These are my notes on how to reverse engineer what tags are doing in a JSF application. In this case, I am trying to figure out what are the classes behind the Configuration tags in the RHQ.  I am trying to figure out what is being done by the tag

onc:config

This tag is activated with the following value at the top of the page:

xmlns:onc=”http://jboss.org/on/component”

To Figure out what this tag means, I look in WEB-INF/web.xml.  The web.xml value

facelets.LIBRARIES

Lets me know where the file is that defines the acceptable tags I can add to an xhtml page for this component.

/WEB-INF/tags/on.component.taglib.xml

This taglib defines the values

tag-name config
component-type org.jboss.on.Config
renderer-type org.jboss.on.Config

Note that these are JSF component names, and not Java class names.  To resolve these to Java classes, we need to find the mappings.  The mapping files are defined in web.xml under the entry:

javax.faces.CONFIG_FILES

In particular, I found what I wanted in

/WEB-INF/jsf-components/configuration-components.xml,

The values I care about are:

component-type org.jboss.on.Config
component-class org.rhq.core.gui.configuration.ConfigUIComponent

and the renderer for Config and ConfigurationSet components

component-family rhq
renderer-type org.jboss.on.Config
renderer-class org.rhq.core.gui.configuration.ConfigRenderer

This render extends javax.faces.render.Renderer.  This is a Flyweight that parses and generates HTML.  It has two main methods: decode an encode. decode parses the request that comes in, encode injects html into the response that goes out.

Decode appears to be called only on a post.  Encode seems to be called even on a get.