Velocity - Case Study: JSP vs. Velocity

I just wanted to share my findings on Velocity. I use velocity as an
embedded mail templating system in our application server.

When I began this subproject, I was using JSP as the language for
generating template output for our application server. It was
horrible. There were many problems, not to mention the difficulty of
embedding a servlet engine in the app server that I could
communicate with through direct method calls instead of over a
socket. Specific to the Velocity argument was the JSP template
versus the VTL template. I'd like to show you what my JSP template
looked like. Package names have been changed to protect the
innocent. Here is an example:

----------------8<---------------

<%@ page session="false"
        import="java.util.*,
        foo.events.*,
        foo.emeeting.*,
        foo.validation.*,
        foo.util.actionevent.ActionEvent,
        java.util.Date"%>

<jsp:useBean id="meeting" scope="request" type="foo.IMeeting"
class="foo.Meeting"/>

<html>

<!-- etc -->

<table width="600" border="0" cellspacing="0" cellpadding="4" 
    bgcolor="white">
<tr>
<td>
<%
Iterator            events = meeting.getStoredEventsIterator();
int                 repId = 0;

%>
<i><b>Topic: <%= meeting.getTopic()%></b></i>
<p>
<%
while (events.hasNext()) {
  Object event = events.next();
  Participation yapper =
meeting.getParticipation(((MeetingEvent)event).getFromId());
  if(event instanceof ChatEvent) {
    if("R".equals(yapper.getRole()) ) {
%>
<font color="#000000"><b><%=yapper.getName()%>:</b></font>
<%
      repId = yapper.getParticipantId();
    } else {
%>
<font color="#0000f0"><b><%=yapper.getName()%>:</b></font>
<%
    }
    ChatEvent ce = (ChatEvent) event;
%>
<br>
<%
  } else if(event instanceof URLPushedEvent) {
    if("R".equals(yapper.getRole()) ) {
%>
<font color="#000000"><b><%=yapper.getName()%>:</b></font>
<%
    } else {
%>
<font color="#0000f0"><b><%=yapper.getName()%>:</b></font>
<%
    }
    URLPushedEvent pe = (URLPushedEvent) event;
%>
<a href="<%=pe.getStoredData()%>">"<%=pe.getStoredData()%>"</a> <br>
<%
  }
}
%>
<hr>
<br><%=meeting.getMeetingId()%>:<%=repId%><br>
</td>
</tr>
</table>
</div>
</body>
</html>

----------------8<---------------

Seasick yet? Now here is the Velocity template accomplishing the
same thing as above:

----------------8<---------------

<html>

<!-- etc -->

<table width="600" border="0" cellspacing="0" cellpadding="4" 
    bgcolor="white">
<tr>
<td>
<i><b>Topic: $meeting.getTopic()</b></i><p>

#foreach( $event in $meeting.getStoredEventsIterator() )
  #set( $yapper = $meeting.getParticipation($event.getFromId()) )
  #if( $event.getClass().getName().equals($urlEvent) )
    #if( $repRole.equals($yapper.getRole()) )
      #set( $repId = $yapper.getParticipantId() )
      <font color="$blk"><b>$yapper.getName()</b></font>
    #else
      <font color="$blu"><b>$yapper.getName()</b></font>
    #end
    <a href="$event.getStoredData()">$event.getStoredData()</a> <br>
  #elseif( $event.getClass().getName().equals($chatEvent) )
    #if($repRole.equals($yapper.getRole()) )
      #set( $repId = $yapper.getParticipantId() )
      <font color="$blk"><b>$yapper.getName()</b></font>
    #else
      <font color="$blu"><b>$yapper.getName()</b></font>
    #end
    $event.getStoredData() <br>
  #end
#end
<hr>
<br>$meeting.getMeetingId():$repId<br>
</td>
</tr>
</table>
</div>
</body>
</html>

----------------8<---------------

I was subsequently able to define that largish foreach loop into a
macro and shrink it even more, using Velocity's #macro function, so
I could do this:

#drawStandardHtmlTranscript ( $meeting )

removing 20 lines of code from each template whilst only adding 2
lines (one for #parse and the other for the
#drawStandardHtmlTranscript.

The call to the Velocity runtime to finally merge the template
consumes about 20-50 milleseconds (on a 400 mHz PII Linux system)
when I pool the contexts (time doubles when I do not). This is great
performance, too!

Last but not least, teaching the web design team to write a template
took literally 10 minutes from start to finish. They haven't asked
me a single question since.

-- 
Nick Bauman
Software Engineer
3600 Dupont
Minneapolis, MN
55412
Mobile Phone: (612) 810-7406
Home Phone: (612) 522-0165