Velocity - Case Study: JSP vs. Velocity

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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
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