How to programmatically add a a4j:commandButton and a4j:actionparam

After spending a few hours I finally managed to programmatically add an ajax command button and action parameter to JSF (1.2) components. So the following

<a4j:commandButton value="Click Me"
	styleClass="buttons" rendered="true" immediate="true"
	id="buttonId" actionListener="#{newRequestBean.doSomething}"
	ignoreDupResponses="true">
	<a4j:actionparam name="theVat" id="vatId" value="IComeFromTheBean" assignTo="#{newRequestBean.vat}" noEscape="false"/>
</a4j:commandButton>

translates to

MethodExpression methodExpression = application.getExpressionFactory().createMethodExpression(
                                FacesContext.getCurrentInstance().getELContext(),
                                "#{newRequestBean.doSomething}",
                                null,
                                new Class[0]);
HtmlAjaxCommandButton button = (HtmlAjaxCommandButton) application.createComponent(HtmlAjaxCommandButton.COMPONENT_TYPE);
button.setValue("Click Me");
button.setStyleClass("buttons");
button.setRendered(true);
button.setImmediate(true);
button.setId("buttonId");
button.setIgnoreDupResponses(true);
button.setActionExpression(methodExpression);

ValueBinding vb = context.getApplication().createValueBinding("#{newRequestBean.vat}");
HtmlActionParameter param = (HtmlActionParameter) application.createComponent(HtmlActionParameter.COMPONENT_TYPE);
param.setId("vatId");
param.setName("theVat");
param.setValue("IComeFromTheBean");
param.setAssignToBinding(vb);
param.setNoEscape(false);

button.addActionListener(param);
button.getChildren().add(param);

Things to notice:

1) The last parameter of the method expression should be an empty array (new Class[0]), otherwise you will get the exception “java.lang.IllegalArgumentException: wrong number of arguments“. Your method should have no parameters.
2) You should add the HtmlActionParameter as the action listener of the command button. This is an absolutely essential step in order to make it work (well, this is only if you want to pass parameters to the call). It took me literally hours to figure this out.
3) The context variable is a FacesContext.

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Unknown runtime error Line: 120 Char: 1 Code: 0 URI: 3_3_3.Finalorg.ajax4jsf.javascript.AjaxScript

Not strictly Java related but I thought I could post it here. I was getting the error

Unknown runtime error Line: 120 Char: 1 Code: 0 URI: 3_3_3.Finalorg.ajax4jsf.javascript.AjaxScript

on I.E. (FF and Chrome worked fine) when I included a form within a form in RichFaces. As soon as I got rid of the second form (in the included file) the problem went away.