先介绍下利用JWT进行鉴权的思路：

1、用户发起登录请求。

2、服务端创建一个加密后的JWT信息，作为Token返回。

3、在后续请求中JWT信息作为请求头，发给服务端。

4、服务端拿到JWT之后进行解密，正确解密表示此次请求合法，验证通过；解密失败说明Token无效或者已过期。

流程图如下：

网图

一、用户发起登录请求

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二、服务端创建一个加密后的JWT信息，作为Token返回

1、用户登录之后把生成的Token返回给前端

@Authorization
@ResponseBody
@GetMapping("user/info/auth")
public Result getUserSecurityInfo(HttpServletRequest request) {
   try {
       UserDTO userDTO = ...
       UserVO userVO = new UserVO();
       //这里调用创建JWT信息的方法
       userVO.setToken(TokenUtil.createJWT(String.valueOf(userDTO.getId())));
       return Result.success(userVO);
   } catch (Exception e) {
       return Result.fail(ErrorEnum.SYSTEM_ERROR);
   }
}

2、创建JWT，Generate Tokens

import javax.crypto.spec.SecretKeySpec;
import javax.xml.bind.DatatypeConverter;
import java.security.Key;
import io.jsonwebtoken.*;
import java.util.Date;    
 
//Sample method to construct a JWT
private String createJWT(String id, String issuer, String subject, long ttlMillis) {
 
    //The JWT signature algorithm we will be using to sign the token
    SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.HS256;
 
    long nowMillis = System.currentTimeMillis();
    Date now = new Date(nowMillis);
 
    //We will sign our JWT with our ApiKey secret
    byte[] apiKeySecretBytes = DatatypeConverter.parseBase64Binary(apiKey.getSecret());
    Key signingKey = new SecretKeySpec(apiKeySecretBytes, signatureAlgorithm.getJcaName());
 
    //Let's set the JWT Claims
    JwtBuilder builder = Jwts.builder().setId(id)
                                .setIssuedAt(now)
                                .setSubject(subject)
                                .setIssuer(issuer)
                                .signWith(signatureAlgorithm, signingKey);
 
    //if it has been specified, let's add the expiration
    if (ttlMillis >= 0) {
    long expMillis = nowMillis + ttlMillis;
        Date exp = new Date(expMillis);
        builder.setExpiration(exp);
    }
 
    //Builds the JWT and serializes it to a compact, URL-safe string
    return builder.compact();
}

3、作为Token返回

看后面有个Token

三、在后续请求中JWT信息作为请求头，发给服务端

缺一个图，马上补

四、服务端拿到JWT之后进行解密，正确解密表示此次请求合法，验证通过；解密失败说明Token无效或者已过期。

1、在拦截器中读取这个Header里面的Token值

@Slf4j
@Component
public class AuthorizationInterceptor extends HandlerInterceptorAdapter {
    private boolean chechToken(HttpServletRequest request, HttpServletResponse response) throws IOException{
        Long userId = ...;

        if (!TokenUtil.parseJWT(request.getHeader("Authorization"), String.valueOf(userId))){
            response.setContentType("text/html;charset=GBK");
            response.setCharacterEncoding("GBK");
            response.setStatus(403);
            response.getWriter().print("<font size=6 color=red>对不起，您的请求非法，系统拒绝响应!</font>");
            return false;
        } else{
            return true;
        }
    }
}

2、拿到之后进行解密校验

Decode and Verify Tokens

import javax.xml.bind.DatatypeConverter;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.Claims;
 
//Sample method to validate and read the JWT
private void parseJWT(String jwt) {
    //This line will throw an exception if it is not a signed JWS (as expected)
    Claims claims = Jwts.parser()         
       .setSigningKey(DatatypeConverter.parseBase64Binary(apiKey.getSecret()))
       .parseClaimsJws(jwt).getBody();
    System.out.println("ID: " + claims.getId());
    System.out.println("Subject: " + claims.getSubject());
    System.out.println("Issuer: " + claims.getIssuer());
    System.out.println("Expiration: " + claims.getExpiration());
}

五、总结

大家知道，我之前做过爬虫，实际这种思路在微博做反爬时也用过，做过我之前文章的同学应该知道。