SpringBoot中Session监听器的使用

灰太狼 2022-05-13 01:42 190阅读 0赞

当需要统计应用的试试在线人数的时候，统计成功登录后创建的session的数量是最为准确的数据。SpringBoot通过SessionListener可以很方便的监听session的生命周期。在SpringBoot中监听session的步骤如下：  
1、创建session监听器.

package com.sds.listenner;
    
    import java.util.HashSet;
    
    import javax.servlet.ServletContext;
    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 SessionListener implements HttpSessionListener, HttpSessionAttributeListener { 
    
        public Logger logger = new Logger();
    
        @Override
        public void attributeAdded(HttpSessionBindingEvent httpSessionBindingEvent) {
            logger.info("--attributeAdded--");
            @SuppressWarnings("unused")
            HttpSession session = httpSessionBindingEvent.getSession();
            logger.info("key----:" + httpSessionBindingEvent.getName());
            logger.info("value---:" + httpSessionBindingEvent.getValue());
    
        }
    
        @Override
        public void attributeRemoved(HttpSessionBindingEvent httpSessionBindingEvent) {
            logger.info("--attributeRemoved--");
        }
    
        @Override
        public void attributeReplaced(HttpSessionBindingEvent httpSessionBindingEvent) {
            logger.info("--attributeReplaced--");
        }
    
        @Override
        public void sessionCreated(HttpSessionEvent event) {
            logger.info("---sessionCreated----");
            HttpSession session = event.getSession();
            ServletContext application = session.getServletContext();
            // 在application范围由一个HashSet集保存所有的session
            @SuppressWarnings("unchecked")
            HashSet<HttpSession> sessions = (HashSet<HttpSession>) application.getAttribute("sessions");
            if (sessions == null) {
                sessions = new HashSet<HttpSession>();
                application.setAttribute("sessions", sessions);
            }
            // 新创建的session均添加到HashSet集中
            sessions.add(session);
            // 可以在别处从application范围中取出sessions集合
            // 然后使用sessions.size()获取当前活动的session数，即为“在线人数”
    
            //添加新建的session到MySessionContext中;
            MySessionContext.AddSession(event.getSession());
        }
    
        @Override
        public void sessionDestroyed(HttpSessionEvent event) throws ClassCastException {
            logger.info("---sessionDestroyed----");
            HttpSession session = event.getSession();
            logger.info("deletedSessionId: " + session.getId());
            System.out.println(session.getCreationTime());
            System.out.println(session.getLastAccessedTime());
            ServletContext application = session.getServletContext();
            HashSet<?> sessions = (HashSet<?>) application.getAttribute("sessions");
            // 销毁的session均从HashSet集中移除
            sessions.remove(session);
    
            //添加新建的session到MySessionContext中;
            MySessionContext.DelSession(session);
        }
    
    }

2、创建session处理工具类，里面需要一个静态的HashMap存储应用中登录后创建的有效的session.

package com.sds.listenner;
    
    import java.util.HashMap;
    
    import javax.servlet.http.HttpSession;
    
    public class MySessionContext { 
        private static HashMap<String, HttpSession> mymap = new HashMap<String, HttpSession>();
            public static synchronized void AddSession(HttpSession session) {
                    if (session != null) {
                            mymap.put(session.getId(), session);
                         }
                 }
             public static synchronized void DelSession(HttpSession session) {
                     if (session != null) {
                             mymap.remove(session.getId());
                         }
                 }
             public static synchronized HttpSession getSession(String session_id) {
                    if (session_id == null)
                         return null;
                     return mymap.get(session_id);
                 }
    }

Logger.java

package com.sds.listenner;
    
    public class Logger {
        public void info(String info) {
            System.out.println(info);
        }
    }

3、添加SessionListener到系统配置中:

package com.sds.cfg;
    
    import org.springframework.context.annotation.Configuration;
    import org.springframework.web.servlet.config.annotation.CorsRegistry;
    import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
    @Configuration
    public class SessionConfiguration extends WebMvcConfigurerAdapter{ 
        //注册session监听器;
        @Bean
        public ServletListenerRegistrationBean<SessionListener> servletListenerRegistrationBean() {
            ServletListenerRegistrationBean<SessionListener> slrBean = new ServletListenerRegistrationBean<SessionListener>();
            slrBean.setListener(new SessionListener());
            return slrBean;
        }
    
    }

原理：通过SessionListener监听session的创建和销毁，并在对应的session生命周期中从静态的HashMap【自定义的session容器】中添加或者删除对应的session，从而实现session的动态管理，提供准确的统计数据。

注意：在本例中提供了根据sessionId获取session的方法。