java-implement a listener HttpServletRequest creation destruction, number of people online (56)

Listener Classification in Javaweb

There are three monitored objects in the javaweb:

HttpServletRequest

Httpsessoin

ServletContext

Monitor Listener	By the Listener	Hear Event Object
Httpsessionactivationlistener	httpsession– monitoring of HttpSession activation and Dayton.	Httpsessionevent
Httpsessionattributelistener [W1]	httpsession– Monitor the properties of the session change. S.setattributee ();	Httpsessionbindingevent
Httpsessionbindinglistener	HttpSession-Listen to which object is bound to the session. S.setatrri (Name,user);
Httpsessionlistener [W2]	httpsesion– Monitor Sessioin Create destroy	Httpsessionevent
Servletcontextattributelistener	servletcontext– property changes.
Servletcontextlistener	ServletContext Create Destroy
Servletrequestlistener -Serlvetrequestattibutelistner	Rrequest-Create Destroy

Implement the creation of a listener httpservletrequest destroy

First step: Implement a class:

Package Cn.hx.listener;

import javax.servlet.ServletRequestEvent;

import Javax.servlet.ServletRequestListener;

Public class Requestlistener implements Servletrequestlistener {

Public void requestdestroyed (servletrequestevent SRE) {

System. err. println ("Request destroyed:");

Object o = Sre.getsource ();

System. err. println ("This O is:" +o);//[email protected]

}

Public void requestinitialized (servletrequestevent SRE) {

System. err. println ("Request created:");

Object o = Sre.getsource ();

System. err. println ("This O is:" +o);//[email protected]

}

}

Step two: Must be configured to Web. xml

<listener>

<listener-class>cn.itcast.listener.RequestListener</listener-class>

</listener>

Description

1: Configuring a listener only requires the class name to be available.

2: This listener class is automatically initialized when Tomcat is started.

The listner,serlvet,filter created by 3:tomcat are single-column.

Number of people online

As long as someone visits this site, the successful creation of a session is a conversation, a session is an online number.

Use Httpssessionlistener to monitor the creation of the session.

The first step:

Package Cn.hx.listener;

import java.util.ArrayList;

import java.util.List;

import Javax.servlet.ServletContext;

import javax.servlet.http.HttpSession;

import javax.servlet.http.HttpSessionEvent;

import Javax.servlet.http.HttpSessionListener;

/**

* The following statistics are implemented for online people

*/

Public class Mysessionlistener implements Httpsessionlistener {

Private Integer online=1;

Request.getsession ();

Public void sessioncreated (httpsessionevent se) {

System. err. println ("Someone has visited this network");

HttpSession HS1 = (HttpSession) se.getsource ();

HttpSession HS2 = Se.getsession ();

System. err. println ("HS1:" +hs1.getid () + "," +hs2.getid () + ", IP:");

Get an entire domain object

ServletContext sc= se.getsession (). Getservletcontext ();

Sc.setattribute ("online", online++);

Place all sessions in ServletContext

Get all the Sesison that have been maintained from application first

list(list"Sessions");

if (list==null) {//First person to visit

List = new arraylist

Sc.setattribute ("Sessions", list);

}

List.add (HS2);

}

Expired (+), s.invalidate ();

Public void sessiondestroyed (httpsessionevent se) {

System. err. println ("Someone Quit ..." +se.getsession (). GetId ());

ServletContext sc= se.getsession (). Getservletcontext ();

Sc.setattribute ("online", online--);

}

}

java-implement a listener HttpServletRequest creation destruction, number of people online (56)