BeanFactory和ApplicationContext

BeanFactory和ApplicationContext

Q：到底什么是 BeanFactory

它是 ApplicationContext 的父接口

它才是 Spring 的核心容器，主要的 ApplicationContext 的实现都是依赖BeanFactory的

package com.hayaizo.springstudy;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;

@SpringBootApplication
public class SpringStudyApplication {

	public static void main(String[] args) {
		ConfigurableApplicationContext context = SpringApplication.run(SpringStudyApplication.class, args);
		System.out.println(context);
	}
}

首先看一下继承关系

再调试打断点看看ApplicationContext这个玩意里有什么东西

package com.hayaizo.springstudy;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ConfigurableApplicationContext;

@SpringBootApplication
public class SpringStudyApplication {

	public static void main(String[] args) {
		ApplicationContext context = SpringApplication.run(SpringStudyApplication.class, args);
		System.out.println(context);
	}
}

包括Spring中的单例对象也都在这里面：

BeanFactory的功能

可以看到还是相对简单的，而BeanFactory有很多实现类：

这个DefaultSingletonBeanRegistry主要是负责注册Bean的。

我们通过反射来获取到所有的单例，但是这里单例太多了，所以我自己创建了两个Bean，让他只把这两个Bean过滤出来。

package com.hayaizo.springstudy;

import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.support.DefaultSingletonBeanRegistry;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ConfigurableApplicationContext;

import java.lang.reflect.Field;
import java.util.Map;

@SpringBootApplication
public class SpringStudyApplication {

	public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException {
		ConfigurableApplicationContext context = SpringApplication.run(SpringStudyApplication.class, args);
		// 获取到Field
		Field singletonObjects = DefaultSingletonBeanRegistry.class.getDeclaredField("singletonObjects");
		singletonObjects.setAccessible(true);
		ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
		Map<String,Object> map = (Map<String, Object>) singletonObjects.get(beanFactory);

		System.out.println("========================================");
		map.entrySet().stream()
				.filter(e -> e.getKey().startsWith("component"))
				.forEach(e -> {
					System.out.println("key: " + e.getKey() + ", value: " + e.getValue());
				});
	}
}

Application的事件发布功能

在 Spring 框架中，事件发布（Event Publishing）是基于观察者模式的一个实现，主要用于在应用程序中实现松耦合的组件之间的通信。事件发布与监听机制通过 Spring 的 ApplicationEvent 和 ApplicationListener 进行操作。

首先我们创建自定义事件类，继承ApplicationEvent

package com.hayaizo.springstudy;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.ApplicationEvent;


public class UserRegisteredEvent extends ApplicationEvent {

    private static final Logger log = LoggerFactory.getLogger(UserRegisteredEvent.class);

    public UserRegisteredEvent(Object source) {
        super(source);
        System.out.println("发送短信");
    }
}

然后创建事件的监听器

package com.hayaizo.springstudy;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.event.EventListener;
import org.springframework.stereotype.Component;

@Component
public class Component2 {
    private static final Logger log = LoggerFactory.getLogger(Component2.class);

    @EventListener
    public void aaa(UserRegisteredEvent event){
        System.out.println("event: "+event);
    }
}

事件发布

package com.hayaizo.springstudy;

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.event.EventListener;
import org.springframework.stereotype.Component;

@Slf4j
@Component
public class Component1 {

    @Autowired
    private ApplicationContext context;


    public void Register(){
        System.out.println("用户注册ing");
        context.publishEvent(new UserRegisteredEvent(this));
    }
}

调用

package com.hayaizo.springstudy;

import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.support.DefaultSingletonBeanRegistry;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.io.Resource;

import java.io.IOException;
import java.lang.reflect.Field;
import java.util.Map;

@SpringBootApplication
public class SpringStudyApplication {

	public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException, IOException {
		ConfigurableApplicationContext context = SpringApplication.run(SpringStudyApplication.class, args);
		System.out.println("==========事件发布测试==========");
		context.publishEvent(new UserRegisteredEvent(context));
		System.out.println("==========用户注册==========");
		context.getBean(Component1.class).Register();
	}
}