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copied!<p>I don't know if you already <a href="http://corej2eepatterns.com/Patterns2ndEd/BusinessDelegate.htm" rel="nofollow">checked this</a> out, but it's a good start.</p> <blockquote> <p>Use a Business Delegate to encapsulate access to a business service. The Business Delegate hides the implementation details of the business service, such as lookup and access mechanisms.</p> </blockquote> <p>A Service Locator encapsulates the logic required to search and/or obtain the location, restrictions and required fields for a certain service based on a general registry. A Business Delegate encapsulates a group of related services and exposes them in a cohesive way to prevent a service customer from having to search and access all the services related to a certain functionality.</p> <p>Plus, you prevent the customer from having to actually know the Service Locator and the services it should consume, leaving that to a particular Business Delegate. A client only needs that delegate to perform a group of related tasks or a task that relies in various services. </p> <hr> <p><strong>Example</strong></p> <p>A Business Delegate doesn't actually encapsulate a group of Service Locators. It provides an abstraction layer over a Service Locator to provide a cohesive subset of services. Usually there's only one instance of a Service Locator, multiple instances require an additional mapping where you should know WHICH Service Locator provides Service X, think of it as if you would need a <em>Service Locator Locator</em>.</p> <p>An example should help clarify things.</p> <p>Think about user account management. The <code>UserBusinessDelegate</code> looksup the registration service to register an user and then looksup the authentication service to allow a log in. The client only needs one Business Delegate to access those services and he doesn't need to know the id of both services.</p> <p>Those service ids are encapsulated in the <code>UserBusinessDelegate</code> avoiding the need of declaring the ids and using a Service Locator everywhere. Think about this, what would happen if one service id changes?.</p> <p>In such cases the Business Delegate in charge is updated, avoiding a direct impact for the client.</p>

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