In my previous article, "Reuse and the Portal Onion," you were introduced to the conceptual model of a portal onion that illustrates how a portal framework enables reuse of front end web application assets across the user experience, portlet catalog, common services, and foundational architecture layers of the onion.
In this article, you will turn your attention to the second layer of the onion, called the portlet catalog, which provides a rich set of sales, service, billing, content, workflow, and other functionality that can be reused and configured at the outer user experience layer. This layer is supported by the underlying common services and foundation layers. The catalog itself is comprised of a set of portlets or interactive application components that can be plugged into the portal framework.

Figure 1: The Portlet Catalog Layer of the Onion
There are two portal standards that enable reuse of portlets in the catalog. The first is a Java Community Process standard called JSR 168 that enables component level reuse of portlets. The second is an OASIS standard called WSRP (Web Services for Remote Portlets) that enables service level reuse of portlets.
In this article, you will examine these complementary standards to gain an understanding of the characteristics of each. You will also review common non-standard approaches to portlet reuse and understand the tradeoffs. Finally, you will consider guidelines for utilizing these standard and non-standard approaches to building out your catalog of reusable portlets.
Component Level Reuse through JSR 168
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