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BeanFactory、ApplicationContext简介

2023/4/7 Java 框架

BeanFactory创建Bean实例对象

示例代码：

xml配置文件

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="userService" class="com.zy.service.impl.UserServiceImpl"></bean>
</beans>

userService接口

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package com.zy.service;

public interface UserService {
}

userServiceImp

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package com.zy.service.impl;

import com.zy.service.UserService;

/**
 * @author Administrator
 * @version 1.0
 * @description TODO
 * @date 2023/4/7 8:56
 */
public class UserServiceImpl implements UserService {
}

核心方法代码

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package com.zy.test;

import com.zy.service.UserService;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;

/**
 * @author Administrator
 * @version 1.0
 * @description TODO
 * @date 2023/4/7 9:04
 */
public class BeanFactoryTest {
    public static void main(String[] args) {
        //创建工厂
        DefaultListableBeanFactory beanFactory=new DefaultListableBeanFactory();
        //创建一个读取器（xml）
        XmlBeanDefinitionReader reader=new XmlBeanDefinitionReader(beanFactory);
        //读取配置文件给工厂
        reader.loadBeanDefinitions("beans.xml");
        //根据id获取Bean实例对象
        UserService userService = (UserService) beanFactory.getBean("userService");
        System.out.println(userService);
    }
}

ApplicationCOntext快速入门

ApplicationContext称为Spring容器，内部封装了BeanFactory,比BeanFactory功能更强大更丰富，使用ApplicationContext进行开发时，xml配置文件的名称习惯写成applicationContext.xml

xml配置文件代码：

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="userService" class="com.zy.service.impl.UserServiceImpl"></bean>
</beans>

核心代码：

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package com.zy.test;

import com.zy.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @author Administrator
 * @version 1.0
 * @description TODO
 * @date 2023/4/7 16:18
 */
public class ApplicationContextTest {
    public static void main(String[] args) {
        ApplicationContext applicationContext=new ClassPathXmlApplicationContext("applicationContext.xml");
        UserService userService = (UserService) applicationContext.getBean("userService");
        System.out.println(userService);
    }
}

- BeanFactory与ApplicationContext的关系

  1. BeanFactory是Spring的早期接口，称为Spring的Bean工厂，ApplicationEontext是后期更高级接口，称之为Spring容器;

2)ApplicationContext在BeanFactory基础上对功能进行了扩展，例如:监听功能、国际化功能等。BeanFactory的API更偏向底层，ApplicationContext的API大多数是对这些底层API的封装;

3)Bean创建的主要逻辑和功能都被封装在BeanFactory中，ApplicationContext不仅继承了BeanFactory，而且ApplicationContext内部还维护着BeanFactory的引用，所以，ApplicationContext与BeanFactory既有继承关系，又有融合关系。

  1. Bean的初始化时机不同，原始BeanFactory是在首次调用getBean时才进行Bean的创建，而ApplicationContext则是配置文件加载，容器一创建就将Bean都实例化并初始化好。