[原创]DWR2.0 与struts集成小记

elevenet

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Struts Java DWR Apache Servlet

    <servlet>
        <servlet-name>action</servlet-name>
        <servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
        <init-param>
            <param-name>config</param-name>
            <param-value>/WEB-INF/struts-config.xml</param-value>
        </init-param>
        <init-param>
            <param-name>debug</param-name>
            <param-value>true</param-value>
        </init-param>
        <init-param>
            <param-name>detail</param-name>
            <param-value>3</param-value>
        </init-param>
        <load-on-startup>0</load-on-startup>
    </servlet>
    
    <servlet>
        <servlet-name>dwr-invoker</servlet-name>
        <display-name>DWR Servlet</display-name>
        <servlet-class>uk.ltd.getahead.dwr.DWRServlet</servlet-class>
        <init-param>
            <param-name>debug</param-name>
            <param-value>true</param-value>
        </init-param>
        <!--the defautl config file would be disable-->
        <!--<init-param>  
            <param-name>config-1</param-name>  
            <param-value>WEB-INF/dwr1.xml</param-value>  
        </init-param>  -->
        <init-param>
            <param-name>logLevel</param-name>
            <param-value>DEBUG</param-value>
        </init-param>
        <load-on-startup>10</load-on-startup>
    </servlet>

按官方的文档上说明，要整合struts需要在dwr的servlet装载之前被容器装载，于是有上面的配置，我用的是tomcat5.5，结果是抛空指针异常

2007-04-16 11:37:42,484 main ERROR impl.DefaultCreatorManager - Error loading class for creator 'StrutsCreator[category]'.
java.lang.NullPointerException
	at org.directwebremoting.struts.StrutsCreator.getType(StrutsCreator.java:121)
	at org.directwebremoting.impl.DefaultCreatorManager.addCreator(DefaultCreatorManager.java:118)
	at org.directwebremoting.impl.DefaultCreatorManager.addCreator(DefaultCreatorManager.java:100)
	at org.directwebremoting.impl.DwrXmlConfigurator.loadCreate(DwrXmlConfigurator.java:274)
	at org.directwebremoting.impl.DwrXmlConfigurator.loadAllows(DwrXmlConfigurator.java:224)
	at org.directwebremoting.impl.DwrXmlConfigurator.configure(DwrXmlConfigurator.java:170)
	at org.directwebremoting.impl.ContainerUtil.configureFromDefaultDwrXml(ContainerUtil.java:253)
	at org.directwebremoting.impl.ContainerUtil.configureContainerFully(ContainerUtil.java:410)
	at org.directwebremoting.servlet.DwrServlet.init(DwrServlet.java:79)
	at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1105)
	at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:932)
	at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:3917)
	at org.apache.catalina.core.StandardContext.start(StandardContext.java:4201)
	at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1013)
	at org.apache.catalina.core.StandardHost.start(StandardHost.java:718)
	at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1013)
	at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:442)
	at org.apache.catalina.core.StandardService.start(StandardService.java:450)
	at org.apache.catalina.core.StandardServer.start(StandardServer.java:709)
	at org.apache.catalina.startup.Catalina.start(Catalina.java:551)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:585)
	at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:294)
	at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:432)

后面将struts的<load-on-startup>0</load-on-startup>级别改为小于10大于0的任意整数结果装载成功。查阅web.xml的DTD说明，上面也说是0会在其它级别之前装载，不解为什么在这边会有这个问题。

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