springboot拦截器无法注入redisTemplate

青旅半醒 2021-10-15 13:33 513阅读 0赞

在工作中我们经常需要做登录拦截验证或者其他拦截认证功能，基于springboot项目下我们很容易想到结合redis做的分布式拦截，把用户登录或者需要验证的信息放到redis里面。但是在写拦截器的时候发现redisTemplate一直无法注入进来，最后查资料才发现springboot拦截器是在Bean实例化之前执行的，所以Bean实例无法注入。

先看下问题，新建一个拦截器，然后注入redisTemplate

/**
     * @author: lockie
     * @Date: 2019/8/13 16:16
     * @Description: 接口限流拦截器
     */
    @Component
    public class AccessLimitIntercept implements HandlerInterceptor {
        private static final Logger logger = LoggerFactory.getLogger(AccessLimitIntercept.class);
    
        @Autowired
        private StringRedisTemplate redisTemplate;
    
        /**
         * 接口调用前检查对方ip是否频繁调用接口
         * @param request
         * @param response
         * @param handler
         * @return
         * @throws Exception
         */
        @Override
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
            try {
    
                String test = redisTemplate.opsForValue().get("test");
                logger.info(test);
            } catch (Exception e) {
                logger.error("API请求限流拦截异常，异常原因：", e);
                throw new ParameterException(e);
            }
            return true;
        }
    
        @Override
        public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    
        }
    
        @Override
        public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    
        }
    
        private boolean setResponse(Results results, HttpServletResponse response) throws IOException {
            ServletOutputStream outputStream = null;
            try {
                response.setHeader("Content-type", "application/json; charset=utf-8");
                outputStream = response.getOutputStream();
                outputStream.write(JsonUtil.toJson(results).getBytes("UTF-8"));
            } catch (Exception e) {
                logger.error("setResponse方法报错", e);
                return false;
            } finally {
                if (outputStream != null) {
                    outputStream.flush();
                    outputStream.close();
                }
            }
            return true;
        }
    }

然后配置拦截器，新建一个拦截器config类，我们这里让所有的url都拦截

@Configuration
    public class WebFilterConfig implements WebMvcConfigurer {
    
    	/**
    	 * 多个拦截器组成一个拦截器链
    	 * @param registry
    	 */
    	@Override
    	public void addInterceptors(InterceptorRegistry registry) {
    		registry.addInterceptor(new AccessLimitIntercept()).addPathPatterns("/**");
    	}
    
    }

新建一个controller里面增加一个接口，使用postman调用接口

@RestController
    @RequestMapping("/")
    public class PingController extends BaseController {
    
    	@GetMapping(value = "/ping")
    	public Results ping() {
    		return succeed("pong", "");
    	}
    
    }

使用postman调用/ping接口，发现返回系统错误

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p4bDY0NjgwMTkyNA_size_16_color_FFFFFF_t_70][]

控制台发现是空指针的错误，定位错误发现当我们想获取redis里面key是test的值时，发现redisTemplate没有是空的没有注入进来

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p4bDY0NjgwMTkyNA_size_16_color_FFFFFF_t_70 1][]

解决问题：

知道拦截器执行在bean实例化前执行的，那么我们就让拦截器执行的时候实例化拦截器Bean，在拦截器配置类里面先实例化拦截器，然后再获取

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p4bDY0NjgwMTkyNA_size_16_color_FFFFFF_t_70 2][]

@Configuration
    public class WebFilterConfig implements WebMvcConfigurer {
    
    	/**
    	 * 这里需要先将限流拦截器入住，不然无法获取到拦截器中的redistemplate
    	 * @return
    	 */
    	@Bean
    	public AccessLimitIntercept getAccessLimitIntercept() {
    		return new AccessLimitIntercept();
    	}
    
    	/**
    	 * 多个拦截器组成一个拦截器链
    	 * @param registry
    	 */
    	@Override
    	public void addInterceptors(InterceptorRegistry registry) {
    		registry.addInterceptor(getAccessLimitIntercept()).addPathPatterns("/**");
    	}
    
    
    }

使用postman再次请求就可以访问到

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p4bDY0NjgwMTkyNA_size_16_color_FFFFFF_t_70 3][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p4bDY0NjgwMTkyNA_size_16_color_FFFFFF_t_70]: /images/20211015/2c01e8649f4445109ca55111e2adfeca.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p4bDY0NjgwMTkyNA_size_16_color_FFFFFF_t_70 1]: /images/20211015/11762bdf947046cb9a8387bc46cc2b5a.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p4bDY0NjgwMTkyNA_size_16_color_FFFFFF_t_70 2]: /images/20211015/7af1d043a8e84b78bbb8b336366cd045.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p4bDY0NjgwMTkyNA_size_16_color_FFFFFF_t_70 3]: /images/20211015/8b7a2ca66b474cb8b54e41795cc65526.png