package cn.mygweb.annotation;

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

/**
 * 访问控制注解（实现接口防刷功能）
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface AccessLimit {
  /**
   * 限制周期（单位为秒）
   *
   * @return
   */
  int seconds();

  /**
   * 规定周期内限制次数
   *
   * @return
   */
  int maxCount();

  /**
   * 是否需要登录
   *
   * @return
   */
  boolean needLogin() default false;
}

package cn.mygweb.interceptor;

import cn.mygweb.annotation.AccessLimit;
import cn.mygweb.entity.Result;
import cn.mygweb.entity.StatusCode;
import com.alibaba.fastjson.JSON;
import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.OutputStream;
import java.util.HashMap;
import java.util.Map;

/**
 * 访问控制拦截器
 */
@Component
public class AccessLimitInterceptor extends HandlerInterceptorAdapter {

  //模拟数据存储，实际业务中可以自定义实现方式
  private static Map<String, AccessInfo> accessInfoMap = new HashMap<>();

  @Override
  public boolean preHandle(HttpServletRequest request, HttpServletResponse response,
               Object handler) throws Exception {
    //判断请求是否属于方法的请求
    if (handler instanceof HandlerMethod) {
      HandlerMethod hm = (HandlerMethod) handler;

      //获取方法中的注解，看是否有该注解
      AccessLimit accessLimit = hm.getMethodAnnotation(AccessLimit.class);
      if (accessLimit == null) {
        return true;
      }
      int seconds = accessLimit.seconds();
      int maxCount = accessLimit.maxCount();
      boolean needLogin = accessLimit.needLogin();
      String key = request.getRequestURI();
      //如果需要登录
      if (needLogin) {
        //获取登录的session进行判断
        //……
        key += " " + "userA";//这里假设用户是userA，实际项目中可以改为userId
      }

      //模拟从redis中获取数据
      AccessInfo accessInfo = accessInfoMap.get(key);
      if (accessInfo == null) {
        //第一次访问
        accessInfo = new AccessInfo();
        accessInfo.setFirstVisitTimestamp(System.currentTimeMillis());
        accessInfo.setAccessCount(1);
        accessInfoMap.put(key, accessInfo);
      } else if (accessInfo.getAccessCount() < maxCount) {
        //访问次数加1
        accessInfo.setAccessCount(accessInfo.getAccessCount() + 1);
        accessInfoMap.put(key, accessInfo);
      } else {
        //超出访问次数，判断时间是否超出设定时间
        if ((System.currentTimeMillis() - accessInfo.getFirstVisitTimestamp()) <= seconds * 1000) {
          //如果还在设定时间内，则为不合法请求，返回错误信息
          render(response, "达到访问限制次数，请稍后重试！");
          return false;
        } else {
          //如果超出设定时间，则为合理的请求，将之前的请求清空，重新计数
          accessInfo.setFirstVisitTimestamp(System.currentTimeMillis());
          accessInfo.setAccessCount(1);
          accessInfoMap.put(key, accessInfo);
        }
      }
    }
    return true;
  }

  /**
   * 向页面发送消息
   *
   * @param response
   * @param msg
   * @throws Exception
   */
  private void render(HttpServletResponse response, String msg) throws Exception {
    response.setContentType("application/json;charset=UTF-8");
    OutputStream out = response.getOutputStream();
    String str = JSON.toJSONString(new Result(true, StatusCode.ACCESSERROR, msg));
    out.write(str.getBytes("UTF-8"));
    out.flush();
    out.close();
  }

  /**
   * 封装的访问信息对象
   */
  class AccessInfo {

    /**
     * 一个计数周期内第一次访问的时间戳
     */
    private long firstVisitTimestamp;
    /**
     * 访问次数统计
     */
    private int accessCount;

    public long getFirstVisitTimestamp() {
      return firstVisitTimestamp;
    }

    public void setFirstVisitTimestamp(long firstVisitTimestamp) {
      this.firstVisitTimestamp = firstVisitTimestamp;
    }

    public int getAccessCount() {
      return accessCount;
    }

    public void setAccessCount(int accessCount) {
      this.accessCount = accessCount;
    }

    @Override
    public String toString() {
      return "AccessInfo{" +
          "firstVisitTimestamp=" + firstVisitTimestamp +
          ", accessCount=" + accessCount +
          '}';
    }
  }
}

package cn.mygweb.config;

import cn.mygweb.interceptor.AccessLimitInterceptor;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

/**
 * 拦截器注册配置
 */
@Configuration
public class WebConfig implements WebMvcConfigurer {

  @Override
  public void addInterceptors(InterceptorRegistry registry) {
    //注册拦截器
    registry.addInterceptor(new AccessLimitInterceptor());
  }
}

package cn.mygweb.controller;

import cn.mygweb.annotation.AccessLimit;
import cn.mygweb.entity.Result;
import cn.mygweb.entity.StatusCode;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/access")
public class AccessController {

  @AccessLimit(seconds = 5, maxCount = 2)//访问控制，5秒内只能访问2次
  @GetMapping
  public Result access() {
    return new Result(true, StatusCode.OK, "访问成功！");
  }

}

package cn.mygweb.entity;

/**
 * 返回状态码
 */
public class StatusCode {
  public static final int OK = 20000;//成功
  public static final int ERROR = 20001;//失败
  public static final int LOGINERROR = 20002;//用户名或密码错误
  public static final int ACCESSERROR = 20003;//权限不足
  public static final int REMOTEERROR = 20004;//远程调用失败
  public static final int REPERROR = 20005;//重复操作
  public static final int NOTFOUNDERROR = 20006;//没有对应的抢购数据
}

package cn.mygweb.entity;

import java.io.Serializable;

/**
 * 响应结果
 */
public class Result<T> implements Serializable {
  private boolean flag;//是否成功
  private Integer code;//返回码
  private String message;//返回消息
  private T data;//返回数据

  public Result(boolean flag, Integer code, String message, Object data) {
    this.flag = flag;
    this.code = code;
    this.message = message;
    this.data = (T) data;
  }

  public Result(boolean flag, Integer code, String message) {
    this.flag = flag;
    this.code = code;
    this.message = message;
  }

  public Result() {
    this.flag = true;
    this.code = StatusCode.OK;
    this.message = "操作成功!";
  }

  public boolean isFlag() {
    return flag;
  }

  public void setFlag(boolean flag) {
    this.flag = flag;
  }

  public Integer getCode() {
    return code;
  }

  public void setCode(Integer code) {
    this.code = code;
  }

  public String getMessage() {
    return message;
  }

  public void setMessage(String message) {
    this.message = message;
  }

  public T getData() {
    return data;
  }

  public void setData(T data) {
    this.data = data;
  }
}

server:
 port: 8080