转自：https://www.cnblogs.com/itfeng813/p/14333422.html

Java JWT做登录认证

1.JWT的介绍

　　知乎有一篇文章介绍的很形象 认证方式的前世今生，以及 JWT 的使用

　　具体和Springboot的集成使用可参考另一篇博客：SpringBoot集成JWT实现token验证

2.使用demo　

  1 package com.drz.proxy.internetProxy.util;
  2 
  3 import java.util.Date;
  4 import java.util.HashMap;
  5 import java.util.Map;
  6 
  7 import org.apache.commons.codec.binary.Base64;
  8 import org.apache.commons.codec.binary.StringUtils;
  9 
 10 import com.auth0.jwt.JWT;
 11 import com.auth0.jwt.JWTVerifier;
 12 import com.auth0.jwt.algorithms.Algorithm;
 13 import com.auth0.jwt.exceptions.JWTCreationException;
 14 import com.auth0.jwt.exceptions.JWTVerificationException;
 15 import com.auth0.jwt.interfaces.DecodedJWT;
 16 
 17 /**
 18  * JWT token串结构: header.payload.signature 
 19  * signature=HMACSHA256(base64UrlEncode(header) + "." +base64UrlEncode(payload),Secret)
 20  * 
 21  * token保存在客户端，每次请求传到后端，服务端只保留密钥,不要把密钥放在header和payload中；
 22  * 
 23  * header中默认传递参数：
 24  * {"typ":"JWT","alg":"HS256"}
 25  * 
 26  * payload官方定义包含属性如下（非强制）：
 27  *     iss: jwt签发者
 28  *     sub: jwt所面向的用户
 29  *     aud: 接收jwt的一方
 30  *     exp: jwt的过期时间，这个过期时间必须要大于签发时间
 31  *     nbf: 定义在什么时间之前，该jwt都是不可用的.
 32  *     iat: jwt的签发时间
 33  *     jti: jwt的唯一身份标识，主要用来作为一次性token,从而回避重放攻击。
 34  * payload 自定义数据:存放我们想放在token中存放的key-value值
 35  */
 36 public class JWTUtil {
 37 
 38     /**
 39      * 过期时间
 40      */
 41     private static final long EXPIRE_TIMEMILLS = 6000;
 42 
 43     /**
 44      * jwt 密钥
 45      */
 46     private static final String SECRET = "jwt_secret";
 47 
 48     public static String create() {
 49         try {
 50             Algorithm algorithm = Algorithm.HMAC256(SECRET);
 51 
 52             Map<String, Object> headerMap = new HashMap<String, Object>();
 53             headerMap.put("date", "2022-01-01 18:00");
 54             headerMap.put("where", "城东小树林");
 55             String token = JWT.create().withHeader(headerMap)//可自定义传递参数
 56                     //                    .withIssuer("auth0")//签发者
 57                     .withIssuedAt(new Date())//签发时间
 58                     .withSubject("subject").withAudience("100102134")
 59                     .withExpiresAt(new Date(System.currentTimeMillis() + EXPIRE_TIMEMILLS))
 60                     //payload中加入自定义数据
 61                     .withClaim("name", "小明").withClaim("introduce", "TTT").sign(algorithm);
 62             System.out.println("当前时间：" + new Date());
 63             System.out.println("jwt token:" + token);
 64             return token;
 65         } catch (JWTCreationException exception) {
 66             //Invalid Signing configuration / Couldn't convert Claims.
 67             throw exception;
 68         }
 69     }
 70 
 71     public static Boolean verify(String token) {
 72         try {
 73             Algorithm algorithm = Algorithm.HMAC256(SECRET);
 74             JWTVerifier verifier = JWT.require(algorithm).build(); //Reusable verifier instance
 75             DecodedJWT jwt = verifier.verify(token);
 76 
 77             String decodeHeader = StringUtils.newStringUtf8(Base64.decodeBase64(jwt.getHeader()));
 78             String decodePayload = StringUtils.newStringUtf8(Base64.decodeBase64(jwt.getPayload()));
 79 
 80             String signature = jwt.getSignature();
 81             String name = jwt.getClaim("name").asString();
 82             String introduce = jwt.getClaim("introduce").asString();
 83 
 84             System.out.println("header:" + jwt.getHeader());
 85             System.out.println("payload:" + jwt.getPayload());
 86             System.out.println("signature:" + signature);
 87 
 88             System.out.println("headerString:" + decodeHeader);
 89             System.out.println("payloadString:" + decodePayload);
 90 
 91             System.out.println("name:" + name);
 92             System.out.println("introduce:" + introduce);
 93             return true;
 94         } catch (JWTVerificationException exception) {
 95             System.out.println("当前时间：" + new Date());
 96             System.out.println("验证token失败：" + exception.getMessage());
 97             return false;
 98         }
 99     }
100 
101     public static void main(String[] args) {
102         String token = create();
103         //        try {
104         //            Thread.sleep(3000l);
105         //        } catch (InterruptedException e) {
106         //            // TODO Auto-generated catch block
107         //            e.printStackTrace();
108         //        }
109         Boolean result = verify(token);
110         System.out.println(result);
111     }
112 }

 输出结果：　

当前时间：Wed Jan 27 10:15:44 CST 2021

jwt token:eyJkYXRlIjoiMjAyMi0wMS0wMSAxODowMCIsIndoZXJlIjoi5Z-O5Lic5bCP5qCR5p6XIiwidHlwIjoiSldUIiwiYWxnIjoiSFMyNTYifQ.eyJzdWIiOiJzdWJqZWN0IiwiYXVkIjoiMTAwMTAyMTM0IiwiaW50cm9kdWNlIjoiVFRUIiwibmFtZSI6IuWwj-aYjiIsImV4cCI6MTYxMTcxMzc1MCwiaWF0IjoxNjExNzEzNzQ0fQ.LQIg264ZYVpq8SfPpv8gwJ3WnZtn_yk8fH8Cwg9Z69k

header:eyJkYXRlIjoiMjAyMi0wMS0wMSAxODowMCIsIndoZXJlIjoi5Z-O5Lic5bCP5qCR5p6XIiwidHlwIjoiSldUIiwiYWxnIjoiSFMyNTYifQ

payload:eyJzdWIiOiJzdWJqZWN0IiwiYXVkIjoiMTAwMTAyMTM0IiwiaW50cm9kdWNlIjoiVFRUIiwibmFtZSI6IuWwj-aYjiIsImV4cCI6MTYxMTcxMzc1MCwiaWF0IjoxNjExNzEzNzQ0fQ

signature:LQIg264ZYVpq8SfPpv8gwJ3WnZtn_yk8fH8Cwg9Z69k

headerString:{"date":"2022-01-01 18:00","where":"城东小树林","typ":"JWT","alg":"HS256"}

payloadString:{"sub":"subject","aud":"100102134","introduce":"TTT","name":"小明","exp":1611713750,"iat":1611713744}

name:小明

introduce:TTT

true