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From Yanroy <rmea...@wpi.edu>
Subject ActionForm is null when using dynabean
Date Fri, 07 Jul 2006 18:51:19 GMT

Hi,
I'm fairly new to struts and I'm having a puzzling problem.  Let me start
with some quick background: I'm attempting to make a highly configurable and
extensible web interface for a statistical analysis engine.  Because of the
large (and arbitrary) number of types of analyses, I opted not to create a
seperate bean and JSP form for each type.  Most of these analyses extend
other analyses, so I have made a JSP for each one that uses an include
directive to bring in the form elements from the base class(es) to prevent
duplicating that code for all the children.  This also entails not having a
specific bean class for each analysis type, so I'm using a LazyDynaBean. 
Keep in mind that I use beans that I actually define as my own classes in
other places in this webapp and it works fine, but I don't use LazyDynaBeans
(or any kind of DynaBean) anywhere else.

I've been assured by many websites that I can specify in my
struts-config.xml a form-bean of type
org.apache.commons.beanutils.LazyDynaBean and it will somehow be wrapped in
some kind of ActionForm automatically.  In an attempt to figure out what
kind of ActionForm subclass this was, I decided to put a System.out in one
of my execute() methods in the strut to tell me via
form.getClass().getName().  To my surprise, I got a null pointer exception,
and after a little more investigation, I found out form was null.  This is
way over my head - like I said, I'm new to struts.  Below, I have what I
believe are relevant excerpts of code and config files...

from struts-config.xml:
<form-bean 
			name="AnalysisForm" 
			type="org.apache.commons.beanutils.LazyDynaBean">
			<form-property 
				name="runnableTables" 
				type="java.lang.Integer"
				initial="1" 
				/>
			<form-property 
				name="runnableTableTypes" 
				type="java.lang.String[]"
				/>
			<form-property
				name="runnableTableNames"
				type="java.lang.String[]"
				/>
			<form-property
				name="outputIntermediaryValues"
				type="java.lang.Boolean"
				/>
			<form-property
				name="filtered"
				type="java.lang.Boolean"
				/>
			<form-property
				name="notifyValues"
				type="java.lang.Float[]"
				/>
			<form-property
				name="notifyComparisons"
				type="java.lang.String[]"
				/>
			<form-property
				name="notifyResults"
				type="java.lang.String[]"
				/>
		</form-bean>

... snip...

<action
			path="/AnalysisConfig"
			name="AnalysisForm"
			type="org.assistment.apps.newReporting.analysis.struts.AnalysisConfig"
			scope="request"
			parameter="method">

			<forward
				name="Sum"
				path="/pages/stats/SumAnalysis.jsp"
				redirect="false"/>
				
			<forward
				name="Count"
				path="/pages/stats/CountAnalysis.jsp"
				redirect="false"/>
				
			<forward
				name="Average"
				path="/pages/stats/AverageAnalysis.jsp"
				redirect="false"/>
				
			<forward
				name="Variance"
				path="/pages/stats/VarianceAnalysis.jsp"
				redirect="false"/>
				
			<forward
				name="TTest"
				path="/pages/stats/TTestAnalysis.jsp"
				redirect="false"/>
		</action>

here's an example of one of the forwards' targets, SumAnalysis.jsp.  The
header includes the appropriate taglibs, and the includes in the table body
contain only <TR>...form stuff...</TR>.  Note that some of them have .html
extensions because tomcat seems to have an issue where it attempts to
compile included JSP's before actually including them (took me hours to
debug that).

<jsp:useBean id="AnalysisForm" scope="request"
class="org.apache.commons.beanutils.LazyDynaBean"/>

<%@ include file="StatsHeader.html" %>

<html:form action="/AnalysisConfig.do">
	<input type="hidden" name="method" value="save">
	<input type="hidden" name="type" value="Sum">
	
	<TABLE WIDTH="85%">

		<%@ include file="StatisticalAnalysis.html" %>
		<%@ include file="FilteredAnalysis.html" %>
		
		<TR>
			<TD>Sum Field</TD>
			<TD>
				Select the field of the result tables to perform the summation on:<BR>
				<html:select property="sumField">
					<html:options name="fieldList"/>
				</html:select>
			</TD>
		</TR>

		<%@ include file="Notification.html" %>

		<TR>
			<TD>
				<html:submit>Save</html:submit>
			</TD>
		</TR>
	</TABLE>
	
</html:form>

<%@ include file="StatsFooter.jsp" %>

Here's the relevant function from my AnalysisConfig.java strut class (which
extends DispatchAction, hence the method name being "save" instead of
"execute"):

public ActionForward save(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) throws Exception {
		Experiment exp =
(Experiment)request.getSession().getAttribute("Experiment");
		if (exp == null) {
			request.setAttribute("errorMessage", "Unable to get Experiment out of the
session attributes.");
			return mapping.findForward("ExperimentManagerError");
		}
		
		if (form == null)
			System.out.println("form is null!");
		else
			System.out.println(form.getClass().getName());
		
		// TODO: I'm creating a CountAnalysis for testing, make this more
intelligent later
		StatisticalAnalysis analysis = new CountAnalysis();
		
		// TODO: configure analysis here
		
		exp.addAnalysis(analysis);
		
		return mapping.findForward("AnalysisConfigReturn");
	}

I hope you'll forgive the long post... I just wanted to provide enough
information for someone to spot my error.  I'd greatly appreciate any help
you can give.  Thank you very much for reading this far!

Ryan (aka Yanroy)
-- 
View this message in context: http://www.nabble.com/ActionForm-is-null-when-using-dynabean-tf1908060.html#a5222710
Sent from the Struts - User forum at Nabble.com.


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