How can I maintain param on ajax call? [duplicate] - jsf

Question

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Retaining GET request query string parameters on JSF form submit
(2 answers)
Closed 6 years ago.
Whenever I make an ajax call, my URL param expires. The workaround I have done is to pass a param request inside every button like in:
<p:commandLink value="Submit" actionListener="#{mybean.dosomething}">
<f:param name="foo" value="#{mybean.bar}"/>
</p:commandLink>
However, in some scenarios I can't do the above workaround. For example when I'm using primefaces rowEditEvent:
<p:ajax event="rowEditCancel" listener="#{mybean.onCancel}"/>
The param expires when I make this ajax call and results in error before invoking #{mybean.onCance} as I'm reading datatable's data from the param in URL.
So how can I maintain the param value when I make such an ajax call?
PS: mybean is ViewScoped
Problem Extension:
The <o:form> has solved part of the problem, but now I can't send params inside the form for dynamic image streaming inside the table. See the following:
<p:dataTable value="#{mybean.data}" var="var">
<p:column headerText="Thumbnail">
<p:graphicImage value="#{streamer.thumbnail}">
<f:param name="id" value="#{var.id}"/>
</p:graphicImage>
</p:column>
</p:dataTable>
Streamer Bean (RequestScoped):
public StreamedContent getThumbnail() throws IOException {
FacesContext context = FacesContext.getCurrentInstance();
if (context.getRenderResponse()) {
return new DefaultStreamedContent();
}
else {
String string = context.getExternalContext().getRequestParameterMap().get("id");
Long id = Long.parseLong(idString);
MyImage img = (MyImage) service.find(MyImage.class, id);//get resource
StreamedContent sc = new DefaultStreamedContent(img.getInputStream(), "image/jpg", img.getName());
return sc;
}
}
Here string is always null and parameter is not passed resulting in error

Answer 1

Register it as a <f:viewParam>
<f:viewParam name="foo" value="#{mybean.bar}" />
and instead of <h:form>, use OmniFaces <o:form> with includeViewParams="true" (which uses under the covers a custom ViewHandler implementation which automatically collects all view parameters and appends them to the outcome of the getActionURL() method which is used as form action URL):
<o:form includeViewParams="true">
...
</o:form>
This way all view params are included in the form's action URL and will therefore end up as request parameters the usual way without the need to fiddle with <f:param> and being clueless inside <p:ajax> (and <f:ajax>).