Spring应用上下文

学习《极客时间、spring全家桶学习记录贴》

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
     */
    @Override
    public 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
     */
    @Bean
    public FatherAspect fatherAspect() {
        return new FatherAspect();
    }

    @Bean
    public TestBean testBeanA() {
        return new TestBean("Father");
    }

    @Bean
    public TestBean testBeanB() {
        return new TestBean("Father");
    }
}

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
     */
    @Bean
    public FatherAspect fatherAspect() {
        return new FatherAspect();
    }

    @Bean
    public TestBean testBeanA() {
        return new TestBean("Father");
    }

    @Bean
    public TestBean testBeanB() {
        return new TestBean("Father");
    }
}

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();
//    }

    @Bean
    public TestBean testBeanA() {
        return new TestBean("Father");
    }

    @Bean
    public TestBean testBeanB() {
        return new TestBean("Father");
    }
}

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 - 

总结：

Father上下文中方法得到AOP增强后，children上下文可以在Father上下文中获取到增强后的方法；

children上下文中方法得到AOP增强后，Father上下文不能够在children上下文获取到增强后的方法；