Hello! I'm just beginning to use struts, and I enjoy it very much. Thank
you to all who have contributed to it. I have encountered a problem and
would like to ask about it. I've searched the archives and couldn't find
anything on this.
My problem: When I configure my ActionServlet without specifiying an
'application' init parameter, I receive a NullPointerException when I use
the <struts:errors /> tag in my jsp page. Has anyone else seen this?
The javadoc states the following:
The initialization parameters supported by the controller servlet are
described below, which is copied from the Javadocs for the ActionServlet
class. Square brackets describe the default values that are assumed if you
do not provide a value for that initialization parameter.
application - Java class name of the application resources bundle base
class. [NONE]
bufferSize - The size of the input buffer used when processing file uploads.
[4096]
config - Context-relative path to the XML resource containing our
configuration information. [/WEB-INF/struts-config.xml]
...
so, it appears to me that if I don't specify an application parameter, I
should be okay. However, I receive the following error:
java.lang.NullPointerException at
org.apache.struts.taglib.ErrorsTag.doStartTag(ErrorsTag.java:201)
at
_0002flogon_0002ejsplogon_jsp_5._jspService(_0002flogon_0002ejsplogon_jsp_5.
java:89)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:119)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at
org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.ja
va:177)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:309)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:382)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java:387)
at org.apache.tomcat.core.Handler.service(Handler.java:263)
at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:371)
at
org.apache.tomcat.facade.RequestDispatcherImpl.forward(RequestDispatcherImpl
.java:191)
at
org.apache.struts.action.ActionServlet.processActionForward(ActionServlet.ja
va:1589)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1432)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:481)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:760)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java:387)
at org.apache.tomcat.core.Handler.service(Handler.java:263)
at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:371)
at
org.apache.tomcat.core.ContextManager.internalService(ContextManager.java:74
9)
at org.apache.tomcat.core.ContextManager.service(ContextManager.java:695)
at
org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpC
onnectionHandler.java:207)
at org.apache.tomcat.service.TcpWorkerThread.runIt(PoolTcpEndpoint.java:403)
at
org.apache.tomcat.util.ThreadPool$ControlRunnable.run(ThreadPool.java:498)
at java.lang.Thread.run(Thread.java:484)
This is my jsp page:
<%@ page errorPage="error.jsp" %>
<%@ taglib uri="/WEB-INF/struts.tld" prefix="struts" %>
<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
<html:html locale="true">
<head>
<!-- BEGIN SCRIPT //-->
<script language="JavaScript">
<!--
function doInit() { document.login_form.username.focus(); }
//-->
</script>
<!-- END SCRIPT //-->
<link REL="stylesheet" HREF="/asmt/asmt.css" TYPE="text/css">
<title>ASMT Library Login</title>
</head>
<body onload="doInit()">
<struts:errors />
<div align="center"><center>
<html:form name="login_form" action="logon.do">
<div align="center"><center>
<table border="0" cellpadding="0" cellspacing="0"
width="423">
<tr align="center">
<td width="423" colspan="3">
<center>
<h2>ASMT Library System</h2>
<h3>Welcome. Please Log In.</h3>
</td>
</tr>
<tr align="center">
<td width="107">
<div align="left"><p>Username
</td>
<td width="209" align="left">
<div align="left"><p>
<html:text property="username" size="20"
tabindex="1"/>
</td>
<td width="107" align="left">
<html:submit value="Logon" style="width:
80px" tabindex="4" />
</td>
</tr>
<tr align="center">
<td width="107">
<div align="left"><p>Password
</td>
<td width="209" align="left">
<html:password property="password" size="20"
tabindex="2" />
</td>
<td width="107" align="left">
<html:reset style="width: 80px" tabindex="5"
/>
</td>
</tr>
</table>
</center></div>
</html:form>
</body>
</html:html>
Prehaps there's something I'm should be doing in my page that I'm not? I've
looked at the source code, and the error is because the 'messages' object is
null. It is assigned a few lines above in the following statement:
MessageResources messages = (MessageResources)
pageContext.getAttribute(Action.MESSAGES_KEY,
PageContext.APPLICATION_SCOPE);
That's all I know to trace, since I'm new to the code. If I remove the
<struts:errors /> tag, the code works fine. I copied the
ApplicationResource.properties file, placed it in my classes directory, and
add the application init parameter and again everything works fine. Have I
done something wrong, is this a bug, or is should the application parameter
be required for correct operation?
Just for completeness, below is my web.xml file and struts-config.xml file.
My apologies if this is too verbose for some.
Thanks for your help,
Perry Tew
Tomcat 3.2
NT4.0 workstation
JDK1.3
____________________________________________________________________________
___________
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN"
"http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">
<web-app>
<servlet>
<servlet-name>libServlet</servlet-name>
<servlet-class>ASMTLibraryServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>libServlet</servlet-name>
<url-pattern>/library/*</url-pattern>
</servlet-mapping>
<!-- Action Servlet Configuration -->
<servlet>
<servlet-name>action</servlet-name>
<servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
<!--
<init-param>
<param-name>application</param-name>
<param-value>ApplicationResources</param-value>
</init-param>
-->
<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>2</param-value>
</init-param>
<init-param>
<param-name>detail</param-name>
<param-value>2</param-value>
</init-param>
<init-param>
<param-name>validate</param-name>
<param-value>true</param-value>
</init-param>
<load-on-startup>2</load-on-startup>
</servlet>
<!-- Action Servlet Mapping -->
<servlet-mapping>
<servlet-name>action</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>
<!-- Struts Tag Library Descriptors -->
<taglib>
<taglib-uri>/WEB-INF/struts-bean.tld</taglib-uri>
<taglib-location>/WEB-INF/struts-bean.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>/WEB-INF/struts-html.tld</taglib-uri>
<taglib-location>/WEB-INF/struts-html.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>/WEB-INF/struts-logic.tld</taglib-uri>
<taglib-location>/WEB-INF/struts-logic.tld</taglib-location>
</taglib>
</web-app>
____________________________________________________________________________
___
<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE struts-config PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 1.0//EN"
"http://jakarta.apache.org/struts/dtds/struts-config_1_0.dtd">
<struts-config>
<form-beans>
<!-- Logon form bean -->
<form-bean name="logonForm"
type="LogonForm"/>
</form-beans>
<global-forwards>
<forward name="logon" path="/logon.jsp"/>
<forward name="success" path="/main.jsp"/>
<forward name="failure" path="/failedLogin.html" />
</global-forwards>
<action-mappings>
<!-- Process a user logon -->
<action path="/logon"
type="LogonAction"
name="logonForm"
scope="request"
input="/logon.jsp"
unknown="true"
>
</action>
</action-mappings>
</struts-config>
