Spring5源碼分析-BeanDefinition詳解

public interface BeanDefinition extends AttributeAccessor, BeanMetadataElement {

	/**
	 * Scope identifier for the standard singleton scope: "singleton".
	 * <p>Note that extended bean factories might support further scopes.
	 * @see #setScope
	 *
	 * 單例
	 */
	String SCOPE_SINGLETON = ConfigurableBeanFactory.SCOPE_SINGLETON;

	/**
	 * Scope identifier for the standard prototype scope: "prototype".
	 * <p>Note that extended bean factories might support further scopes.
	 * @see #setScope
	 *
	 * 多例
	 */
	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.
	 */
	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.
	 *
	 * 期初理解是填的被集成類的名稱，然而經過註解或者XML導入的方式都試過了，都沒有設置這個值，
	 * 最後發現只有當經過XML（groovy沒測試）導入的時候而且設置了<bean parent="parentName"></>纔會真正設置parentName
	 * 這個值應該沒什麼用吧，找了一些也就是在MergeBeanDefinition的時候調用了getParentName，其餘時候好像並無
	 */
	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
	 *
	 * 當前Bean的類名稱，全路徑名。該名稱能夠在自定義的BeanFactoryPostProcessor中進行修改
	 * 若是你願意設置能夠強轉beanFactory爲BeanDefinitionRegistry以後remove掉這個BeanName的BD
	 */
	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
	 *
	 * 設置單例仍是原型（本身更願意叫多例，實在不知道怎麼去理解「原型」 --！）
	 */
	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.
	 * 設置Bean是否「懶加載」，若是是false，默認也是false，則在啓動Spring容器的時候beanFactory就會初始化它
	 */
	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.
	 *
	 * 設置當前Bean要依賴於@DependsOn的這些Bean都實例化以後才能進行實例化
	 */
	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.
	 *
	 * 只有須要注入的Bean使用的by type注入，且autowireCandidate設置爲true纔會注入成功
	 * 測試一下自定義一個BeanFactoryPostProcessor把Dept的autowireCandidate設置爲false，且使用by type注入是否成功
	 * --通過測試Dept的BeanDefinition的autowireCandidate=false確實會致使注入失敗，有興趣的能夠試試
	 *
	 * @Component
	 * public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
	 *        @Override
	 *    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
	 * 		BeanDefinition dept = beanFactory.getBeanDefinition("dept");
	 * 		dept.setAutowireCandidate(false);
	 *    }
	 * }
	 *
	 */
	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.
	 *
	 * 設置當前的Bean是優先被注入的，好比同一個類型使用兩個不一樣的beanName在Spring中存在兩個對象，
	 * 那麼被標記爲primary=true的在根據by type注入的時候會優先被注入
	 */
	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.
	 * @see #setFactoryMethodName
	 *
	 * 設置FactoryBean的名稱  FactoryBean就是能夠產生Spring Bean的Bean，經過beanName和&beanName分別獲得Bean和FactoryBean實例
	 */
	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.
	 * @see #setFactoryBeanName
	 * @see #setBeanClassName
	 *
	 * 設置FactoryBeanMethod
	 */
	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.
	 * @return the ConstructorArgumentValues object (never {@code null})
	 *
	 * 返回構造函數的參數，能夠使用BeanFactoryPostProcessor修改參數
	 */
	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.
	 * @return the MutablePropertyValues object (never {@code null})
	 * 返回Bean的屬性對應的值，能夠使用BeanFactoryPostProcessor修改這些值
	 */
	MutablePropertyValues getPropertyValues();

	/**
	 * Return if there are property values values defined for this bean.
	 * @since 5.0.2
	 */
	default boolean hasPropertyValues() {
		return !getPropertyValues().isEmpty();
	}

	/**
	 * Set the name of the initializer method.
	 * @since 5.1
	 *
	 * 當前Bean中添加一個初始化方法，再使用BeanFactoryPostProcessor設置它的BeanDefinition initMethodName
	 * Spring initMethod在BeanPostProcessor的postProcessBeforeInitialization以後，postProcessAfterInitialization以前被調用
	 */
	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.
	 * @since 5.1
	 *
	 * 設置Bean被銷燬時要執行的方法，能夠作一些清理工做
	 */
	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 with 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 with 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.
	 * @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
	 * 返回Bean是不是單例
	 */
	boolean isSingleton();

	/**
	 * Return whether this a <b>Prototype</b>, with an independent instance
	 * returned for each call.
	 * @since 3.0
	 * @see #SCOPE_PROTOTYPE
	 *
	 * 返回Bean是不是原型
	 */
	boolean isPrototype();

	/**
	 * Return whether this bean is "abstract", that is, not meant to be instantiated.
	 *
	 * 返回對象是不是抽象的，覺得着不會被實例化。。。這有什麼用喃？？？？
	 */
	boolean isAbstract();

	/**
	 * 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();

}

 BeanDefinition是Spring描述一個Bean的包裝類，Spring後面的操做都依賴於解析對應Bean的屬性作出相應的動做執行，完成咱們所感覺到的功能

好比Bean是否單例，是否延遲加載，是不是Primary Bean，是否有DependsOn的條件，是否容許被用於自動注入，是否有INIT方法等等，Spring解析到這些內容都會作出對應的響應。