Recording problems in the spring boot interceptor null pointer @Autowired

Their own learning project encountered this problem, recorded
reference to the teacher's blog https://www.cnblogs.com/weknow619/p/8549566.html

The reason is because the interceptor null load is completed before springcontext created, so inject entities interceptor naturally is null

Error wording

@Autowired return a null pointer
interceptor

package com.jsong.wiki.backend.interceptor;

import com.jsong.wiki.backend.bean.CookieProperties;
import lombok.extern.log4j.Log4j2;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;

import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@Component
@Log4j2
public class CommonInterceptor implements HandlerInterceptor {

    // interceptor 里的注入为空指针，因为拦截器实在springcontext创建之前的
    @Autowired
    private CookieProperties cookieProperties;
    /**
     * 跨域拦截器
     *
     * @param request
     * @param response
     * @param handler
     * @return boolean
     * @date 2020/2/27 21:56
     * @author Jsong
     */
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
        log.info("拦截器");
        response.setHeader("Access-Control-Allow-Origin", "null");
//        Cookie cookie = new Cookie("front-url", request.getHeader("front-url"));
//        response.addCookie(cookie);
        Cookie[] cookies = request.getCookies();
        for (int i = 0; i < cookies.length; i++) {
            cookies[i].setPath(cookieProperties.getPath());
            cookies[i].setDomain(cookieProperties.getDomain());
            response.addCookie(cookies[i]);
        }
//        response.setHeader("Access-Control-Allow-Origin", "http://localhost:28080");
        if (request.getMethod().equals("OPTIONS")) {
            response.addHeader("Access-Control-Allow-Methods", "GET,HEAD,POST,PUT,DELETE,TRACE,OPTIONS,PATCH");
            response.addHeader("Access-Control-Allow-Headers", "Content-Type,Accept,Authorization");
        }
        return true;
    }
}

Configuration

package com.jsong.wiki.backend.config;

import com.jsong.wiki.backend.interceptor.CommonInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

    /**
     * 配置跨域拦截器
     * @param registry
     */
    @Override
    public void addInterceptors(InterceptorRegistry registry){
        CommonInterceptor commonInterceptor = new CommonInterceptor();
        registry.addInterceptor(commonInterceptor).addPathPatterns("/**");
    }
}

Resolved

Solutions using @Bean the interceptor to sprting container
interceptor

package com.jsong.wiki.backend.interceptor;

import com.jsong.wiki.backend.bean.CookieProperties;
import lombok.extern.log4j.Log4j2;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.servlet.HandlerInterceptor;

import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

//@Component
@Log4j2
public class CommonInterceptor implements HandlerInterceptor {

    // interceptor 里的注入为空指针，因为拦截器实在springcontext创建之前的
    @Autowired
    private CookieProperties cookieProperties;
    /**
     * 跨域拦截器
     *
     * @param request
     * @param response
     * @param handler
     * @return boolean
     * @date 2020/2/27 21:56
     * @author Jsong
     */
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
        log.info("拦截器");
        response.setHeader("Access-Control-Allow-Origin", "null");
//        Cookie cookie = new Cookie("front-url", request.getHeader("front-url"));
//        response.addCookie(cookie);
        Cookie[] cookies = request.getCookies();
        for (int i = 0; i < cookies.length; i++) {
            cookies[i].setPath(cookieProperties.getPath());
            cookies[i].setDomain(cookieProperties.getDomain());
            response.addCookie(cookies[i]);
        }
//        response.setHeader("Access-Control-Allow-Origin", "http://localhost:28080");
        if (request.getMethod().equals("OPTIONS")) {
            response.addHeader("Access-Control-Allow-Methods", "GET,HEAD,POST,PUT,DELETE,TRACE,OPTIONS,PATCH");
            response.addHeader("Access-Control-Allow-Headers", "Content-Type,Accept,Authorization");
        }
        return true;
    }
}

Configuration

package com.jsong.wiki.backend.config;

import com.jsong.wiki.backend.interceptor.CommonInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

    /***
     * 不注入bean 在commoninterceptor中
     * @Autowired为null
     * @date 2020/3/3 20:20
     * @author Jsong
     * @param
     * @return com.jsong.wiki.backend.interceptor.CommonInterceptor
     */
    @Bean
    public CommonInterceptor  commonInterceptor(){
        return new CommonInterceptor();
    }

    /**
     * 配置跨域拦截器
     * @param registry
     */
    @Override
    public void addInterceptors(InterceptorRegistry registry){
//        CommonInterceptor commonInterceptor = new CommonInterceptor();
//        registry.addInterceptor(commonInterceptor).addPathPatterns("/**");

        registry.addInterceptor(commonInterceptor()).addPathPatterns("/**");
    }
}