1. 引入依赖

<dependency>
    <groupId>com.auth0</groupId>
    <artifactId>java-jwt</artifactId>
    <version>3.4.0</version>
 </dependency>

2. JWT工具类

public class JWTUtil {
    

    //签名
    private static final String SING = "#$er#$#%AFD(";
    //生成token
    public static String getToken(Map<String,Object> map) {
    
        Calendar instance = Calendar.getInstance();
        instance.add(Calendar.DATE,7);
        JWTCreator.Builder builder = JWT.create();
        map.forEach((k,v)->{
    
            builder.withClaim(k, v.toString());
        });
        builder.withExpiresAt(instance.getTime());
        String token = builder.sign(Algorithm.HMAC256(SING));
        return token;
    }
    //验证token合法性
    public static DecodedJWT verifyToken(String token) {
    
       return JWT.require(Algorithm.HMAC256(SING)).build().verify(token);//
    }
}

3. 拦截器拦截每一个请求，验证身份

前端发送请求，将token放进Header中，拦截器拦截请求后，获取token，并验证是否合格。

@Configuration
public class JWTInterceptor implements HandlerInterceptor {
    
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    
        Map<String,Object> map = new HashMap<>();
        //获取请求头中令牌
        String token = request.getHeader("token");
        try{
    
            JWTUtil.verifyToken(token);
            return true;
        }catch (SignatureVerificationException e) {
    
            e.printStackTrace();
            map.put("msg","无效签名");
        }catch(TokenExpiredException e){
    
            e.printStackTrace();
            map.put("msg","token过期");
        }catch (AlgorithmMismatchException e) {
    
            e.printStackTrace();
            map.put("msg","token算法不一致");
        }catch (InvalidClaimException e) {
    
            e.printStackTrace();
            map.put("msg","token无效");
        }
        map.put("token",false);
        String json = new ObjectMapper().writeValueAsString(map);
        response.setContentType("application/json;charset=UTF-8");
        response.getWriter().println(json);
        return false;
    }
}

/**
并在WebMvcConfigurer配置类中注册拦截器，添加拦截目标
*/
@Configuration
public class InterceptorConfig implements WebMvcConfigurer {
    
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
    
        registry.addInterceptor(new JWTInterceptor())
                .addPathPatterns("/**")
                .excludePathPatterns("/login");
    }
}

4. 生成token
   用户第一次登陆，如果账号密码验证成功，就会给其生成一个token，并将其返还给用户

 @GetMapping("/login")
    public Map<String,Object> login(String name,String password){
    

        Map<String,Object> map = new HashMap<>();
        try{
    
            User user = iLeaderService.login(name,password);
            Map<String,Object> payload = new HashMap<>();
            payload.put("id",user.getId());
            payload.put("name",user.getname());
            payload.put("password",user.getPassword());
            String token = JWTUtil.getToken(payload);

            map.put("state",true);
            map.put("msg","登陆成功成功");
            map.put("token",token);

        }catch (Exception e) {
    
            map.put("state",false);
            map.put("msg",e.getMessage());
        }
       return map;
    }

5. 获取token存储信息

    public void test(HttpServletRequest request) {
    
        String token = request.getHeader("token");
        JWTVerifier jwtVerifier = JWT.require(Algorithm.HMAC256("#$er#$#%AFD(")).build();
        DecodedJWT verify = jwtVerifier.verify(token);
        
        Integer id = verify.getClaim("userId").asInt();
        String username = verify.getClaim("userName").asString();
    }