bean的作用域

singleton与prototype都是spring内置的，默认是singleton。prototype是每次获取bean都会创建新的bean. request、session、application都是在web应用中生效。websocket是指在一个websocket链接中生效。

自定义scope,实现org.springframework.beans.factory.config.Scope接口即可。参考org.springframework.context.support.SimpleThreadScope

@Override
    public Object get(String name, ObjectFactory<?> objectFactory) {
        Map<String, Object> scope = this.threadScope.get();
        Object scopedObject = scope.get(name);
        if (scopedObject == null) {
            scopedObject = objectFactory.getObject();
            scope.put(name, scopedObject);
        }
        return scopedObject;
    }

prototype范围的bean生命周期创建后，不受spring容器管理。即<bean id="person" class="com.test.Person" init-method="init" destroy-method="destory" > init方法会调用，但是destory不会调用。prototype范围的bean销毁要交给客户端代码销毁。

自定义bean的属性

1. Lifecycle Callbacks（生命周期回调)
   初始化回调：1. 实现InitializingBean接口，则会回调afterPropertiesSet()方法
2. 方法上加注解@PostConstruct。3. 指定init-method方法
   销毁回调：1. 实现DisposableBean接口，则会回调destroy()方法。2. 方法加注解

调用顺序：
初始化：

1. Methods annotated with @PostConstruct

2.afterPropertiesSet() as defined by the InitializingBean callback interface

3. A custom configured init() method

销毁：Destroy methods are called in the same order:

1. Methods annotated with @PreDestroy

2. destroy() as defined by the DisposableBean callback interface

3. A custom configured destroy() method

Lifecycle接口

。。。。。。

Aware接口，事件回调机制

ApplicationContextAware、ApplicationEventPublisherAware、BeanFactoryAware、ServletContextAware

ApplicationEventPublisherAware实现了该接口的bean，可以获取applicationEventPublisher，用来发布事件。如下代码可以实现事件的监听机制。

1. 事件信息载体

package com.league.chase.event;

public class User {
    private String name;

    public String getName() {
        return name;
    }

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

2. 事件

package com.league.chase.event;

import org.springframework.context.ApplicationEvent;

public class RegisterEvent extends ApplicationEvent {
    /**
     * Create a new ApplicationEvent.
     *
     * @param source the component that published the event (never {@code null})
     */
    private User user;

    public RegisterEvent(Object source, User user) {
        super(source);
        this.user = user;
    }

    public User getUser() {
        return user;
    }
}

3. 事件发布者

package com.league.chase.event;


import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.stereotype.Service;

@Service
public class UserService implements ApplicationEventPublisherAware {

    private ApplicationEventPublisher applicationEventPublisher;

    @Override
    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        this.applicationEventPublisher = applicationEventPublisher;

    }

    public void register(String userName){
        applicationEventPublisher.publishEvent(new RegisterEvent(this,new User()));
    }

    public void sayHello(){
        System.out.println("userService sayHello");
    };
}

4. 事件监听者

package com.league.chase.event;

import org.springframework.context.ApplicationListener;
import org.springframework.stereotype.Service;

@Service
public class RegisterEventListener implements ApplicationListener<RegisterEvent> {

    @Override
    public void onApplicationEvent(RegisterEvent applicationEvent) {
        System.out.println("事件---"+applicationEvent.getSource().getClass().getName());
        UserService service = (UserService) applicationEvent.getSource();
        service.sayHello();

    }

}

spring的扩展点

BeanPostProcessor

在bean创建、实例化之后，初始化调用前后进行一些逻辑的操作，可以修改bean的属性，返回等等。

package org.springframework.beans.factory.config;

import org.springframework.beans.BeansException;


public interface BeanPostProcessor {

    //@PostConstruct注解方法、InitializingBean接口的afterPropertiesSet方法、init-method方法**调用之前执行**。
    Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException;

    //@PostConstruct注解方法、InitializingBean接口的afterPropertiesSet方法、init-method方法**调用之后执行**。
    Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException;

}

demo如下代码

package com.league.chase.beanPostProcessor;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Service;

import javax.annotation.PostConstruct;

@Service
public class BeanPostProcessorService implements InitializingBean {

    private int age = 1;

    @PostConstruct
    public void init(){
        System.out.println("BeanPostProcessorService----> init");
    }


    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.println("BeanPostProcessorService----> afterPropertiesSet");
    }

    public int getAge() {
        return age;
    }

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

package com.league.chase.beanPostProcessor;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.stereotype.Component;


@Component
public class MyBeanPostProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        if(beanName.equals("beanPostProcessorService")){
            System.out.println("postProcessBeforeInitialization beanName---->"+beanName);
            BeanPostProcessorService newBean = (BeanPostProcessorService) bean;
            ((BeanPostProcessorService) bean).setAge(2);

        }

        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        if(beanName.equals("beanPostProcessorService")){
            System.out.println("postProcessAfterInitialization beanName---->"+beanName);
            System.out.println("postProcessAfterInitialization beanName---->"+((BeanPostProcessorService)bean).getAge());
            BeanPostProcessorService newBean  = new BeanPostProcessorService();
            newBean = new BeanPostProcessorService();
            newBean.setAge(3);
            return newBean;
        }

        return bean;
    }
}

输出
postProcessBeforeInitialization beanName---->beanPostProcessorService
BeanPostProcessorService----> init
BeanPostProcessorService----> afterPropertiesSet
postProcessAfterInitialization beanName---->beanPostProcessorService
postProcessAfterInitialization beanName---->2

AutowiredAnnotationBeanPostProcessor实现了BeanPostProcessor接口

AutowiredAnnotationBeanPostProcessor.png

AutowiredAnnotationBeanPostProcessor调用堆栈.png

BeanFactoryPostProcessor

在bean实例化之前，对bean的元数据进行逻辑操作处理
PropertySourcesPlaceholderConfigurer对@Value属性进行解析。
下面的demo，模拟PropertySourcesPlaceholderConfigurer,对bean的属性进行注入值。

package com.league.chase.beanFactoryPostProcessor;


import org.springframework.stereotype.Service;

/**
 * BeanFactoryPostProcessor实现类
 * @author chase
 */
@Service
public class BeanFactoryPostProcessorService {

    private String name;


    public String getName() {
        return name;
    }

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

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

package com.league.chase.beanFactoryPostProcessor;

import org.springframework.beans.BeansException;
import org.springframework.beans.MutablePropertyValues;
import org.springframework.beans.PropertyValue;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.context.annotation.ScannedGenericBeanDefinition;
import org.springframework.core.PriorityOrdered;
import org.springframework.stereotype.Service;

/**
 * @author chase
 */
@Service
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor, PriorityOrdered {
    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {

        //configurableListableBeanFactory可以修改bean的定义，注册新的bean等。
        BeanDefinition service = configurableListableBeanFactory.getBeanDefinition("beanFactoryPostProcessorService");

        //模拟 PropertySourcesPlaceholderConfigurer向 bean的属性设置值。
        MutablePropertyValues pvs = new MutablePropertyValues();
        pvs.addPropertyValue(new PropertyValue("name","zhangsan"));
        ((ScannedGenericBeanDefinition) service).setPropertyValues(pvs);

        System.out.println("MyBeanFactoryPostProcessor postProcessBeanFactory():"+service.getBeanClassName());
    }

    @Override
    public int getOrder() {
        return 0;
    }
}

package com.league.chase.beanFactoryPostProcessor;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@SpringBootTest
public class MyBeanFactoryPostProcessorTest {

    @Autowired
    private BeanFactoryPostProcessorService service;

    @Test
    public void postProcessBeanFactoryTest() {
        System.out.println("MyBeanFactoryPostProcessorTest---->"+service.getName());
    }
}

输出如下，从输出可以看出BeanFactoryPostProcessor是作用于实例化之前，BeanPostProcessor作用于bean实例化之后，且初始化方法调用之前后。

MyBeanFactoryPostProcessor postProcessBeanFactory():com.league.chase.beanFactoryPostProcessor.BeanFactoryPostProcessorService
2021-05-11 17:02:54.756 INFO 28341 --- [ main] trationDelegateBeanPostProcessorChecker : Bean 'com.alibaba.cloud.sentinel.custom.SentinelAutoConfiguration' of type [com.alibaba.cloud.sentinel.custom.SentinelAutoConfiguration] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
postProcessBeforeInitialization beanName---->beanPostProcessorService
BeanPostProcessorService----> init
BeanPostProcessorService----> afterPropertiesSet
postProcessAfterInitialization beanName---->beanPostProcessorService
postProcessAfterInitialization beanName---->2
2021-05-11 17:02:56.195 INFO 28341 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
2021-05-11 17:02:56.282 INFO 28341 --- [ main] c.a.c.s.SentinelWebAutoConfiguration : [Sentinel Starter] register SentinelWebInterceptor with urlPatterns: [/**].
2021-05-11 17:02:57.814 INFO 28341 --- [ main] o.s.cloud.commons.util.InetUtils : Cannot determine local hostname
2021-05-11 17:02:57.896 INFO 28341 --- [ main] c.l.c.b.MyBeanFactoryPostProcessorTest : Started MyBeanFactoryPostProcessorTest in 1454.614 seconds (JVM running for 1456.377)

MyBeanFactoryPostProcessorTest---->zhangsan

自定义bean的实例化逻辑接口FactoryBean

Environment Abstraction

。。。。。