1.JWT是什么？

JWT，英文全称JSON Web Token：JSON网络令牌。为了在网络应用环境间传递声明而制定的一种基于JSON的开放标准(RFC 7519)。这个规范允许我们使用JWT在客户端和服务端之间传递安全可靠的信息。JWT是一个轻便的安全跨平台传输格式，定义了一个紧凑自包含的方式，用于通信双方之间作为 JSON 对象安全地传递信息。此信息可以通过数字签名进行验证和信任。

紧凑：这个字符串简洁，数据量小，传输速度快，能通过URL参数、HTTP请求提交的数据以及HTTP Header的方式进行传递。
自包含：负载中包含很多信息，比如用户的ID等。别人拿到这个字符串，就能拿到这些关键的业务信息，从而避免再通过数据库查询等方式得到它们。

JWT的结构 JWT由三段信息用.连接构成的字符串。

Header.Payload.Signature 例如：

eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJhdWQiOiIxIn0.ihOZFzg3ZGIbBMneRy-4RMqors1P3nuO-wRJnQtTzWQ

Header头部

承载两部分信息：token类型和采用的加密算法

{   "typ": "JWT",  "alg": "HS256"}

token类型：JWT 加密算法：HS256

Payload负载

存放有效信息的地方

iss: jwt签发者 sub: jwt所面向的用户 aud: 接收jwt的一方 exp: 过期时间戳(jwt的过期时间，这个过期时间必须要大于签发时间) nbf: 定义在什么时间之前，该jwt都是不可用的 iat: jwt的签发时间 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

Signature签名

对头部及负载内容进行签证。采用Header中声明的算法，接收三个参数：base64编码的Header、base64编码的Payload和密钥（secret）进行运算。密钥secret是保存在服务端的，服务端会根据这个密钥进行生成token和进行验证。

2.环境搭建

参考代码仓库里面的mysql模块，这里只贴出docker-compose.yml

version: '3'services:  mysql:    image: registry.cn-hangzhou.aliyuncs.com/zhengqing/mysql:5.7    container_name: mysql_3306    restart: unless-stopped                                       volumes:      - "./mysql/my.cnf:/etc/mysql/my.cnf"      - "./mysql/init-file.sql:/etc/mysql/init-file.sql"      - "./mysql/data:/var/lib/mysql"#      - "./mysql/conf.d:/etc/mysql/conf.d"      - "./mysql/log/mysql/error.log:/var/log/mysql/error.log"      - "./mysql/docker-entrypoint-initdb.d:/docker-entrypoint-initdb.d" # init sql script directory -- tips: it can be excute  when `/var/lib/mysql` is empty    environment:                        # set environment,equals docker run -e      TZ: Asia/Shanghai      LANG: en_US.UTF-8      MYSQL_ROOT_PASSWORD: root         # set root password      MYSQL_DATABASE: demo              # init database name    ports:                              # port mappping      - "3306:3306"

运行

docker-compose -f docker-compose.yml -p mysql5.7 up -d

初始化表

DROP TABLE IF EXISTS `jwt_user`; CREATE TABLE `jwt_user`( `id` varchar(32) CHARACTER SET utf8 NOT NULL COMMENT '用户ID', `username` varchar(100) CHARACTER SET utf8 NULL DEFAULT NULL COMMENT '登录账号', `password` varchar(255) CHARACTER SET utf8 NULL DEFAULT NULL COMMENT '密码')ENGINE = InnoDB CHARACTER SET = utf8 COMMENT = '用户表' ROW_FORMAT = Compact;
INSERT INTO jwt_user VALUES('1','admin','123');

3.代码工程

实验目标：实现JWT的签发和验证

pom.xml

<?xml version="1.0" encoding="UTF-8"?><project xmlns="http://maven.apache.org/POM/4.0.0"         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">    <parent>        <artifactId>springboot-demo</artifactId>        <groupId>com.et</groupId>        <version>1.0-SNAPSHOT</version>    </parent>    <modelVersion>4.0.0</modelVersion>
    <artifactId>jwt</artifactId>
    <properties>        <maven.compiler.source>8</maven.compiler.source>        <maven.compiler.target>8</maven.compiler.target>    </properties>    <dependencies>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-web</artifactId>        </dependency>
        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-autoconfigure</artifactId>        </dependency>        <!--mysql-->        <dependency>            <groupId>mysql</groupId>            <artifactId>mysql-connector-java</artifactId>            <version>8.0.29</version>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-jdbc</artifactId>        </dependency>        <dependency>            <groupId>com.baomidou</groupId>            <artifactId>mybatis-plus-boot-starter</artifactId>            <version>3.5.1</version>        </dependency>        <dependency>            <groupId>org.projectlombok</groupId>            <artifactId>lombok</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-test</artifactId>            <scope>test</scope>        </dependency>        <dependency>            <groupId>com.alibaba</groupId>            <artifactId>fastjson</artifactId>            <version>1.2.47</version>        </dependency>        <dependency>            <groupId>io.jsonwebtoken</groupId>            <artifactId>jjwt</artifactId>            <version>0.9.1</version>        </dependency>        <dependency>            <groupId>com.auth0</groupId>            <artifactId>java-jwt</artifactId>            <version>3.4.0</version>        </dependency>

    </dependencies></project>

application.yaml

spring:  datasource:    driver-class-name: com.mysql.cj.jdbc.Driver    url: jdbc:mysql://localhost:3306/demo?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=GMT    username: root    password: root
server:  port: 8088

Jwt生成

package com.et.jwt.service;
import com.auth0.jwt.JWT;import com.auth0.jwt.algorithms.Algorithm;
import com.et.jwt.entity.User;import org.springframework.stereotype.Service;
import java.time.Instant;import java.time.LocalDateTime;import java.time.ZoneId;import java.util.Date;

@Service("TokenService")
public class TokenService {    long  outHours=1;    public String getToken(User user) {        Instant instant = LocalDateTime.now().plusHours(outHours).atZone(ZoneId.systemDefault()).toInstant();        Date expire = Date.from(instant);        String token="";        // save information  to token ,such as: user id and Expires time        token= JWT.create()                .withAudience(user.getId())                .withExpiresAt(expire)                .sign(Algorithm.HMAC256(user.getPassword()));        // use HMAC256 to generate token,key is user's password        return token;    }}

jwt验证

package com.et.jwt.interceptor;
import com.auth0.jwt.JWT;import com.auth0.jwt.JWTVerifier;import com.auth0.jwt.algorithms.Algorithm;import com.auth0.jwt.exceptions.JWTDecodeException;import com.auth0.jwt.exceptions.JWTVerificationException;
import com.et.jwt.annotation.PassToken;import com.et.jwt.annotation.UserLoginToken;import com.et.jwt.entity.User;import com.et.jwt.service.UserService;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.method.HandlerMethod;import org.springframework.web.servlet.HandlerInterceptor;import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.lang.reflect.Method;import java.util.Date;

public class AuthenticationInterceptor implements HandlerInterceptor {    @Autowired    UserService userService;    @Override    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object object) throws Exception {        //  get token  from http header        String token = httpServletRequest.getHeader("token");        if(!(object instanceof HandlerMethod)){            return true;        }        HandlerMethod handlerMethod=(HandlerMethod)object;        Method method=handlerMethod.getMethod();        //check is included @passtoken annotation? jump if have        if (method.isAnnotationPresent(PassToken.class)) {            PassToken passToken = method.getAnnotation(PassToken.class);            if (passToken.required()) {                return true;            }        }        //check is included @UserLoginToken ?        if (method.isAnnotationPresent(UserLoginToken.class)) {            UserLoginToken userLoginToken = method.getAnnotation(UserLoginToken.class);            if (userLoginToken.required()) {                // excute verify                if (token == null) {                    throw new RuntimeException("token invalid，please login again");                }                // get  user id  from  token                String userId;                try {                    userId = JWT.decode(token).getAudience().get(0);                } catch (JWTDecodeException j) {                    throw new RuntimeException("401");                }                User user = userService.findUserById(userId);                if (user == null) {                    throw new RuntimeException("user is not exist，please login again");                }                // verify token                JWTVerifier jwtVerifier = JWT.require(Algorithm.HMAC256(user.getPassword())).build();                try {                    jwtVerifier.verify(token);                    if (JWT.decode(token).getExpiresAt().before(new Date())) {                        throw new RuntimeException("token Expires");                    }
                } catch (JWTVerificationException e) {                    throw new RuntimeException("401");                }
                return true;            }        }        return true;    }
    @Override    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
    }    @Override    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
    }}

以上只是一些关键代码，所有代码请参见下面代码仓库

代码仓库

https://github.com/Harries/springboot-demo

4.测试

启动Spring Boot应用
登录系统

http://localhost:8088/api/login?username=admin&password=123

{ "user": { "username": "admin", "password": "123", "id": "1" }, "token": "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJhdWQiOiIxIn0.ihOZFzg3ZGIbBMneRy-4RMqors1P3nuO-wRJnQtTzWQ"}

在header里面设置 token，访问

http://localhost:8088/api/getMessage

5.引用

https://www.v2ex.com/t/817906
http://www.liuhaihua.cn/archives/710374.html
https://github.com/ChuaWi/SpringBoot-JWT/tree/master

6.Questions

这里留2个问题给读者

过期了如何刷新token呢？保证过期时候重新登录，而不是后台自动刷新，一直不过期？
如果要实现强制下线用户功能，该如何实现呢？

ITPub博客

Spring Boot集成JWT快速入门demo