JWT 鉴权 应用

package com.example.demo.common;

import io.jsonwebtoken.security.Keys;
import javax.crypto.SecretKey;

public class JwtUtil {
    private static final SecretKey SECRET_KEY = Keys.secretKeyFor(io.jsonwebtoken.SignatureAlgorithm.HS256);

    public static SecretKey getSecretKey() {
        return SECRET_KEY;
    }
}

package com.example.demo.common;

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.HandlerInterceptor;

import javax.crypto.SecretKey;

public class JwtInterceptor implements HandlerInterceptor {

    private static final SecretKey SECRET_KEY = JwtUtil.getSecretKey(); // 使用公共工具类获取密钥

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        // 允许 CORS 预检请求
        if ("OPTIONS".equalsIgnoreCase(request.getMethod())) {
            return true;
        }

        String authHeader = request.getHeader("Authorization");
        if (authHeader != null && authHeader.startsWith("Bearer ")) {
            String token = authHeader.substring(7);
            try {
                Claims claims = Jwts.parserBuilder()
                        .setSigningKey(SECRET_KEY)
                        .build()
                        .parseClaimsJws(token)
                        .getBody();
                return true;
            } catch (Exception e) {
                e.printStackTrace();  // 打印错误信息
                response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
                return false;
            }
        }
        response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
        return false;
    }
}

package com.example.demo.service;

import com.example.demo.common.JwtUtil;
import com.example.demo.entity.User;
import com.example.demo.mapper.UserMapper;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import javax.crypto.SecretKey;
import java.util.Date;
import java.util.List;

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserMapper userMapper;

    private static final SecretKey SECRET_KEY = JwtUtil.getSecretKey(); // 使用公共工具类获取密钥

    @Override
    public void insertUser(User user) {
        userMapper.insertUser(user);
    }

    @Override
    public User getUserById(Integer id) {
        return userMapper.getUserById(id);
    }

    @Override
    public void updateUser(User user) {
        userMapper.updateUser(user);
    }

    @Override
    public void deleteUser(Integer id) {
        userMapper.deleteUser(id);
    }

    @Override
    public List<User> getAllUsers() {
        return userMapper.getAllUsers();
    }

    @Override
    public List<User> getUsersByPage(int pageNumber, int pageSize) {
        int offset = (pageNumber - 1) * pageSize;
        return userMapper.getUsersByPage(offset, pageSize);
    }

    @Override
    public long getTotalUsers() {
        return userMapper.getTotalUsers();
    }

    @Override
    public User login(String username, String password) {
        User user = userMapper.getUserByUsername(username);
        if (user != null && user.getPassword().equals(password)) {
            return user;
        }
        return null;
    }

    @Override
    public void register(User user) {
        // 检查用户名是否已经存在
        User existingUser = userMapper.getUserByUsername(user.getUsername());
        if (existingUser != null) {
            throw new RuntimeException("用户名已存在");
        }
        userMapper.insertUser(user);
    }

    @Override
    public String generateJwtToken(User user) {
        return Jwts.builder()
                .setSubject(user.getId().toString())
                .setIssuedAt(new Date())
                .setExpiration(new Date(System.currentTimeMillis() + 86400000))
                .signWith(SECRET_KEY, SignatureAlgorithm.HS256) // 推荐使用此方式
                .compact();
    }
}