Spring应用上下文

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Spring application context介绍：

Spring applicationcontext包含了业务pojo对象，还有配置的信息，Spring applicationcontext管理了所有的组件的生命周期，比如Inventoryservice、Productservice等组件。spring依赖注入也是通过上下文的实现的，在受托管的组件中，声明A组件依赖B组件，然后spring容器就会把依赖注入进去。

Spring应用上下文常用的接口

BeanFactory

DefaultListableBeanFactory

ApplicationContext的实现类：

ClassPathxmlApplicationContext

FileSystemXmlApplicationContext

AnnotationConfigApplicationContext

一般我们使用ApplicationContext接口及其实现，BeanFactory是最近本的应用上下文，springapplication context扩展了BeanFactory。开发过程中不建议直接使用BeanFactory。

web上下文层次：

当需要在Servlet中寻找某个Bean时,如果找不到，sping会到Root中去寻找。

通过Aop增强类方法的方式理解应用上下文

/*** 在方法结束打印信息*/
@Aspect
@Slf4j
public class FooAspect {@AfterReturning("bean(testBean*)")public void printAfter() {log.info("after hello()");}
}

/*** 打印信息，知道哪个上下文做了增强*/
@Data
@NoArgsConstructor
@AllArgsConstructor
@Slf4j
public class TestBean {private String context;public void hello() {log.info("hello " + context);}
}

/*** implements ApplicationRunner 重写run方法* @param args* @throws Exception*/@Overridepublic void run(ApplicationArguments args) throws Exception {//注解方式的上下文ApplicationContext fatherContext = new AnnotationConfigApplicationContext(FatherConfig.class);//声明fatherContext与childrenContext两个上下文是集成关系ClassPathXmlApplicationContext childrenContext = new ClassPathXmlApplicationContext(new String[] {"applicationContext.xml"}, fatherContext);TestBean bean = fatherContext.getBean("testBeanA", TestBean.class);bean.hello();log.info("=============");TestBean bean1 = childrenContext.getBean("testBeanA", TestBean.class);bean1.hello();TestBean bean2 = childrenContext.getBean("testBeanB", TestBean.class);bean2.hello();}

第一种情况：Father和children上下文中都对testBeanA做了AOP增强

@Configuration
@EnableAspectJAutoProxy
public class FatherConfig {/*** 声明AOPAspect* @return*/@Beanpublic FatherAspect fatherAspect() {return new FatherAspect();}@Beanpublic TestBean testBeanA() {return new TestBean("Father");}@Beanpublic TestBean testBeanB() {return new TestBean("Father");}
}

<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:aop="http://www.springframework.org/schema/aop"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/aophttp://www.springframework.org/schema/aop/spring-aop.xsd"><aop:aspectj-autoproxy/><bean id="testBeanA" class="com.springwork.high.context.TestBean"><constructor-arg name="context" value="children" /></bean><!--    <bean id="fatherAspect" class="com.springwork.high.context.FatherAspect" />-->
</beans>

结果：Father上下文中的了testBeanA、testBeanB都得到AOP增强，同时children可以得到Father上下文中testBeanA的增强方法

23:09:56.847 [main] INFO  com.springwork.high.HighApplication - Started HighApplication in 2.261 seconds (JVM running for 3.135)
23:09:56.919 [main] INFO  com.springwork.high.context.TestBean - hello Father
23:09:56.920 [main] INFO  com.springwork.high.context.FatherAspect - after hello()
23:09:56.920 [main] INFO  com.springwork.high.HighApplication - =============
23:09:56.920 [main] INFO  com.springwork.high.context.TestBean - hello children
23:09:56.920 [main] INFO  com.springwork.high.context.FatherAspect - after hello()
23:09:56.920 [main] INFO  com.springwork.high.context.TestBean - hello Father
23:09:56.920 [main] INFO  com.springwork.high.context.FatherAspect - after hello()
23:09:56.921 [main] INFO  com.springwork.high.HighApplication -

第二种情况：Father上下文中做了AOP增强，children上下文中没有AOP增强

/*** @author high* @version 1.0.0* @date 2023/3/26 21:45* @EnableAspectJAutoProxy 开启AspectJAutoProxy支持*/
@Configuration
@EnableAspectJAutoProxy
public class FatherConfig {/*** 声明AOPAspect* @return*/@Beanpublic FatherAspect fatherAspect() {return new FatherAspect();}@Beanpublic TestBean testBeanA() {return new TestBean("Father");}@Beanpublic TestBean testBeanB() {return new TestBean("Father");}
}

<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:aop="http://www.springframework.org/schema/aop"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/aophttp://www.springframework.org/schema/aop/spring-aop.xsd">
<!--    <aop:aspectj-autoproxy/>--><bean id="testBeanA" class="com.springwork.high.context.TestBean"><constructor-arg name="context" value="children" /></bean><!--    <bean id="fatherAspect" class="com.springwork.high.context.FatherAspect" />-->
</beans>

结果：代表children的testBeanA没有被增强，发现children可以得到Father上下文中testBeanB增强

22:55:05.895 [main] INFO  com.springwork.high.context.TestBean - hello Father
22:55:05.896 [main] INFO  com.springwork.high.context.FatherAspect - after hello()
22:55:05.896 [main] INFO  com.springwork.high.HighApplication - =============
22:55:05.896 [main] INFO  com.springwork.high.context.TestBean - hello children
22:55:05.896 [main] INFO  com.springwork.high.context.TestBean - hello Father
22:55:05.896 [main] INFO  com.springwork.high.context.FatherAspect - after hello()
22:55:05.897 [main] INFO  com.springwork.high.HighApplication -

第三种情况：Father上下文中没有AOP增强，children上下文中AOP增强了

@Configuration
@EnableAspectJAutoProxy
public class FatherConfig {/*** 声明AOPAspect* @return*/
//    @Bean
//    public FatherAspect fatherAspect() {
//        return new FatherAspect();
//    }@Beanpublic TestBean testBeanA() {return new TestBean("Father");}@Beanpublic TestBean testBeanB() {return new TestBean("Father");}
}

<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:aop="http://www.springframework.org/schema/aop"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/aophttp://www.springframework.org/schema/aop/spring-aop.xsd"><aop:aspectj-autoproxy/><bean id="testBeanA" class="com.springwork.high.context.TestBean"><constructor-arg name="context" value="children" /></bean><bean id="fatherAspect" class="com.springwork.high.context.FatherAspect" />
</beans>

结果：Father上下文中的没有testBeanA、testBeanB没有AOP增强，children上下文中testBeanA得到AOP增强了

23:02:16.950 [main] INFO  com.springwork.high.HighApplication - Started HighApplication in 2.175 seconds (JVM running for 3.014)
23:02:17.070 [main] INFO  com.springwork.high.context.TestBean - hello Father
23:02:17.070 [main] INFO  com.springwork.high.HighApplication - =============
23:02:17.075 [main] INFO  com.springwork.high.context.TestBean - hello children
23:02:17.076 [main] INFO  com.springwork.high.context.FatherAspect - after hello()
23:02:17.076 [main] INFO  com.springwork.high.context.TestBean - hello Father
23:02:17.077 [main] INFO  com.springwork.high.HighApplication -