Spring Bean后处理器详细介绍

   public static void main(String[] args) {
        // ⬇️GenericApplicationContext 是一个【干净】的容器  干净:没有额外的添加bean工厂处理器,bean处理器,消除一些干拢
        GenericApplicationContext context = new GenericApplicationContext();
        // ⬇️用原始方法注册三个 bean
        context.registerBean("bean1", Bean1.class);
        context.registerBean("bean2", Bean2.class);
        context.registerBean("bean3", Bean3.class);
        // ⬇️初始化容器
        context.refresh(); // 执行beanFactory后处理器, 添加bean后处理器, 初始化所有单例
        // ⬇️销毁容器
        context.close();
    }

public class Bean1 {
    private static final Logger log = LoggerFactory.getLogger(Bean1.class);
    private Bean2 bean2;
    @Autowired
    public void setBean2(Bean2 bean2) {
        log.debug("@Autowired 生效: {}", bean2);
        this.bean2 = bean2;
    }
    @Autowired
    private Bean3 bean3;
    @Resource
    public void setBean3(Bean3 bean3) {
        log.debug("@Resource 生效: {}", bean3);
        this.bean3 = bean3;
    }
    private String home;
    @Autowired
    public void setHome(@Value("${JAVA_HOME}") String home) {
        log.debug("@Value 生效: {}", home);
        this.home = home;
    }
    @PostConstruct
    public void init() {
        log.debug("@PostConstruct 生效");
    }
    @PreDestroy
    public void destroy() {
        log.debug("@PreDestroy 生效");
    }
    @Override
    public String toString() {
        return "Bean1{" +
               "bean2=" + bean2 +
               ", bean3=" + bean3 +
               ", home='" + home + '\'' +
               '}';
    }

//注册bean context.registerBean(AutowiredAnnotationBeanPostProcessor.class); //解析 @Autowired @Value注解 依赖注入阶段解析

  //默认解析器不能解析值注入
     //获取@Autowired的注入
        context.getDefaultListableBeanFactory().setAutowireCandidateResolver(new    ContextAnnotationAutowireCandidateResolver());

@value 生效：D:\tools\jdk1.8
@Autowired 生效：com.tangyuan.ao4.Bean2@59d016c9

  context.registerBean(CommonAnnotationBeanPostProcessor.class); // @Resource @PostConstruct @PreDestroy  依赖注入 初始化前 销毁前

/*
    java.home=
    java.version=
 */
@ConfigurationProperties(prefix = "java")
public class Bean4 {
    private String home;
    private String version;
    public String getHome() {
        return home;
    }
    public void setHome(String home) {
        this.home = home;
    }
    public String getVersion() {
        return version;
    }
    public void setVersion(String version) {
        this.version = version;
    }
    @Override
    public String toString() {
        return "Bean4{" +
               "home='" + home + '\'' +
               ", version='" + version + '\'' +
               '}';
    }
}

context.registerBean("bean4", Bean4.class);

ConfigurationPropertiesBindingPostProcessor.register(context.getDefaultListableBeanFactory()); 初始化前 @ConfigurationProperties 属性绑定

// AutowiredAnnotationBeanPostProcessor 运行分析
public class DigInAutowired {
    public static void main(String[] args) throws Throwable {
   //创建 beanFactory
        DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
    //注册两个单例
        beanFactory.registerSingleton("bean2", new Bean2()); // 缺点：认为bean是成熟的bean,bean工厂不会执行创建过程,依赖注入,初始化
        beanFactory.registerSingleton("bean3", new Bean3());
        beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver()); // @Value
        beanFactory.addEmbeddedValueResolver(new StandardEnvironment()::resolvePlaceholders); // ${} 的解析器
        // 1. 查找哪些属性、方法加了 @Autowired, 这称之为 InjectionMetadata
        //创建后处理器对象
        AutowiredAnnotationBeanPostProcessor processor = new AutowiredAnnotationBeanPostProcessor();
      //bean后处理器会间接用到beanFactory根据类型找bean
        processor.setBeanFactory(beanFactory);
         //实例化bean1
        Bean1 bean1 = new Bean1();
//        System.out.println(bean1);
//        processor.postProcessProperties(null, bean1, "bean1"); // 执行依赖注入 @Autowired @Value   参数：是否需要自动装配，被注入的目标，bean的名字
//        System.out.println(bean1);
//        Method findAutowiringMetadata = AutowiredAnnotationBeanPostProcessor.class.getDeclaredMethod("findAutowiringMetadata", String.class, Class.class, PropertyValues.class);
//        findAutowiringMetadata.setAccessible(true);
//        InjectionMetadata metadata = (InjectionMetadata) findAutowiringMetadata.invoke(processor, "bean1", Bean1.class, null);// 获取 Bean1 上加了 @Value @Autowired 的成员变量，方法参数信息
      后处理器的对象，bean的名字，类型，PropertyValue
//        System.out.println(metadata);
        // 2. 调用 InjectionMetadata 来进行依赖注入, 注入时按类型查找值
//        metadata.inject(bean1, "bean1", null);
//        System.out.println(bean1);
        // 3. 如何按类型查找值
       //获取bean3类中的加了@Autowired注解的成员变量
        Field bean3 = Bean1.class.getDeclaredField("bean3");
      //封装成对象 false---->可选的
        DependencyDescriptor dd1 = new DependencyDescriptor(bean3, false);
       //根据成员变量去找要注入哪里
        Object o = beanFactory.doResolveDependency(dd1, null, null, null);
        System.out.println(o);
      //获取bean3类中的加了@Autowired注解的方法
        Method setBean2 = Bean1.class.getDeclaredMethod("setBean2", Bean2.class);
        DependencyDescriptor dd2 =
                new DependencyDescriptor(new MethodParameter(setBean2, 0), true);
        Object o1 = beanFactory.doResolveDependency(dd2, null, null, null);
        System.out.println(o1);
       //获取bean3类中的加了@Autowired注解的参数的值注入方法
        Method setHome = Bean1.class.getDeclaredMethod("setHome", String.class);
        DependencyDescriptor dd3 = new DependencyDescriptor(new MethodParameter(setHome, 0), true);
        Object o2 = beanFactory.doResolveDependency(dd3, null, null, null);
        System.out.println(o2);
    }
         //Bean3
          @Autowired
          private Bean3 bean3;
          @Resource
          public void setBean3(Bean3 bean3) {
           log.debug("@Resource 生效: {}", bean3);
           this.bean3 = bean3;
         }
           private String home;
           @Autowired
           public void setHome(@Value("${JAVA_HOME}") String home) {
             log.debug("@Value 生效: {}", home);
             this.home = home;
         }
        @PostConstruct
          public void init() {
          log.debug("@PostConstruct 生效");
      }
        @PreDestroy
       public void destroy() {
          log.debug("@PreDestroy 生效");
      }