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The information contained in this section applies to IBM WebSphere Commerce Version 7.0.0.9 and Feautre Pack 8. The documentation also applies to all subsequent releases and modifications until otherwise indicated in new editions.
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Dynamic caching
In general, caching improves response time and reduces system load. Caching techniques are used to improve the performance of World Wide Web Internet applications. Most techniques cache static content (content that rarely changes) such as graphic and text files. However, many websites serve dynamic content, containing personalized information or data that changes more frequently. Caching dynamic content requires more sophisticated caching techniques, such as those provided by the WebSphere Application Server dynamic cache, a built-in service for caching and serving dynamic content.
Dynamic caching considerations with JSTL
WebSphere Commerce uses the Java Server Tag Library (JSTL) to create new JSP pages. If <% out.flush(); %> does not surround the <c:import> tag, using dynacache introduces strange behavior. The out.flush statement is required for all <c:import> statements, not just those for fragments. Even if the page is being cached using full-page caching, the out.flush tags are still required to surround the <c:import> tags.

Dynamic caching considerations with JSTL

WebSphere Commerce uses the Java Server Tag Library (JSTL) to create new JSP pages. If <% out.flush(); %> does not surround the <c:import> tag, using dynacache introduces strange behavior. The out.flush statement is required for all <c:import> statements, not just those for fragments. Even if the page is being cached using full-page caching, the out.flush tags are still required to surround the <c:import> tags.

When using the JSTL import tag, the JSPWriter buffers the data. It does not flush the data to the cache's writer. Because of this buffering, dynacache does not know when the application stopped writing the data to the parent writer. As a result, the child's content might also be cached as part of parent cache entry, and causes the child fragment to appear twice.

To prevent this problem, surround the <c:import> tags with <% out.flush(); %>. You flush the buffer before the import begins, and after it ends, to ensure that none of the child content is written to the parent's cache entry.