其他監(jiān)聽器

1ServletContextListener 用于監(jiān)聽SevletContext的創(chuàng)建

在web中的所的監(jiān)聽器都是全局的 － 都是在項(xiàng)目啟動(dòng)時(shí)直接由tomcat創(chuàng)建。

監(jiān)聽器沒有順序。只是監(jiān)聽的對(duì)象不一樣。

在一個(gè)項(xiàng)目中可以存在多個(gè)監(jiān)聽器。

package cn.hx.listener;

import java.io.BufferedReader;

import java.io.File;

import java.io.FileNotFoundException;

import java.io.FileReader;

import java.io.PRintWriter;

import java.net.URL;

import javax.servlet.ServletContextEvent;

import javax.servlet.ServletContextListener;

public class MyContextListener implements ServletContextListener {

//在啟動(dòng)時(shí)讀取數(shù)據(jù)庫(kù)之前保存的數(shù)據(jù)

public void contextInitialized(ServletContextEvent sc) {

System.err.println("application被創(chuàng)建了:"+sc.getServletContext());

URL url = MyContextListener.class.getClassLoader().getResource("count.txt");

String path = url.getFile();

System.err.println(path);

try {

BufferedReader bf = new BufferedReader(new FileReader(path));

String line = bf.readLine();

Integer count = Integer.valueOf(line);

sc.getServletContext().setAttribute("count",count);

System.err.println("初始的值是:"+count);

} catch (Exception e) {

e.printStackTrace();

}

}

//在銷毀這個(gè)對(duì)象時(shí)保存一些數(shù)據(jù)到數(shù)據(jù)庫(kù)或是文件中

public void contextDestroyed(ServletContextEvent e) {

System.err.println("銷毀了:"+e.getServletContext());

//保存到文件中去

URL url = MyContextListener.class.getClassLoader().getResource("count.txt");

String path = url.getFile();

System.err.println(path);

File file = new File(path);

try {

PrintWriter out = new PrintWriter(file);

//獲取applicat的數(shù)據(jù)

Integer count = (Integer) e.getServletContext().getAttribute("count");

out.print(count);

out.close();

} catch (FileNotFoundException e1) {

e1.printStackTrace();

}

}

}

在項(xiàng)目啟動(dòng)時(shí)一次加載所有的配置文件。

第一步：書寫B(tài)ean實(shí)現(xiàn)HttpSessionActivationListener

package cn.hx.domain;

import java.io.Serializable;

import javax.servlet.http.HttpSessionActivationListener;

import javax.servlet.http.HttpSessionEvent;

public class Person implements Serializable,HttpSessionActivationListener{

private String name;

public Person() {

}

public Person(String name) {

this.name = name;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public void sessionWillPassivate(HttpSessionEvent se) {

System.err.println("保存到文件中去了..."+this.getName());

}

public void sessionDidActivate(HttpSessionEvent se) {

System.err.println("從文件中活化了...."+this.getName());

}

@Override

public String toString() {

return "Person [name=" + name + "]";

}

}

第二步：配置這個(gè)項(xiàng)目

<Context docBase="D://programfiles//MyEcl

<Manager className="org.apache.catalina.session.PersistentManager"

saveOnRestart="true">

<Store className="org.apache.catalina.session.FileStore"

directory="d:/a">

</Store>

</Manager>

</Context>

第三步：測(cè)試

<%

if(session.getAttribute("p")==null){

int a = new Random().nextInt(100);

Person p = new Person(""+a);

session.setAttribute("p",p);

}

//保存cookie

Cookie c = new Cookie("JSESSIONID",session.getId());

c.setMaxAge(60*30);

c.setPath(request.getContextPath());

response.addCookie(c);

%>

<hr/>

${p}

<hr/>

<%=session.getId()%>