# How the button is created and how it acts

Due to specific design of the buttons in the Photo Album application, it's necessary to clarify some design and development points about the button. The button is visually represented by Facelets template stored in the button.xhtml file.

Please have a look at the content of the file:

    ...
    <ui:composition xmlns="http://www.w3.org/1999/xhtml"
    	xmlns:s="http://jboss.com/products/seam/taglib"
    	xmlns:c="http://java.sun.com/jstl/core"
    	xmlns:ui="http://java.sun.com/jsf/facelets"
    	xmlns:f="http://java.sun.com/jsf/core"
    	xmlns:h="http://java.sun.com/jsf/html"
    	xmlns:rich="http://richfaces.org/rich"
    	xmlns:a4j="http://richfaces.org/a4j"
    	xmlns:richx="http://richfaces.org/richx">
    	<a4j:loadScript src="/scripts/buttons.js" />
    	<richx:actionMapper>
    		<a4j:outputPanel layout="block" style="#{style}" styleClass="photoalbumButton #{styleClass}" lang="#{lang}" dir="#{dir}" title="#{title}"
    			rendered="#{empty rendered or rendered}"
    			onmousedown="RF_RW_DEMO.toPressed(this)" onmouseup="RF_RW_DEMO.toReleased(this)" onmouseout="RF_RW_DEMO.toReleased(this)">
    				<h:graphicImage value="/img/shell/button.png" alt="" />
    				<h:graphicImage value="/img/shell/button_press.png" style="display: none;" alt="" />
    				<div>#{value}</div>
    				<a4j:commandButton accesskey="#{accesskey}" ajaxSingle="#{ajaxSingle}" alt="#{alt}" type="image" image="/img/shell/spacer.gif"
    					actionListener="#{mappedActionListener}" action="#{mappedAction}" bypassUpdates="#{bypassUpdates}" data="#{data}" disabled="#{disabled}"
    					eventsQueue="#{eventsQueue}" focus="#{focus}" ignoreDupResponses="#{ignoreDupResponses}" immediate="#{immediate}" limitToList="#{limitToList}"
    					onbeforedomupdate="#{onbeforedomupdate}" timeout="#{timeout}" tabindex="#{tabindex}" status="#{status}" similarityGroupingId="#{similarityGroupingId}"
    					reRender="#{reRender}" requestDelay="#{requestDelay}" process="#{process}" oncomplete="#{oncomplete}"
    					onblur="#{onblur}" onclick="#{onclick}" ondblclick="#{ondblclick}" onfocus="#{onfocus}" onkeydown="#{onkeydown}" onkeypress="#{onkeypress}" onkeyup="#{onkeyup}"
    					onmousedown="#{onmousedown}" onmousemove="#{onmousemove}" onmouseout="#{onmouseout}" onmouseover="#{onmouseover}" onmouseup="#{onmouseup}" />
    		</a4j:outputPanel>
    	</richx:actionMapper>
    </ui:composition>

    ...

The <richx:actionMapper> tag is covered in more detail further in the text. In brief, it's a special tag developed deliberately to pass to the button a method expression of the action which must be performed when the button is clicked.

To make sure the button works correctly we include the required JavaScript code that is located in the button.js file using `<a4j:loadScript src="/scripts/buttons.js" />` component.

The button consists of several parts:

- 2 images (pressed and not pressed)

- <div> element that displays the button's text

- <a4j:commandButton> that sends Ajax request to the server

These elements are wrapped by <a4j:outputPanel> to adjust the look-and-feel.

In the application the button is used for example like this:

    ...
    <richx:commandButton actionListener="#{authenticator.register(user)}" reRender="mainform, headerPanel" value="#{messages['user.register']}" />
    ...

We can pass to the <richx:commandButton> all required attributes, in the example only actionListener, reRender and value are passed.

<richx:commandButton> is a custom tag that is declared in the photoalbum-taglib.xml tag library:

    ...
    <?xml version="1.0"?>
    <!DOCTYPE facelet-taglib PUBLIC
      "-//Sun Microsystems, Inc.//DTD Facelet Taglib 1.0//EN"
      "facelet-taglib_1_0.dtd">
    <facelet-taglib>
       <namespace>http://richfaces.org/richx</namespace>
    	<tag>
    	   <tag-name>commandButton</tag-name>
    	   <source>templates/button.xhtml</source>
    	</tag>
    	<tag>
    		<tag-name>actionMapper</tag-name>
    		<handler-class>org.richfaces.photoalbum.util.ActionMapperTagHandler</handler-class>
    	</tag>
    </facelet-taglib>
    ...

In order to use the <richx:commandButton> on the page the namespace of the taglib must be declared:

    ...
    <ui:composition xmlns="http://www.w3.org/1999/xhtml"
    	...
    xmlns:richx="http://richfaces.org/richx">
    ...

A more complex part of the button implementation, as we said earlier, is <richx:actionMapper> which is also described in tablib. But it is not just a simple tag-template since it has Facelets handler-class which specifies how it is handled when declared on the page. It is created because Facelets templates do not allow to make the MethodExpression a Facelets-template parameter. Please find below the code of the class(some irrelevant details are omitted):

    ...
      public class ActionMapperTagHandler extends TagHandler {

    	private static final Class<?>[] ACTION_PARAM_TYPES = new Class[0];

    	private static final Class<?>[] ACTION_LISTENER_PARAM_TYPES = new Class[] {ActionEvent.class};

    	private static final String ACTION = "action";

    	private static final String ACTION_LISTENER = "actionListener";

    	private static final String MAPPED_ACTION = "mappedAction";

    	private static final String MAPPED_ACTION_LISTENER = "mappedActionListener";

    	public ActionMapperTagHandler(TagConfig config) {
    		super(config);
    	}

    	private MethodExpression remap(FaceletContext faceletContext, String varName,
    			Class<?> expectedReturnType, Class<?>[] expectedParamTypes) {

    		MethodExpression result = null;

    		VariableMapper mapper = faceletContext.getVariableMapper();
    		ValueExpression valueExpression = mapper.resolveVariable(varName);
    		if (valueExpression != null) {
    			ExpressionFactory ef = faceletContext.getExpressionFactory();
    			ELContext elContext = faceletContext.getFacesContext().getELContext();

    			result = ef.createMethodExpression(elContext, valueExpression.getExpressionString(),
    				expectedReturnType, expectedParamTypes);
    		}

    		return result;
    	}

    	public void apply(FaceletContext ctx, UIComponent parent)
    			throws IOException, FacesException, FaceletException, ELException {

    		MethodExpression actionExpression = remap(ctx, ACTION, String.class, ACTION_PARAM_TYPES);
    		MethodExpression actionListenerExpression = remap(ctx, ACTION_LISTENER, null, ACTION_LISTENER_PARAM_TYPES);

    		if (actionExpression != null || actionListenerExpression != null) {
    			VariableMapper initialVarMapper = ctx.getVariableMapper();
    			try {
    				VariableMapperWrapper varMapper = new VariableMapperWrapper(initialVarMapper);

    				if (actionExpression == null) {
    					actionExpression = NOOP_ACTION_EXPRESSION;
    				}

    				varMapper.setVariable(MAPPED_ACTION,
    					ctx.getExpressionFactory().createValueExpression(actionExpression,
    						MethodExpression.class));

    				if (actionListenerExpression == null) {
    					actionListenerExpression = NOOP_ACTION_LISTENER_EXPRESSION;
    				}

    				varMapper.setVariable(MAPPED_ACTION_LISTENER,
    						ctx.getExpressionFactory().createValueExpression(actionListenerExpression,
    							MethodExpression.class));

    				ctx.setVariableMapper(varMapper);

    				nextHandler.apply(ctx, parent);

    			} finally {
    				ctx.setVariableMapper(initialVarMapper);
    			}
    		} else {
    			nextHandler.apply(ctx, parent);
    		}
    	}
    }

    ...

You can find more infromation about Facelets, custom tags, taglibs, Facelets tag handlers and Facelets templates here.