Sometimes its quite handy to center align an HTML DIV element which is positioned absolute.

Easy way of doing this is to use positioning with combination of pixel and percentage. One important thing in this case is that the DIV needs to be fixed in width - as the solution is based on that. The solution is to use left: 50% as one of positioning attributes. This one will cause the layer to be placed in the center of window. In fact, a left side of layer is placed exactly in the center of browser window. Now we only need to move the window left by half of its width. We do it using negative value for margin-left attribute. The value for it shall be half of the DIV overall width. Voila - there it is.

	/** css part */
	div#popup {
		position: absolute;
		top: 200px;
		left: 50%;
		width: 400px;
		margin-left: -200px;    /* negative half of the width value */
	}
		

How to embed images inside the email and use these images for layouting of this email contents?

First we have to have an email with a body part of type text/html where images can be used. Whenever we try to link any of such images to an external internet address it will be blocked by email client before displaying. What we need to do to overcome such problems is that we need to attach the images we want to use for layouting into the email.

Attaching of images can be done using JavaMail api methods like MimeBodyPart.attachFile( File ) but if you have the images deployed in your service EAR file it can be done as following:

	// create proper mesage container
	MimeMultipart ourMessage = new MimeMultipart( "related" );
	
	MimeBodyPart attachmentPart = new MimeBodyPart();
	URL urlToImg = class.getResource( "/com/package/../image_file.jpg" );
	attachmentPart.setDataHandler( new DataHandler( urlToImg ) );
	
	// set the ID of this attachment - so it can be referrenced from HTML
	attachmentPart.setContentID( "<image>" );
	
	// and add the part to message
	ourMessage.addBodyPart( attachmentPart );
		

Having such attachment we have to reference it somehow from the HTML code. We now that the attachment ID is image as we specified it using setContentID method. To reference that attachment from the HTML contents we have to use cid: prefix which email clients resolve to content identifier, so eg. referencing our image would mean using the following HTML code:

	<IMG SRC="cid:image"/>
		

Additionally all the body parts of the email need to be a part of a message of type multipart/related which can be seen as first line of the example code.

There is a great need of creating a button/action that leads to the same page it is displayed on, but needs to do some server side logic. To achieve this in without creation of additional XML navigation entry we can simply assign no action to a link component.

So the code like:

	<h:commandButton value="Refresh" actionListener="#{doThelogic}" immediate="true"/>
		

will do just fine - it will reload current page doing the business logic inside action listener.

The same can be done using an action attribute binding to a method which returns null.

Problem here is that the JSF view is not recunstructed but the previous one is used. This will lead to the situation when all the values entered by used to any input components will still be there in the page. To solve this problem and force discarding of all input components submitted values we can do the following..

Let's imagine the situation where we want to create a DB state refresh button. It shall load the state from the DB/model and present it on a page. Unfortunatelly using such refresh strategy I presented we will still have the problem of input components submitted values returning to a browser after page reload. If we need to discard the submitted values of all input components we will have to define the action attribute in a link component and additionally make a dummy refresh navigation entry in faces-config.xml file.

So the link component, which needs to discard all submitted values of input components will be defined like (e.g. the JSP file is /editMe.jsp):

	<h:commandButton value="Refresh" actionListener="#{doThelogic}" action="refresh" immediate="true"/>
		

and with navigation rule:

	<navigation-rule>
		<from-view-id>/editMe.jsp</from-view-id>
		<navigation-case>
			<from-outcome>refresh</from-outcome>
			<to-view-id>/editMe.jsp</to-view-id>
		</navigation-case>
	</navigation-rule>
		

the JSF engine will be forced to create a new view with id /editMe.jsp which will cause recreation of all input components with submitted values set to initial, null value.

The idea is to specify "<url-pattern>" as "*.jsf" and map it to Faces Servlet using "<servlet-mapping>".

In default implementation of Application and ViewHandler (JspViewHandler) the extension will be replaced with the extension defined as "javax.faces.DEFAULT_SUFFIX". The default value is set to ".jsp" so whenever the "xx.jsf" request comes it will be processed as "xx.jsp" underneath but the browser URL will stay "xx.jsf".

javax.servlet.ServletException: Original SevletResponse or wrapped original ServletResponse
	not passed to RequestDispatcher in violation of SRV.8.2 and SRV.14.2.5.1

This is because of more strict Servlet 2.5 specifications on JBoss (which is default for Tomcat 6+). This can be thrown on JBoss 4.2.0+ GA and can be fixed by adding the following directive to the server startup parameters:

-Dorg.apache.catalina.STRICT_SERVLET_COMPLIANCE=false