolver);
	}
	//为容器注册一个要被处理的注解Bean，新注册的Bean，必须手动调用容器的
//refresh()方法刷新容器，触发容器对新注册的Bean的处理
	public void register(Class<?>... annotatedClasses) {
		this.reader.register(annotatedClasses);
	}
	//扫描指定包路径及其子包下的注解类，为了使新添加的类被处理，必须手动调用
	//refresh()方法刷新容器
	public void scan(String... basePackages) {
		this.scanner.scan(basePackages);
	}
}

//注册多个注解Bean定义类
public void register(Class<?>... annotatedClasses) {
		for (Class<?> annotatedClass : annotatedClasses) {
			registerBean(annotatedClass);
		}
	}
	//注册一个注解Bean定义类
	public void registerBean(Class<?> annotatedClass) {
		registerBean(annotatedClass, null, (Class<? extends Annotation>[]) null);
	}
	//Bean定义读取器注册注解Bean定义的入口方法
	public void registerBean(Class<?> annotatedClass, Class<? extends Annotation>... qualifiers) {
		registerBean(annotatedClass, null, qualifiers);
	}
	//Bean定义读取器向容器注册注解Bean定义类
	public void registerBean(Class<?> annotatedClass, String name, Class<? extends Annotation>... qualifiers) {
		//根据指定的注解Bean定义类，创建Spring容器中对注解Bean的封装的数据结构
		AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(annotatedClass);
		//解析注解Bean定义的作用域，若@Scope("prototype")，则Bean为原型类型；
		//若@Scope("singleton")，则Bean为单态类型
		ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd);
		//为注解Bean定义设置作用域
		abd.setScope(scopeMetadata.getScopeName());
		//为注解Bean定义生成Bean名称
		String beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry));
		//处理注解Bean定义中的通用注解
		AnnotationConfigUtils.processCommonDefinitionAnnotations(abd);
		//如果在向容器注册注解Bean定义时，使用了额外的限定符注解，则解析限定符注解。
	//主要是配置的关于autowiring自动依赖注入装配的限定条件，即@Qualifier
//注解，Spring自动依赖注入装配默认是按类型装配，如果使用@Qualifier则按名称
		if (qualifiers != null) {
			for (Class<? extends Annotation> qualifier : qualifiers) {
//如果配置了@Primary注解，设置该Bean为autowiring自动依赖注入装//配时的首选
				if (Primary.class.equals(qualifier)) {
					abd.setPrimary(true);
				}
				//如果配置了@Lazy注解，则设置该Bean为非延迟初始化，如果没有配置，
				//则该Bean为预实例化
				else if (Lazy.class.equals(qualifier)) {
					abd.setLazyInit(true);
				}
				//如果使用了除@Primary和@Lazy以外的其他注解，则为该Bean添加一
//个autowiring自动依赖注入装配限定符，该Bean在进autowiring
//自动依赖注入装配时，根据名称装配限定符指定的Bean
				else {
					abd.addQualifier(new AutowireCandidateQualifier(qualifier));
				}
			}
		}
		//创建一个指定Bean名称的Bean定义对象，封装注解Bean定义类数据
		BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName);
		//根据注解Bean定义类中配置的作用域，创建相应的代理对象
		definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
	//向IoC容器注册注解Bean类定义对象	BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);
	}

//解析注解Bean定义类中的作用域元信息
public ScopeMetadata resolveScopeMetadata(BeanDefinition definition) {
		ScopeMetadata metadata = new ScopeMetadata();
		if (definition instanceof AnnotatedBeanDefinition) {
			AnnotatedBeanDefinition annDef = (AnnotatedBeanDefinition) definition;
			//从注解Bean定义类的属性中查找属性为”Scope”的值，即@Scope注解的值
			// annDef.getMetadata().getAnnotationAttributes方法将Bean
//中所有的注解和注解的值存放在一个map集合中
			Map<String, Object> attributes =
	annDef.getMetadata().getAnnotationAttributes(this.scopeAnnotationType.getName());
			//将获取到的@Scope注解的值设置到要返回的对象中
			if (attributes != null) {
				metadata.setScopeName((String) attributes.get("value"));
				//获取@Scope注解中的proxyMode属性值，在创建代理对象时会用到
				ScopedProxyMode proxyMode = (ScopedProxyMode) attributes.get("proxyMode");
				//如果@Scope的proxyMode属性值为null、DEFAULT或者NO
				if (proxyMode == null || proxyMode == ScopedProxyMode.DEFAULT) {
					//设置proxyMode为NO
					proxyMode = this.defaultProxyMode;
				}
				//为返回的元数据设置proxyMode
				metadata.setScopedProxyMode(proxyMode);
			}
		}
		//返回解析的作用域元信息对象
		return metadata;
	}

//根据作用域为Bean应用引用的代码模式
static BeanDefinitionHolder applyScopedProxyMode(
			ScopeMetadata metadata, BeanDefinitionHolder definition, BeanDefinitionRegistry registry) {
		//获取注解Bean定义类中@Scope注解的proxyMode属性值
		ScopedProxyMode scopedProxyMode = metadata.getScopedProxyMode();
		//如果配置的@Scope注解的proxyMode属性值为NO，则不应用代理模式
		if (scopedProxyMode.equals(ScopedProxyMode.NO)) {
			return definition;
		}
//获取配置的@Scope注解的proxyMode属性值，如果为TARGET_CLASS，则返
//回true，如果为INTERFACES，则返回false
		boolean proxyTargetClass = scopedProxyMode.equals(ScopedProxyMode.TARGET_CLASS);
		//为注册的Bean创建相应模式的代理对象
		return ScopedProxyCreator.createScopedProxy(definition, registry, proxyTargetClass);
	} 

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Component {
	String value() default "";
}

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Service {
	String value() default "";
}

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Controller {
	String value() default "";
}

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Repository {
	String value() default "";
}

public class ClassPathScanningCandidateComponentProvider implements ResourceLoaderAware {
//保存过滤规则要包含的注解，即Spring默认的@Component、@Repository、@Service、//@Controller注解的Bean，以及JavaEE6的@ManagedBean和JSR-330的@Named注解
private final List<TypeFilter> includeFilters = new LinkedList<TypeFilter>();
//保存过滤规则要排除的注解
private final List<TypeFilter> excludeFilters = new LinkedList<TypeFilter>();
//构造方法，该方法在子类ClassPathBeanDefinitionScanner的构造方法中被调用
public ClassPathScanningCandidateComponentProvider(boolean useDefaultFilters) {
		//如果使用Spring默认的过滤规则，则向容器注册过滤规则
		if (useDefaultFilters) {
			registerDefaultFilters();
		}
	}
//向容器注册过滤规则
protected void registerDefaultFilters() {
//向要包含的过滤规则中添加@Component注解类，注意Spring中@Repository
//@Service和@Controller都是Component，因为这些注解都添加了@Component注解
		this.includeFilters.add(new AnnotationTypeFilter(Component.class));
		//获取当前类的类加载器
		ClassLoader cl = ClassPathScanningCandidateComponentProvider.class.getClassLoader();
		try {
			//向要包含的过滤规则添加JavaEE6的@ManagedBean注解
			this.includeFilters.add(new AnnotationTypeFilter(
					((Class<? extends Annotation>) cl.loadClass("javax.annotation.ManagedBean")), false));
			logger.info("JSR-250 ‘javax.annotation.ManagedBean‘ found and supported for component scanning");
		}
		catch (ClassNotFoundException ex) {
			// JSR-250 1.1 API (as included in Java EE 6) not available - simply skip.
		}
		try {
			//向要包含的过滤规则添加@Named注解
			this.includeFilters.add(new AnnotationTypeFilter(
					((Class<? extends Annotation>) cl.loadClass("javax.inject.Named")), false));
			logger.info("JSR-330 ‘javax.inject.Named‘ annotation found and supported for component scanning");
		}
		catch (ClassNotFoundException ex) {
			// JSR-330 API not available - simply skip.
		}
	}
//扫描给定类路径的包
public Set<BeanDefinition> findCandidateComponents(String basePackage) {
		//创建存储扫描到的类的集合
		Set<BeanDefinition> candidates = new LinkedHashSet<BeanDefinition>();
		try {
			//解析给定的包路径，this.resourcePattern=” **/*.class”，
	//ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX=“classpath:”
	//resolveBasePackage方法将包名中的”.”转换为文件系统的”/”
			String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
					resolveBasePackage(basePackage) + "/" + this.resourcePattern;
			//将给定的包路径解析为Spring资源对象
			Resource[] resources = this.resourcePatternResolver.getResources(packageSearchPath);
			boolean traceEnabled = logger.isTraceEnabled();
			boolean debugEnabled = logger.isDebugEnabled();
			//遍历扫描到的资源
			for (Resource resource : resources) {
				if (traceEnabled) {
					logger.trace("Scanning " + resource);
				}
				if (resource.isReadable()) {
					try {
//为指定资源获取元数据读取器，元信息读取器通过汇编(ASM)读//取资源元信息
						MetadataReader metadataReader = this.metadataReaderFactory.getMetadataReader(resource);
						//如果扫描到的类符合容器配置的过滤规则
						if (isCandidateComponent(metadataReader)) {
							//通过汇编(ASM)读取资源字节码中的Bean定义元信息
							ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
							//设置Bean定义来源于resource
							sbd.setResource(resource);
							//为元数据元素设置配置资源对象
							sbd.setSource(resource);
							//检查Bean是否是一个可实例化的对象
							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;
	}
//判断元信息读取器读取的类是否符合容器定义的注解过滤规则
protected boolean isCandidateComponent(MetadataReader metadataReader) throws IOException {
		//如果读取的类的注解在排除注解过滤规则中，返回false
		for (TypeFilter tf : this.excludeFilters) {
			if (tf.match(metadataReader, this.metadataReaderFactory)) {
				return false;
			}
		}
		//如果读取的类的注解在包含的注解的过滤规则中，则返回ture
		for (TypeFilter tf : this.includeFilters) {
			if (tf.match(metadataReader, this.metadataReaderFactory)) {
				return true;
			}
		}
		//如果读取的类的注解既不在排除规则，也不在包含规则中，则返回false
		return false;
	}
……
}

//载入注解Bean定义资源
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) {
		//为容器设置注解Bean定义读取器
		AnnotatedBeanDefinitionReader reader = new AnnotatedBeanDefinitionReader(beanFactory);
		//为容器设置类路径Bean定义扫描器
		ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(beanFactory);
		//获取容器的Bean名称生成器
		BeanNameGenerator beanNameGenerator = getBeanNameGenerator();
		//获取容器的作用域元信息解析器
		ScopeMetadataResolver scopeMetadataResolver = getScopeMetadataResolver();
		//为注解Bean定义读取器和类路径扫描器设置Bean名称生成器
		if (beanNameGenerator != null) {
			reader.setBeanNameGenerator(beanNameGenerator);
			scanner.setBeanNameGenerator(beanNameGenerator);
		}
//为注解Bean定义读取器和类路径扫描器设置作用域元信息解析器
		if (scopeMetadataResolver != null) {
			reader.setScopeMetadataResolver(scopeMetadataResolver);
			scanner.setScopeMetadataResolver(scopeMetadataResolver);
		}
		//获取容器定义的Bean定义资源路径
		String[] configLocations = getConfigLocations();
		//如果定位的Bean定义资源路径不为空
		if (configLocations != null) {
			for (String configLocation : configLocations) {
				try {
					//使用当前容器的类加载器加载定位路径的字节码类文件
					Class<?> clazz = getClassLoader().loadClass(configLocation);
					if (logger.isInfoEnabled()) {
						logger.info("Successfully resolved class for [" + configLocation + "]");
					}
					reader.register(clazz);
				}
				catch (ClassNotFoundException ex) {
					if (logger.isDebugEnabled()) {
						logger.debug("Could not load class for config location [" + configLocation +
								"] - trying package scan. " + ex);
					}
					//如果容器类加载器加载定义路径的Bean定义资源失败，则启用
//容器类路径扫描器扫描给定路径包及其子包中的类
					int count = scanner.scan(configLocation);
					if (logger.isInfoEnabled()) {
						if (count == 0) {
							logger.info("No annotated classes found for specified class/package [" + configLocation + "]");
						}
						else {
							logger.info("Found " + count + " annotated classes in package [" + configLocation + "]");
						}
					}
				}
			}
		}
	}