BeanDefinition
BeanDefinition 主要是用来描述Bean，主要包括：Bean的属性、是否单例、延迟加载、Bean的名称、构造方法等。
简而言之: 在容器中的 一个Bean 对应一个 BeanDefinition 的封装描述; Spring 使用 BeanDefinitionRegistry 管理BeanDefinition
org.springframework.beans.factory.config.BeanDefinition
/*
* Copyright 2002-2020 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
*
* https://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.core.ResolvableType;
import org.springframework.lang.Nullable;
/**
*
* BeanDefinition 描述一个bean实例，该实例具有属性值、构造函数参数值以及由具体实现提供的进一步信息。
* 简而言之: 在容器中的Bean 对应一个 BeanDefinition的封装描述
*
* 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} 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 {
/**
* Scope identifier for the standard singleton scope: {@value}.
* <p>Note that extended bean factories might support further scopes.
* Bean 的作用域标识: 单例标记, 可通过setScope方法设置
* MVC的Session Request 等不在这里..
* @see #setScope
* @see ConfigurableBeanFactory#SCOPE_SINGLETON
*/
String SCOPE_SINGLETON = ConfigurableBeanFactory.SCOPE_SINGLETON;
/**
* Scope identifier for the standard prototype scope: {@value}.
* <p>Note that extended bean factories might support further scopes.
* Bean 的作用域标识: 原型标记, 可通过setScope方法设置
* MVC的Session Request 等不在这里..
* @see #setScope
* @see ConfigurableBeanFactory#SCOPE_PROTOTYPE
*/
String SCOPE_PROTOTYPE = ConfigurableBeanFactory.SCOPE_PROTOTYPE;
/**
* 以下三个属性, 标识 Bean 的角色, 可通过 setRole 方法设置
* ROLE_APPLICATION = 0; //应用程序定义, 或用户定义的bean
* ROLE_SUPPORT = 1; //比较复杂的配置, 值得注意的? 目前没搞明白..
* ROLE_INFRASTRUCTURE = 2;//Spring内部定义的Bean
*/
/**
* 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.
*/
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}.
*/
int ROLE_INFRASTRUCTURE = 2;
// Modifiable attributes
/**
* Set the name of the parent definition of this bean definition, if any.
* 设置 父Bean Definition 的名称, 如果有的话
* 对应XML定义: `<bean parent="">`
*/
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.
*
* bean的类名, 对应XML定义: `<bean class="">`
* @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
* 设置bean作用域
*/
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();
/**
* 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.
* 设置是否懒加载
*/
void setLazyInit(boolean lazyInit);
/**
* Return whether this bean should be lazily initialized, i.e. not
* eagerly instantiated on startup. Only applicable to a singleton bean.
*/
boolean isLazyInit();
/**
* Set the names of the beans that this bean depends on being initialized.
* The bean factory will guarantee that these beans get initialized first.
*
* dependsOn 一般用于两个bean之间没有显示依赖, 但后一个Bean需要用到前一个Bean执行初始方法后的结果;
* 例如在 `< bean id="a" dependsOn="b"/> ` 时, 在初始化a时首先先初始化b, 在销毁b之前会先销毁a;
*/
void setDependsOn(@Nullable String... dependsOn);
/**
* Return the bean names that this bean depends on.
*/
@Nullable
String[] getDependsOn();
/**
* 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.
*
* 是否 能被自动装配 <bean autowire-candidate="true/false">
*
* 设置该对象是否可以被其他对象自动装配(可以作为自动注入的候选); spring通过配置bean的autowire属性设置自动装配方式
*/
void setAutowireCandidate(boolean autowireCandidate);
/**
* Return whether this bean is a candidate for getting autowired into some other bean.
*/
boolean isAutowireCandidate();
/**
* 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.
* `@Primary` 注解就是通过它去设置的; 如果存在同类型的 bean 是否这个bean优先
*/
void setPrimary(boolean primary);
/**
* 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.
* 定义创建该 Bean对象的工厂类, 对应XML定义: `<bean factory-bean="">`
* @see #setFactoryMethodName
*/
void setFactoryBeanName(@Nullable String factoryBeanName);
/**
* Return the factory bean name, if any.
*/
@Nullable
String getFactoryBeanName();
/**
* 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.
*
* 定义创建该Bean对象的工厂方法, 对应XML定义 ` <bean factory-method="">`
* @see #setFactoryBeanName
* @see #setBeanClassName
*/
void setFactoryMethodName(@Nullable String factoryMethodName);
/**
* Return a factory method, if any.
*/
@Nullable
String getFactoryMethodName();
/**
* Return the constructor argument values for this bean.
* <p>The returned instance can be modified during bean factory post-processing.
* 返回此bean的构造函数参数值;
* @return the ConstructorArgumentValues object (never {@code null})
*/
ConstructorArgumentValues getConstructorArgumentValues();
/**
* Return if there are constructor argument values defined for this bean.
* @since 5.0.2
*/
default boolean hasConstructorArgumentValues() {
return !getConstructorArgumentValues().isEmpty();
}
/**
* 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.
*
* 普通属性的集合, 如:
*
* <bean id="student" class="com.rc.sp.Student">
* <property name="id" value="1"/>
* <property name="dao" ref="dao" />
* <property name="map">
* <map>
* <entry key="math" value="90"/>
* <entry key="english" value="85"/>
* </map>
* </property>
* </bean>
*
* @return the MutablePropertyValues object (never {@code null})
*/
MutablePropertyValues getPropertyValues();
/**
* Return if there are property values defined for this bean.
* @since 5.0.2
*/
default boolean hasPropertyValues() {
return !getPropertyValues().isEmpty();
}
/**
* Set the name of the initializer method.
* 初始化方法名 对应XML 定义: `<bean id="address" class="org.yang.learn.spring.dto.Address" init-method="" destroy-method="">`
* @since 5.1
*/
void setInitMethodName(@Nullable String initMethodName);
/**
* Return the name of the initializer method.
* @since 5.1
*/
@Nullable
String getInitMethodName();
/**
* Set the name of the destroy method.
* 销毁方法名 对应XML 定义: `<bean id="address" class="org.yang.learn.spring.dto.Address" init-method="" destroy-method="">`
* @since 5.1
*/
void setDestroyMethodName(@Nullable String destroyMethodName);
/**
* Return the name of the destroy method.
* @since 5.1
*/
@Nullable
String getDestroyMethodName();
/**
* Set the role hint for this {@code BeanDefinition}. The role hint
* provides the frameworks as well as tools an indication of
* the role and importance of a particular {@code BeanDefinition}.
* @since 5.1
* @see #ROLE_APPLICATION
* @see #ROLE_SUPPORT
* @see #ROLE_INFRASTRUCTURE
*/
void setRole(int role);
/**
* Get the role hint for this {@code BeanDefinition}. The role hint
* provides the frameworks as well as tools an indication of
* the role and importance of a particular {@code BeanDefinition}.
* @see #ROLE_APPLICATION
* @see #ROLE_SUPPORT
* @see #ROLE_INFRASTRUCTURE
*/
int getRole();
/**
* Set a human-readable description of this bean definition.
* @since 5.1
*/
void setDescription(@Nullable String description);
/**
* Return a human-readable description of this bean definition.
*/
@Nullable
String getDescription();
// Read-only attributes
/**
* Return a resolvable type for this bean definition,
* based on the bean class or other specific metadata.
* <p>This is typically fully resolved on a runtime-merged bean definition
* but not necessarily on a configuration-time definition instance.
*
* 这个 ResolvableType 作用, 大概是封装java的类型描述
* ResolvableTypes may be obtained from fields, method parameters, method returns or classes.
* For example:
* private HashMap<Integer, List<String>> myMap;
* public void example() {
* ResolvableType t = ResolvableType.forField(getClass().getDeclaredField("myMap"));
* t.getSuperType(); // AbstractMap<Integer, List<String>>
* t.asMap(); // Map<Integer, List<String>>
* t.getGeneric(0).resolve(); // Integer
* t.getGeneric(1).resolve(); // List
* t.getGeneric(1); // List<String>
* t.resolveGeneric(1, 0); // String
* }
* @return the resolvable type (potentially {@link ResolvableType#NONE})
* @since 5.2
* @see ConfigurableBeanFactory#getMergedBeanDefinition
*/
ResolvableType getResolvableType();
/**
* Return whether this a <b>Singleton</b>, with a single, shared instance
* returned on all calls.
* @see #SCOPE_SINGLETON
*/
boolean isSingleton();
/**
* Return whether this a <b>Prototype</b>, with an independent instance
* returned for each call.
* @since 3.0
* @see #SCOPE_PROTOTYPE
*/
boolean isPrototype();
/**
* Return whether this bean is "abstract", that is, not meant to be instantiated.
*/
boolean isAbstract();
/**
* Return a description of the resource that this bean definition
* came from (for the purpose of showing context in case of errors).
*
* 返回该bean定义来自的资源的描述（用于在出现错误时显示上下文）
*/
@Nullable
String getResourceDescription();
/**
* Return the originating BeanDefinition, or {@code null} if none.
* <p>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.
* 返回原始 BeanDefinition 定义; 可null
*/
@Nullable
BeanDefinition getOriginatingBeanDefinition();
}
关于 role 属性
getRole 属性 ; Spring将bean分为三种角色
- ROLE_APPLICATION = 0;//应用程序定义, 或用户定义的bean
- ROLE_SUPPORT = 1; //比较复杂的配置, 值得注意的? 目前没搞明白
- ROLE_INFRASTRUCTURE = 2;//Spring内部定义的Bean, 与用户完全无关
BeanDefinition 的常见实现
-
GenericBeanDefinition：
BeanDefinition接口的通用实现，可以用于大多数 bean 定义情况。它提供了许多属性和方法，可以用来配置 bean 的各种属性和行为。 -
RootBeanDefinition：
GenericBeanDefinition的子类，提供了更多针对父子 bean 配置的支持。它可以用于定义根 bean，同时允许其他 bean 对其进行扩展。 -
ChildBeanDefinition： 同样是
GenericBeanDefinition的子类，用于定义子 bean。它可以继承另一个 bean 的配置，并可以进行进一步的定制和覆盖。 -
AnnotatedBeanDefinition 这是用于 基于注解的配置的
BeanDefinition实现。它可以用来描述通过注解（如@Component、@Service、@Repository等）定义的 bean。