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.

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: https://stackoverflow.com/questions/4338538/error-parsing-xhtml-the-content-of-elements-must-consist-of-well-formed-charact.

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)

See also:

• Jakarta EE Eutorial - Chapter 9. Expression Language

• https://stackoverflow.com/questions/16360687/how-to-show-jsf-components-if-list-is-not-null-and-has-size-0

• https://stackoverflow.com/questions/9010734/why-do-i-need-to-nest-a-component-with-rendered-some-in-another-component-w

In addition to previous post you can have

<h:form rendered="#{!bean.boolvalue}" />
<h:form rendered="#{bean.textvalue == 'value'}" />

Jsf 2.0

Similarly we can disable a component in the form, for that we will use 'disabled'.

This attribute takes true/false. If the expression evaluates to a true then the specified component will be disabled otherwise it is enabled.

Ex: I want to disable a button for some condition.

<p:commandButton id="addInformedConsentBtn"
	value="Add Comments" title="Add Comments"
	disabled="#{backingBean.booleanResultOrVariable}">
</p:commandButton>