import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.security.Keys;

import java.security.Key;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

public class JwtUtil {

    private static final String SECRET = "12345678901234567890123456789012";
    private static final Key KEY = Keys.hmacShaKeyFor(SECRET.getBytes());
    private static final long EXPIRATION = 7200000; // 2小时
    private static final long REFRESH_BEFORE = 10 * 60 * 1000; // 剩余<10分钟就续期

    // 创建Token
    public static String createToken(String userId, String username) {
        Map<String, Object> map = new HashMap<>();
        map.put("userId", userId);
        map.put("username", username);
        return Jwts.builder()
                .setClaims(map)
                .setSubject(username)
                .setIssuedAt(new Date())
                .setExpiration(new Date(System.currentTimeMillis() + EXPIRATION))
                .signWith(KEY)
                .compact();
    }

    // 解析
    public static Claims getClaims(String token) {
        return Jwts.parserBuilder()
                .setSigningKey(KEY)
                .build()
                .parseClaimsJws(token)
                .getBody();
    }

    // ====================== 【自动续期核心方法】 ======================
    // 判断是否需要刷新
    public static boolean needRefresh(String token) {
        try {
            Claims claims = getClaims(token);
            long expire = claims.getExpiration().getTime();
            long now = System.currentTimeMillis();
            return (expire - now) < REFRESH_BEFORE;
        } catch (Exception e) {
            return false;
        }
    }

    // 刷新Token（用旧信息生成新Token）
    public static String refreshToken(String token) {
        Claims claims = getClaims(token);
        String userId = (String) claims.get("userId");
        String username = claims.getSubject();
        return createToken(userId, username);
    }

    // 获取用户ID
    public static String getUserId(String token) {
        return (String) getClaims(token).get("userId");
    }
}

import io.jsonwebtoken.ExpiredJwtException;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;

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

@Component
public class JwtRefreshInterceptor implements HandlerInterceptor {

    // 前端传过来的 header 名称
    private static final String TOKEN_HEADER = "Authorization";

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
        String token = request.getHeader(TOKEN_HEADER);

        // 没有token → 放行（登录接口等）
        if (token == null || token.isEmpty()) {
            return true;
        }

        try {
            // 1. 先验证token是否合法
            String userId = JwtUtil.getUserId(token);
            request.setAttribute("userId", userId);

            // 2. 判断是否需要续期（剩余<10分钟）
            if (JwtUtil.needRefresh(token)) {
                String newToken = JwtUtil.refreshToken(token);
                System.out.println("自动续期新Token：" + newToken);

                // 把新Token放回响应头，前端自动替换即可
                response.setHeader("Authorization", newToken);
                response.setHeader("Access-Control-Expose-Headers", "Authorization");
            }

            return true;

        } catch (ExpiredJwtException e) {
            response.setStatus(401);
            return false;
        } catch (Exception e) {
            response.setStatus(401);
            return false;
        }
    }
}

import org.springframework.beans.factory.annotation.Autowired;
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 WebConfig implements WebMvcConfigurer {

    @Autowired
    private JwtRefreshInterceptor jwtRefreshInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(jwtRefreshInterceptor)
                .addPathPatterns("/api/**")        // 你的接口前缀
                .excludePathPatterns("/api/login");// 登录接口不拦截
    }
}

js

// 请求拦截器 → 带上token
axios.interceptors.request.use(config => {
  config.headers.Authorization = localStorage.getItem('token')
  return config
})

// 响应拦截器 → 如果有新token，自动更新
axios.interceptors.response.use(res => {
  let newToken = res.headers.authorization
  if (newToken) {
    localStorage.setItem('token', newToken)
  }
  return res
})

1. Frontend calls /api/login → Retrieves token
2. Frontend places the token in the request header:Authorization: token
3. Interceptor automatically authenticates
4. Auto-renews when nearing expiration
5. Frontend automatically updates the local token

Same experience as Session, but completely stateless JWT!

• ✅ JWT generation / parsing
• ✅ Automatic renewal (sliding expiration, like Session)
• ✅ Login interface
• ✅ Authentication interceptor
• ✅ Compatible with jjwt 0.13.0
• ✅ Compatible with Spring 5.x
• ✅ Does not affect old project Session

SeparateNative JS, Axios, Mini ProgramsThree common scenarios, just copy the code, and also explain the corresponding rules with the backend.

Front-end note

I. Axios (most commonly used, Vue/React/regular front-end)

1. Global unified settings (Recommended, all requests automatically include token)

// 1. 先从本地存储取出登录后拿到的token
const token = localStorage.getItem('token');

// 2. 全局请求拦截器，自动附加请求头
axios.interceptors.request.use(function (config) {
    // 存在token就加到请求头
    if (token) {
        config.headers.Authorization = token;
    }
    return config;
}, function (error) {
    return Promise.reject(error);
});

// 3. 响应拦截器：接收后端续期返回的新token，自动更新本地
axios.interceptors.response.use(function (response) {
    const newToken = response.headers.authorization;
    if (newToken) {
        localStorage.setItem('token', newToken);
    }
    return response;
}, function (error) {
    // 401 未授权，跳转到登录页
    if (error.response && error.response.status === 401) {
        localStorage.removeItem('token');
        window.location.href = '/login';
    }
    return Promise.reject(error);
});

2. Individual request settings (Local use)

axios.post('/api/test', {}, {
    headers: {
        Authorization: localStorage.getItem('token')
    }
}).then(res => {
    console.log(res.data);
})

II. Native JavaScript (fetch / XMLHttpRequest)

1. fetch method

const token = localStorage.getItem('token');

fetch('/api/test', {
    method: 'GET',
    headers: {
        'Content-Type': 'application/json',
        'Authorization': token  // 放置token
    }
}).then(res => {
    // 接收续期新token
    const newToken = res.headers.get('authorization');
    if (newToken) {
        localStorage.setItem('token', newToken);
    }
    return res.json();
}).then(data => {
    console.log(data);
});

2. XMLHttpRequest method

const xhr = new XMLHttpRequest();
const token = localStorage.getItem('token');
xhr.open('GET', '/api/test', true);
// 设置请求头
xhr.setRequestHeader('Authorization', token);
xhr.setRequestHeader('Content-Type', 'application/json');

xhr.onload = function() {
    // 更新新token
    const newToken = xhr.getResponseHeader('authorization');
    if (newToken) {
        localStorage.setItem('token', newToken);
    }
    console.log(xhr.responseText);
};
xhr.send();

3. WeChat Mini Program

const token = wx.getStorageSync('token');

wx.request({
    url: 'https://xxx/api/test',
    header: {
        'Authorization': token, // 携带token
        'content-type': 'application/json'
    },
    success: (res) => {
        // 接收续期token
        const newToken = res.header.authorization;
        if (newToken) {
            wx.setStorageSync('token', newToken);
        }
        console.log(res.data);
    },
    fail: (err) => {
        console.log(err);
    }
})

Additional Key Points