BeanFactory实现特点

beanFactory不会做的事情

• 不会主动调用BeanFactory后处理器
• 不会主动添加Bean后处理器
• 不会主动初始化单例
• 不会解析beanFactory 还不会解析${}、#{}

bean后处理器会有排序的逻辑，后处理都实现order接口实现的，有的是解析@Autowired注解有的是解析@Resource注解

package com.example;
 
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.context.annotation.AnnotationConfigUtils;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
 
import java.util.logging.Logger;
 
public class TestBeanFactory {
    public static void main(String[] args) {
        DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
        // 为beanFactory添加一些bean的定义，beanFactory根据添加的bean的定义来传创建bean对象
        // 定义包括：bean的类型（class）、bean的作用域（scope）、bean是否含有初始化、销毁
        AbstractBeanDefinition beanDefinition = BeanDefinitionBuilder.genericBeanDefinition(Config.class).setScope("singleton").getBeanDefinition();
        beanFactory.registerBeanDefinition("config", beanDefinition);
        for (String name : beanFactory.getBeanDefinitionNames()) {
            System.out.println(name);  // config  todo 目前beanFactory还缺少解析注解的功能
        }
        // 给beanFactory添加一些常用的后处理器
        AnnotationConfigUtils.registerAnnotationConfigProcessors(beanFactory);
        for (String name : beanFactory.getBeanDefinitionNames()) {
            System.out.println(name);     /*config
                                        org.springframework.context.annotation.internalConfigurationAnnotationProcessor
                                        org.springframework.context.annotation.internalAutowiredAnnotationProcessor
                                        org.springframework.context.annotation.internalCommonAnnotationProcessor
                                        org.springframework.context.event.internalEventListenerProcessor
                                        org.springframework.context.event.internalEventListenerFactory*/
        }
        // 获取beanFactory后处理器，补充了一些bean的定义
        beanFactory.getBeansOfType(BeanFactoryPostProcessor.class).values().stream().forEach(beanFactoryPostProcessor -> {
            beanFactoryPostProcessor.postProcessBeanFactory(beanFactory);
        });
        // bean的后处理器，针对bean的生命周期的各个阶段来拓展一些功能,例如@Autowired、@Resource....
        beanFactory.getBeansOfType(BeanPostProcessor.class).values().stream().forEach(beanFactory::addBeanPostProcessor);
        for (String name : beanFactory.getBeanDefinitionNames()) {
            System.out.println(name);
        }/*config
org.springframework.context.annotation.internalConfigurationAnnotationProcessor
org.springframework.context.annotation.internalAutowiredAnnotationProcessor
org.springframework.context.annotation.internalCommonAnnotationProcessor
org.springframework.context.event.internalEventListenerProcessor
org.springframework.context.event.internalEventListenerFactory
bean1
bean2*/
        beanFactory.preInstantiateSingletons();// 准备好所有单例。初始化单例对象
        System.out.println("+++++++++++++++++++++++++++++++++++");
        System.out.println(beanFactory.getBean(Bean1.class).getBean2());
    }
 
    @Configuration
    static class Config {
        @Bean
        public Bean1 bean1() {
            return new Bean1();
        }
 
        @Bean
        public Bean2 bean2() {
            return new Bean2();
        }
    }
 
    static class Bean1 {
        private static final org.slf4j.Logger log = LoggerFactory.getLogger(Bean1.class);
 
        public Bean1() {
            log.info("构造Bean1()");
        }
 
        @Autowired
        private Bean2 bean2;
 
        public Bean2 getBean2() {
            return bean2;
        }
    }
 
    static class Bean2 {
        private static final org.slf4j.Logger log = LoggerFactory.getLogger(Bean2.class);
 
        public Bean2() {
            log.info("构造Bean2()");
        }
    }
}