Session防止重复登录

网上有很多关于重复登录的文章，我总结了一下，然后根据自己的业务做了一个：但是我觉得应该还有更好的解决办法

如果有同志有其他的办法的话欢迎留言哦！

原理也很简单：首先需要实现一个Session监听类SessionListener 使用HttpSessionListener接口实现 sessionCreated 和 sessionDestroyed方法：记得需要写上@WebListener注解

@WebListener
public class SessionListener implements HttpSessionListener {

    public static boolean isExpired = false;

    public static SessionManagement sessionManagement = SessionManagement.getInstance();

    @Override
    public void sessionCreated(HttpSessionEvent httpSessionEvent) {

        System.out.println("------------ sessionCreated");
        //session被创建 添加到HashMap
        sessionManagement.addSession(httpSessionEvent.getSession().getId(), httpSessionEvent.getSession());
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {

        System.out.println("------------ sessionDestroyed");

        isExpired = true; //标记 判断session是否过期
        sessionManagement.removeSession(httpSessionEvent.getSession().getId());
    }

}

第二步：创建一个Session管理类SessionManagement 和 HashMap

public class SessionManagement {

    private static SessionManagement sessionManagement;
    private HashMap sessionHashMap;
    private ReadWriteLock readWriteLock = new ReentrantReadWriteLock(); //线程同步

    private SessionManagement() {
        sessionHashMap = new HashMap<>();
    }

    public static SessionManagement getInstance() {
        if (sessionManagement == null) {
            sessionManagement = new SessionManagement();
        }
        return sessionManagement;
    }

    public void addSession(String id, HttpSession httpSession) {

        readWriteLock.writeLock().lock();
        try {

            if (httpSession != null && id != null && id.length() > 0) {
                sessionHashMap.put(id, httpSession);
            }

        } finally {
            readWriteLock.writeLock().unlock();
        }
    }

    public void removeSession(String id) {

        readWriteLock.writeLock().lock();
        try {

            if (id != null && id.length() > 0) {
                sessionHashMap.remove(id);
            }

        } finally {
            readWriteLock.writeLock().unlock();
        }
    }

    public HttpSession getSession(String sessionId) {

        readWriteLock.readLock().lock();
        try {
            if (sessionId == null) {
                return null;
            }

            return sessionHashMap.get(sessionId);

        } finally {
            readWriteLock.readLock().unlock();
        }

    }

    public HashMap getSessionHashMap() {
        return sessionHashMap;
    }

    public void setSessionHashMap(HashMap sessionHashMap) {
        this.sessionHashMap = sessionHashMap;
    }
}

第三：在登录接口处理业务逻辑

      //已登录 && session未过期
        HttpSession session_old = SessionManagement.getInstance().getSession(userID);
        if (!SessionListener.isExpired && session_old != null) {

            //强制过期
            session_old.invalidate();

            SessionManagement.getInstance().removeSession(String.valueOf(accountEntity.getId()));

            //更新 -- 将sessionId 更换为 userID
            SessionManagement.getInstance().removeSession(session.getId());
            SessionManagement.getInstance().addSession(String.valueOf(userID), session);
        }

        //未登录
        else {

            HttpSession session_admin = SessionManagement.getInstance().getSession(session.getId());

            if (session_admin == null) {
                throw new ControllerException("业务异常");
            }

            //替换id - session
            SessionManagement.getInstance().addSession(userID), session_admin);
            SessionManagement.getInstance().removeSession(session.getId());
        }

这样可以实现效果。如果有更好的办法欢迎大家留言 大家一起交流。