filter过滤器注入bean实例时注入失败null

朴灿烈づ我的快乐病毒、 2022-05-23 01:40 426阅读 0赞

### 1、问题描述 ###

> `SpringBoot`中`filter注入bean`时注入失败，`bean`一直为空。

@Slf4j
    @Component
    public class RestAuthFilter extends FormAuthenticationFilter { 
    
        //实际注入为null
        @Autowired
        MobileDeviceService mobileDeviceService;
    
        @Autowired
        UserService userService;
    
        ...
    }

### 2、问题探究 ###

> 其实`Spring`中，web应用启动的顺序是：`listener->filter->servlet`，先初始化`listener`，然后再来就`filter`的初始化，再接着才到我们的`dispathServlet`的初始化，因此，当我们需要在`filter`里注入一个注解的`bean`时，就会注入失败，因为`filter`初始化时，注解的`bean`还没初始化，没法注入。

### 3、解决方法 ###

/** * 解决Filter中注入Bean失败 * Created by hoaven on 2018/5/30. */
    @Slf4j
    @Component
    public class SpringUtils implements ApplicationContextAware { 
    
        private static ApplicationContext applicationContext;
    
        @Override
        public void setApplicationContext(ApplicationContext applicationContext)
                throws BeansException {
            if (SpringUtils.applicationContext == null) {
                SpringUtils.applicationContext = applicationContext;
            }
    
        }
    
        public static ApplicationContext getApplicationContext() {
            return applicationContext;
        }
    
        //根据name
        public static Object getBean(String name) {
            return getApplicationContext().getBean(name);
        }
    
        //根据类型
        public static <T> T getBean(Class<T> clazz) {
            return getApplicationContext().getBean(clazz);
        }
    
        public static <T> T getBean(String name, Class<T> clazz) {
            return getApplicationContext().getBean(name, clazz);
        }
    
    }

**使用：**

if (mobileDeviceService == null) {
        mobileDeviceService = (MobileDeviceService) SpringUtils.getBean("mobileDeviceServiceImpl");
    }
    if (userService == null) {
        userService = (UserService) SpringUtils.getBean("userServiceImpl");
    }