《Java Spring框架》Spring BeanDefinition源码分析

阅读目录

• 功能说明

回到目录

功能说明

BeanDefinition：是用于记录需要Spring初始化对象的信息，例如对象的路径，名称，修饰方式等待。

下面是BeanDefinition的继承关系图：

顶层接口BeanDefinition 每一个方法的中文注释说明：

/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.beans.factory.config;

import org.springframework.beans.BeanMetadataElement;
import org.springframework.beans.MutablePropertyValues;
import org.springframework.core.AttributeAccessor;
import org.springframework.lang.Nullable;

/**
 *
 * @author hubt spring当中用来描述bean的一个接口
 * A BeanDefinition describes a bean instance, which has property values,
 * constructor argument values, and further information supplied by
 * concrete implementations.
 *
 * <p>This is just a minimal interface: The main intention is to allow a
 * {@link BeanFactoryPostProcessor} such as {@link PropertyPlaceholderConfigurer}
 * to introspect and modify property values and other bean metadata.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @since 19.03.2004
 * @see ConfigurableListableBeanFactory#getBeanDefinition
 * @see org.springframework.beans.factory.support.RootBeanDefinition
 * @see org.springframework.beans.factory.support.ChildBeanDefinition
 */
public interface BeanDefinition extends AttributeAccessor, BeanMetadataElement {

    /**
     * @author hubt 标准单例作用域的作用域标识符：“singleton”。
     * Scope identifier for the standard singleton scope: "singleton".
     * <p>Note that extended bean factories might support further scopes.
     * @see #setScope
     */
    String SCOPE_SINGLETON = ConfigurableBeanFactory.SCOPE_SINGLETON;

    /**
     * @author hubt 原型
     * Scope identifier for the standard prototype scope: "prototype".
     * <p>Note that extended bean factories might support further scopes.
     * @see #setScope
     */
    String SCOPE_PROTOTYPE = ConfigurableBeanFactory.SCOPE_PROTOTYPE;


    /**
     * Role hint indicating that a {@code BeanDefinition} is a major part
     * of the application. Typically corresponds to a user-defined bean.
     *
     */
    int ROLE_APPLICATION = 0;

    /**
     * Role hint indicating that a {@code BeanDefinition} is a supporting
     * part of some larger configuration, typically an outer
     * {@link org.springframework.beans.factory.parsing.ComponentDefinition}.
     * {@code SUPPORT} beans are considered important enough to be aware
     * of when looking more closely at a particular
     * {@link org.springframework.beans.factory.parsing.ComponentDefinition},
     * but not when looking at the overall configuration of an application.
     * ROLE_SUPPORT =1实际上就是说，我这个Bean是用户的，是从配置文件中过来的
     */
    int ROLE_SUPPORT = 1;

    /**
     * Role hint indicating that a {@code BeanDefinition} is providing an
     * entirely background role and has no relevance to the end-user. This hint is
     * used when registering beans that are completely part of the internal workings
     * of a {@link org.springframework.beans.factory.parsing.ComponentDefinition}.
     * 就是我这Bean是Spring自己的，和你用户没有一毛钱关系
     */
    int ROLE_INFRASTRUCTURE = 2;


    // Modifiable attributes

    /**
     * 设置一个BeanDefinition的子类，则该BeanDefinition就继承设置的子类的一些设置比如属性值，单例原型。该BeanDefinition可以不设置这些信息
     * 保持和设置类一致。
     * Set the name of the parent definition of this bean definition, if any.
     */
    void setParentName(@Nullable String parentName);

    /**
     * Return the name of the parent definition of this bean definition, if any.
     */
    @Nullable
    String getParentName();

    /**
     * Specify the bean class name of this bean definition.
     * <p>The class name can be modified during bean factory post-processing,
     * typically replacing the original class name with a parsed variant of it.
     * @see #setParentName
     * @see #setFactoryBeanName
     * @see #setFactoryMethodName
     */
    void setBeanClassName(@Nullable String beanClassName);

    /**
     * Return the current bean class name of this bean definition.
     * <p>Note that this does not have to be the actual class name used at runtime, in
     * case of a child definition overriding/inheriting the class name from its parent.
     * Also, this may just be the class that a factory method is called on, or it may
     * even be empty in case of a factory bean reference that a method is called on.
     * Hence, do <i>not</i> consider this to be the definitive bean type at runtime but
     * rather only use it for parsing purposes at the individual bean definition level.
     * @see #getParentName()
     * @see #getFactoryBeanName()
     * @see #getFactoryMethodName()
     */
    @Nullable
    String getBeanClassName();

    /**
     * Override the target scope of this bean, specifying a new scope name.
     * @see #SCOPE_SINGLETON
     * @see #SCOPE_PROTOTYPE
     */
    void setScope(@Nullable String scope);

    /**
     * Return the name of the current target scope for this bean,
     * or {@code null} if not known yet.
     */
    @Nullable
    String getScope();

    /**
     * @author hubt 设置懒加载
     * Set whether this bean should be lazily initialized.
     * <p>If {@code false}, the bean will get instantiated on startup by bean
     * factories that perform eager initialization of singletons.
     */
    void setLazyInit(boolean lazyInit);

    /**
     * @author hubt 判断是否是懒加载
     * Return whether this bean should be lazily initialized, i.e. not
     * eagerly instantiated on startup. Only applicable to a singleton bean.
     */
    boolean isLazyInit();

    /**
     * @author hubt 设置实例化bean 顺序。
     * Set the names of the beans that this bean depends on being initialized.
     * The bean factory will guarantee that these beans get initialized first.
     */
    void setDependsOn(@Nullable String... dependsOn);

    /**
     * @author hubt 获取设置DependsOn的数组。
     * Return the bean names that this bean depends on.
     */
    @Nullable
    String[] getDependsOn();

    /**
     * @author hubt 可以通过该字段设置是否参与bean的注入。 true 参与，false 不参与，
     * 主要用途在class 名称或者类型一致时。
     * Set whether this bean is a candidate for getting autowired into some other bean.
     * <p>Note that this flag is designed to only affect type-based autowiring.
     * It does not affect explicit references by name, which will get resolved even
     * if the specified bean is not marked as an autowire candidate. As a consequence,
     * autowiring by name will nevertheless inject a bean if the name matches.
     */
    void setAutowireCandidate(boolean autowireCandidate);

    /**
     * @author hubt 根据setAutowireCandidate 设置结果判断该Bean 是否参与spring初始化。
     * @author hubt 获取通过setAutowireCandidate方法设置的值。
     * Return whether this bean is a candidate for getting autowired into some other bean.
     */
    boolean isAutowireCandidate();

    /**
     * @author hubt 注入Bean 的时候将一个Bean设置成主要可以被注入的Bean.
     * Set whether this bean is a primary autowire candidate.
     * <p>If this value is {@code true} for exactly one bean among multiple
     * matching candidates, it will serve as a tie-breaker.
     */
    void setPrimary(boolean primary);

    /**
     * @author hubt 判断是否是主要bean.
     * Return whether this bean is a primary autowire candidate.
     */
    boolean isPrimary();

    /**
     *
     * Specify the factory bean to use, if any.
     * This the name of the bean to call the specified factory method on.
     * @see #setFactoryMethodName
     */
    void setFactoryBeanName(@Nullable String factoryBeanName);

    /**
     * Return the factory bean name, if any.
     */
    @Nullable
    String getFactoryBeanName();

    /**
     * @author hubt 设置一个方法，该方法返回的bean 替换原来的Bean。
     * Specify a factory method, if any. This method will be invoked with
     * constructor arguments, or with no arguments if none are specified.
     * The method will be invoked on the specified factory bean, if any,
     * or otherwise as a static method on the local bean class.
     * @see #setFactoryBeanName
     * @see #setBeanClassName
     */
    void setFactoryMethodName(@Nullable String factoryMethodName);

    /**
     * Return a factory method, if any.
     */
    @Nullable
    String getFactoryMethodName();

    /**
     * @author hubt 存放构造函数入参的值
     * Return the constructor argument values for this bean.
     * <p>The returned instance can be modified during bean factory post-processing.
     * @return the ConstructorArgumentValues object (never {@code null})
     */
    ConstructorArgumentValues getConstructorArgumentValues();

    /**
     * @author hubt 判断构造方法是否传值。
     * Return if there are constructor argument values defined for this bean.
     * @since 5.0.2
     */
    default boolean hasConstructorArgumentValues() {
        return !getConstructorArgumentValues().isEmpty();
    }

    /**
     * @author hubt 获取Beanz中设置的属性值； setPropertyValues方法在其子类AbstractBeanDefinition中。
     * Return the property values to be applied to a new instance of the bean.
     * <p>The returned instance can be modified during bean factory post-processing.
     * @return the MutablePropertyValues object (never {@code null})
     */
    MutablePropertyValues getPropertyValues();

    /**
     * @author hubt 判断是否存在设置的属性值。
     * Return if there are property values values defined for this bean.
     * @since 5.0.2
     */
    default boolean hasPropertyValues() {
        return !getPropertyValues().isEmpty();
    }


    // Read-only attributes

    /**
     * @author hubt 判断是否单例
     * Return whether this a <b>Singleton</b>, with a single, shared instance
     * returned on all calls.
     * @see #SCOPE_SINGLETON
     */
    boolean isSingleton();

    /**
     * @author hubt 判断是否原型
     * Return whether this a <b>Prototype</b>, with an independent instance
     * returned for each call.
     * @since 3.0
     * @see #SCOPE_PROTOTYPE
     */
    boolean isPrototype();

    /**
     * @author hubt 判断是否是抽象类，一般用于BeanDefinition实现类作为模板使用还是Class的Beandefinition。
     * 为true 就表示是仅仅只是一个模板。
     * Return whether this bean is "abstract", that is, not meant to be instantiated.
     */
    boolean isAbstract();

    /**
     * Get the role hint for this {@code BeanDefinition}. The role hint
     * provides the frameworks as well as tools with an indication of
     * the role and importance of a particular {@code BeanDefinition}.
     * @see #ROLE_APPLICATION
     * @see #ROLE_SUPPORT
     * @see #ROLE_INFRASTRUCTURE
     */
    int getRole();

    /**
     * @author hubt 获取描述（给Bean增加一些备注信息，无实际用途），setDescription在其子类AbstractBeanDefinition中。
     * Return a human-readable description of this bean definition.
     */
    @Nullable
    String getDescription();

    /**
     * @author hubt 获取描述（对原文件java文件的描述），setResourceDescription在其子类AbstractBeanDefinition中。
     * Return a description of the resource that this bean definition
     * came from (for the purpose of showing context in case of errors).
     */
    @Nullable
    String getResourceDescription();

    /**
     * Return the originating BeanDefinition, or {@code null} if none.
     * Allows for retrieving the decorated bean definition, if any.
     * <p>Note that this method returns the immediate originator. Iterate through the
     * originator chain to find the original BeanDefinition as defined by the user.
     */
    @Nullable
    BeanDefinition getOriginatingBeanDefinition();

}

下面是两个辅助接口的方法说明：AttributeAccessor和BeanMetadataElement 是对BeanDefinition的扩展

/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core;

import org.springframework.lang.Nullable;

/**
 * @author hubt 为BeanDefinition 额外提供一些类的信息，比如一些注解等。
 * Interface defining a generic contract for attaching and accessing metadata
 * to/from arbitrary objects.
 *
 * @author Rob Harrop
 * @since 2.0
 */
public interface AttributeAccessor {

    /**
     * Set the attribute defined by {@code name} to the supplied    {@code value}.
     * If {@code value} is {@code null}, the attribute is {@link #removeAttribute removed}.
     * <p>In general, users should take care to prevent overlaps with other
     * metadata attributes by using fully-qualified names, perhaps using
     * class or package names as prefix.
     * @param name the unique attribute key
     * @param value the attribute value to be attached
     */
    void setAttribute(String name, @Nullable Object value);

    /**
     * Get the value of the attribute identified by {@code name}.
     * Return {@code null} if the attribute doesn't exist.
     * @param name the unique attribute key
     * @return the current value of the attribute, if any
     */
    @Nullable
    Object getAttribute(String name);

    /**
     * Remove the attribute identified by {@code name} and return its value.
     * Return {@code null} if no attribute under {@code name} is found.
     * @param name the unique attribute key
     * @return the last value of the attribute, if any
     */
    @Nullable
    Object removeAttribute(String name);

    /**
     * Return {@code true} if the attribute identified by {@code name} exists.
     * Otherwise return {@code false}.
     * @param name the unique attribute key
     */
    boolean hasAttribute(String name);

    /**
     * Return the names of all attributes.
     */
    String[] attributeNames();

}

/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.beans;

import org.springframework.lang.Nullable;

/**
 * @author hubt java文件的原始路径。
 * Interface to be implemented by bean metadata elements
 * that carry a configuration source object.
 *
 * @author Juergen Hoeller
 * @since 2.0
 */
public interface BeanMetadataElement {

    /**
     * Return the configuration source {@code Object} for this metadata element
     * (may be {@code null}).
     */
    @Nullable
    Object getSource();

} 

AbstractBeanDefinition作为抽象类扩展BeanDefinition接口。主要讲讲三个实现类：GenericBeanDefinition、ChildBeanDefinition和RootBeanDefinition

Spring之前是没有GenericBeanDefinition，只有ChildBeanDefinition和RootBeanDefinition实现类。

RootBeanDefinition 可以作为模板，保存一些信息提供给继承版本的ChildBeanDefinition类使用。

案例：

package accelerate1.bean;

public class Person {
    protected String name;
    protected String age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age='" + age + '\'' +
                '}';
    }
}

package accelerate1.bean;

public class Student extends Person {

    private String schoolName;

    public String getSchoolName() {
        return schoolName;
    }

    public void setSchoolName(String schoolName) {
        this.schoolName = schoolName;
    }

    @Override
    public String toString() {
        return "Student{" +
                "schoolName='" + schoolName + '\'' +
                "name='" + name + '\'' +
                "age='" + age + '\'' +
                '}';
    }
}

package accelerate1.test;

import accelerate1.app.AppConfig;
import accelerate1.bean.Student;
import org.springframework.beans.factory.support.ChildBeanDefinition;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Demo2 {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext annotationConfigApplicationContext =
                new AnnotationConfigApplicationContext();
        annotationConfigApplicationContext.register(AppConfig.class);

        /**
         * 设置模板
         */
        RootBeanDefinition personBeanDefinition = new RootBeanDefinition();
        personBeanDefinition.setAbstract(true); //表示该BeanDefinition作为模板不需要实例化对象。
        personBeanDefinition.getPropertyValues().addPropertyValue("name","李磊");
        personBeanDefinition.getPropertyValues().addPropertyValue("age","18");

        /**
         * 继承模板，就不需要设置之前的内容，现在只需要设置不同的地方即可。
         */
        ChildBeanDefinition childBeanDefinition = new ChildBeanDefinition("personBeanDefinition");
        childBeanDefinition.setBeanClass(Student.class);
        childBeanDefinition.getPropertyValues().addPropertyValue("schoolName","XXX学校");

        annotationConfigApplicationContext.registerBeanDefinition("personBeanDefinition",personBeanDefinition);
        annotationConfigApplicationContext.registerBeanDefinition("childBeanDefinition",childBeanDefinition);

        annotationConfigApplicationContext.refresh();

        System.out.println(annotationConfigApplicationContext.getBean(Student.class));

    }
}

运行结果：（与理论一致）

GenericBeanDefinition出现之后就替代了ChildBeanDefinition全部功能和大部分RootBeanDefinition的功能。

/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core.type;

import java.util.Set;

/**
 * @author 用于处理类上面注解的接口定义
 * Interface that defines abstract access to the annotations of a specific
 * class, in a form that does not require that class to be loaded yet.
 *
 * @author Juergen Hoeller
 * @author Mark Fisher
 * @author Phillip Webb
 * @author Sam Brannen
 * @since 2.5
 * @see StandardAnnotationMetadata
 * @see org.springframework.core.type.classreading.MetadataReader#getAnnotationMetadata()
 * @see AnnotatedTypeMetadata
 */
public interface AnnotationMetadata extends ClassMetadata, AnnotatedTypeMetadata {

    /**
     * @author hubt 获取所有注释类型的完全限定类名
     * Get the fully qualified class names of all annotation types that
     * are <em>present</em> on the underlying class.
     * @return the annotation type names
     */
    Set<String> getAnnotationTypes();

    /**
     * @author hubt 获取annotationName注释类型的完全限定类名
     * Get the fully qualified class names of all meta-annotation types that
     * are <em>present</em> on the given annotation type on the underlying class.
     * @param annotationName the fully qualified class name of the meta-annotation
     * type to look for
     * @return the meta-annotation type names, or an empty set if none found
     */
    Set<String> getMetaAnnotationTypes(String annotationName);

    /**
     * @author hubt 是否存在annotationName注解
     * Determine whether an annotation of the given type is <em>present</em> on
     * the underlying class.
     * @param annotationName the fully qualified class name of the annotation
     * type to look for
     * @return {@code true} if a matching annotation is present
     */
    boolean hasAnnotation(String annotationName);

    /**
     * @author hubt 是否存在annotationName元注解
     * Determine whether the underlying class has an annotation that is itself
     * annotated with the meta-annotation of the given type.
     * @param metaAnnotationName the fully qualified class name of the
     * meta-annotation type to look for
     * @return {@code true} if a matching meta-annotation is present
     */
    boolean hasMetaAnnotation(String metaAnnotationName);

    /**
     * @author hubt 确定基础类是否存在注解或者元注解
     * Determine whether the underlying class has any methods that are
     * annotated (or meta-annotated) with the given annotation type.
     * @param annotationName the fully qualified class name of the annotation
     * type to look for
     */
    boolean hasAnnotatedMethods(String annotationName);

    /**
     * @author hubt 返回类中所有被注解注释的方法
     * Retrieve the method metadata for all methods that are annotated
     * (or meta-annotated) with the given annotation type.
     * <p>For any returned method, {@link MethodMetadata#isAnnotated} will
     * return {@code true} for the given annotation type.
     * @param annotationName the fully qualified class name of the annotation
     * type to look for
     * @return a set of {@link MethodMetadata} for methods that have a matching
     * annotation. The return value will be an empty set if no methods match
     * the annotation type.
     */
    Set<MethodMetadata> getAnnotatedMethods(String annotationName);

}

/*
 * Copyright 2002-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core.type;

/**
 * Interface that defines abstract access to the annotations of a specific
 * class, in a form that does not require that class to be loaded yet.
 *
 * @author Juergen Hoeller
 * @author Mark Pollack
 * @author Chris Beams
 * @author Phillip Webb
 * @since 3.0
 * @see StandardMethodMetadata
 * @see AnnotationMetadata#getAnnotatedMethods
 * @see AnnotatedTypeMetadata
 */
public interface MethodMetadata extends AnnotatedTypeMetadata {

    /**
     * @author hubt 返回方法名字
     * Return the name of the method.
     */
    String getMethodName();

    /**
     * @author hubt 返回该方法所属的类的全限定名(带路径例如：com/baidu/test.java)
     * Return the fully-qualified name of the class that declares this method.
     */
    String getDeclaringClassName();

    /**
     * @author hubt 返回该方法返回类型的全限定名(带路径例如：com/baidu/test.java)
     * Return the fully-qualified name of this method's declared return type.
     * @since 4.2
     */
    String getReturnTypeName();

    /**
     * @author hubt 判断是否抽象类
     * Return whether the underlying method is effectively abstract:
     * i.e. marked as abstract on a class or declared as a regular,
     * non-default method in an interface.
     * @since 4.2
     */
    boolean isAbstract();

    /**
     * @author hubt 判断是否静态
     * Return whether the underlying method is declared as 'static'.
     */
    boolean isStatic();

    /**
     * @author hubt 判断是否Final
     * Return whether the underlying method is marked as 'final'.
     */
    boolean isFinal();

    /**
     * @author hubt 是否重写方法
     * Return whether the underlying method is overridable,
     * i.e. not marked as static, final or private.
     */
    boolean isOverridable();

}

/*
 * Copyright 2002-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core.type;

import java.util.Map;

import org.springframework.lang.Nullable;
import org.springframework.util.MultiValueMap;

/**
 * Defines access to the annotations of a specific type ({@link AnnotationMetadata class}
 * or {@link MethodMetadata method}), in a form that does not necessarily require the
 * class-loading.
 *
 * @author Juergen Hoeller
 * @author Mark Fisher
 * @author Mark Pollack
 * @author Chris Beams
 * @author Phillip Webb
 * @author Sam Brannen
 * @since 4.0
 * @see AnnotationMetadata
 * @see MethodMetadata
 */
public interface AnnotatedTypeMetadata {

    /**
     * @author hubt 是否存在 annotationName 注解
     * Determine whether the underlying element has an annotation or meta-annotation
     * of the given type defined.
     * <p>If this method returns {@code true}, then
     * {@link #getAnnotationAttributes} will return a non-null Map.
     * @param annotationName the fully qualified class name of the annotation
     * type to look for
     * @return whether a matching annotation is defined
     */
    boolean isAnnotated(String annotationName);

    /**
     * @author hubt 取得指定 annotationName 类型注解的所有的属性 - 值（k-v）
     * Retrieve the attributes of the annotation of the given type, if any (i.e. if
     * defined on the underlying element, as direct annotation or meta-annotation),
     * also taking attribute overrides on composed annotations into account.
     * @param annotationName the fully qualified class name of the annotation
     * type to look for
     * @return a Map of attributes, with the attribute name as key (e.g. "value")
     * and the defined attribute value as Map value. This return value will be
     * {@code null} if no matching annotation is defined.
     */
    @Nullable
    Map<String, Object> getAnnotationAttributes(String annotationName);

    /**
     * @author hubt 取得指定 annotationName 类型注解的所有的属性 - 值（k-v）
     * classValuesAsString：若是true表示 Class用它的字符串的全类名来表示。这样可以避免Class被提前加载
     * Retrieve the attributes of the annotation of the given type, if any (i.e. if
     * defined on the underlying element, as direct annotation or meta-annotation),
     * also taking attribute overrides on composed annotations into account.
     * @param annotationName the fully qualified class name of the annotation
     * type to look for
     * @param classValuesAsString whether to convert class references to String
     * class names for exposure as values in the returned Map, instead of Class
     * references which might potentially have to be loaded first
     * @return a Map of attributes, with the attribute name as key (e.g. "value")
     * and the defined attribute value as Map value. This return value will be
     * {@code null} if no matching annotation is defined.
     */
    @Nullable
    Map<String, Object> getAnnotationAttributes(String annotationName, boolean classValuesAsString);

    /**
     * @author hubt 取得指定 annotationName 类型注解的所有的属性 - 值（k-v） 存在进MultiValueMap
     * Retrieve all attributes of all annotations of the given type, if any (i.e. if
     * defined on the underlying element, as direct annotation or meta-annotation).
     * Note that this variant does <i>not</i> take attribute overrides into account.
     * @param annotationName the fully qualified class name of the annotation
     * type to look for
     * @return a MultiMap of attributes, with the attribute name as key (e.g. "value")
     * and a list of the defined attribute values as Map value. This return value will
     * be {@code null} if no matching annotation is defined.
     * @see #getAllAnnotationAttributes(String, boolean)
     */
    @Nullable
    MultiValueMap<String, Object> getAllAnnotationAttributes(String annotationName);

    /**
     * @author hubt 取得指定 annotationName 类型注解的所有的属性 - 值（k-v） 存在进MultiValueMap
     * classValuesAsString：若是true表示 Class用它的字符串的全类名来表示。这样可以避免Class被提前加载
     * Retrieve all attributes of all annotations of the given type, if any (i.e. if
     * defined on the underlying element, as direct annotation or meta-annotation).
     * Note that this variant does <i>not</i> take attribute overrides into account.
     * @param annotationName the fully qualified class name of the annotation
     * type to look for
     * @param classValuesAsString  whether to convert class references to String
     * @return a MultiMap of attributes, with the attribute name as key (e.g. "value")
     * and a list of the defined attribute values as Map value. This return value will
     * be {@code null} if no matching annotation is defined.
     * @see #getAllAnnotationAttributes(String)
     */
    @Nullable
    MultiValueMap<String, Object> getAllAnnotationAttributes(String annotationName, boolean classValuesAsString);

}

说明：AnnotatedGenericBeanDefinition和ScannedGenericBeanDefinition。

AnnotatedGenericBeanDefinition作用是：用于的通过注解获取BeanDefinition的对象(比如@Bean)。

ScannedGenericBeanDefinition作用是：扫描文件将获取到的对象生成BeanDefinition。