Spring + DWR Comet 實現無刷新多人聊天室（二）：專案搭建、web.xml 與基礎配置全記錄

依賴準備

• DWR 3.x：官方構建包；
• Spring 3.0.5：SpringSource EBR；
• 所需 JAR (參考截圖)：spring-core, context, web, beans, aop, tx, expression, asm, commons-logging, dwr 等。

Web 專案創建：DWRComet

web.xml 完整配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="https://java.sun.com/xml/ns/javaee"
         xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="https://java.sun.com/xml/ns/javaee
                             https://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

    <!-- Spring 容器啟動 -->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath*:applicationContext-*.xml</param-value>
    </context-param>

    <!-- DWR 核心 -->
    <listener>
        <listener-class>org.directwebremoting.servlet.DwrListener</listener-class>
    </listener>
    <servlet>
        <servlet-name>dwr-invoker</servlet-name>
        <servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class>
        <init-param>
            <param-name>debug</param-name>
            <param-value>true</param-value>
        </init-param>
        <!-- 關鍵：啟用 Comet (Reverse Ajax) -->
        <init-param>
            <param-name>pollAndCometEnabled</param-name>
            <param-value>true</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>dwr-invoker</servlet-name>
        <url-pattern>/dwr/*</url-pattern>
    </servlet-mapping>

</web-app>

關鍵配置解讀

Spring Bean 配置 applicationContext-beans.xml (初始骨架)

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="https://www.springframework.org/schema/beans"
       xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
       xmlns:aop="https://www.springframework.org/schema/aop"
       xmlns:tx="https://www.springframework.org/schema/tx"
       xmlns:util="https://www.springframework.org/schema/util"
       xmlns:context="https://www.springframework.org/schema/context"
       xsi:schemaLocation="
           https://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans-3.0.xsd
           https://www.springframework.org/schema/aop https://www.springframework.org/schema/aop/spring-aop-3.0.xsd
           https://www.springframework.org/schema/tx https://www.springframework.org/schema/tx/spring-tx-3.0.xsd
           https://www.springframework.org/schema/util https://www.springframework.org/schema/util/spring-util-3.0.xsd
           https://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context-3.0.xsd">
    <!-- 具體 Bean 於後續篇幅註冊 -->
</beans>

DWR 配置 dwr.xml (最小骨架)

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE dwr PUBLIC "-//GetAhead Limited//DTD Direct Web Remoting 3.0//EN"
        "https://getahead.org/dwr/dwr30.dtd">
<dwr>
    <!-- 具體 allow/create/convert 於後續篇幅配置 -->
</dwr>

開發環境記錄

• OS：Windows；
• 瀏覽器：IE6+ / Firefox 3+；
• 容器：Tomcat 5.5 / 6.0 (生產建議 Jetty 以支援 Continuation)；
• IDE：Eclipse / MyEclipse 8；
• 規範：Java EE 5、Spring 3.0.5、DWR 3。

基礎設施就緒，下一篇進入業務邏輯實現：Message 實體、ChatMessageEvent、ChatService。