Spring 源码解析四（Bean 的构造装载、属性值解析、注解扫描）
Spring 源码解析四：Bean 的构造装载、属性值解析、注解扫描
上一篇主要介绍了 Bean 的注册、解析、实例化，但留下一些点待解析：
ConstructorResolver.autowireConstructor如何进行构造装载并实例化的CglibSubclassingInstantiationStrategy.instantiate如何动态实例化 bean 的BeanDefinitionValueResolver.resolveValueIfNecessary如何解析属性值的MergedAnnotations.from如何扫描注解的
1. ConstructorResolver.autowireConstructor ConstructorResolver
的主要功能是在构造时载入依赖的 bean 和用 factory-method 实例化 bean，这里只讲第一个：在构造时载入依赖的 bean ConstructorResolver.autowireConstructor
class ConstructorResolver {
public BeanWrapper autowireConstructor(String beanName, RootBeanDefinition mbd,
@Nullable Constructor[] chosenCtors, @Nullable Object[] explicitArgs) {
// 实例化一个封装对象
BeanWrapperImpl bw = new BeanWrapperImpl();
// 需要使用的构造方法
Constructor constructorToUse = null;
// 需要使用的构造参数
Object[] argsToUse = null;
// 如果指定了参数，就使用指定的参数
if (explicitArgs != null) {
argsToUse = explicitArgs;
}
else {
Object[] argsToResolve = null;
// 并发处理
synchronized (mbd.constructorArgumentLock) {
// 获取定义中已解析的构造方法
constructorToUse = (Constructor) mbd.resolvedConstructorOrFactoryMethod;
if (constructorToUse != null && mbd.constructorArgumentsResolved) {
// 获取定义中已解析的参数，首先是resolvedConstructorArguments，其次是preparedConstructorArguments
argsToUse = mbd.resolvedConstructorArguments;
if (argsToUse == null) {
argsToResolve = mbd.preparedConstructorArguments;
}
}
}
if (argsToResolve != null) {
// 把参数解析成实际要用的数据，如bean装配、属性载入
argsToUse = resolvePreparedArguments(beanName, mbd, bw, constructorToUse, argsToResolve);
}
}// 如果没有指定的构造方法或参数
if (constructorToUse == null || argsToUse == null) {
Constructor[] candidates = chosenCtors;
if (candidates == null) {
// 如果传入的chosenCtors是空，则获取beanClass的构造方法
Class beanClass = mbd.getBeanClass();
try {
candidates = (mbd.isNonPublicAccessAllowed() ?
beanClass.getDeclaredConstructors() : beanClass.getConstructors());
}
catch (Throwable ex) {
// ... 代码省略
}
}// 如果只有一个构造方法，并且没有指定explicitArgs和constructorArgumentValues
if (candidates.length == 1 && explicitArgs == null && !mbd.hasConstructorArgumentValues()) {
Constructor uniqueCandidate = candidates[0];
// 如果构造方法没有参数需要装配，直接实例化返回
if (uniqueCandidate.getParameterCount() == 0) {
synchronized (mbd.constructorArgumentLock) {
mbd.resolvedConstructorOrFactoryMethod = uniqueCandidate;
mbd.constructorArgumentsResolved = true;
mbd.resolvedConstructorArguments = EMPTY_ARGS;
}
// 实例化bean
bw.setBeanInstance(instantiate(beanName, mbd, uniqueCandidate, EMPTY_ARGS));
return bw;
}
}// 有构造方法，且构造模式为AUTOWIRE_CONSTRUCTOR，则需要自动装配bean
boolean autowiring = (chosenCtors != null ||
mbd.getResolvedAutowireMode() == AutowireCapableBeanFactory.AUTOWIRE_CONSTRUCTOR);
ConstructorArgumentValues resolvedValues = null;
// ... 代码省略// 选择一个参数数量、参数类型、参数顺序与需要实例化参数对象最接近的一个构造方法
// 这里的计算比较复杂，有兴趣的朋友可以自行探索一下
for (Constructor candidate : candidates) {
// ... 代码省略
}// ... 代码省略
}// 实例化bean
bw.setBeanInstance(instantiate(beanName, mbd, constructorToUse, argsToUse));
return bw;
}// 实例化bean，默认使用CglibSubclassingInstantiationStrategy.instantiate来实例化
private Object instantiate(
String beanName, RootBeanDefinition mbd, Constructor constructorToUse, Object[] argsToUse) {try {
InstantiationStrategy strategy = this.beanFactory.getInstantiationStrategy();
if (System.getSecurityManager() != null) {
return AccessController.doPrivileged((PrivilegedAction最终的实例化仍然需要
CglibSubclassingInstantiationStrategy.instantiate来实现2. CglibSubclassingInstantiationStrategy.instantiate CglibSubclassingInstantiationStrategy
的主要功能是使用 cglib 的方式实例化 bean
public class CglibSubclassingInstantiationStrategy extends SimpleInstantiationStrategy {}我们先来看看 SimpleInstantiationStrategy
public class SimpleInstantiationStrategy implements InstantiationStrategy {
// 用于调用factory-method
private static final ThreadLocal currentlyInvokedFactoryMethod = new ThreadLocal<>();
@Override
public Object instantiate(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner) {
// 没有方法需要重载
if (!bd.hasMethodOverrides()) {
Constructor constructorToUse;
synchronized (bd.constructorArgumentLock) {
// 首先获取已解析的构造方法
constructorToUse = (Constructor) bd.resolvedConstructorOrFactoryMethod;
if (constructorToUse == null) {
// 没有已解析的构造方法，则用beanClass获取
final Class clazz = bd.getBeanClass();
// 接口不能实例化
if (clazz.isInterface()) {
throw new BeanInstantiationException(clazz, "Specified class is an interface");
}
try {
if (System.getSecurityManager() != null) {
constructorToUse = AccessController.doPrivileged(
(PrivilegedExceptionAction>) clazz::getDeclaredConstructor);
}
else {
// 通过Class获取构造方法
constructorToUse = clazz.getDeclaredConstructor();
}
// 设为已解析的构造方法
bd.resolvedConstructorOrFactoryMethod = constructorToUse;
}
catch (Throwable ex) {
// 如果Class没有构造方法，报错
}
}
}
// 调用Constructor..newInstance实例化
return BeanUtils.instantiateClass(constructorToUse);
}
else {
// 有方法需要重载，则需要用cglib生成一个新的子类
return instantiateWithMethodInjection(bd, beanName, owner);
}
}// 方法注入实例化，留给子类实现
protected Object instantiateWithMethodInjection(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner) {
throw new UnsupportedOperationException("Method Injection not supported in SimpleInstantiationStrategy");
}@Override
public Object instantiate(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner,
final Constructor ctor, Object... args) {
// 没有方法需要重载
if (!bd.hasMethodOverrides()) {
// ... 代码省略// 调用Constructor.newInstance实例化
return BeanUtils.instantiateClass(ctor, args);
}
else {
// 有方法需要重载，则需要用cglib生成一个新的子类
return instantiateWithMethodInjection(bd, beanName, owner, ctor, args);
}
}// 方法注入实例化，留给子类实现
protected Object instantiateWithMethodInjection(RootBeanDefinition bd, @Nullable String beanName,
BeanFactory owner, @Nullable Constructor ctor, Object... args) {
throw new UnsupportedOperationException("Method Injection not supported in SimpleInstantiationStrategy");
}// 通过factory-method初始化
@Override
public Object instantiate(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner,
@Nullable Object factoryBean, final Method factoryMethod, Object... args) {try {
// ... 代码省略// 直接调用Method.invoke实例化
Object result = factoryMethod.invoke(factoryBean, args);
// 如果为null，实例化一个NullBean
if (result == null) {
result = new NullBean();
}
return result;
}
catch (IllegalArgumentException ex) {
// ... 代码省略
}
catch (IllegalAccessException ex) {
// ... 代码省略
}
catch (InvocationTargetException ex) {
// ... 代码省略
}
}
} 我们先来看看 CglibSubclassingInstantiationStrategy
public class CglibSubclassingInstantiationStrategy extends SimpleInstantiationStrategy {
@Override
protected Object instantiateWithMethodInjection(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner) {
return instantiateWithMethodInjection(bd, beanName, owner, null);
}@Override
protected Object instantiateWithMethodInjection(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner,
@Nullable Constructor ctor, Object... args) {
// 生成一个CglibSubclassCreator来实例化
return new CglibSubclassCreator(bd, owner).instantiate(ctor, args);
}
}CglibSubclassCreator是CglibSubclassingInstantiationStrategy的内部类private static class CglibSubclassCreator {
// 实例化一个构造函数
public Object instantiate(@Nullable Constructor ctor, Object... args) {
// 使用cglib Enhancer创建一个加强子类
Class subclass = createEnhancedSubclass(this.beanDefinition);
Object instance;
if (ctor == null) {
// 如果没有指定构造函数，调用Constructor.newInstance实例化
instance = BeanUtils.instantiateClass(subclass);
}
else {
try {
// 获取与ctor参数匹配的子类构造函数，再调用Constructor.newInstance实例化
Constructor enhancedSubclassConstructor = subclass.getConstructor(ctor.getParameterTypes());
instance = enhancedSubclassConstructor.newInstance(args);
}
catch (Exception ex) {
// ... 代码省略
}
}// ... 代码省略return instance;
}// 使用cglib Enhancer创建一个加强子类
private Class createEnhancedSubclass(RootBeanDefinition beanDefinition) {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(beanDefinition.getBeanClass());
enhancer.setNamingPolicy(SpringNamingPolicy.INSTANCE);
if (this.owner instanceof ConfigurableBeanFactory) {
ClassLoader cl = ((ConfigurableBeanFactory) this.owner).getBeanClassLoader();
enhancer.setStrategy(new ClassLoaderAwareGeneratorStrategy(cl));
}
enhancer.setCallbackFilter(new MethodOverrideCallbackFilter(beanDefinition));
enhancer.setCallbackTypes(CALLBACK_TYPES);
return enhancer.createClass();
}
}3. BeanDefinitionValueResolver.resolveValueIfNecessary BeanDefinitionValueResolver
的主要功能是将配置的属性值装载到 bean 中
class BeanDefinitionValueResolver {
public Object resolveValueIfNecessary(Object argName, @Nullable Object value) {
// 在运行时对其他bean的引用
if (value instanceof RuntimeBeanReference) {
RuntimeBeanReference ref = (RuntimeBeanReference) value;
// 解析引用bean
return resolveReference(argName, ref);
}
// 在运行时对其他bean name的引用
else if (value instanceof RuntimeBeanNameReference) {
String refName = ((RuntimeBeanNameReference) value).getBeanName();
// 使用doEvaluate解析bean名字，执行SpEL表达式
refName = String.valueOf(doEvaluate(refName));
if (!this.beanFactory.containsBean(refName)) {
// 没注册过bean name，报错
}
return refName;
}
// 包含别名的bean定义
else if (value instanceof BeanDefinitionHolder) {
BeanDefinitionHolder bdHolder = (BeanDefinitionHolder) value;
// 解析内部bean
return resolveInnerBean(argName, bdHolder.getBeanName(), bdHolder.getBeanDefinition());
}
// bean定义
else if (value instanceof BeanDefinition) {
BeanDefinition bd = (BeanDefinition) value;
// 内部bean名字
String innerBeanName = "(inner bean)" + BeanFactoryUtils.GENERATED_BEAN_NAME_SEPARATOR +
ObjectUtils.getIdentityHexString(bd);
// 解析内部bean
return resolveInnerBean(argName, innerBeanName, bd);
}
// 注入依赖描述(类、方法、属性)
else if (value instanceof DependencyDescriptor) {
Set autowiredBeanNames = new LinkedHashSet<>(4);
// 解析依赖
Object result = this.beanFactory.resolveDependency(
(DependencyDescriptor) value, this.beanName, autowiredBeanNames, this.typeConverter);
for (String autowiredBeanName : autowiredBeanNames) {
if (this.beanFactory.containsBean(autowiredBeanName)) {
// 注册依赖
this.beanFactory.registerDependentBean(autowiredBeanName, this.beanName);
}
}
return result;
}// ... 代码省略// 是字符类型的值
else if (value instanceof TypedStringValue) {
TypedStringValue typedStringValue = https://www.it610.com/article/(TypedStringValue) value;
// 使用evaluate解析bean名字，执行SpEL表达式
Object valueObject = evaluate(typedStringValue);
try {
// 解析类型
Class resolvedTargetType = resolveTargetType(typedStringValue);
// 如果有类型，把valueObject转换成这个类型
if (resolvedTargetType != null) {
return this.typeConverter.convertIfNecessary(valueObject, resolvedTargetType);
}
// 没有指定类型，则返回原本的
else {
return valueObject;
}
}
catch (Throwable ex) {
// ... 代码省略
}
}
// 如果是NullBean，返回null
else if (value instanceof NullBean) {
return null;
}
// 默认当成SpEL表达式解析了
else {
return evaluate(value);
}
}
}BeanDefinitionValueResolver.resolveReference
解析引用 bean
class BeanDefinitionValueResolver {
private Object resolveReference(Object argName, RuntimeBeanReference ref) {
try {
Object bean;
// 获取bean类型
Class beanType = ref.getBeanType();
if (ref.isToParent()) {
// 指明从父BeanFactory中获取
BeanFactory parent = this.beanFactory.getParentBeanFactory();
if (beanType != null) {
// 如果有beanType，直接通过类型获取bean
bean = parent.getBean(beanType);
}
else {
// 使用doEvaluate解析bean名字，执行SpEL表达式，然后根据名字查找bean
bean = parent.getBean(String.valueOf(doEvaluate(ref.getBeanName())));
}
}
else {
String resolvedName;
if (beanType != null) {
// 如果有beanType，直接通过类型获取bean
NamedBeanHolder namedBean = this.beanFactory.resolveNamedBean(beanType);
bean = namedBean.getBeanInstance();
resolvedName = namedBean.getBeanName();
}
else {
// 使用doEvaluate解析bean名字，执行SpEL表达式，然后根据名字查找bean
resolvedName = String.valueOf(doEvaluate(ref.getBeanName()));
bean = this.beanFactory.getBean(resolvedName);
}
// 注册依赖
this.beanFactory.registerDependentBean(resolvedName, this.beanName);
}
// 如果是NullBean，返回null
if (bean instanceof NullBean) {
bean = null;
}
return bean;
}
catch (BeansException ex) {
// ... 代码省略
}
}// 调用beanFactory来解析bean名字，执行SpEL表达式
private Object doEvaluate(String value) {
return this.beanFactory.evaluateBeanDefinitionString(value, this.beanDefinition);
}
}BeanDefinitionValueResolver.resolveInnerBean
解析内部 bean
class BeanDefinitionValueResolver {
private Object resolveInnerBean(Object argName, String innerBeanName, BeanDefinition innerBd) {
RootBeanDefinition mbd = null;
try {
// 获取合并父bean定义的bean定义
mbd = this.beanFactory.getMergedBeanDefinition(innerBeanName, innerBd, this.beanDefinition);
String actualInnerBeanName = innerBeanName;
if (mbd.isSingleton()) {
// 如果同类型的bean被实例化多次，则使用后缀#1,#2...来命名之后的bean
actualInnerBeanName = adaptInnerBeanName(innerBeanName);
}
// 把新生成的名字注册到beanFactory
this.beanFactory.registerContainedBean(actualInnerBeanName, this.beanName);
// 获取依赖
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
for (String dependsOnBean : dependsOn) {
// 注册依赖
this.beanFactory.registerDependentBean(dependsOnBean, actualInnerBeanName);
// 确保加载
this.beanFactory.getBean(dependsOnBean);
}
}
// 创建bean
Object innerBean = this.beanFactory.createBean(actualInnerBeanName, mbd, null);
// 如果bean实例是FactoryBean，则调用factory-method获取真正的bean
if (innerBean instanceof FactoryBean) {
boolean synthetic = mbd.isSynthetic();
innerBean = this.beanFactory.getObjectFromFactoryBean(
(FactoryBean) innerBean, actualInnerBeanName, !synthetic);
}
// 如果是NullBean，返回null
if (innerBean instanceof NullBean) {
innerBean = null;
}
return innerBean;
}
catch (BeansException ex) {
// ... 代码省略
}
}// 如果同类型的bean被实例化多次，则使用后缀#1,#2...来命名之后的bean
private String adaptInnerBeanName(String innerBeanName) {
String actualInnerBeanName = innerBeanName;
int counter = 0;
String prefix = innerBeanName + BeanFactoryUtils.GENERATED_BEAN_NAME_SEPARATOR;
while (this.beanFactory.isBeanNameInUse(actualInnerBeanName)) {
counter++;
actualInnerBeanName = prefix + counter;
}
return actualInnerBeanName;
}
}4. MergedAnnotations.from MergedAnnotations.from
的底层实现其实是 TypeMappedAnnotations.from
TypeMappedAnnotations的主要功能就是搜索、操作注解final class TypeMappedAnnotations implements MergedAnnotations {
static MergedAnnotations from(AnnotatedElement element, SearchStrategy searchStrategy,
RepeatableContainers repeatableContainers, AnnotationFilter annotationFilter) {
// 没有可用的注解，直接返回NONE
if (AnnotationsScanner.isKnownEmpty(element, searchStrategy)) {
return NONE;
}
return new TypeMappedAnnotations(element, searchStrategy, repeatableContainers, annotationFilter);
}static MergedAnnotations from(@Nullable Object source, Annotation[] annotations,
RepeatableContainers repeatableContainers, AnnotationFilter annotationFilter) {
// 没有要查找的注解，直接返回NONE
if (annotations.length == 0) {
return NONE;
}
return new TypeMappedAnnotations(source, annotations, repeatableContainers, annotationFilter);
}
}final class TypeMappedAnnotations implements MergedAnnotations {
// 检查是否有annotationType
@Override
publicboolean isPresent(Class annotationType) {
// 过滤器没通过，返回false
if (this.annotationFilter.matches(annotationType)) {
return false;
}
// 扫描目标元素(类、方法、属性)
return Boolean.TRUE.equals(scan(annotationType,
IsPresent.get(this.repeatableContainers, this.annotationFilter, false)));
}// 检查是否有annotationType
@Override
public boolean isPresent(String annotationType) {
// 过滤器没通过，返回false
if (this.annotationFilter.matches(annotationType)) {
return false;
}
// 扫描目标元素(类、方法、属性)
return Boolean.TRUE.equals(scan(annotationType,
IsPresent.get(this.repeatableContainers, this.annotationFilter, false)));
}// 获取目标元素的annotationType注解对象
@Override
publicMergedAnnotation get(Class annotationType,
@Nullable Predicate predicate,
@Nullable MergedAnnotationSelector selector) {
// 过滤器没通过，返回空
if (this.annotationFilter.matches(annotationType)) {
return MergedAnnotation.missing();
}
// 扫描目标元素(类、方法、属性)
MergedAnnotation result = scan(annotationType,
new MergedAnnotationFinder<>(annotationType, predicate, selector));
return (result != null ? result : MergedAnnotation.missing());
}// 获取目标元素的annotationType注解对象
@Override
publicMergedAnnotation get(String annotationType,
@Nullable Predicate predicate,
@Nullable MergedAnnotationSelector selector) {
// 过滤器没通过，返回空
if (this.annotationFilter.matches(annotationType)) {
return MergedAnnotation.missing();
}
// 扫描目标元素(类、方法、属性)
MergedAnnotation result = scan(annotationType,
new MergedAnnotationFinder<>(annotationType, predicate, selector));
return (result != null ? result : MergedAnnotation.missing());
}// 扫描目标元素(类、方法、属性)
private R scan(C criteria, AnnotationsProcessor processor) {
// 如果有传入的注解对象，就不扫描目标元素了
if (this.annotations != null) {
R result = processor.doWithAnnotations(criteria, 0, this.source, this.annotations);
return processor.finish(result);
}
// 有目标元素和扫描策略，扫描目标元素
if (this.element != null && this.searchStrategy != null) {
return AnnotationsScanner.scan(criteria, this.element, this.searchStrategy, processor);
}
return null;
}
} TypeMappedAnnotations.scan 的底层实现是 AnnotationsScanner.scanabstract class AnnotationsScanner {
// 扫描注解
static R scan(C context, AnnotatedElement source, SearchStrategy searchStrategy,
AnnotationsProcessor processor) {
// 实际扫描处理
R result = process(context, source, searchStrategy, processor);
return processor.finish(result);
}// 实际扫描处理
private static R process(C context, AnnotatedElement source,
SearchStrategy searchStrategy, AnnotationsProcessor processor) {
// 如果目标元素是类，按类处理
if (source instanceof Class) {
return processClass(context, (Class) source, searchStrategy, processor);
}
// 如果目标元素是方法，按方法处理
if (source instanceof Method) {
return processMethod(context, (Method) source, searchStrategy, processor);
}
// 不然按普通处理
return processElement(context, source, processor);
}
} 4.1. 按类处理
abstract class AnnotationsScanner {
private static R processClass(C context, Class source,
SearchStrategy searchStrategy, AnnotationsProcessor processor) {switch (searchStrategy) {
// 只搜索自身的注解，按普通处理
case DIRECT:
return processElement(context, source, processor);
// 搜索自身与标记为@Inherited父类的注解
case INHERITED_ANNOTATIONS:
return processClassInheritedAnnotations(context, source, searchStrategy, processor);
// 搜索自身与父类的注解
case SUPERCLASS:
return processClassHierarchy(context, source, processor, false, false);
// 搜索自身、父类、接口的注解
case TYPE_HIERARCHY:
return processClassHierarchy(context, source, processor, true, false);
// 搜索自身、父类、接口、getEnclosingClass()的注解
case TYPE_HIERARCHY_AND_ENCLOSING_CLASSES:
return processClassHierarchy(context, source, processor, true, true);
}
throw new IllegalStateException("Unsupported search strategy " + searchStrategy);
}// 搜索自身与标记为@Inherited父类的注解
private static R processClassInheritedAnnotations(C context, Class source,
SearchStrategy searchStrategy, AnnotationsProcessor processor) {
try {
// 如果除了自身以外，没有父类、接口、getEnclosingClass()的注解，按普通处理
if (isWithoutHierarchy(source, searchStrategy)) {
return processElement(context, source, processor);
}
Annotation[] relevant = null;
int remaining = Integer.MAX_VALUE;
int aggregateIndex = 0;
Class root = source;
// source对象还可以继续向父类上溯
// 非Object，非Ordered，非"java."开头
while (source != null && source != Object.class && remaining > 0 &&
!hasPlainJavaAnnotationsOnly(source)) {// 聚合处理，如果有了，直接返回（默认未实现）
R result = processor.doWithAggregate(context, aggregateIndex);
if (result != null) {
return result;
}// 获取所有public的注解
Annotation[] declaredAnnotations = getDeclaredAnnotations(source, true);
// ... 代码省略// 处理器自定义处理
result = processor.doWithAnnotations(context, aggregateIndex, source, declaredAnnotations);
// 如果有了，返回
if (result != null) {
return result;
}
// 上溯父类，继续扫描
source = source.getSuperclass();
aggregateIndex++;
}
}
catch (Throwable ex) {
// ... 代码省略
}
return null;
}// 搜索自身、父类、接口、getEnclosingClass()的注解
private static R processClassHierarchy(C context, int[] aggregateIndex, Class source,
AnnotationsProcessor processor, boolean includeInterfaces, boolean includeEnclosing) {
try {
// 聚合处理，如果有了，直接返回（默认未实现）
R result = processor.doWithAggregate(context, aggregateIndex[0]);
if (result != null) {
return result;
}
// 如果是Ordered或"java."开头，返回
if (hasPlainJavaAnnotationsOnly(source)) {
return null;
}
// 获取所有public的注解
Annotation[] annotations = getDeclaredAnnotations(source, false);
// 处理器自定义处理
result = processor.doWithAnnotations(context, aggregateIndex[0], source, annotations);
// 如果有了，返回
if (result != null) {
return result;
}
aggregateIndex[0]++;
// 如果包括接口，继续搜索接口的
if (includeInterfaces) {
for (Class interfaceType : source.getInterfaces()) {
R interfacesResult = processClassHierarchy(context, aggregateIndex,
interfaceType, processor, true, includeEnclosing);
if (interfacesResult != null) {
return interfacesResult;
}
}
}// 如果有父类，继续搜索父类的
Class superclass = source.getSuperclass();
if (superclass != Object.class && superclass != null) {
R superclassResult = processClassHierarchy(context, aggregateIndex,
superclass, processor, includeInterfaces, includeEnclosing);
if (superclassResult != null) {
return superclassResult;
}
}// 如果包括getEnclosingClass()，继续搜索getEnclosingClass()的
if (includeEnclosing) {
try {
Class enclosingClass = source.getEnclosingClass();
if (enclosingClass != null) {
R enclosingResult = processClassHierarchy(context, aggregateIndex,
enclosingClass, processor, includeInterfaces, true);
if (enclosingResult != null) {
return enclosingResult;
}
}
}
catch (Throwable ex) {
// ... 代码省略
}
}
}
catch (Throwable ex) {
// ... 代码省略
}
return null;
}
} 4.2. 按方法处理
abstract class AnnotationsScanner {
private static R processMethod(C context, Method source,
SearchStrategy searchStrategy, AnnotationsProcessor processor) {switch (searchStrategy) {
// 只搜索自身的注解
case DIRECT:
// 搜索自身与标记为@Inherited父类的注解
case INHERITED_ANNOTATIONS:
return processMethodInheritedAnnotations(context, source, processor);
// 搜索自身与父类的注解
case SUPERCLASS:
return processMethodHierarchy(context, new int[] {0}, source.getDeclaringClass(),
processor, source, false);
// 搜索自身、父类、接口的注解
case TYPE_HIERARCHY:
// 搜索自身、父类、接口、getEnclosingClass()的注解
case TYPE_HIERARCHY_AND_ENCLOSING_CLASSES:
return processMethodHierarchy(context, new int[] {0}, source.getDeclaringClass(),
processor, source, true);
}
throw new IllegalStateException("Unsupported search strategy " + searchStrategy);
}// 搜索自身与标记为@Inherited父类的注解
private static R processMethodInheritedAnnotations(C context, Method source,
AnnotationsProcessor processor) {try {
// 聚合处理，如果有了，直接返回（默认未实现）
// 不然，用processMethodAnnotations处理
R result = processor.doWithAggregate(context, 0);
return (result != null ? result :
processMethodAnnotations(context, 0, source, processor));
}
catch (Throwable ex) {
// ... 代码省略
}
return null;
}// 处理方法的注解
private static R processMethodAnnotations(C context, int aggregateIndex, Method source,
AnnotationsProcessor processor) {// 获取所有public的注解
Annotation[] annotations = getDeclaredAnnotations(source, false);
// 处理器自定义处理
R result = processor.doWithAnnotations(context, aggregateIndex, source, annotations);
// 如果有了，返回
if (result != null) {
return result;
}// ... 代码省略，桥接方法的处理return null;
}// 搜索自身、父类、接口、getEnclosingClass()的注解
private static R processMethodHierarchy(C context, int[] aggregateIndex,
Class sourceClass, AnnotationsProcessor processor, Method rootMethod,
boolean includeInterfaces) {
try {
// 聚合处理，如果有了，直接返回（默认未实现）
R result = processor.doWithAggregate(context, aggregateIndex[0]);
if (result != null) {
return result;
}
// 如果是Ordered或"java."开头，返回
if (hasPlainJavaAnnotationsOnly(sourceClass)) {
return null;
}boolean calledProcessor = false;
// 如果rootMethod是sourceClass的，直接处理
if (sourceClass == rootMethod.getDeclaringClass()) {
result = processMethodAnnotations(context, aggregateIndex[0],
rootMethod, processor);
calledProcessor = true;
if (result != null) {
return result;
}
}
else {
// 获取sourceClass的public方法
for (Method candidateMethod : getBaseTypeMethods(context, sourceClass)) {
// 如果方法不是private，并且参数与rootMethod一直，直接处理
if (candidateMethod != null && isOverride(rootMethod, candidateMethod)) {
result = processMethodAnnotations(context, aggregateIndex[0],
candidateMethod, processor);
calledProcessor = true;
if (result != null) {
return result;
}
}
}
}
// 如果rootMethod是private，返回null
if (Modifier.isPrivate(rootMethod.getModifiers())) {
return null;
}// 如果包括接口，继续搜索接口的
if (includeInterfaces) {
for (Class interfaceType : sourceClass.getInterfaces()) {
R interfacesResult = processMethodHierarchy(context, aggregateIndex,
interfaceType, processor, rootMethod, true);
if (interfacesResult != null) {
return interfacesResult;
}
}
}// 如果有父类，继续搜索父类的
Class superclass = sourceClass.getSuperclass();
if (superclass != Object.class && superclass != null) {
R superclassResult = processMethodHierarchy(context, aggregateIndex,
superclass, processor, rootMethod, includeInterfaces);
if (superclassResult != null) {
return superclassResult;
}
}
}
catch (Throwable ex) {
// ... 代码省略
}
return null;
}
} 4.3 按普通处理
abstract class AnnotationsScanner {
private static R processElement(C context, AnnotatedElement source,
AnnotationsProcessor processor) {try {
// 聚合处理，如果有了，直接返回（默认未实现）
// 不然，调用getDeclaredAnnotations获取注解来处理
R result = processor.doWithAggregate(context, 0);
return (result != null ? result : processor.doWithAnnotations(
context, 0, source, getDeclaredAnnotations(source, false)));
}
catch (Throwable ex) {
// ... 代码省略
}
return null;
}
} 后续 【Spring 源码解析四（Bean 的构造装载、属性值解析、注解扫描）】更多博客，查看 https://github.com/senntyou/blogs
作者：深予之 (@senntyou)
版权声明：自由转载-非商用-非衍生-保持署名（创意共享 3.0 许可证）
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