使用session实现防止重复登录

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目前我用的是Struts2的拦截器

1:利用拦截器，配置拦截器  在Struts2中配置

		
		
			
			
			
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2：创建LoginInterceptor类 extends AbstractInterceptor    

package com.enet.fileter;

import java.net.URLDecoder;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import org.apache.struts2.ServletActionContext;
import com.enet.action.UsersAction;
import com.enet.entity.Userinfo;
import com.opensymphony.xwork2.Action;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.interceptor.AbstractInterceptor;


public class LoginInterceptor extends AbstractInterceptor {

	@Override
	public String intercept(ActionInvocation invaction) throws Exception {
		// TODO Auto-generated method stub
		HttpSession sessiona = ServletActionContext.getRequest().getSession();
		Map session= invaction.getInvocationContext().getSession();  
		System.out.println(session.toString());
		if(UsersAction.class == invaction.getAction().getClass()){
			 return invaction.invoke();  
		}
		Userinfo sss= (Userinfo)sessiona.getAttribute("user");
		Userinfo ss= (Userinfo) ServletActionContext.getRequest().getSession().getAttribute("user");
		
        if(sessiona.getAttribute("user") != null){  
            return invaction.invoke();  
        }else{  
            //若为空，直接跳转到登录页面  
            return Action.ERROR;  
        }  
	}
}

PS:这个session获取的是JSP中的值，不是action中的

3：创建一个UserAction，有登录和登出的方法

public String login(){
		HttpServletRequest httpRequest = ServletActionContext.getRequest();
		HttpSession httpSession = httpRequest.getSession();
		//加密
		user.setPassword(MD5Util.MD5(user.getPassword()));
		//判断用户名密码是否正确，返回这个用户的对象
		Xuser users=biz.getlogin(user);
		//查看是否有用户
		if(users !=null){
             //查看判断是否登录过
			if(MyHttpSessionListener.OnLineSession.containsKey(users.getLoginname())){
				HttpSession session=MyHttpSessionListener.OnLineSession.get(users.getLoginname());
				if(!httpSession.getId().equals(session.getId())){
					session.invalidate();
				}
			}
			MyHttpSessionListener.OnLineSession.put(users.getLoginname(), httpSession);
			ServletActionContext.getRequest().getSession().setAttribute("user", users);
			return SUCCESS;
		}else{
			return ERROR;
		}
	}
	public String logout(){
		return ERROR;
	}

我是把用户的名称作为KEY保存到Session中，

现在还有会有错误的，因为你没有写MyHttpSessionListener这个类

4：创建MyHttpSessionListener类 implements HttpSessionListener

package com.enet.fileter;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

@WebListener
public class MyHttpSessionListener implements HttpSessionListener {
	public static final Map OnLineSession = new HashMap();
	private int userNumber;
	//获取人数
	@Override
	public void sessionCreated(HttpSessionEvent event) {
		// TODO Auto-generated method stub
		userNumber++;
		event.getSession().getServletContext().setAttribute("userNumber", userNumber);
	
	}

	@Override
	public void sessionDestroyed(HttpSessionEvent event) {
		HttpSession httpSession = event.getSession();
		for (String key : OnLineSession.keySet()) {
			if (httpSession.getId().equals(OnLineSession.get(key).getId())) {
				OnLineSession.remove(key);
				break;
			}
		}
	}

	
}

  PS：这个是清除session中的值，判断key中是否有重复的值

 

 

 

 

 

 

转载于:https://my.oschina.net/u/3578766/blog/1557032