JavaServer Pages[tm] (JSP[tm]) Technology Migration from
iPlanet [tm] Application Server, Enterprise Edition 6.0 Service Pack 2 to Later Versions

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The following article/tutorial may contain actual software programs in source code form. This source code is made available for developers to use as needed, pursuant to the terms and conditions of this license.

Overview

Starting with the release of iPlanet[tm] Application Server ("iAS") Enterprise Edition 6.0 service pack 3, the native JavaServer Pages[tm] (JSP[tm]) compiler was migrated to Apache's Jasper JSP compiler. This compiler, which is based on Tomcat 3.2.1, is compliant with the JSP 1.1 specification.

Currently the Jasper JSP compiler is integrated into iAS Enterprise Edition 6.0 service packs 3 and 4, and also into iAS Enterprise Edition 6.5.

The previous JSP compiler was fairly lenient with regard to the specification and case sensitivity. One issue is the use of the subelement <rtexprvalue> of the <attribute> element in the XML Tag Library Descriptor of a Tag Extension.  This subelement signifies whether the value of the attribute may be dynamically calculated at runtime by a scriptlet expression. For example, the following JSP sets the value of "sayThis".  There are two ways to parse the value - either as a string or as an expression to be resolved during the generation of the response.

<MyTags:test
    sayThis="<%=(String)session.getAttribute("lang")%>"
/>

The original JSP compiler allowed dynamic calculation of the scriptlet expression regardless of whether <rtexprvalue> was set. An example output would be:

eu

In service pack 3 and later, this would show the scriptlet expression as a string by default, outputting:

<%=(String)session.getAttribute("lang")%>

If the <rtexprvalue> is set to "true" in the Tag Library Descriptor XML file, the expression is evaluated.  For example:

<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<taglib>
        <tlibversion>1.1</tlibversion>
        <shortname></shortname>     
        <tag>
               <name>test</name>
               <tagclass>MyTagTest</tagclass>
               <bodycontent>EMPTY</bodycontent> 
               <info>Outputs a passed string</info>
               <attribute>
                        <name>sayThis</name>
                        <required>true</required>
                      <rtexprvalue>true</rtexprvalue>
               </attribute>
        </tag>
</taglib>

As mentioned previously, there are a few issues to be aware of with the migration to the new parser. The above example just demonstrates one issue that may arise. Although the new parser is strict in following the specification with regard to case sensitivity, by using the following 'methods' it is possible to return the Application Server to the old behaviour without modification to the code:

• allow the case-sensitivity to be relaxed

• allow the use of the old JSP compiler

These are documented in the service pack 3 release notes (as linked in the Resource section of this article), although it is recommended that you update the code as per the JSP specifications for portability and for future releases.
 

Resources