在Spring 2中整合DWR 2

前些日子看了一篇关于在Spring 2中整合DWR 2的文章《AJAX, DWR and Spring》。最近，想动手试一下，就下载其源代码回来看看，依葫芦画瓢做了一遍。在运行时，得到XML验证错误。经过一翻折腾，终于把问题解决。

Spring 2基于XML Schema的配置

众所周知，Spring 2通过XML Schema配置方式极大地简化的其配置，而且使得第三方扩展变为可能。配置如下代码所示：

<? xml version="1.0" encoding="UTF-8" ?>
< beans xmlns ="http://www.springframework.org/schema/beans"
    xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation ="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd" >    
    
    <!-- <bean /> definitions here -->
    
</ beans >

清单1 applicationContext.xml

不知大家有没有想过spring-beans-2.0.xsd位置在那里？其实，大家可以用Eclipse打开Spring的jar包，展开META-INF，并双击打开其中的spring.schemas文件，内容如下：

http\://www.springframework.org/schema/beans/spring-beans- 2.0 .xsd = org/springframework/beans/factory/xml/spring-beans- 2.0 .xsd
http\://www.springframework.org/schema/tool/spring-tool- 2.0 .xsd = org/springframework/beans/factory/xml/spring-tool- 2.0 .xsd
http\://www.springframework.org/schema/util/spring-util- 2.0 .xsd = org/springframework/beans/factory/xml/spring-util- 2.0 .xsd
http\://www.springframework.org/schema/aop/spring-aop- 2.0 .xsd = org/springframework/aop/config/spring-aop- 2.0 .xsd
http\://www.springframework.org/schema/lang/spring-lang- 2.0 .xsd = org/springframework/scripting/config/spring-lang- 2.0 .xsd
http\://www.springframework.org/schema/tx/spring-tx- 2.0 .xsd = org/springframework/transaction/config/spring-tx- 2.0 .xsd
http\://www.springframework.org/schema/jee/spring-jee- 2.0 .xsd = org/springframework/ejb/config/spring-jee- 2.0 .xsd

http\://www.springframework.org/schema/beans/spring-beans.xsd = org/springframework/beans/factory/xml/spring-beans- 2.0 .xsd
http\://www.springframework.org/schema/tool/spring-tool.xsd = org/springframework/beans/factory/xml/spring-tool- 2.0 .xsd
http\://www.springframework.org/schema/util/spring-util.xsd = org/springframework/beans/factory/xml/spring-util- 2.0 .xsd
http\://www.springframework.org/schema/aop/spring-aop.xsd = org/springframework/aop/config/spring-aop- 2.0 .xsd
http\://www.springframework.org/schema/lang/spring-lang.xsd = org/springframework/scripting/config/spring-lang- 2.0 .xsd
http\://www.springframework.org/schema/tx/spring-tx.xsd = org/springframework/transaction/config/spring-tx- 2.0 .xsd
http\://www.springframework.org/schema/jee/spring-jee.xsd = org/springframework/ejb/config/spring-jee- 2.0 .xsd

清单2 spring.schemas

从以上的文件中，可以看出XML Sechema文件在类包中位置。

DWR 2.0 RC 2中的XML Schema文件

根据上面的描述，我打开DWR的jar包中spring.schemas文件，内容如下：

http\://www.directwebremoting.org/schema/spring-dwr- 2.0 .xsd = org/directwebremoting/spring/spring-dwr- 2.0 .xsd

然后，按照上面的路径打开spring-dwr-2.0.xsd文件，内容如下：

<? xml version="1.0" encoding="UTF-8" standalone="no" ?>

<!-- 省略了版权信息 -->

< xsd:schema xmlns ="http://www.directwebremoting.org/schema/spring-dwr"
            xmlns:xsd ="http://www.w3.org/2001/XMLSchema"
            targetNamespace ="http://www.directwebremoting.org/schema/spring-dwr"
            elementFormDefault ="qualified"
            attributeFormDefault ="unqualified" >

<!-- 省略了具体的定义 -->
</ xsd:schema >

清单3 spring-dwr-2.0.xsd

文件spring-dwr-2.0.xsd告诉我们，其名称空间应为“http://www.directwebremoting.org/schema/spring-dwr”，所以我们在配置Spring 2时，应使用以上的名称空间，如下面的代码片段所示：

<? xml version="1.0" encoding="UTF-8" ?>

< beans xmlns ="http://www.springframework.org/schema/beans"
    xmlns:dwr ="http://www.directwebremoting.org/schema/spring-dwr"
    xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation ="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.directwebremoting.org/schema/spring-dwr http://www.directwebremoting.org/schema/spring-dwr-2.0.xsd" >

    < dwr:configuration >
        < dwr:convert class ="net.blogjava.max.pws.domain.Album" type ="bean" >
            < dwr:exclude method ="photos" />
        </ dwr:convert >
        < dwr:convert class ="net.blogjava.max.pws.domain.Photo" type ="bean" >
            < dwr:exclude method ="original, poster, thumb, full, album" />
        </ dwr:convert >
    </ dwr:configuration >

    < bean id ="ajaxFacade"
        class ="net.blogjava.max.pws.web.ajax.AjaxFacade" >
        < dwr:remote javascript ="AjaxFacade" />
        < property name ="personalWebSite" ref ="personalWebSite" />
    </ bean >

</ beans >

清单3 ajaxContext.xml

WEB-INF/web.xml配置

通过上面的配置，我们可以省去dwr.xml配置，不过在web.xml配置dwr的Servlet时，要使用新的Servlet类。配置代码片段如下：

< servlet >
    < servlet-name > dwr </ servlet-name >
    < servlet-class > org.directwebremoting.spring.DwrSpringServlet </ servlet-class >
    < init-param >
        < param-name > debug </ param-name >
        < param-value > true </ param-value >
    </ init-param >
    < load-on-startup > 1 </ load-on-startup >
</ servlet >

< servlet-mapping >
    < servlet-name > dwr </ servlet-name >
    < url-pattern > /dwr/* </ url-pattern >
</ servlet-mapping >

清单4 web.xml

总结

通过在Spring 2整合DWR 2配置，可以集中管理应用程序的配置，从一定程度上解决JavaEE开发中的配置文件泛滥的问题。