bean的作用域

singleton與prototype都是spring內(nèi)置的赂毯，默認(rèn)是singleton。prototype是每次獲取bean都會創(chuàng)建新的bean. request拣宰、session党涕、application都是在web應(yīng)用中生效。websocket是指在一個(gè)websocket鏈接中生效巡社。

自定義scope,實(shí)現(xiàn)org.springframework.beans.factory.config.Scope接口即可膛堤。參考o(jì)rg.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范圍的bean生命周期創(chuàng)建后，不受spring容器管理晌该。即<bean id="person" class="com.test.Person" init-method="init" destroy-method="destory" > init方法會調(diào)用肥荔，但是destory不會調(diào)用绿渣。prototype范圍的bean銷毀要交給客戶端代碼銷毀。

自定義bean的屬性

1. Lifecycle Callbacks（生命周期回調(diào))
   初始化回調(diào)：1. 實(shí)現(xiàn)InitializingBean接口燕耿，則會回調(diào)afterPropertiesSet()方法
2. 方法上加注解@PostConstruct中符。3. 指定init-method方法
   銷毀回調(diào)：1. 實(shí)現(xiàn)DisposableBean接口，則會回調(diào)destroy()方法誉帅。2. 方法加注解

調(diào)用順序：
初始化：

1. Methods annotated with @PostConstruct

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

3. A custom configured init() method

銷毀：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

淀散。。蚜锨。档插。。踏志。

Aware接口阀捅，事件回調(diào)機(jī)制

ApplicationContextAware、ApplicationEventPublisherAware针余、BeanFactoryAware、ServletContextAware

ApplicationEventPublisherAware實(shí)現(xiàn)了該接口的bean凄诞，可以獲取applicationEventPublisher圆雁，用來發(fā)布事件。如下代碼可以實(shí)現(xiàn)事件的監(jiān)聽機(jī)制帆谍。

1. 事件信息載體

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. 事件發(fā)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. 事件監(jiān)聽者

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的擴(kuò)展點(diǎn)

BeanPostProcessor

在bean創(chuàng)建伪朽、實(shí)例化之后，初始化調(diào)用前后進(jìn)行一些邏輯的操作汛蝙，可以修改bean的屬性烈涮，返回等等。

package org.springframework.beans.factory.config;

import org.springframework.beans.BeansException;


public interface BeanPostProcessor {

    //@PostConstruct注解方法窖剑、InitializingBean接口的afterPropertiesSet方法坚洽、init-method方法**調(diào)用之前執(zhí)行**。
    Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException;

    //@PostConstruct注解方法西土、InitializingBean接口的afterPropertiesSet方法讶舰、init-method方法**調(diào)用之后執(zhí)行**。
    Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException;

}

demo如下代碼

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;
    }
}

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

AutowiredAnnotationBeanPostProcessor實(shí)現(xiàn)了BeanPostProcessor接口

AutowiredAnnotationBeanPostProcessor.png

AutowiredAnnotationBeanPostProcessor調(diào)用堆棧.png

BeanFactoryPostProcessor

在bean實(shí)例化之前肋乍，對bean的元數(shù)據(jù)進(jìn)行邏輯操作處理
PropertySourcesPlaceholderConfigurer對@Value屬性進(jìn)行解析鹅颊。
下面的demo，模擬PropertySourcesPlaceholderConfigurer,對bean的屬性進(jìn)行注入值墓造。

package com.league.chase.beanFactoryPostProcessor;


import org.springframework.stereotype.Service;

/**
 * BeanFactoryPostProcessor實(shí)現(xiàn)類
 * @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的定義堪伍，注冊新的bean等锚烦。
        BeanDefinition service = configurableListableBeanFactory.getBeanDefinition("beanFactoryPostProcessorService");

        //模擬 PropertySourcesPlaceholderConfigurer向 bean的屬性設(shè)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());
    }
}

輸出如下杠娱，從輸出可以看出BeanFactoryPostProcessor是作用于實(shí)例化之前挽牢，BeanPostProcessor作用于bean實(shí)例化之后，且初始化方法調(diào)用之前后摊求。

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

自定義bean的實(shí)例化邏輯接口FactoryBean

Environment Abstraction

禽拔。。室叉。睹栖。。