原文网址：Spring(SpringBoot)--解决拦截器中注入Bean失败的问题_IT利刃出鞘的博客-CSDN博客

简介

说明

        本文用示例介绍如何解决拦截器中注入Bean失败的问题。

场景

        Token拦截器中需要用@Autowired注入JavaJwtUtil类，结果发现注入的JavaJwtUtil为Null。

原因

        拦截器的配置类是以new JwtInterceptor的方式使用的，那么这个JwtInterceptor不受Spring管理。因此，里边@Autowired注入JavaJwtUtil是不会注入进去的。

问题重现

代码

application.yml

server:
  port: 8080
spring:
  application:
    name: springboot-jwt
config:
  jwt:
    # 密钥
    secret: abcd1234
    # token过期时间（5分钟）。单位：毫秒.
    expire: 300000

拦截器配置

@Configuration
public class InterceptorConfig implements WebMvcConfigurer {
 
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new JwtInterceptor());
    }
}

拦截器

package com.example.demo.interceptor;
 
import com.example.demo.util.JavaJwtUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
 
import javax.annotation.PostConstruct;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Arrays;
import java.util.List;
 
@Slf4j
@Component
public class JwtInterceptor implements HandlerInterceptor {
    @Autowired
    JavaJwtUtil javaJwtUtil;
 
    List<String> whiteList = Arrays.asList(
            "/auth/login",
            "/error"
    );
 
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response,
                             Object handler) throws Exception {
        // 如果不是映射到方法直接通过
        if (!(handler instanceof HandlerMethod)) {
            return true;
        }
 
 
        //放过不需要验证的页面。
        String uri = request.getRequestURI();
        if (whiteList.contains(uri)) {
            return true;
        }
 
        // 头部和参数都查看一下是否有token
        String token = request.getHeader("token");
        if (StringUtils.isEmpty(token)) {
            token = request.getParameter("token");
            if (StringUtils.isEmpty(token)) {
                throw new RuntimeException("token是空的");
            }
        }
 
        if (!javaJwtUtil.verifyToken(token)) {
            log.error("token无效");
            return false;
        }
 
        String userId = javaJwtUtil.getUserIdByToken(token);
        log.info("userId:" + userId);
        String userName = javaJwtUtil.getUserNameByToken(token);
        log.info("userName:" + userName);
        return true;
    }
}

Jwt工具类

package com.example.demo.util;
 
import com.auth0.jwt.JWT;
import com.auth0.jwt.JWTVerifier;
import com.auth0.jwt.algorithms.Algorithm;
import com.auth0.jwt.exceptions.JWTDecodeException;
import com.auth0.jwt.exceptions.JWTVerificationException;
import com.auth0.jwt.interfaces.DecodedJWT;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
 
import java.util.Date;
 
@Component
public class JavaJwtUtil {
    //过期时间
    @Value("${config.jwt.expire}")
    private Long EXPIRE_TIME;
 
    //密钥
    @Value("${config.jwt.secret}")
    private String SECRET;
 
    // 生成Token，五分钟后过期
    public String createToken(String userId) {
        try {
            Date date = new Date(System.currentTimeMillis() + EXPIRE_TIME);
            Algorithm algorithm = Algorithm.HMAC256(SECRET);
            return JWT.create()
                    // 将 user id 保存到 token 里面
                    .withAudience(userId)
                    // date之后，token过期
                    .withExpiresAt(date)
                    // token 的密钥
                    .sign(algorithm);
        } catch (Exception e) {
            return null;
        }
    }
 
    // 根据token获取userId
    public String getUserIdByToken(String token) {
        try {
            String userId = JWT.decode(token).getAudience().get(0);
            return userId;
        } catch (JWTDecodeException e) {
            return null;
        }
    }
 
    // 根据token获取userName
    public String getUserNameByToken(String token) {
        try {
            String userName = JWT.decode(token).getSubject();
            return userName;
        } catch (JWTDecodeException e) {
            return null;
        }
    }
 
    //校验token
    public boolean verifyToken(String token) {
        try {
            Algorithm algorithm = Algorithm.HMAC256(SECRET);
            JWTVerifier verifier = JWT.require(algorithm)
                    // .withIssuer("auth0")
                    // .withClaim("username", username)
                    .build();
            DecodedJWT jwt = verifier.verify(token);
            return true;
        } catch (JWTVerificationException exception) {
//            throw new RuntimeException("token 无效，请重新获取");
            return false;
        }
    }
}

 Controller

package com.example.demo.controller;
 
import com.example.demo.util.JavaJwtUtil;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
 
@RestController
@RequestMapping("/auth")
public class AuthController {
    @Autowired
    JavaJwtUtil javaJwtUtil;
 
    @RequestMapping("/login")
    public String login() {
        // 验证userName，password和数据库中是否一致，如不一致，直接返回失败
        // 通过userName，password从数据库中获取userId
 
        String userId = 5 + "";
        String token = javaJwtUtil.createToken(userId);
        System.out.println("token:" + token);
        return token;
    }
 
    //需要token验证
    @RequestMapping("/info")
    public String info() {
        return  "验证通过";
    }
}

测试

访问：http://localhost:8080/auth/login 

前端结果：一串token字符串

访问：http://localhost:8080/auth/info(以token作为header或者参数）

后端结果

java.lang.NullPointerException: null
	at com.example.demo.interceptor.JwtInterceptor.preHandle(JwtInterceptor.java:55) ~[main/:na]

解决方案

方案简述

配置类中将new JwtInterceptor()改为Bean的方式

配置类

package com.example.demo.interceptor;
 
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 InterceptorConfig implements WebMvcConfigurer {
 
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(getJwtInterceptor());
    }
 
    @Bean
    JwtInterceptor getJwtInterceptor() {
        return new JwtInterceptor();
    }
}

拦截器（此时无需@Component）

package com.example.demo.interceptor;
 
import com.example.demo.util.JavaJwtUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.util.StringUtils;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
 
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Arrays;
import java.util.List;
 
@Slf4j
public class JwtInterceptor implements HandlerInterceptor {
    @Autowired
    JavaJwtUtil javaJwtUtil;
 
    List<String> whiteList = Arrays.asList(
            "/auth/login",
            "/error"
    );
 
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response,
                             Object handler) throws Exception {
        // 如果不是映射到方法直接通过
        if (!(handler instanceof HandlerMethod)) {
            return true;
        }
 
 
        //放过不需要验证的页面。
        String uri = request.getRequestURI();
        if (whiteList.contains(uri)) {
            return true;
        }
 
        // 头部和参数都查看一下是否有token
        String token = request.getHeader("token");
        if (StringUtils.isEmpty(token)) {
            token = request.getParameter("token");
            if (StringUtils.isEmpty(token)) {
                throw new RuntimeException("token是空的");
            }
        }
 
        if (!javaJwtUtil.verifyToken(token)) {
            log.error("token无效");
            return false;
        }
 
        String userId = javaJwtUtil.getUserIdByToken(token);
        log.info("userId:" + userId);
        String userName = javaJwtUtil.getUserNameByToken(token);
        log.info("userName:" + userName);
        return true;
    }
}