BeanFactory 与 ApplicationContext 的区别

深碍√TFBOYSˉ_ 2022-10-30 06:24 195阅读 0赞

BeanFactory 是 Spring IoC 容器的底层实现；

ApplicationContext 拥有 BeanFactory 的所有能力，还提供了

*  Easier integration with Spring’s AOP features
 *  Message resource handling (for use in internationalization)
 *  Event publication
 *  Application-layer specific contexts such as the WebApplicationContext for use in web applications

摘自：[https://docs.spring.io/spring-framework/docs/5.2.2.RELEASE][https_docs.spring.io_spring-framework_docs_5.2.2.RELEASE]

即更易集成 aop 特性、消息资源处理(国际化)、事件发布、应用程序层面特定的上下文如 WebApplicationContext。

除了以上，细节上还包括：

*  BeanFactory 在启动的时候不会去实例化 bean，从容器中拿 bean 时才会去实例化；ApplicationContext 在启动时就把所有的 bean 全部实例化了
 *  BeanPostProcessor、BeanFactoryPostProcessor 接口的注册：BeanFactory 需要手动注册，ApplicationContext 则是自动

总之，ApplicationContext 是具备应用特性的 BeanFactory 超集。

代码示例：

pom

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <parent>
            <groupId>constxiong</groupId>
            <artifactId>spring-study</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </parent>
    	
        <artifactId>003-spring-beanfactory-applicationcontext</artifactId>
    
        <properties>
            <spring-version>5.2.2.RELEASE</spring-version>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-context</artifactId>
                <version>${spring-version}</version>
            </dependency>
        </dependencies>
    
        <build>
    
        </build>
    </project>

User.java

package constxiong;
    
    public class User {
    	
    	private Integer id;
    	
    	private String name;
    
    	public Integer getId() {
    		return id;
    	}
    
    	public void setId(Integer id) {
    		this.id = id;
    	}
    
    	public String getName() {
    		return name;
    	}
    
    	public void setName(String name) {
    		this.name = name;
    	}
    
    	@Override
    	public String toString() {
    		return "User [id=" + id + ", name=" + name + "]";
    	}
    	
    }

spring 配置文件

<?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 class="constxiong.User">
    		<property name="id" value="1"/>
    		<property name="name" value="constxiong"/>
    	</bean>
    
    </beans>

测试代码

package constxiong;
    
    import org.springframework.beans.factory.support.DefaultListableBeanFactory;
    import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    /**
     * 测试 BeanFactory 与 ApplicationContext 的区别
     * @author ConstXiong
     */
    public class Test {
    	
    	public static void main(String[] args) {
    		String xmlPath = "META-INF/spring-beanfactory-applicationcontext.xml";
    		getBeanByBeanFactory(xmlPath);
    		getBeanByApplicationContext(xmlPath);
    	}
    
    	/**
    	 * 通过 ClassPathXmlApplicationContext 获取 bean
    	 */
    	private static void getBeanByApplicationContext(String xmlPath) {
    		ApplicationContext applicationContext = new ClassPathXmlApplicationContext(xmlPath);
    		User user = applicationContext.getBean(User.class);
    		System.out.println(user);
    	}
    
    	/**
    	 *  通过 DefaultListableBeanFactory 获取 bean
    	 */
    	private static void getBeanByBeanFactory(String xmlPath) {
    		DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
    		XmlBeanDefinitionReader xmlReader = new XmlBeanDefinitionReader(beanFactory);
    		xmlReader.loadBeanDefinitions(xmlPath);
    		User user = beanFactory.getBean(User.class);
    		System.out.println(user);
    	}
    
    }

说明：

*  通过在 BeanFactory\#getBean，ApplicationContext\#getBean 方法这两行、User\#setId 方法打上断点，可以看出 BeanFactory 是在调用 getBean 时初始化 User 这个 bean，ApplicationContext 是提前初始化完成的。
 *  通过查看源码可以看出，AbstractRefreshableApplicationContext 类间接继承了 BeanFactory 接口，同时持有 DefaultListableBeanFactory 对象 beanFactory；所有 BeanFactory 的能力都来自于 beanFactory。这点用到了装饰器设计模式。
 *  ApplicationContext 对 BeanFactory 的能力的扩展体现在 AbstractApplicationContext\#refresh 方法内。

--------------------

### 【Java学习资源】整理推荐 ###

*  [Spring 依赖注入的处理过程与 DependencyDescriptor 的说明][Spring _ DependencyDescriptor]
 *  [Spring 各种 Aware 接口回调注入][Spring _ Aware]
 *  [Spring Bean 生命周期内的 Exception 复现][Spring Bean _ Exception]
 *  [Spring 内建 Bean][Spring _ Bean]
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 *  [ObjectFactory 与 BeanFactory 的区别][ObjectFactory _ BeanFactory]
 *  [Bean 销毁的方式与顺序][Bean]
 *  [Bean 初始化的方式与顺序][Bean 1]
 *  [Bean 的实例化方式][Bean 2]
 *  [Bean的注册方式][Bean 3]
 *  [什么是 BeanDefinition？][BeanDefinition]
 *  [Spring IoC 容器启动时做了什么？][Spring IoC]
 *  [BeanFactory 与 FactoryBean 的区别][BeanFactory _ FactoryBean]
 *  [BeanFactory 与 ApplicationContext 的区别][BeanFactory _ ApplicationContext]
 *  [Spring IoC 依赖注入的实现方式][Spring IoC 1]
 *  [Spring IoC 依赖注入(支持哪些数据类型？)][Spring IoC 2]
 *  [Spring bean 依赖查找][Spring bean]
 *  [Spring-IoC][]
 *  [Spring 的核心特性][Spring]

--------------------

### 【Java面试题与答案】整理推荐 ###

*  [基础与语法][Link 1]
 *  [集合][Link 2]
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 *  [并发编程][Link 4]
 *  [Web][]
 *  [安全][Link 5]
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 *  [异常][Link 9]
 *  [文件解析与生成][Link 10]
 *  [Linux][]
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 *  [Redis][]
 *  [Dubbo][]

[https_docs.spring.io_spring-framework_docs_5.2.2.RELEASE]: https://docs.spring.io/spring-framework/docs/5.2.2.RELEASE/spring-framework-reference/core.html#beans-introduction
[Spring _ DependencyDescriptor]: https://www.javanav.com/val/152161d266a94fd38efb365a78d8f9a3.html
[Spring _ Aware]: https://www.javanav.com/val/089b3993c8bc4dec891ea677c104c5e4.html
[Spring Bean _ Exception]: https://www.javanav.com/val/2b31b7061b3342c0a67f8d7fc7373ed3.html
[Spring _ Bean]: https://www.javanav.com/val/92f9e0951b19454196b645bb3cb1a0b9.html
[Spring Bean]: https://www.javanav.com/val/4d39ffc772184e10827d741b1b5ba787.html
[Spring Bean 1]: https://www.javanav.com/val/76a8f38c9f5f42ce8487ad490b41223b.html
[Bean _ GC]: https://www.javanav.com/val/ca4a8f696ee5440bb5d87d3397b59004.html
[Spring Bean 2]: https://www.javanav.com/val/b197550be7ba4bd8b4d82f6835d1abb1.html
[ObjectFactory _ BeanFactory]: https://www.javanav.com/val/016d62d99b0148feaf13529a841f4e46.html
[Bean]: https://www.javanav.com/val/a5a7f97894f9499b90e27dbd98124a1c.html
[Bean 1]: https://www.javanav.com/val/cd53474ce0ca4b85ad3c9cf4ed35c13a.html
[Bean 2]: https://www.javanav.com/val/2a6dbdb701804b15a216d409abe83b6b.html
[Bean 3]: https://www.javanav.com/val/a5f8bf440848487bb0c0bdaa6c846cc6.html
[BeanDefinition]: https://www.javanav.com/val/e82279480ec24184bcaf723a50ef08b3.html
[Spring IoC]: https://www.javanav.com/val/d382c8380fc2480788a35a7e671b5e9b.html
[BeanFactory _ FactoryBean]: https://www.javanav.com/val/173e873a2c98499a8a08a13b4f88ae10.html
[BeanFactory _ ApplicationContext]: https://www.javanav.com/val/bbc2c9580b7045e583855925d5f1a50b.html
[Spring IoC 1]: https://www.javanav.com/val/a835e6c709ea439ebb21a80f1bf77926.html
[Spring IoC 2]: https://www.javanav.com/val/e377beac22644c2c85308079b239a0fd.html
[Spring bean]: https://www.javanav.com/val/7f8c2e1f24db46e79bc4b9b04f9ad715.html
[Spring-IoC]: https://www.javanav.com/val/a412668efda74412a13f6df9a6d2c714.html
[Spring]: https://www.javanav.com/val/6eac12a548ea40c68ff64b1af307563a.html
[Link 1]: https://www.javanav.com/interview/93b0069472fd479393006c0e73043fc4.html
[Link 2]: https://www.javanav.com/interview/4147d95e693945e7a50345fd33ec817e.html
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[Link 9]: https://www.javanav.com/interview/d3f058cfc05d4c6dadd821b622e84d36.html
[Link 10]: https://www.javanav.com/interview/67a50996c28f418e83b109ea42fc3eff.html
[Linux]: https://www.javanav.com/interview/00cccb81729540d1923bd0a0ef49533a.html
[MySQL]: https://www.javanav.com/interview/d311e78502a845f1a4bb307bd6aec2b3.html
[Oracle]: https://www.javanav.com/interview/5f29e9677edf4a16be3dce30d257c9ab.html
[Redis]: https://www.javanav.com/interview/066c62b3af4d4827b2243a822c3084a9.html
[Dubbo]: https://www.javanav.com/interview/9a3e7a7740324757abaab953f7ebc455.html