Aware 接口及 InitializingBean 接口

Aware接口作用

Aware 接口用于注入一些与容器相关信息

BeanNameAware 注入 bean 的名字

BeanFactoryAware 注入 BeanFactory 容器

ApplicationContextAware 注入 ApplicationContext 容器

EmbeddedValueResolverAware ${}

案例


public class MyBean implements BeanNameAware, ApplicationContextAware, InitializingBean {

    private static final Logger log = LoggerFactory.getLogger(MyBean.class);

    @Override
    public void setBeanName(String name) {
        log.debug("当前bean " + this + " 名字叫:" + name);
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        log.debug("当前bean " + this + " 容器是:" + applicationContext);
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        log.debug("当前bean " + this + " 初始化");
    }

    @Autowired
    public void aaa(ApplicationContext applicationContext) {
        log.debug("当前bean " + this + " 使用@Autowired 容器是:" + applicationContext);
    }

    @PostConstruct
    public void init() {
        log.debug("当前bean " + this + " 使用@PostConstruct 初始化");
    }
}

注册MyBean


public class A06 {
    private static final Logger log = LoggerFactory.getLogger(A06.class);

    public static void main(String[] args) {
        /*
            1. Aware 接口用于注入一些与容器相关信息, 例如
                a. BeanNameAware 注入 bean 的名字
                b. BeanFactoryAware 注入 BeanFactory 容器
                c. ApplicationContextAware 注入 ApplicationContext 容器
                d. EmbeddedValueResolverAware ${}

         */
        GenericApplicationContext context = new GenericApplicationContext();
        context.registerBean("myBean", MyBean.class);
        context.registerBean(AutowiredAnnotationBeanPostProcessor.class);
        context.registerBean(CommonAnnotationBeanPostProcessor.class);
        context.registerBean(ConfigurationClassPostProcessor.class);

        
        context.refresh(); // 1. beanFactory 后处理器,  2. 添加 bean 后处理器, 3. 初始化单例
        context.close();

       
    }
}


[INFO ] 10:03:41.050 [main] o.s.c.a.ConfigurationClassEnhancer  - @Bean method MyConfig1.processor1 is non-static and returns an object assignable to Spring's BeanFactoryPostProcessor interface. This will result in a failure to process annotations such as @Autowired, @Resource and @PostConstruct within the method's declaring @Configuration class. Add the 'static' modifier to this method to avoid these container lifecycle issues; see @Bean javadoc for complete details. 
[DEBUG] 10:03:41.062 [main] com.onethink.a06.MyConfig1          - 执行 processor1 
[DEBUG] 10:03:41.099 [main] com.onethink.a06.MyBean             - 当前bean com.onethink.a06.MyBean@23f5b5dc 使用@Autowired 容器是:org.springframework.context.support.GenericApplicationContext@de3a06f, started on Sun Apr 02 10:03:40 CST 2023 
[DEBUG] 10:03:41.099 [main] com.onethink.a06.MyBean             - 当前bean com.onethink.a06.MyBean@23f5b5dc 名字叫:myBean 
[DEBUG] 10:03:41.099 [main] com.onethink.a06.MyBean             - 当前bean com.onethink.a06.MyBean@23f5b5dc 容器是:org.springframework.context.support.GenericApplicationContext@de3a06f, started on Sun Apr 02 10:03:40 CST 2023 
[DEBUG] 10:03:41.101 [main] com.onethink.a06.MyBean             - 当前bean com.onethink.a06.MyBean@23f5b5dc 使用@PostConstruct 初始化 
[DEBUG] 10:03:41.101 [main] com.onethink.a06.MyBean             - 当前bean com.onethink.a06.MyBean@23f5b5dc 初始化

和@Autowired 的区别

@Autowired 的解析需要用到 bean 后处理器, 属于扩展功能

而 Aware 接口属于内置功能, 不加任何扩展, Spring 就能识别某些情况下, 扩展功能会失效, 而内置功能不会失效

`@Autowired` 注入失效

例1: Aware 注入 ApplicationContext 成功, 而 @Autowired 注入 ApplicationContext 失败



@Configuration
public class MyConfig1 {

    private static final Logger log = LoggerFactory.getLogger(MyConfig1.class);

    @Autowired
    public void setApplicationContext(ApplicationContext applicationContext) {
        log.debug("注入 ApplicationContext");
    }

    @PostConstruct
    public void init() {
        log.debug("初始化");
    }


}

在配置类里初始化一个BeanFactoryPostProcessor对象


@Configuration
public class MyConfig1 {

    private static final Logger log = LoggerFactory.getLogger(MyConfig1.class);

    @Autowired
    public void setApplicationContext(ApplicationContext applicationContext) {
        log.debug("注入 ApplicationContext");
    }

    @PostConstruct
    public void init() {
        log.debug("初始化");
    }

    @Bean //  beanFactory 后处理器
    public BeanFactoryPostProcessor processor1() {
        return beanFactory -> {
            log.debug("执行 processor1");
        };
    }

}

配置类 `@Autowired` 失效分析

context.refresh()的作用

beanFactory 后处理器

添加 bean 后处理器

初始化单例

Java 配置类不包含 BeanFactoryPostProcessor 的情况


sequenceDiagram 
participant ac as ApplicationContext
participant bfpp as BeanFactoryPostProcessor
participant bpp as BeanPostProcessor
participant config as Java配置类
ac ->> bfpp : 1. 执行 BeanFactoryPostProcessor
ac ->> bpp : 2. 注册 BeanPostProcessor
ac ->> +config : 3. 创建和初始化
bpp ->> config : 3.1 依赖注入扩展(如 @Value 和 @Autowired)
bpp ->> config : 3.2 初始化扩展(如 @PostConstruct)
ac ->> config : 3.3 执行 Aware 及 InitializingBean
config -->> -ac : 3.4 创建成功

Java 配置类包含 BeanFactoryPostProcessor 的情况，

要创建其中的 BeanFactoryPostProcessor 必须提前创建 Java 配置类，而此时的 BeanPostProcessor 还未准备好，导致 @Autowired 等注解失效


sequenceDiagram 
participant ac as ApplicationContext
participant bfpp as BeanFactoryPostProcessor
participant bpp as BeanPostProcessor
participant config as Java配置类
ac ->> +config : 3. 创建和初始化
ac ->> config : 3.1 执行 Aware 及 InitializingBean
config -->> -ac : 3.2 创建成功

ac ->> bfpp : 1. 执行 BeanFactoryPostProcessor
ac ->> bpp : 2. 注册 BeanPostProcessor

解决方法：

用内置依赖注入和初始化取代扩展依赖注入和初始化

用静态工厂方法代替实例工厂方法，避免工厂对象提前被创建


@Configuration
public class MyConfig2 implements InitializingBean, ApplicationContextAware {

    private static final Logger log = LoggerFactory.getLogger(MyConfig2.class);

    @Override
    public void afterPropertiesSet() throws Exception {
        log.debug("初始化");
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        log.debug("注入 ApplicationContext");
    }

    @Bean //  beanFactory 后处理器
    public BeanFactoryPostProcessor processor2() {
        return beanFactory -> {
            log.debug("执行 processor2");
        };
    }
}


public class A06 {
    private static final Logger log = LoggerFactory.getLogger(A06.class);

    public static void main(String[] args) {
        /*
            1. Aware 接口用于注入一些与容器相关信息, 例如
                a. BeanNameAware 注入 bean 的名字
                b. BeanFactoryAware 注入 BeanFactory 容器
                c. ApplicationContextAware 注入 ApplicationContext 容器
                d. EmbeddedValueResolverAware ${}

         */
        GenericApplicationContext context = new GenericApplicationContext();

//        context.registerBean("myConfig1", MyConfig1.class);
        context.registerBean("myConfig2", MyConfig2.class);
        context.registerBean(AutowiredAnnotationBeanPostProcessor.class);
        context.registerBean(CommonAnnotationBeanPostProcessor.class);
        context.registerBean(ConfigurationClassPostProcessor.class);

       
        context.refresh(); // 1. beanFactory 后处理器,  2. 添加 bean 后处理器, 3. 初始化单例
        context.close();

         
			}
}

Aware 接口及 InitializingBean 接口

Aware接口作用

和@Autowired 的区别

@Autowired 注入失效

配置类 @Autowired 失效分析

`Aware 接口及 InitializingBean 接口`

`@Autowired` 注入失效

配置类 `@Autowired` 失效分析