Tuesday, May 22, 2007

Portlet with Ajax Tech (Jetspeed)

I was required to upload a large file via portlet with the process message displaying in the client side, and ajax would be the best choice. In order to ease the job, prototype was included first, so that the Ajax instance would do me a great help.

I've referred so many articles about the ajax application in portal, mostly work for WebSphere Portal rather than Jetspeed, tomcat-based portal. At last, I solved this problem, and as a conclude, I found that the problem could be broken down into three problem:

  1. Understanding the principle of the ajax application in portal, JSR-168 would be the most helpful reference. And here is a well-spread diagram to show this principle:

    As JSR168 said, portlet session could share the data with servlet session, so render the page via portlet and request the update from servlet, which makes the ajax realizable. Here is the article where the above diagram from.

  2. Share the data between portlet and servlet. Of cause, there are some applications do not need the servlet and portlet bundled, there would be unnecessary to consider this problem in such cases. But as to my problem, portlet and servlet should bundled together. As the articles I have read, I found it maybe was not a problem for WebSphere, but it's really a problem for tomcat based portal. The solution was so easy, just configure the server.xml like this, I mean to add emptySessionPath="true" attribute:

    <connector port="8080"
    maxthreads="150" minsparethreads="25" maxsparethreads="75"
    enablelookups="false" redirectport="8443" acceptcount="100"
    connectiontimeout="20000" disableuploadtimeout="true"
    emptysessionpath="true" />

    And read this article to know what the session identifier do to make such tricky problem.

  3. Last work is to write the codes and test it. So the last problem is about the coding.
    Most of these coding barriers could be taken easily via careful reading JSR168 Spec. Such as, portlet and servlet share data in APPLICATION_SCOPE, so using APPLICATION_SCOPE to store session. Url and javascript debuging would also cost a lot of time.

A good article about Ajax with WebSphere Portal:

So, it's really fun to work with portal, especially that using the ajax tech to make the portal more vivid. Hope this article help you solve your problem, thanks.

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