1.首先了解一下Token

• uid: 使用者唯一身份標識
• time: 當前時間的時間戳
• sign: 簽名, 使用 hash/encrypt 壓縮成定長的十六進位制字串，以防止第三方惡意拼接
• 固定引數(可選): 將一些常用的固定引數加入到 token 中是為了避免重複查資料庫

2.token 驗證的機制（流程）

1. 使用者登入校驗，校驗成功後就返回Token給客戶端。
2. 客戶端收到資料後儲存在客戶端
3. 客戶端每次訪問API是攜帶Token到伺服器端。
4. 伺服器端採用filter過濾器校驗。校驗成功則返回請求資料，校驗失敗則返回錯誤碼

3.使用SpringBoot搭建基於token驗證

3.1 引入 POM 依賴

<!--Json web token-->
        <dependency>
            <groupId>com.auth0</groupId>
            <artifactId>java-jwt</artifactId>
            <version>3.4.0</version>
        </dependency>

3.2 新建一個攔截器配置 用於攔截前端請求 實現 WebMvcConfigurer

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
 
public class InterceptorConfig implements WebMvcConfigurer {

  @Override
  public void addInterceptors(InterceptorRegistry registry) {
    registry.addInterceptor(authenticationInterceptor())
        .addPathPatterns("/**");//攔截所有請求，通過判斷是否有 @LoginRequired 註解 決定是否需要登入
  }

  @Bean
  public AuthenticationInterceptor authenticationInterceptor() {
    
 
return new AuthenticationInterceptor();
  }
}

3.3 新建一個AuthenticationInterceptor實現HandlerInterceptor介面 實現攔截還是放通的邏輯

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.my_springboot.rbac.pojo.Admin;
import com.my_springboot.rbac.service.IAdminService;
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;

/**
 * 攔截器去獲取token並驗證token*/
public class AuthenticationInterceptor implements HandlerInterceptor {

    @Autowired
    private IAdminService adminService;

    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest,
                             HttpServletResponse httpServletResponse, Object object) {
        String token = httpServletRequest.getHeader ("token");// 從 http 請求頭中取出 token
        // 如果不是對映到方法直接通過
        if (!(object instanceof HandlerMethod)) {
            return true;
        }
        HandlerMethod handlerMethod = (HandlerMethod) object;
        Method method = handlerMethod.getMethod ();
        //檢查是否有@passtoken註解，有則跳過認證
        if (method.isAnnotationPresent (PassToken.class)) {
            PassToken passToken = method.getAnnotation (PassToken.class);
            if (passToken.required ()) {
                return true;
            }
        }
        //檢查有沒有需要使用者許可權的註解
        if (method.isAnnotationPresent (UserLoginToken.class)) {
            UserLoginToken userLoginToken = method.getAnnotation (UserLoginToken.class);
            if (userLoginToken.required ()) {
                // 執行認證
                if (token == null) {
                    throw new RuntimeException ("無token");
                }
                // 獲取 token 中的 user id
                String adminId;
                try {
                    adminId = JWT.decode (token).getAudience ().get (0);
                } catch (JWTDecodeException j) {
                    throw new RuntimeException ("401");
                }
                Admin admin = adminService.getById (adminId);
                if (admin == null) {
                    throw new RuntimeException ("使用者不存在");
                }
                // 驗證 token
                JWTVerifier jwtVerifier = JWT.require (Algorithm.HMAC256 (admin.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 { }
}

3.4 新建兩個註解 用於標識請求是否需要進行Token 驗證

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

/**
 * 需要登入才能進行操作的註解UserLoginToken*/

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface UserLoginToken {

    boolean required() default true;
}

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

/**
 * 用來跳過驗證的PassToken*/
@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface PassToken {

    boolean required() default true;
}

3.5 新建一個Service用於下發Token

import com.auth0.jwt.JWT;
import com.auth0.jwt.algorithms.Algorithm;
import com.my_springboot.rbac.pojo.Admin;
import org.springframework.stereotype.Service;

import java.util.Date;

/**
 * 下發token*/
@Service
public class TokenService {

    public String getToken(Admin admin) {
        Date start = new Date ();
        long currentTime = System.currentTimeMillis () + 60 * 60 * 1000;//一小時有效時間
        Date end = new Date (currentTime);
        return JWT.create ().withAudience (admin.getId ()).withIssuedAt (start)
                .withExpiresAt (end)
                .sign (Algorithm.HMAC256 (admin.getPassword ()));
    }
}

3.6 新建一個工具類 使用者從token中取出使用者Id

import com.auth0.jwt.JWT;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

import javax.servlet.http.HttpServletRequest;

/**
 * token工具類*/
public class TokenUtil {
    public static String getTokenUserId() {
        String token = getRequest().getHeader("token");// 從 http 請求頭中取出 token
        String userId = JWT.decode(token).getAudience().get(0);
        return userId;
    }

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

以上。