Can not instantiate Action Form bean

[xing wogong]

I have encountered this problem as below. When I deleted all property in the form bean, I did not have the problem. When I even added one property, the form can not be instantiated thus in my action class I got a null pointer exception.

BTW, other formbean in my application is working.

Appreiciate if you have any clue.






Nov 8, 2004 6:23:28 PM org.apache.struts.util.RequestUtils createActionForm
SEVERE: Error creating form bean of class com.web.form.MCAddComponentForm
java.lang.InstantiationException: com.web.form.MCAddComponentForm
at java.lang.Class.newInstance0(Class.java:293)
at java.lang.Class.newInstance(Class.java:261)
at org.apache.struts.util.RequestUtils.applicationInstance(RequestUtils.java:231)
at org.apache.struts.util.RequestUtils.createActionForm(RequestUtils.java:837)
at org.apache.struts.action.RequestProcessor.processActionForm(RequestProcessor.java:364)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:253)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:525)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:760)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2422)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:163)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:199)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:828)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:700)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:584)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
at java.lang.Thread.run(Thread.java:534)

[Nicholas Cheung]

Seems that it is a configuration problem. Could you also post the configuration of this action form?

Nick

[xing wogong]

The form and action are defined as follow.

<form-bean name="addComponentForm" type="com.web.form.MCAddComponentForm" />

<action path="/AppAddComponentAction" type="com.web.action.MCAddComponentAction" name="addComponentForm" validate="false">
<forward name="AddComponent" path="/AppAddComponent.do" redirect="false" />
<forward name="AddProperty" path="/AppAddProperty.do" redirect="false" />
<forward name="AddConfig" path="/AppAddConfig.do" redirect="false" />
<forward name="Failure" path="/AppError.do" redirect="true" />
</action>
[ November 09, 2004: Message edited by: xingwogong ]

[Nicholas Cheung]

Seems that you havent put down the property configuration. But anyway, if you put down the property, does your Form extends DynaForm? Otherwise, you need to provide the getter and setter for the property.

I guess, since you havent provide getter and setter, and your form is not dynamic form, when you put down the property, the Struts engine cannot set the value for the object.

Nick

[xing wogong]

Hi, thanks

My form extends ActionForm, and I have the getter and setter for the properties in the form bean.

BTW, I am using TOMCAT 4 and I did not use Struts HTML custom tag in my jsp
[ November 09, 2004: Message edited by: xingwogong ]

[xing wogong]

Hi, I had no idea on what was going on in strut, thus I solve this problem in an old fashion -- to instantiate my own form which was not declared in config file. Of course this works but I still lookinf forward for any answer to the question.
[ November 09, 2004: Message edited by: xingwogong ]