I think you should build an independent component that displays the jtreemap. This can be enabled or disabled with a toolbar button for example.

I'd suggest the following:

First of course you should check out the code from Sourceforge CVS and build. You will have to check out all three projects (jpivot, jpivot_repository and wcf), then build wcf first and jpivot afterwards.

Then take a look at src/webapps/WEB-INF/jpivot-tags.xml where the tags are defined - the corresponding tld's are generated (together with the tag docs) during build. Say you have a tag

<jp:treemap query="${query01}" />

The tag could to the following

String query;

int doStartTag() {
  RequestContext context = RequestContext.instance();
  OlapModel om = context.getModelReference(query);
  Result result = om.getResult();

  // Now you have access to the OLAP result

Read + understand the class org.jfree.chart.servlet.ServletUtilities

create a temp file in that contains the file as jpeg or png

Use ServletUtilities to make sure that your temp file is deleted on session timeout

Use the JFreeChart Servlet to display your chart.