content: package com.java2nb.novel.core.utils;
  
  import com.fasterxml.jackson.databind.ObjectMapper;
  import com.java2nb.novel.core.bean.UserDetails;
  import io.jsonwebtoken.Claims;
  import io.jsonwebtoken.Jwts;
  import io.jsonwebtoken.SignatureAlgorithm;
  import lombok.SneakyThrows;
  import lombok.extern.slf4j.Slf4j;
  import org.springframework.beans.factory.annotation.Value;
  import org.springframework.stereotype.Component;
  
  import java.util.Date;
  import java.util.HashMap;
  import java.util.Map;
  
  /**
   * @author 11797
   */
  @Component
  @Slf4j
  public class JwtTokenUtil {
  
      private static final String CLAIM_KEY_USERNAME = "sub";
      private static final String CLAIM_KEY_CREATED = "created";
      @Value("${jwt.secret}")
      private String secret;
      @Value("${jwt.expiration}")
      private Long expiration;
  
      /**
       * 根据负责生成JWT的token
       */
      private String generateToken(Map<String, Object> claims) {
          return Jwts.builder()
                  .setClaims(claims)
                  .setExpiration(generateExpirationDate())
                  .signWith(SignatureAlgorithm.HS512, secret)
                  .compact();
      }
  
      /**
       * 从token中获取JWT中的负载
       */
      private Claims getClaimsFromToken(String token) {
          Claims claims = null;
          try {
              claims = Jwts.parser()
                      .setSigningKey(secret)
                      .parseClaimsJws(token)
                      .getBody();
          } catch (Exception e) {
              log.info("JWT格式验证失败:{}",token);
          }
          return claims;
      }
  
      /**
       * 生成token的过期时间
       */
      private Date generateExpirationDate() {
          return new Date(System.currentTimeMillis() + expiration * 1000);
      }
  
      /**
       * 从token中获取用户信息
       */
      public UserDetails getUserDetailsFromToken(String token) {
          if(isTokenExpired(token)){
              return null;
          }
          UserDetails userDetail;
          try {
              Claims claims = getClaimsFromToken(token);
               userDetail = new ObjectMapper().readValue(claims.getSubject(),UserDetails.class);
          } catch (Exception e) {
              log.error(e.getMessage(),e);
              userDetail = null;
          }
          return userDetail;
      }
  
  
      /**
       * 判断token是否已经失效
       */
      private boolean isTokenExpired(String token) {
          Date expiredDate = getExpiredDateFromToken(token);
          if(expiredDate == null){
              return true;
          }else {
              return expiredDate.before(new Date());
          }
      }
  
      /**
       * 从token中获取过期时间
       */
      private Date getExpiredDateFromToken(String token) {
          Claims claims = getClaimsFromToken(token);
          return claims != null ? claims.getExpiration() : null;
      }
  
      /**
       * 根据用户信息生成token
       */
      @SneakyThrows
      public String generateToken(UserDetails userDetails) {
          Map<String, Object> claims = new HashMap<>(2);
          claims.put(CLAIM_KEY_USERNAME, new ObjectMapper().writeValueAsString(userDetails));
          claims.put(CLAIM_KEY_CREATED, new Date());
          return generateToken(claims);
      }
  
      /**
       * 判断token是否可以被刷新
       */
      public boolean canRefresh(String token) {
          return !isTokenExpired(token);
      }
  
      /**
       * 刷新token
       */
      public String refreshToken(String token) {
          Claims claims = getClaimsFromToken(token);
          claims.put(CLAIM_KEY_CREATED, new Date());
          return generateToken(claims);
      }
  
  
  }
  