【面试】spring中BeanFactory和ApplicationContext的区别

1. 共同点

• 1.都可以作为容器。

2. 区别

• 1.ApplicationContext不生产Bean，而是通知BeanFactory来生产，getBean是一个表面方法。
• 2. ApplicationContext会自动把配置的bean注册进来。
• 3.ApplicationContext会加载环境变量。
• 4.ApplicationContext支持多语言。
• 5.ApplicationContext实现事件监听。
• 6.ApplicationContext注册了很多对外的扩展点。

3. 关系

• 1.ApplicationContext实现了BeanFactory接口。

4. 类关系图

5. ApplicationContext实现的接口

5.1 MessageSource

5.1.1 说明

• 1.支持国际化语言

5.1.2 接口源码

package org.springframework.context;

import java.util.Locale;
import org.springframework.lang.Nullable;

public interface MessageSource {
    @Nullable
    String getMessage(String var1, @Nullable Object[] var2, @Nullable String var3, Locale var4);

    String getMessage(String var1, @Nullable Object[] var2, Locale var3) throws NoSuchMessageException;

    String getMessage(MessageSourceResolvable var1, Locale var2) throws NoSuchMessageException;
}

5.1.3 代码示例

package com.learning;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.scheduling.annotation.EnableScheduling;

import java.util.Locale;

/**
 * @Author wangyouhui
 **/
@SpringBootApplication
@EnableCaching
@EnableScheduling
public class SpringBootLearningApplication {
    public static void main(String[] args) {
        ConfigurableApplicationContext configurableApplicationContext = SpringApplication.run(SpringBootLearningApplication.class, args);
        System.out.println(configurableApplicationContext.getMessage("hi", null, Locale.CHINA));
        System.out.println(configurableApplicationContext.getMessage("hi", null, Locale.ENGLISH));
    }
}

5.1.4 示例截图

• 1. 配置文件
  
  
  
• 2. 结果截图
  

5.2 ResourcePatternResolver

5.2.1 说明

• 1.通配符匹配资源（磁盘、类路径获取的文件）的能力。
• 2.classpath是在类路径中查找，若在jar包中则找不到，加*可在jar中查找，即classpath*。

5.2.2 代码示例

package com.learning;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.io.Resource;

import java.io.IOException;

@SpringBootApplication
public class SpringBootLearningApplication {
    public static void main(String[] args) throws IOException {
        ConfigurableApplicationContext configurableApplicationContext = SpringApplication.run(SpringBootLearningApplication.class, args);

        Resource[] resources = configurableApplicationContext.getResources("classpath*:META-INF/spring.factories");
        for (Resource resource : resources) {
            System.out.println(resource);
        }
    }
}

5.2.3 截图示例

6.3 ApplicationEventPublisher

5.3.1 说明

• 1.用来发布事件对象。
• 2.事件可以用来解耦。

5.3.2 代码示例

• 1.带事件监听的方法

package com.learning.component;

import com.learning.event.UserRegisterEvent;
import lombok.extern.slf4j.Slf4j;
import org.springframework.context.event.EventListener;
import org.springframework.stereotype.Component;

@Component
@Slf4j
public class ComponentTwo {

    @EventListener
    public void sendMessage(UserRegisterEvent event){
        log.info("{}", event);
        log.info("发送短信");
    }
}

• 2.事件类

package com.learning.event;

import org.springframework.context.ApplicationEvent;

public class UserRegisterEvent extends ApplicationEvent {
    public UserRegisterEvent(Object source) {
        super(source);
    }
}

• 3.发布类

package com.learning.component;

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

@Component
@Slf4j
public class ComponentOne {
    @Autowired
    private ApplicationContext applicationContext;

    public void register(){
        log.info("用户注册");
        applicationContext.publishEvent(new UserRegisterEvent(this));
    }
}

• 4.启动类

package com.learning;

import com.learning.component.ComponentOne;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;

import java.io.IOException;

@SpringBootApplication
public class SpringBootLearningApplication {
    public static void main(String[] args) throws IOException {
        ConfigurableApplicationContext configurableApplicationContext = SpringApplication.run(SpringBootLearningApplication.class, args);
        ComponentOne componentOne = configurableApplicationContext.getBean(ComponentOne.class);
        componentOne.register();
    }
}

5.3.3 效果示例

5.4 EnvironmentCapable

5.4.1 说明

• 1.读取系统环境变量、*.yml文件、*.property文件信息。

5.4.2 代码示例

package com.learning;

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

import java.io.IOException;

@SpringBootApplication
public class SpringBootLearningApplication {
    public static void main(String[] args) {
        ConfigurableApplicationContext configurableApplicationContext = SpringApplication.run(SpringBootLearningApplication.class, args);
        String javaHome = configurableApplicationContext.getEnvironment().getProperty("java_home");
        String port = configurableApplicationContext.getEnvironment().getProperty("server.port");
        System.out.println(javaHome);
        System.out.println(port);
    }
}

5.4.3 截图示例