2.spring源码-BeanPostProcessor后置处理之ApplicationContextAwareProcessor，实现spring容器中某一个类的bean对象在初始化时需要得到Spring容器内容。

需求：我们的需求是，在spring初始化完毕时，使我们自定义一个类Bird类可以得到spring容器内容。

实现步骤：

1.首先我们来看一下ApplicationContextAwareProcessor这个类，它是BeanPostProcessor(后置处理器)的一个实现类。所以ApplicationContextAwareProcessor里面也必定有后置处理器接口的两个前置和后置方法。

我们来看一下ApplicationContextAwareProcessor的前置方法：由前面讲解的后置处理器(链接：https://www.cnblogs.com/WNof11020520/p/10598745.html)可知，所有bean对象初始化前都会执行BeanPostProcessor接口实现类的前置方法postProcessBeforeInitialization，所以所有bean对象初始化前都会执行ApplicationContextAwareProcessor的postProcessBeforeInitialization方法。

@Nullable
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        AccessControlContext acc = null;
        if(System.getSecurityManager() != null && (bean instanceof EnvironmentAware || 
                                                    bean instanceof EmbeddedValueResolverAware || 
                                                    bean instanceof ResourceLoaderAware || 
                                                    bean instanceof ApplicationEventPublisherAware || 
                                                    bean instanceof MessageSourceAware || 
                                                    bean instanceof ApplicationContextAware)) {
            acc = this.applicationContext.getBeanFactory().getAccessControlContext();
        }

        if(acc != null) {
            AccessController.doPrivileged(() -> {
                this.invokeAwareInterfaces(bean);
                return null;
            }, acc);
        } else {
            this.invokeAwareInterfaces(bean);
        }

        return bean;
    }

    private void invokeAwareInterfaces(Object bean) {
        if(bean instanceof Aware) {
            if(bean instanceof EnvironmentAware) {
                ((EnvironmentAware)bean).setEnvironment(this.applicationContext.getEnvironment());
            }

            if(bean instanceof EmbeddedValueResolverAware) {
                ((EmbeddedValueResolverAware)bean).setEmbeddedValueResolver(this.embeddedValueResolver);
            }

            if(bean instanceof ResourceLoaderAware) {
                ((ResourceLoaderAware)bean).setResourceLoader(this.applicationContext);
            }

            if(bean instanceof ApplicationEventPublisherAware) {
                ((ApplicationEventPublisherAware)bean).setApplicationEventPublisher(this.applicationContext);
            }

            if(bean instanceof MessageSourceAware) {
                ((MessageSourceAware)bean).setMessageSource(this.applicationContext);
            }

            if(bean instanceof ApplicationContextAware) {
                ((ApplicationContextAware)bean).setApplicationContext(this.applicationContext);
            }
        }

    }

2.看以上代码第9、15、19、48行可知，假若bean对象的类是ApplicationContextAware类型的话，就会调用invokeAwareInterfaces方法，然后执行第48行，将spring容器赋值给bean对象的applicationContext属性。

所以重要的实现思路来了：

　　a.Bird类实现ApplicationContextAware接口，并添加一个ApplicationContext类型的属性context，并实现ApplicationContextAware接口的方法：

@Component
public class Bird implements ApplicationContextAware {
    //得到管理它的Spring容器
    private ApplicationContext context;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.context = applicationContext;
    }

    @Override
    public String toString() {
        return "Bird [context=" + context + "]";
    }
}

　　b.写一个测试类，测试结果：

public class TestMain {

    public static void main(String[] args) {
        // 1.获得Spring容器对象
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ApplicationConfig.class);
        System.out.println("Spring容器 " + context);
        Bird bird = (Bird) context.getBean("bird");
        System.out.println(bird);
    }
}

　　c.查看测试输出的结果：输出结果显示，TestMain 类的main方法中new出来的context和Bird组件的bean对象的context属性地址相同，所以Bird的bean对象得到了spring容器内容。

"C:Program FilesJavajdk1.8.0_25injava" -agentlib:jdwp=transport=dt_socket,address=127.0.0.1:52099,suspend=y,server=n -Dfile.encoding=UTF-8 -classpath "C:Program FilesJavajdk1.8.0_25jrelibcharsets.jar;C:Program FilesJavajdk1.8.0_25jrelibdeploy.jar;C:Program FilesJavajdk1.8.0_25jrelibextaccess-bridge-64.jar;C:Program FilesJavajdk1.8.0_25jrelibextcldrdata.jar;C:Program FilesJavajdk1.8.0_25jrelibextdnsns.jar;C:Program FilesJavajdk1.8.0_25jrelibextjaccess.jar;C:Program FilesJavajdk1.8.0_25jrelibextjfxrt.jar;C:Program FilesJavajdk1.8.0_25jrelibextlocaledata.jar;C:Program FilesJavajdk1.8.0_25jrelibext
ashorn.jar;C:Program FilesJavajdk1.8.0_25jrelibextsunec.jar;C:Program FilesJavajdk1.8.0_25jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.8.0_25jrelibextsunmscapi.jar;C:Program FilesJavajdk1.8.0_25jrelibextsunpkcs11.jar;C:Program FilesJavajdk1.8.0_25jrelibextzipfs.jar;C:Program FilesJavajdk1.8.0_25jrelibjavaws.jar;C:Program FilesJavajdk1.8.0_25jrelibjce.jar;C:Program FilesJavajdk1.8.0_25jrelibjfr.jar;C:Program FilesJavajdk1.8.0_25jrelibjfxswt.jar;C:Program FilesJavajdk1.8.0_25jrelibjsse.jar;C:Program FilesJavajdk1.8.0_25jrelibmanagement-agent.jar;C:Program FilesJavajdk1.8.0_25jrelibplugin.jar;C:Program FilesJavajdk1.8.0_25jrelib
esources.jar;C:Program FilesJavajdk1.8.0_25jrelib
t.jar;D:kaikeba_java2018-11-28-spring-beanpostprocessor2-项目11_Spring_BeanPostProcessor的实现类介绍	arget	est-classes;D:kaikeba_java2018-11-28-spring-beanpostprocessor2-项目11_Spring_BeanPostProcessor的实现类介绍	argetclasses;D:caowenlongjavaDevelopToolapache-maven-3.5.3-bin
epoorgspringframeworkspring-context5.0.5.RELEASEspring-context-5.0.5.RELEASE.jar;D:caowenlongjavaDevelopToolapache-maven-3.5.3-bin
epoorgspringframeworkspring-aop5.0.5.RELEASEspring-aop-5.0.5.RELEASE.jar;D:caowenlongjavaDevelopToolapache-maven-3.5.3-bin
epoorgspringframeworkspring-beans5.0.5.RELEASEspring-beans-5.0.5.RELEASE.jar;D:caowenlongjavaDevelopToolapache-maven-3.5.3-bin
epoorgspringframeworkspring-core5.0.5.RELEASEspring-core-5.0.5.RELEASE.jar;D:caowenlongjavaDevelopToolapache-maven-3.5.3-bin
epoorgspringframeworkspring-jcl5.0.5.RELEASEspring-jcl-5.0.5.RELEASE.jar;D:caowenlongjavaDevelopToolapache-maven-3.5.3-bin
epoorgspringframeworkspring-expression5.0.5.RELEASEspring-expression-5.0.5.RELEASE.jar;D:caowenlongjavaDevelopToolIntelliJ IDEA 2016.2libidea_rt.jar" com.kkb.test.TestMain
Connected to the target VM, address: '127.0.0.1:52099', transport: 'socket'
三月 26, 2019 11:26:26 上午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@2ed94a8b: startup date [Tue Mar 26 11:26:26 CST 2019]; root of context hierarchy
Spring容器 org.springframework.context.annotation.AnnotationConfigApplicationContext@2ed94a8b: startup date [Tue Mar 26 11:26:26 CST 2019]; root of context hierarchy
Bird [context=org.springframework.context.annotation.AnnotationConfigApplicationContext@2ed94a8b: startup date [Tue Mar 26 11:26:26 CST 2019]; root of context hierarchy]
Disconnected from the target VM, address: '127.0.0.1:52099', transport: 'socket'

Process finished with exit code 0