直接在监听器定义四个变量存储数据

首先在session监听器中定义4个变量：

当前在线用户数(count)、总访问量(all)、今日访问量(today)、今日日期(day)

然后session监听器SessionCounter实现了HttpSessionListener接口，所以类中包含了sessionCreated以及sessionDestroyed方法， sessionCreated方法是在session创建的时候执行，而sessionDestroyed方法则是在session销毁时执行。在session创建时对当前在线用户数 (count)、总访问量(all)的值进行++操作，然后通过对比今日日期(day) 的值以及直接获取到的日期，对今日访问量(today)进行不同的操作即可。所以具体的实现代码如下：

实现代码：

package com.pwt.utils;

import org.springframework.stereotype.Component;

import javax.servlet.ServletContext;

import javax.servlet.http.HttpSessionEvent;

import javax.servlet.http.HttpSessionListener;

import java.util.Date;

/**

* count 当前在线用户数

* all 总访问量

* today 今日访问量

* day 今日日期

*/

@Component

public class SessionCounter implements HttpSessionListener {

private static Integer count = 0;

private static long today = 0;

private static long all = 0;

private static int day = 0;

//session创建

@Override

public void sessionCreated(HttpSessionEvent arg0) {

ServletContext context = arg0.getSession().getServletContext();

count = (Integer) context.getAttribute("onlineCount");

if (count == null) {

count = new Integer(1);

} else {

int co = count.intValue();

count = new Integer(co + 1);

}

// 保存人数

context.setAttribute("onlineCount", count);

all++;

Date date=new Date();

int tday=date.getDate();

//如果日期发生变化则将today置为1，否则将today加1

if(tday!=day){

day=tday;

today=1;

}else{

today++;

}

}

@Override

public void sessionDestroyed(HttpSessionEvent arg0) {

ServletContext context = arg0.getSession().getServletContext();

count = (Integer) context.getAttribute("onlineCount");

int co = count.intValue();

count = new Integer(co - 1);

count = count >= 0 ? count : 0;

context.setAttribute("onlineCount", count);

}

public static Integer getCount() {

return count;

}

public long getAll(){

return all;

}

public long getToday(){

return today;

}

}

在项目数据库中设计一张数据表来专门存储数据

经过我的深思熟虑，我就想把在线人数存储在session中，而今日访问量和总访问量则存储在mysql数据库中。所以我的数据表字段设计如下：

visit_id：某天访问量的id

visit_date：访问日期

visit_count：某天的访问量

到此，数据库设计完成，你们可能会说怎么没有存储总访问量的字段呢？因为我是通过数据库的sum函数来对每条数据的visit_count字段进行求和，从而得到总的访问量。

具体代码如下：

package com.pwt.utils;

import com.pwt.model.vo.VisitTotalVo;

import com.pwt.service.IVisitTotalService;

import org.springframework.stereotype.Component;

import javax.servlet.ServletContext;

import javax.servlet.http.HttpSessionEvent;

import javax.servlet.http.HttpSessionListener;

import java.text.SimpleDateFormat;

import java.util.Date;

import java.util.HashMap;

import java.util.Map;

import org.springframework.beans.factory.annotation.Autowired;

/**

* @author pwt

*/

@Component

public class SessionCounter implements HttpSessionListener {

@Autowired

private IVisitTotalService iVisitTotalService;

private static Map sessionMap = new HashMap();

public SessionCounter() {}

@Override

public void sessionCreated(HttpSessionEvent arg0) {

ServletContext context = arg0.getSession().getServletContext();

Date date = new Date();

boolean flag = true;

for(Object key : sessionMap.keySet()){

if(key.toString().equals(arg0.getSession().getId())){

flag = false;

}

}

if(flag){

sessionMap.put(arg0.getSession().getId(), arg0.getSession());

}

context.setAttribute("onlineCount", sessionMap.size());

VisitTotalVo visitTotalVo = new VisitTotalVo();

SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");

try {

visitTotalVo.setVisitDate(new java.sql.Date(sdf.parse(sdf.format(date)).getTime()));

iVisitTotalService.queryVisitTotalByVisitDate(visitTotalVo);

} catch (Exception e) {

e.printStackTrace();

}

}

@Override

public void sessionDestroyed(HttpSessionEvent arg0) {

boolean flag = false;

for(Object key : sessionMap.keySet()){

if(key.toString().equals(arg0.getSession().getId())){

flag = true;

}

}

if(flag){

sessionMap.remove(arg0.getSession().getId());

}

ServletContext context = arg0.getSession().getServletContext();

context.setAttribute("onlineCount", sessionMap.size());

}

}

从代码中可以看到，我直接在监听器中调用了service层的方法，如果你直接这样运行项目的话，项目会出现空指针异常，原因是监听器属于sevlet容器，不属于 Spring 框架的管理范围，拿不到spring注解注入的bean。要想让项目不会报错，我是这样解决的：

代码：

package com.pwt.utils;

import com.pwt.service.IVisitTotalService;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;

@Component

public class InjectServiceUtil {

@Autowired

private IVisitTotalService iVisitTotalService;

@PostConstruct

public void init(){

InjectServiceUtil.getInstance().iVisitTotalService = this.iVisitTotalService;

}

/**

* 实现单例 start

*/

private static class SingletonHolder {

private static final InjectServiceUtil INSTANCE = new InjectServiceUtil();

}

private InjectServiceUtil (){}

public static final InjectServiceUtil getInstance() {

return SingletonHolder.INSTANCE;

}

/**

* 实现单例 end

*/

public static IVisitTotalService getIVisitTotalService(){

return InjectServiceUtil.getInstance().iVisitTotalService;

}

}

修改监听器如下：

package com.pwt.utils;

import com.pwt.model.vo.VisitTotalVo;

import com.pwt.service.IVisitTotalService;

import org.springframework.stereotype.Component;

import javax.servlet.ServletContext;

import javax.servlet.http.HttpSessionEvent;

import javax.servlet.http.HttpSessionListener;

import java.text.SimpleDateFormat;

import java.util.Date;

import java.util.HashMap;

import java.util.Map;

/**

* @author pwt

*/

@Component

public class SessionCounter implements HttpSessionListener {

private static IVisitTotalService iVisitTotalService;

private static Map sessionMap = new HashMap();

public SessionCounter() {}

@Override

public void sessionCreated(HttpSessionEvent arg0) {

ServletContext context = arg0.getSession().getServletContext();

Date date = new Date();

boolean flag = true;

for(Object key : sessionMap.keySet()){

if(key.toString().equals(arg0.getSession().getId())){

flag = false;

}

}

if(flag){

sessionMap.put(arg0.getSession().getId(), arg0.getSession());

}

context.setAttribute("onlineCount", sessionMap.size());

VisitTotalVo visitTotalVo = new VisitTotalVo();

iVisitTotalService = InjectServiceUtil.getIVisitTotalService();

SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");

try {

visitTotalVo.setVisitDate(new java.sql.Date(sdf.parse(sdf.format(date)).getTime()));

iVisitTotalService.queryVisitTotalByVisitDate(visitTotalVo);

} catch (Exception e) {

e.printStackTrace();

}

}

@Override

public void sessionDestroyed(HttpSessionEvent arg0) {

boolean flag = false;

for(Object key : sessionMap.keySet()){

if(key.toString().equals(arg0.getSession().getId())){

flag = true;

}

}

if(flag){

sessionMap.remove(arg0.getSession().getId());

}

ServletContext context = arg0.getSession().getServletContext();

context.setAttribute("onlineCount", sessionMap.size());

}

}

这样项目运行就不会再出现空指针异常。最后两种思路还需要配置web.xml文件：

<listener>

<listener-class>com.pwt.utils.SessionCounter</listener-class>

</listener>



<session-config>

<session-timeout>3</session-timeout>

</session-config>

ssm如何在监听器中使用spring注解注入的service层？