一、JWT是什么？

在介绍JWT之前，我们先来回顾一下利用token进行用户身份验证的流程：

1、客户端使用用户名和密码请求登录

2、服务端收到请求，验证用户名和密码

3、验证成功后，服务端会签发一个token，再把这个token返回给客户端

4、客户端收到token后可以把它存储起来，比如放到cookie中

5、客户端每次向服务端请求资源时需要携带服务端签发的token，可以在cookie或者header中携带

6、服务端收到请求，然后去验证客户端请求里面带着的token，如果验证成功，就向客户端返回请求数据

这种基于token的认证方式相比传统的session认证方式更节约服务器资源，并且对移动端和分布式更加友好。其优点如下：

支持跨域访问：cookie是无法跨域的，而token由于没有用到cookie(前提是将token放到请求头中)，所以跨域后不会存在信息丢失问题
无状态：token机制在服务端不需要存储session信息，因为token自身包含了所有登录用户的信息，所以可以减轻服务端压力
更适用CDN：可以通过内容分发网络请求服务端的所有资料
更适用于移动端：当客户端是非浏览器平台时，cookie是不被支持的，此时采用token认证方式会简单很多
无需考虑CSRF：由于不再依赖cookie，所以采用token认证方式不会发生CSRF，所以也就无需考虑CSRF的防御

而JWT就是上述流程当中token的一种具体实现方式，其全称是JSON Web Token，官网地址：https://jwt.io/

通俗地说，JWT的本质就是一个字符串，它是将用户信息保存到一个Json字符串中，然后进行编码后得到一个JWT token，并且这个JWT token带有签名信息，接收后可以校验是否被篡改，所以可以用于在各方之间安全地将信息作为Json对象传输。JWT的认证流程如下：

1、首先，前端通过Web表单将自己的用户名和密码发送到后端的接口，这个过程一般是一个POST请求。建议的方式是通过SSL加密的传输(HTTPS)，从而避免敏感信息被嗅探

2、后端核对用户名和密码成功后，将包含用户信息的数据作为JWT的Payload，将其与JWT Header分别进行Base64编码拼接后签名，形成一个JWT Token，形成的JWT Token就是一个如同lll.zzz.xxx的字符串
3、后端将JWT Token字符串作为登录成功的结果返回给前端。前端可以将返回的结果保存在浏览器中，退出登录时删除保存的JWT Token即可

4、前端在每次请求时将JWT Token放入HTTP请求头中的Authorization属性中(解决XSS和XSRF问题)

5、后端检查前端传过来的JWT Token，验证其有效性，比如检查签名是否正确、是否过期、token的接收方是否是自己等等

6、验证通过后，后端解析出JWT Token中包含的用户信息，进行其他逻辑操作(一般是根据用户信息得到权限等)，返回结果
在这里插入图片描述

最后：说白了，JWT：JSON Web Token，其实token就是一段字符串，由三部分组成：Header，Payload，Signature

二、使用步骤

1.项目结构

在这里插入图片描述

2.相关依赖

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.22</version>
        </dependency>

        <dependency>
            <groupId>cn.hutool</groupId>
            <artifactId>hutool-all</artifactId>
            <version>5.7.21</version>
        </dependency>

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.4.3.2</version>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.79</version>
        </dependency>

        <dependency>
            <groupId>commons-beanutils</groupId>
            <artifactId>commons-beanutils</artifactId>
            <version>1.9.4</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.22</version>
        </dependency>

        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.11.0</version>
        </dependency>

        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi-ooxml</artifactId>
            <version>4.1.2</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.1</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <version>2.3.8.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>com.auth0</groupId>
            <artifactId>java-jwt</artifactId>
            <version>3.18.3</version>
        </dependency>

        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
        </dependency>
    </dependencies>

3.数据库

这里进行测试，所以用户类只有用户名密码，自行创建
在这里插入图片描述

4.相关代码

1、annotation包
PassToken：

package com.geesun.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * @author ：Mr.ZJW
 * @date ：Created 2022/2/28 10:26
 * @description：用来跳过验证的 PassToken
 */
@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface PassToken {
    boolean required() default true;
}

UserLoginToken：

package com.geesun.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * @author ：Mr.ZJW
 * @date ：Created 2022/2/28 10:26
 * @description：用于登录后才能操作的token
 */
/*RetentionPolicy.RUNTIME:这种类型的Annotations将被JVM保留,
所以他们能在运行时被JVM或其他使用反射机制的代码所读取和使用。*/
@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface UserLoginToken {
    boolean required() default true;
}

2、common包
CodeMsg：

package com.geesun.common;

/**
 * @author ：Mr.ZJW
 * @date ：Created 2022/2/28 10:26
 * @description：返回提示
 */
public class CodeMsg {
    private int retCode;
    private String message;
    // 按照模块定义CodeMsg
    // 通用异常
    public static CodeMsg SUCCESS = new CodeMsg(0,"success");
    public static CodeMsg SERVER_EXCEPTION = new CodeMsg(500100,"服务端异常");
    public static CodeMsg PARAMETER_ISNULL = new CodeMsg(500101,"输入参数为空");
    // 业务异常
    public static CodeMsg USER_NOT_EXSIST = new CodeMsg(500102,"用户不存在");
    public static CodeMsg ONLINE_USER_OVER = new CodeMsg(500103,"在线用户数超出允许登录的最大用户限制。");
    public static CodeMsg SESSION_NOT_EXSIST =  new CodeMsg(500104,"不存在离线session数据");
    public static CodeMsg NOT_FIND_DATA = new CodeMsg(500105,"查找不到对应数据");
    public static CodeMsg USER_OR_PASS_ERROR = new CodeMsg(500102,"账号或者密码错误，请重试！");


    private CodeMsg(int retCode, String message) {
        this.retCode = retCode;
        this.message = message;
    }

    public int getRetCode() {
        return retCode;
    }
    public String getMessage() {
        return message;
    }
    public void setMessage(String message) {
        this.message = message;
    }
}

Result：

package com.geesun.common;

/**
 * @author ：Mr.ZJW
 * @date ：Created 2022/2/28 10:26
 * @description：返回统一结果集
 */
public class Result<T> {

    private String message;
    private int retCode;
    private T data;

    private Result(T data) {
        this.retCode = 200;
        this.message = "成功";
        this.data = data;
    }

    private Result(CodeMsg cm) {
        if(cm == null){
            return;
        }
        this.retCode = cm.getRetCode();
        this.message = cm.getMessage();
    }

    /**
     * 成功时候的调用
     * @return
     */
    public static <T> Result<T> success(T data){
        return new Result<T>(data);
    }

    /**
     * 成功，不需要传入参数
     * @return
     */
    @SuppressWarnings("unchecked")
    public static <T> Result<T> success(){
        return (Result<T>) success("");
    }
    /**
     * 失败时候的调用
     * @return
     */
    public static <T> Result<T> error(CodeMsg cm){
        return new Result<T>(cm);
    }
    /**
     * 失败时候的调用,扩展消息参数
     * @param cm
     * @param msg
     * @return
     */
    public static <T> Result<T> error(CodeMsg cm,String msg){
        cm.setMessage(cm.getMessage()+"--"+msg);
        return new Result<T>(cm);
    }
    public T getData() {
        return data;
    }
    public String getMessage() {
        return message;
    }
    public int getRetCode() {
        return retCode;
    }
}

3、config包
InterceptorConfig：

package com.geesun.config;

import com.geesun.Interceptor.AuthenticationInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.format.FormatterRegistry;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.validation.MessageCodesResolver;
import org.springframework.validation.Validator;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.config.annotation.*;
import java.util.List;

/**
 * @author ：Mr.ZJW
 * @date ：Created 2022/2/28 10:25
 * @description：新建Token拦截器
 */
@Configuration
public class InterceptorConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(authenticationInterceptor())
                .addPathPatterns("/**");    // 拦截所有请求，通过判断是否有 @LoginRequired 注解 决定是否需要登录
    }
    @Bean
    public AuthenticationInterceptor authenticationInterceptor() {
        return new AuthenticationInterceptor();
    }
    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public void addCorsMappings(CorsRegistry arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public void addFormatters(FormatterRegistry arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public void addViewControllers(ViewControllerRegistry arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public void configureAsyncSupport(AsyncSupportConfigurer arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public void configureContentNegotiation(ContentNegotiationConfigurer arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public void configurePathMatch(PathMatchConfigurer arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public void configureViewResolvers(ViewResolverRegistry arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public void extendHandlerExceptionResolvers(List<HandlerExceptionResolver> arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public void extendMessageConverters(List<HttpMessageConverter<?>> arg0) {
        // TODO Auto-generated method stub

    }
    @Override
    public MessageCodesResolver getMessageCodesResolver() {
        // TODO Auto-generated method stub
        return null;
    }
    @Override
    public Validator getValidator() {
        // TODO Auto-generated method stub
        return null;
    }

}

4、Interceptor包
AuthenticationInterceptor：

package com.geesun.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.geesun.annotation.PassToken;
import com.geesun.annotation.UserLoginToken;
import com.geesun.pojo.User;
import com.geesun.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;

/**
 * @author ：Mr.ZJW
 * @date ：Created 2022/2/28 10:24
 * @description：拦截器
 */
public class AuthenticationInterceptor implements HandlerInterceptor {

    @Autowired
    UserService userService;

    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object object) throws Exception {
        String token = httpServletRequest.getHeader("token");// 从 http 请求头中取出 token
        // 如果不是映射到方法直接通过
        if(!(object instanceof HandlerMethod)){
            return true;
        }
        HandlerMethod handlerMethod=(HandlerMethod)object;
        Method method=handlerMethod.getMethod();
        //检查是否有passtoken注释，有则跳过认证
        if (method.isAnnotationPresent(PassToken.class)) {
            PassToken passToken = method.getAnnotation(PassToken.class);
            if (passToken.required()) {
                return true;
            }
        }
        //检查有没有需要用户权限的注解
        if (method.isAnnotationPresent(UserLoginToken.class)) {
            UserLoginToken userLoginToken = method.getAnnotation(UserLoginToken.class);
            if (userLoginToken.required()) {
                // 执行认证
                if (token == null) {
                    throw new RuntimeException("无token，请重新登录");
                }
                // 获取 token 中的 user id
                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("用户不存在，请重新登录");
                }
                // 验证 token
                JWTVerifier jwtVerifier = JWT.require(Algorithm.HMAC256(user.getPassword())).build();
                try {
                    jwtVerifier.verify(token);
                } 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 {

    }
}

5、utils包
TokenUtil：

package com.geesun.utils;

import com.auth0.jwt.JWT;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import javax.servlet.http.HttpServletRequest;

/**
 * @author ：Mr.ZJW
 * @date ：Created 2022/2/28 10:24
 * @description：
 */
public class TokenUtil {

    public static String getTokenUserId() {
        String token = getRequest().getHeader("token");// 从 http 请求头中取出 token
        String userId = JWT.decode(token).getAudience().get(0);
        return userId;
    }

    /**
     * 获取request
     * @return
     */
    public static HttpServletRequest getRequest() {
        ServletRequestAttributes requestAttributes = (ServletRequestAttributes) RequestContextHolder
                .getRequestAttributes();
        return requestAttributes == null ? null : requestAttributes.getRequest();
    }

}

6、pojo包
User：

package com.geesun.pojo;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;

@Data
@AllArgsConstructor
@NoArgsConstructor
@TableName(value = "`user`")
public class User implements Serializable {
    @TableId(value = "id", type = IdType.NONE)
    private String id;

    @TableField(value = "username")
    private String username;

    @TableField(value = "password")
    private String password;

    private static final long serialVersionUID = 1L;
}

7、controller包
UserController：

package com.geesun.controller;

import cn.hutool.json.JSONObject;
import com.geesun.annotation.UserLoginToken;
import com.geesun.common.CodeMsg;
import com.geesun.common.Result;
import com.geesun.pojo.User;
import com.geesun.service.UserService;
import com.geesun.service.impl.TokenService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletResponse;

/**
 * @author ：Mr.ZJW
 * @date ：Created 2022/2/26 10:47
 * @description：
 */
@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    private UserService userService;

    @Autowired
    private TokenService tokenService;

    /**
     * 查询用户信息
     * @return
     */
    @UserLoginToken
    @GetMapping("/list")
    public Result<Object> list(){
        return Result.success(userService.list());
    }


    /**
     * 登录验证
     * @param user
     * @param response
     * @return
     */
    @RequestMapping(value = "/login" ,method = RequestMethod.GET)
    public Result<Object> login(User user, HttpServletResponse response) {
        JSONObject jsonObject = new JSONObject();
        //获取用户账号密码
        User userForBase = new User();
        userForBase.setId(userService.findByUsername(user).getId());
        userForBase.setUsername(userService.findByUsername(user).getUsername());
        userForBase.setPassword(userService.findByUsername(user).getPassword());
        //判断账号或密码是否正确
        if (!userForBase.getPassword().equals(user.getPassword())) {
            return Result.error(CodeMsg.USER_OR_PASS_ERROR);
        } else {
            String token = tokenService.getToken(userForBase);
            jsonObject.put("token", token);
            Cookie cookie = new Cookie("token", token);
            cookie.setPath("/");
            response.addCookie(cookie);
            return Result.success(jsonObject);
        }
    }
    
}

8、service包
UserService接口：

package com.geesun.service;

import com.baomidou.mybatisplus.extension.service.IService;
import com.geesun.pojo.User;

public interface UserService extends IService<User> {


    int deleteByIds(Long[] ids);

    int addUser(User user);

    User findByUsername(User user);

    User findUserById(String userId);
}

UserServiceImpl实现类:

package com.geesun.service.impl;

import cn.hutool.core.util.ArrayUtil;
import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.geesun.mapper.UserMapper;
import com.geesun.pojo.User;
import com.geesun.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.Arrays;

@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {

    @Autowired
    private UserMapper userMapper;
    
    /**
     * 判断用户名
     * @param user
     * @return
     */
    public User findByUsername(User user){
        return userMapper.selectOne(new LambdaQueryWrapper<User>().eq(User::getUsername,user.getUsername()));
    }

    public User findUserById(String userId) {
        return userMapper.selectById(userId);
    }

}

TokenService:

package com.geesun.service.impl;

import com.auth0.jwt.JWT;
import com.auth0.jwt.algorithms.Algorithm;
import com.geesun.pojo.User;
import org.springframework.stereotype.Service;
import java.util.Date;

/**
 * @author ：Mr.ZJW
 * @date ：Created 2022/2/28 10:20
 * @description：
 */
@Service
public class TokenService {

    public String getToken(User user) {
        Date start = new Date();
        long currentTime = System.currentTimeMillis() + 60* 60 * 1000;//一小时有效时间
        Date end = new Date(currentTime);
        String token = "";

        token = JWT.create().withAudience(user.getId()).withIssuedAt(start).withExpiresAt(end)
                .sign(Algorithm.HMAC256(user.getPassword()));
        return token;
    }
}

9、mapper包

package com.geesun.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.geesun.pojo.User;

public interface UserMapper extends BaseMapper<User> {

}