content: package com.ruoyi.framework.shiro.web.filter.kickout;
  
  import java.io.IOException;
  import java.io.Serializable;
  import java.util.ArrayDeque;
  import java.util.Deque;
  import javax.servlet.ServletRequest;
  import javax.servlet.ServletResponse;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import org.apache.shiro.cache.Cache;
  import org.apache.shiro.cache.CacheManager;
  import org.apache.shiro.session.Session;
  import org.apache.shiro.session.mgt.DefaultSessionKey;
  import org.apache.shiro.session.mgt.SessionManager;
  import org.apache.shiro.subject.Subject;
  import org.apache.shiro.web.filter.AccessControlFilter;
  import org.apache.shiro.web.util.WebUtils;
  import com.fasterxml.jackson.databind.ObjectMapper;
  import com.ruoyi.common.constant.ShiroConstants;
  import com.ruoyi.common.core.domain.AjaxResult;
  import com.ruoyi.common.core.domain.entity.SysUser;
  import com.ruoyi.common.utils.ServletUtils;
  import com.ruoyi.common.utils.ShiroUtils;
  
  /**
   * 登录帐号控制过滤器
   * 
   * @author ruoyi
   */
  public class KickoutSessionFilter extends AccessControlFilter
  {
      private final static ObjectMapper objectMapper = new ObjectMapper();
  
      /**
       * 同一个用户最大会话数
       **/
      private int maxSession = -1;
  
      /**
       * 踢出之前登录的/之后登录的用户 默认false踢出之前登录的用户
       **/
      private Boolean kickoutAfter = false;
  
      /**
       * 踢出后到的地址
       **/
      private String kickoutUrl;
  
      private SessionManager sessionManager;
      private Cache<String, Deque<Serializable>> cache;
  
      @Override
      protected boolean isAccessAllowed(ServletRequest servletRequest, ServletResponse servletResponse, Object o)
              throws Exception
      {
          return false;
      }
  
      @Override
      protected boolean onAccessDenied(ServletRequest request, ServletResponse response) throws Exception
      {
          Subject subject = getSubject(request, response);
          if (!subject.isAuthenticated() && !subject.isRemembered() || maxSession == -1)
          {
              // 如果没有登录或用户最大会话数为-1，直接进行之后的流程
              return true;
          }
          try
          {
              Session session = subject.getSession();
              // 当前登录用户
              SysUser user = ShiroUtils.getSysUser();
              String loginName = user.getLoginName();
              Serializable sessionId = session.getId();
  
              // 读取缓存用户 没有就存入
              Deque<Serializable> deque = cache.get(loginName);
              if (deque == null)
              {
                  // 初始化队列
                  deque = new ArrayDeque<Serializable>();
              }
  
              // 如果队列里没有此sessionId，且用户没有被踢出；放入队列
              if (!deque.contains(sessionId) && session.getAttribute("kickout") == null)
              {
                  // 将sessionId存入队列
                  deque.push(sessionId);
                  // 将用户的sessionId队列缓存
                  cache.put(loginName, deque);
              }
  
              // 如果队列里的sessionId数超出最大会话数，开始踢人
              while (deque.size() > maxSession)
              {
                  // 是否踢出后来登录的，默认是false；即后者登录的用户踢出前者登录的用户；
                  Serializable kickoutSessionId = kickoutAfter ? deque.removeFirst() : deque.removeLast();
                  // 踢出后再更新下缓存队列
                  cache.put(loginName, deque);
  
                  try
                  {
                      // 获取被踢出的sessionId的session对象
                      Session kickoutSession = sessionManager.getSession(new DefaultSessionKey(kickoutSessionId));
                      if (null != kickoutSession)
                      {
                          // 设置会话的kickout属性表示踢出了
                          kickoutSession.setAttribute("kickout", true);
                      }
                  }
                  catch (Exception e)
                  {
                      // 面对异常，我们选择忽略
                  }
              }
  
              // 如果被踢出了，(前者或后者)直接退出，重定向到踢出后的地址
              if (session.getAttribute("kickout") != null && (Boolean) session.getAttribute("kickout") == true)
              {
                  // 退出登录
                  subject.logout();
                  saveRequest(request);
                  return isAjaxResponse(request, response);
              }
              return true;
          }
          catch (Exception e)
          {
              return isAjaxResponse(request, response);
          }
      }
  
      private boolean isAjaxResponse(ServletRequest request, ServletResponse response) throws IOException
      {
          HttpServletRequest req = (HttpServletRequest) request;
          HttpServletResponse res = (HttpServletResponse) response;
          if (ServletUtils.isAjaxRequest(req))
          {
              AjaxResult ajaxResult = AjaxResult.error("您已在别处登录，请您修改密码或重新登录");
              ServletUtils.renderString(res, objectMapper.writeValueAsString(ajaxResult));
          }
          else
          {
              WebUtils.issueRedirect(request, response, kickoutUrl);
          }
          return false;
      }
  
      public void setMaxSession(int maxSession)
      {
          this.maxSession = maxSession;
      }
  
      public void setKickoutAfter(boolean kickoutAfter)
      {
          this.kickoutAfter = kickoutAfter;
      }
  
      public void setKickoutUrl(String kickoutUrl)
      {
          this.kickoutUrl = kickoutUrl;
      }
  
      public void setSessionManager(SessionManager sessionManager)
      {
          this.sessionManager = sessionManager;
      }
  
      // 设置Cache的key的前缀
      public void setCacheManager(CacheManager cacheManager)
      {
          // 必须和ehcache缓存配置中的缓存name一致
          this.cache = cacheManager.getCache(ShiroConstants.SYS_USERCACHE);
      }
  }