Because JSP-based applications rely on the application server’s JSP compiler, any differences between DAS’s JSP compiler and the JSP compiler on the application server you are migrating to must be taken into account. This section describes some practices to follow in your JSPs to ensure they are portable.

Using Java Expressions in Pages
Using the DSP Tag Library

To learn about the DSP tag library, see the ATG Page Developer's Guide.

  • Each JSP that uses the DSP tag library must enclose its contents in beginning and ending dsp:page tags, like this:

    ... body of page ...

  • In pages that use the DSP tag library, you should avoid using standard JSP tags and instead use DSP tags wherever possible. The JSP tags do not work reliably with the DSP tag library, and the DSP tags provide additional features, such as support for the passing of object parameters between pages. In particular, use dsp:include rather than jsp:include or jsp:forward, and use dsp:param rather than jsp:param.

  • Do not use value="param:paramName" to get the value of a parameter. Instead use dsp:getvalueof to expose a scripting variable.

JSP Syntax
<dsp:param name='<%="abc"%>' value="17">
Servlet Pipeline

When an ATG application processes a request for a JSP that includes the DSP tag library, it invokes a servlet pipeline whose Nucleus address is /atg/dynamo/servlet/dafpipeline. The DAF pipeline has fewer servlets than the DAS servlet pipeline, because it is not doing any request dispatching, mime typing, or file finding in normal operation. These operations are handled by the application server rather than by the ATG platform.

If your application adds any servlets to the DAS servlet pipeline, you will need to add these servlets to the DAF pipeline to run your application on another application server. You create a new instance of your servlet (since each pipeline servlet can be in only a single pipeline), and then insert it in the DAF servlet pipeline at the appropriate place.

There are some differences between how the DAF servlet pipeline and the DAS servlet pipeline work. For information about these differences, see Request Handling with Servlet Pipelines in the ATG Programming Guide.

Other Issues
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