Dynamic components in JSF

I am interested in creating a dynamic component in JSF. By that I mean a component that looks and acts differently dependent on the variables it is passed.

Let's take an easy example that actually works. A composite component (facelet) that hides/shows different parts of itself dependent on the data. In this case, it takes an attribute named "myBean", which you may imagine having a "value" field and "type" field. The "type" field determines what component should be rendered.

<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"&gt;
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:jsp="http://java.sun.com/JSP/Page"
      xmlns:h="http://java.sun.com/jsf/html"
      xmlns:ui="http://java.sun.com/jsf/facelets"
      xmlns:f="http://java.sun.com/jsf/core"
      xmlns:c="http://java.sun.com/jsp/jstl/core"
      xmlns:cc="http://java.sun.com/jsf/composite"&gt;

    <cc:interface>
        <cc:attribute name="myBean" />
    </cc:interface>

    <cc:implementation>

        <!-- Small input field if type is "shorttext"  -->
        <h:inputText value="#{myBean.value}" rendered="#{myBean.type == 'shorttext'}" />

        <!-- Text area input field if type is "longtext"  -->
        <h:inputTextArea value="#{myBean.value}" rendered="#{myBean.type == 'longtext'}" />

    </cc:implementation>
</html>

While this works, it quickly becomes unwieldy. If I have twenty different types, I have them all specified in the same document and that clearly violates good design.

Instead, I would like to be able to replace the implementation with something like:

    <ui:include value="#{myBean.type}"/>

Which I understand is not possible, since ui:include occurs when building the component tree, and the the component is processed during the rendering phase.

Yet this must be a common problem. What is the best approach to achieve dynamic components? I am using JSF 2.0, if that makes a difference.

You know, I am coming to the same conclusion myself. It seems there might even be a benefit to this approach over dynamically modifying the component tree: the component will only be ONCE in the component tree even if it's inside a ui:repeat (fly-weight pattern). +1, but for now I will leave the question open.

waxwing 2010-08-17 12:05:09

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Dynamic components in JSF

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