Conditionally displaying JSF components
First, I am new to Java EE, came from a strong ASP .NET development background. I have gone through the net, and I might miss this but it seems like there is no simple and straight-to-the-point tutorials on how I could connect backing bean class to a JSF components.
A good example is like this, currently I am trying to create a JSF page where there is a set of links as menu bar and a set of forms. What I am planning to do is, when clicking a link, a particular form will be rendered.
In ASP.NET, I could easily retrieve the element and then set the attribute to be displayable. I am wondering if there is easy way (heck, even any way) to do this in JSF.
The forms is already in the page, it is just a matter of setting the "render" attribute to true when I click a particular link.
Answer
Yes, use the rendered attribute.
<h:form rendered="#{some boolean condition}">
You usually tie it to the model rather than letting the model grab the component and manipulate it.
E.g.
<h:form rendered="#{bean.booleanValue}" />
<h:form rendered="#{bean.intValue gt 10}" />
<h:form rendered="#{bean.objectValue eq null}" />
<h:form rendered="#{bean.stringValue ne 'someValue'}" />
<h:form rendered="#{not empty bean.collectionValue}" />
<h:form rendered="#{not bean.booleanValue and bean.intValue ne 0}" />
<h:form rendered="#{bean.enumValue eq 'ONE' or bean.enumValue eq 'TWO'}" />
Note the importance of keyword based EL operators such as gt, ge, le and lt instead of >, >=, <= and < as angle brackets < and > are reserved characters in XML. See also this related Q&A: Error parsing XHTML: The content of elements must consist of well-formed character data or markup.
As to your specific use case, let's assume that the link is passing a parameter like below:
<a href="page.xhtml?form=1">link</a>
You can then show the form as below:
<h:form rendered="#{param.form eq '1'}">
(the #{param} is an implicit EL object referring to a Map representing the request parameters)