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<h2 class="first-section-title"><a name="176"></a><a name="ch05lev1sec7"></a>Architectural Component Layer</h2><p class="first-para">Ideally, all general utilities and components would be provided natively in the Java Development Kit (JDK). But in reality, a gap exists between what the JDK provides and the capabilities applications need. Third-party utilities, APIs, and packages fill a significant portion of this gap, but they do not have complete coverage. Your object-modeling activities probably identify a need for architectural components and utilities that don't yet exist in open <a name="177"></a><a name="IDX-69"></a>source form or otherwise. These common components are candidates for sharing across the enterprise.</p>
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<p class="para">Whenever possible, use existing architecture utilities as opposed to building them from scratch. Look first to the open source community (it's free and sure to fit in any organization's budget). If you do opt to use an open source package, make sure that you download a copy of the source for the version that you're going to use. If you have production bugs involving an open source package, having the source makes the investigation easier.</p>
<p class="para">Be sure to perform technical feasibility testing for any open source package you select if none of the development team has experience with it. The earlier you find out the limitations of a package, the more time you'll have to react to those limitations and the less they will impact your project timeline.</p>
<p class="para">Although looking for an open source package is a bit like looking for a needle in a haystack, you can shorten the search by starting at the Open Source Developer's Kit site (<a target="_top" class="url" href="http://www.osdk.com/">http://www.osdk.com/</a>). This site surveys and categorizes the most popular open source packages.</p>
<p class="para">Architectural components should be kept application generic for two reasons. First, if they are important enough to share across the enterprise (or perhaps across the Java community as an open source package), they'll be easier to share if they don't have hooks into a specific application. If someone creates an open source package to do this in the future, your home-grown utility will be easier to obsolete.</p>
<p class="last-para">At this point, you'll want to identify the components and classes that your application will commonly use and leave the details to the developers. The abstract nature and complexity of architectural components can lead to analysis paralysis for many development groups. Specify and model the capabilities and the objects the application will interact with, but leave the details to your most advanced developers.</p>
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