初学Struts，写了一个很简单的应用，主要功能和页面如下：
1、首页显示一个“添加新用户”的链接，点击该链接出发一个forward动作，页面导向到添加用户的jsp页面
2、添加用户的jsp页面中，可供用户输入“用户名”和“用户描述”两项
3、用户输入完毕，将做输入数据合法性检查，检查通过，将输入信息保存进入文件（使用了Properties类），然后返回首页；检查失败返回添加用户页面
4、数据合法性检查分成两块，第一部分检查条件使用Struts的Validator，检查条件配置在Validator.xml中；第二部分检查放在ActionForm中，
检查失败将错误信息置入ActionErrors中，然后返回到添加用户的页面并显示错误信息。

JSP页面、ActionForm和Action类的代码书写都参照了struts-example应用，所以这里代码不再列举，请看附件中的代码包
这里值得一提的是，在开发过程中，碰到了一个小问题，正是由于该问题，才导致查看Struts源码，刨根问底的查找错误原因的过程
该错误发生在Struts的配置文件中，首先将错误的配置文件列出如下：
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<?xml version="1.0" encoding="ISO-8859-1" ?>

<!DOCTYPE struts-config PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 1.1//EN"
"http://jakarta.apache.org/struts/dtds/struts-config_1_1.dtd">

<struts-config>

<!-- ======================================== Form Bean Definitions -->

<form-beans>

<form-bean

name="CreateUserForm"

type="com.zchome.CreateUserForm"/>


</form-beans>

<!-- ================================= Global Exception Definitions -->

<global-exceptions>

</global-exceptions>

<!-- =================================== Global Forward Definitions -->

<global-forwards>

<!-- Default forward to "Welcome" action -->

<!-- Demonstrates using index.jsp to forward -->

<forward name="welcome" path="/Welcome.do"/>

</global-forwards>

<!-- =================================== Action Mapping Definitions -->

<action-mappings>

<!-- Default "Welcome" action -->

<!-- Forwards to Welcome.jsp -->

<action

path="/Welcome"

type="org.apache.struts.actions.ForwardAction"

parameter="/jsp/Welcome.jsp"/>


<action path="/createuserpage" forward="/jsp/createuser.jsp">
</action>


<action

path="/docreateuser"

type="com.zchome.CreateUserAction"

name="CreateUserForm"

scope="request"

input="createuser">

<forward name="createusersuccess" path="/jsp/Welcome.jsp"/>

<forward name="createuser" path="/jsp/createuser.jsp"/>

</action>


</action-mappings>


<!-- ===================================== Controller Configuration -->

<controller>
<set-property property="processorClass" value="org.apache.struts.tiles.TilesRequestProcessor"/>
</controller>

<!-- ================================ Message Resources Definitions -->

<message-resources parameter="resources.application"/>

<!-- ======================================= Plug Ins Configuration -->

<!-- ========== Tiles plugin =================== -->
<!-- -->
<!--
This plugin initialize Tiles definition factory. This later can takes some
parameters explained here after. The plugin first read parameters from web.xml, then
overload them with parameters defined here. All parameters are optional.
The plugin should be declared in each struts-config file.
- definitions-config: (optional)
Specify configuration file names. There can be several comma
separated file names (default: ?? )
- moduleAware: (optional - struts1.1)
Specify if the Tiles definition factory is module aware. If true (default),
there will be one factory for each Struts module.
If false, there will be one common factory for all module. In this later case,
it is still needed to declare one plugin per module. The factory will be
initialized with parameters found in the first initialized plugin (generally the
one associated with the default module).
true : One factory per module. (default)
false : one single shared factory for all modules
- definitions-parser-validate: (optional)
Specify if xml parser should validate the Tiles configuration file.
true : validate. DTD should be specified in file header. (default)
false : no validation

Paths found in Tiles definitions are relative to the main context.
-->
<!-- comment following if struts1.0.x -->
<plug-in className="org.apache.struts.tiles.TilesPlugin" >
<set-property property="definitions-config"
value="/WEB-INF/tiles-defs.xml" />
<set-property property="moduleAware" value="true" />
<set-property property="definitions-parser-validate" value="true" />
</plug-in>

<!-- end comment if struts1.0.x -->

<plug-in className="org.apache.struts.validator.ValidatorPlugIn">
<set-property
property="pathnames"
value="/WEB-INF/validator-rules.xml,/WEB-INF/validation.xml"/>
</plug-in>

</struts-config>
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首先描述一下系统的出错背景：
1、从首页点击链接来到添加用户的页面 正常