java服务器推的实现
转载自：http://vincent-yy.iteye.com/blog/427922
小型聊天室--DWR实现服务器推技术
当看到DWR2也可以实现推技术之后，想尝试一下！
首先当官方上下载一个dwr的jar文件和commons-logging-1.1.1.jar
先从配置文件入手
web.xml
Xml代码
<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<!-- 以设置下格式固定，可复制使用 -->
<display-name>ajaxDWR</display-name>
<servlet>
<servlet-name>dwr-invoker</servlet-name>
<!--
<servlet-class>uk.ltd.getahead.dwr.DWRServlet</servlet-class>
-->
<servlet-class>
org.directwebremoting.servlet.DwrServlet
</servlet-class>
<init-param>
<description>实现调试，在debug请设置为false</description>
<param-name>debug</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<description>使用服务器推技术(反转AJAX)</description>
<param-name>activeReverseAjaxEnabled</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>
initApplicationScopeCreatorsAtStartup
</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>maxWaitAfterWrite</param-name>
<param-value>100</param-value>
</init-param>
<load-on-startup>4</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>dwr-invoker</servlet-name>
<url-pattern>/dwr/*</url-pattern>
</servlet-mapping>
</web-app>
dwr.xml
Xml代码
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE dwr PUBLIC "-//GetAhead Limited//DTD Direct Web Remoting 2.0//EN" "http://www.getahead.ltd.uk/dwr/dwr20.dtd">
<dwr>
<!-- 对后台类的配置格式确定 -->
<allow>
<create creator="new" javascript="Chat">
<param name="class" value="com.dwr.chat.Chat" />
</create>
</allow>
</dwr>
编写好配置文件之后，开始编写页面，我们可以选择html或者jsp都可以
index3.html
Html代码
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>index3.html</title>
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<script type='text/javascript' src='dwr/util.js'></script>
<script type='text/javascript' src='dwr/engine.js'></script>
<script type='text/javascript' src='dwr/interface/Chat.js'></script>
<!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
</head>
<body>
<center>
<table width="600px" border="1">
<tr>
<td colspan="3" align="center">
XXXXXX Chat
</td>
<td>
User List
</td>
</tr>
<tr>
<td colspan="3" style="height: 300px">
<textarea rows="20" cols="60" readonly id="showmessage" name="showmessage"></textarea>
</td>
<td style="height: 300px" valign="top">
<div id="userlist" style="height:310px;overflow : scroll;"></div>
</td>
</tr>
<tr>
<td colspan="3" align="center">
<span id="say_name" ></span>
<textarea rows="3" cols="50" id="say_message" name="say_message"></textarea><input type="button" value="say" id="say" onclick="sayMessage()"/>
</td>
<td>
先录入你的昵称<br/>
<input type="text" style="width: 125px" name="name" id="name" />
<input type="button" value="确定" onclick="register()" />
</td>
</tr>
</table>
</center>
</body>
<script type="text/javascript">
dwr.engine.setActiveReverseAjax(true); // 激活反转 重要
init();
function init(){
document.getElementById('say_message').disabled = true;
document.getElementById('say').disabled = true;
}
function sayMessage(){
var message_content = DWRUtil.getValue('say_message');
var message_head = document.getElementById('say_name').innerHTML;
Chat.sayMessage(message_head+message_content);
document.getElementById('say_message').value = '';
}
function register() {
var name = DWRUtil.getValue("name");
Chat.addUser(name,callback);
}
function callback(str) {
if(str != ''){
alert(str);
}else{
document.getElementById('say_name').innerHTML = DWRUtil.getValue("name") + " 说：";
document.getElementById('say_message').disabled = false;
document.getElementById('say').disabled = false;
}
}
</script>
</html>
这个页面比较简陋，建议js写在下方，否则firefox会报错
Chat.java
Java代码
package com.dwr.chat;
import java.util.ArrayList;
import java.util.Collection;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import org.directwebremoting.ServerContext;
import org.directwebremoting.ServerContextFactory;
import org.directwebremoting.proxy.dwr.Util;
public class Chat {
static ArrayList<String> name_list = new ArrayList<String>();
static StringBuffer show_message = new StringBuffer();
public String addUser(String name,HttpServletRequest request) {
System.out.println("list.size() = "+name_list.size());
for (String s : name_list) {
if (name == null || name.trim().equals(s)) {
return "用户名已存在";
}
}
name_list.add(name.trim());
ServletContext sc = request.getSession().getServletContext();
ServerContext sctx = ServerContextFactory.get(sc);
Collection sessions = sctx.getScriptSessionsByPage("/dwr2Demo/index3.html");
Util util = new Util(sessions);
show_message.append("\n欢迎"+name+"来到 XXX Chat");
trimMessage();
util.setValue("showmessage", show_message.toString());
printUserList(util);
return "";
}
public void sayMessage(String message,HttpServletRequest request){
ServletContext sc = request.getSession().getServletContext();
ServerContext sctx = ServerContextFactory.get(sc);
Collection sessions = sctx.getScriptSessionsByPage("/dwr2Demo/index3.html");
Util util = new Util(sessions);
show_message.append("\n"+message);
trimMessage();
util.setValue("showmessage", show_message.toString());
printUserList(util);
}
public void trimMessage(){
if(show_message.length() > 2000){
show_message.delete(0, ((show_message.length() - 2000)*2+2));
}
}
public void printUserList(Util util){
StringBuffer userlist = new StringBuffer();
userlist.append("<table>");
for(String s : name_list){
userlist.append("<tr><td><font color='blue'>"+s+"</font></td></tr>");
}
userlist.append("</table>");
util.setValue("userlist", userlist.toString());
}
}
编写好这个之后，可以运行一下。
经过测试，发现几个问题 浏览器我现在测试了三种发现三种都有自己的特性
IE ：比较正常，有时候会慢一些
firefox ：每次刷新访问的时候服务器会出现一个异常
google浏览器：在刷新的时候会无限等待，一直到接收到信息
另一教程：http://hintcnuie.iteye.com/blog/175828
小型聊天室--DWR实现服务器推技术
当看到DWR2也可以实现推技术之后，想尝试一下！
首先当官方上下载一个dwr的jar文件和commons-logging-1.1.1.jar
先从配置文件入手
web.xml
Xml代码
<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<!-- 以设置下格式固定，可复制使用 -->
<display-name>ajaxDWR</display-name>
<servlet>
<servlet-name>dwr-invoker</servlet-name>
<!--
<servlet-class>uk.ltd.getahead.dwr.DWRServlet</servlet-class>
-->
<servlet-class>
org.directwebremoting.servlet.DwrServlet
</servlet-class>
<init-param>
<description>实现调试，在debug请设置为false</description>
<param-name>debug</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<description>使用服务器推技术(反转AJAX)</description>
<param-name>activeReverseAjaxEnabled</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>
initApplicationScopeCreatorsAtStartup
</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>maxWaitAfterWrite</param-name>
<param-value>100</param-value>
</init-param>
<load-on-startup>4</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>dwr-invoker</servlet-name>
<url-pattern>/dwr/*</url-pattern>
</servlet-mapping>
</web-app>
dwr.xml
Xml代码
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE dwr PUBLIC "-//GetAhead Limited//DTD Direct Web Remoting 2.0//EN" "http://www.getahead.ltd.uk/dwr/dwr20.dtd">
<dwr>
<!-- 对后台类的配置格式确定 -->
<allow>
<create creator="new" javascript="Chat">
<param name="class" value="com.dwr.chat.Chat" />
</create>
</allow>
</dwr>
编写好配置文件之后，开始编写页面，我们可以选择html或者jsp都可以
index3.html
Html代码
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>index3.html</title>
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<script type='text/javascript' src='dwr/util.js'></script>
<script type='text/javascript' src='dwr/engine.js'></script>
<script type='text/javascript' src='dwr/interface/Chat.js'></script>
<!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
</head>
<body>
<center>
<table width="600px" border="1">
<tr>
<td colspan="3" align="center">
XXXXXX Chat
</td>
<td>
User List
</td>
</tr>
<tr>
<td colspan="3" style="height: 300px">
<textarea rows="20" cols="60" readonly id="showmessage" name="showmessage"></textarea>
</td>
<td style="height: 300px" valign="top">
<div id="userlist" style="height:310px;overflow : scroll;"></div>
</td>
</tr>
<tr>
<td colspan="3" align="center">
<span id="say_name" ></span>
<textarea rows="3" cols="50" id="say_message" name="say_message"></textarea><input type="button" value="say" id="say" onclick="sayMessage()"/>
</td>
<td>
先录入你的昵称<br/>
<input type="text" style="width: 125px" name="name" id="name" />
<input type="button" value="确定" onclick="register()" />
</td>
</tr>
</table>
</center>
</body>
<script type="text/javascript">
dwr.engine.setActiveReverseAjax(true); // 激活反转 重要
init();
function init(){
document.getElementById('say_message').disabled = true;
document.getElementById('say').disabled = true;
}
function sayMessage(){
var message_content = DWRUtil.getValue('say_message');
var message_head = document.getElementById('say_name').innerHTML;
Chat.sayMessage(message_head+message_content);
document.getElementById('say_message').value = '';
}
function register() {
var name = DWRUtil.getValue("name");
Chat.addUser(name,callback);
}
function callback(str) {
if(str != ''){
alert(str);
}else{
document.getElementById('say_name').innerHTML = DWRUtil.getValue("name") + " 说：";
document.getElementById('say_message').disabled = false;
document.getElementById('say').disabled = false;
}
}
</script>
</html>
这个页面比较简陋，建议js写在下方，否则firefox会报错
Chat.java
Java代码
package com.dwr.chat;
import java.util.ArrayList;
import java.util.Collection;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import org.directwebremoting.ServerContext;
import org.directwebremoting.ServerContextFactory;
import org.directwebremoting.proxy.dwr.Util;
public class Chat {
static ArrayList<String> name_list = new ArrayList<String>();
static StringBuffer show_message = new StringBuffer();
public String addUser(String name,HttpServletRequest request) {
System.out.println("list.size() = "+name_list.size());
for (String s : name_list) {
if (name == null || name.trim().equals(s)) {
return "用户名已存在";
}
}
name_list.add(name.trim());
ServletContext sc = request.getSession().getServletContext();
ServerContext sctx = ServerContextFactory.get(sc);
Collection sessions = sctx.getScriptSessionsByPage("/dwr2Demo/index3.html");
Util util = new Util(sessions);
show_message.append("\n欢迎"+name+"来到 XXX Chat");
trimMessage();
util.setValue("showmessage", show_message.toString());
printUserList(util);
return "";
}
public void sayMessage(String message,HttpServletRequest request){
ServletContext sc = request.getSession().getServletContext();
ServerContext sctx = ServerContextFactory.get(sc);
Collection sessions = sctx.getScriptSessionsByPage("/dwr2Demo/index3.html");
Util util = new Util(sessions);
show_message.append("\n"+message);
trimMessage();
util.setValue("showmessage", show_message.toString());
printUserList(util);
}
public void trimMessage(){
if(show_message.length() > 2000){
show_message.delete(0, ((show_message.length() - 2000)*2+2));
}
}
public void printUserList(Util util){
StringBuffer userlist = new StringBuffer();
userlist.append("<table>");
for(String s : name_list){
userlist.append("<tr><td><font color='blue'>"+s+"</font></td></tr>");
}
userlist.append("</table>");
util.setValue("userlist", userlist.toString());
}
}
编写好这个之后，可以运行一下。
经过测试，发现几个问题 浏览器我现在测试了三种发现三种都有自己的特性
IE ：比较正常，有时候会慢一些
firefox ：每次刷新访问的时候服务器会出现一个异常
google浏览器：在刷新的时候会无限等待，一直到接收到信息
另一教程：http://hintcnuie.iteye.com/blog/175828