spring 后置处理器

BeanFactoryPostProcessor 干预初始化过程(各种属性的填充和修改)
BeanPostProcessor 干预实例化(怎么new出来)和初始化(各种属性的填充和修改)过程

Bean后置处理器，用来干预bean的实例化过程(包括初始化)。是spring扩展点之一
InstantiationAwareBeanPostProcess

1、postProcessBeforInstantiation()================》》》第一次后置处理器

如果返回值不为空，只有postProcessAfterInitialization()会执行，

否则返回空。正常执行

2、postProcessAfterInstantiation()================》》》第五次

改方法是实例化之后调用，这个时候对象已经被实例化，但是属性还没有设置 都是null

如果返回true 会正常流程设置属性

3、postProcessPropertyValues===================》》》第六次

对属性修改

InstantiationAwareBeanPostProcessor 类

package org.springframework.beans.factory.config;
/**
 * Subinterface of {@link BeanPostProcessor} that adds a before-instantiation callback,
 * and a callback after instantiation but before explicit properties are set or
 * autowiring occurs.
 *
 * <p>Typically used to suppress default instantiation for specific target beans,
 * for example to create proxies with special TargetSources (pooling targets,
 * lazily initializing targets, etc), or to implement additional injection strategies
 * such as field injection.
 *
 * <p><b>NOTE:</b> This interface is a special purpose interface, mainly for
 * internal use within the framework. It is recommended to implement the plain
 * {@link BeanPostProcessor} interface as far as possible, or to derive from
 * {@link InstantiationAwareBeanPostProcessorAdapter} in order to be shielded
 * from extensions to this interface.
 *
 * @author Juergen Hoeller
 * @author Rod Johnson
 * @since 1.2
 * @see org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator#setCustomTargetSourceCreators
 * @see org.springframework.aop.framework.autoproxy.target.LazyInitTargetSourceCreator
 */
public interface InstantiationAwareBeanPostProcessor extends BeanPostProcessor {

    /**
     * Apply this BeanPostProcessor <i>before the target bean gets instantiated</i>.
     * The returned bean object may be a proxy to use instead of the target bean,
     * effectively suppressing default instantiation of the target bean.
     * <p>If a non-null object is returned by this method, the bean creation process
     * will be short-circuited. The only further processing applied is the
     * {@link #postProcessAfterInitialization} callback from the configured
     * {@link BeanPostProcessor BeanPostProcessors}.
     * <p>This callback will be applied to bean definitions with their bean class,
     * as well as to factory-method definitions in which case the returned bean type
     * will be passed in here.
     * <p>Post-processors may implement the extended
     * {@link SmartInstantiationAwareBeanPostProcessor} interface in order
     * to predict the type of the bean object that they are going to return here.
     * <p>The default implementation returns {@code null}.
     * @param beanClass the class of the bean to be instantiated
     * @param beanName the name of the bean
     * @return the bean object to expose instead of a default instance of the target bean,
     * or {@code null} to proceed with default instantiation
     * @throws org.springframework.beans.BeansException in case of errors
     * @see #postProcessAfterInstantiation
     * @see org.springframework.beans.factory.support.AbstractBeanDefinition#getBeanClass()
     * @see org.springframework.beans.factory.support.AbstractBeanDefinition#getFactoryMethodName()
     */
    @Nullable
    default Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
        return null;
    }

    /**
     * Perform operations after the bean has been instantiated, via a constructor or factory method,
     * but before Spring property population (from explicit properties or autowiring) occurs.
     * <p>This is the ideal callback for performing custom field injection on the given bean
     * instance, right before Spring's autowiring kicks in.
     * <p>The default implementation returns {@code true}.
     * @param bean the bean instance created, with properties not having been set yet
     * @param beanName the name of the bean
     * @return {@code true} if properties should be set on the bean; {@code false}
     * if property population should be skipped. Normal implementations should return {@code true}.
     * Returning {@code false} will also prevent any subsequent InstantiationAwareBeanPostProcessor
     * instances being invoked on this bean instance.
     * @throws org.springframework.beans.BeansException in case of errors
     * @see #postProcessBeforeInstantiation
     */
    default boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {
        return true;
    }

    /**
     * Post-process the given property values before the factory applies them
     * to the given bean. Allows for checking whether all dependencies have been
     * satisfied, for example based on a "Required" annotation on bean property setters.
     * <p>Also allows for replacing the property values to apply, typically through
     * creating a new MutablePropertyValues instance based on the original PropertyValues,
     * adding or removing specific values.
     * <p>The default implementation returns the given {@code pvs} as-is.
     * @param pvs the property values that the factory is about to apply (never {@code null})
     * @param pds the relevant property descriptors for the target bean (with ignored
     * dependency types - which the factory handles specifically - already filtered out)
     * @param bean the bean instance created, but whose properties have not yet been set
     * @param beanName the name of the bean
     * @return the actual property values to apply to the given bean (can be the passed-in
     * PropertyValues instance), or {@code null} to skip property population
     * @throws org.springframework.beans.BeansException in case of errors
     * @see org.springframework.beans.MutablePropertyValues
     */
    @Nullable
    default PropertyValues postProcessPropertyValues(
            PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeansException {

        return pvs;
    }

}

BeanPostProcessor

4、postProcessBeforInitialization&& postProcessAfterInitlization=====》》 七八次

package org.springframework.beans.factory.config;
public interface BeanPostProcessor {

    /**
     * Apply this BeanPostProcessor to the given new bean instance <i>before</i> any bean
     * initialization callbacks (like InitializingBean's {@code afterPropertiesSet}
     * or a custom init-method). The bean will already be populated with property values.
     * The returned bean instance may be a wrapper around the original.
     * <p>The default implementation returns the given {@code bean} as-is.
     * @param bean the new bean instance
     * @param beanName the name of the bean
     * @return the bean instance to use, either the original or a wrapped one;
     * if {@code null}, no subsequent BeanPostProcessors will be invoked
     * @throws org.springframework.beans.BeansException in case of errors
     * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet
     */
    @Nullable
    default Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        return bean;
    }

    /**
     * Apply this BeanPostProcessor to the given new bean instance <i>after</i> any bean
     * initialization callbacks (like InitializingBean's {@code afterPropertiesSet}
     * or a custom init-method). The bean will already be populated with property values.
     * The returned bean instance may be a wrapper around the original.
     * <p>In case of a FactoryBean, this callback will be invoked for both the FactoryBean
     * instance and the objects created by the FactoryBean (as of Spring 2.0). The
     * post-processor can decide whether to apply to either the FactoryBean or created
     * objects or both through corresponding {@code bean instanceof FactoryBean} checks.
     * <p>This callback will also be invoked after a short-circuiting triggered by a
     * {@link InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation} method,
     * in contrast to all other BeanPostProcessor callbacks.
     * <p>The default implementation returns the given {@code bean} as-is.
     * @param bean the new bean instance
     * @param beanName the name of the bean
     * @return the bean instance to use, either the original or a wrapped one;
     * if {@code null}, no subsequent BeanPostProcessors will be invoked
     * @throws org.springframework.beans.BeansException in case of errors
     * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet
     * @see org.springframework.beans.factory.FactoryBean
     */
    @Nullable
    default Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        return bean;
    }

}

SmartInstantiationAwareBeanPostProcessor
1、determineCandidateConstructors========》》》第二次
推断构造方法
2、getEarlyBeanReference()=============》》第四次
解决循环引用，提前暴露bean的引用
3、predictBeanType
预测bean的类型

package org.springframework.beans.factory.config;
/**
 * Extension of the {@link InstantiationAwareBeanPostProcessor} interface,
 * adding a callback for predicting the eventual type of a processed bean.
 *
 * <p><b>NOTE:</b> This interface is a special purpose interface, mainly for
 * internal use within the framework. In general, application-provided
 * post-processors should simply implement the plain {@link BeanPostProcessor}
 * interface or derive from the {@link InstantiationAwareBeanPostProcessorAdapter}
 * class. New methods might be added to this interface even in point releases.
 *
 * @author Juergen Hoeller
 * @since 2.0.3
 * @see InstantiationAwareBeanPostProcessorAdapter
 */
public interface SmartInstantiationAwareBeanPostProcessor extends InstantiationAwareBeanPostProcessor {

    /**
     * Predict the type of the bean to be eventually returned from this
     * processor's {@link #postProcessBeforeInstantiation} callback.
     * <p>The default implementation returns {@code null}.
     * @param beanClass the raw class of the bean
     * @param beanName the name of the bean
     * @return the type of the bean, or {@code null} if not predictable
     * @throws org.springframework.beans.BeansException in case of errors
     */
    @Nullable
    default Class<?> predictBeanType(Class<?> beanClass, String beanName) throws BeansException {
        return null;
    }

    /**
     * Determine the candidate constructors to use for the given bean.
     * <p>The default implementation returns {@code null}.
     * @param beanClass the raw class of the bean (never {@code null})
     * @param beanName the name of the bean
     * @return the candidate constructors, or {@code null} if none specified
     * @throws org.springframework.beans.BeansException in case of errors
     */
    @Nullable
    default Constructor<?>[] determineCandidateConstructors(Class<?> beanClass, String beanName)
            throws BeansException {

        return null;
    }

    /**
     * Obtain a reference for early access to the specified bean,
     * typically for the purpose of resolving a circular reference.
     * <p>This callback gives post-processors a chance to expose a wrapper
     * early - that is, before the target bean instance is fully initialized.
     * The exposed object should be equivalent to the what
     * {@link #postProcessBeforeInitialization} / {@link #postProcessAfterInitialization}
     * would expose otherwise. Note that the object returned by this method will
     * be used as bean reference unless the post-processor returns a different
     * wrapper from said post-process callbacks. In other words: Those post-process
     * callbacks may either eventually expose the same reference or alternatively
     * return the raw bean instance from those subsequent callbacks (if the wrapper
     * for the affected bean has been built for a call to this method already,
     * it will be exposes as final bean reference by default).
     * <p>The default implementation returns the given {@code bean} as-is.
     * @param bean the raw bean instance
     * @param beanName the name of the bean
     * @return the object to expose as bean reference
     * (typically with the passed-in bean instance as default)
     * @throws org.springframework.beans.BeansException in case of errors
     */
    default Object getEarlyBeanReference(Object bean, String beanName) throws BeansException {
        return bean;
    }

}

MergedBeanDefinitionPostProcess
1、postProcessMergedBeanDefinition ========》》第三次
缓存注入信息，仅仅缓存或者叫查找更合适

import org.springframework.beans.factory.config.BeanPostProcessor;
/**
 * Post-processor callback interface for <i>merged</i> bean definitions at runtime.
 * {@link BeanPostProcessor} implementations may implement this sub-interface in order
 * to post-process the merged bean definition (a processed copy of the original bean
 * definition) that the Spring {@code BeanFactory} uses to create a bean instance.
 *
 * <p>The {@link #postProcessMergedBeanDefinition} method may for example introspect
 * the bean definition in order to prepare some cached metadata before post-processing
 * actual instances of a bean. It is also allowed to modify the bean definition but
 * <i>only</i> for definition properties which are actually intended for concurrent
 * modification. Essentially, this only applies to operations defined on the
 * {@link RootBeanDefinition} itself but not to the properties of its base classes.
 *
 * @author Juergen Hoeller
 * @since 2.5
 * @see org.springframework.beans.factory.config.ConfigurableBeanFactory#getMergedBeanDefinition
 */
public interface MergedBeanDefinitionPostProcessor extends BeanPostProcessor {

    /**
     * Post-process the given merged bean definition for the specified bean.
     * @param beanDefinition the merged bean definition for the bean
     * @param beanType the actual type of the managed bean instance
     * @param beanName the name of the bean
     */
    void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName);

}