CommandButton don't work with Ajax and Param - JSF 2.0 - ajax

Question

I was trying to implement a command button with f:ajax and f:param in my project, but I'm not being successfull.
I have one Bean called "disciplinaMBean" that have a #SessionScoped. In the respective JSF (let's say, index.xhtml) I have one p:dataTable showing some disciplines (this is what "disciplina" means in English :P). When I click in one row, a modal is opened showing to user options to "edit" or "delete" discipline. The selected object is stored in "disciplinaSelecionada" by selection attribute of Primefaces dataTable. See by yourself:
The code of this modal is inside "edit.xhtml" file. See the code below:
<h:form>
<label for="nome">Nome:</label>
<h:inputText styleClass="form-control adicionar" id="nome"
value="#{disciplinaMBean.disciplinaSelecionada.nome}">
</h:inputText>
<h:commandButton id="excluir" styleClass="btn btn-md btn-danger pull-left" value="Excluir" >
<f:param name="idDisciplina" value="#{disciplinaSelecionada.id}" />
<f:ajax event="click" listener="#{disciplinaMBean.deletar}" />
</h:commandButton>
</h:form>
And the method "Deletar" (means delete) in disciplineMBean:
public void deletar(){
String param1 = FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap().get("idDisciplina");
System.out.println("Disciplina deletada: " + param1);
int idDisciplina = Integer.parseInt(param1);
controleDisciplina.remover(idDisciplina);
}
I know I called the method because the log of console, but I can't delete the discipline because I have one error (a empty string is stored in "idDisciplina" param).
Following is the error:
Disciplina deletada:
Nov 01, 2013 10:26:31 PM com.sun.faces.lifecycle.InvokeApplicationPhase execute
WARNING: /edit.xhtml #31,72 listener="#{disciplinaMBean.deletar}": java.lang.NumberFormatException: For input string: ""
javax.el.ELException: /edit.xhtml #31,72 listener="#{disciplinaMBean.deletar}": java.lang.NumberFormatException: For input string: ""
at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:111)
at com.sun.faces.facelets.tag.jsf.core.AjaxBehaviorListenerImpl.processAjaxBehavior(AjaxHandler.java:447)
at javax.faces.event.AjaxBehaviorEvent.processListener(AjaxBehaviorEvent.java:113)
at javax.faces.component.behavior.BehaviorBase.broadcast(BehaviorBase.java:106)
at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:760)
at javax.faces.component.UICommand.broadcast(UICommand.java:300)
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:791)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1256)
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:250)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:724)
Caused by: java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:592)
at java.lang.Integer.parseInt(Integer.java:615)
at mbeans.DisciplinaMBean.deletar(DisciplinaMBean.java:143)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:491)
at org.apache.el.parser.AstValue.invoke(AstValue.java:262)
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:278)
at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
... 27 more
What can I do to solve this issue?

Answer 1

If you have EL 2.2, you can do it like this (assuming disciplinaSelecionada.id is an int)
<h:commandButton id="excluir" action="#{disciplinaMBean.deletar(disciplinaSelecionada.id)}" styleClass="btn btn-md btn-danger pull-left" value="Excluir" />
....
public void deletar(int idDisciplina)
{
System.out.println("Disciplina deletada: " + idDisciplina);
controleDisciplina.remover(idDisciplina);
}