46 lines
1.7 KiB
Markdown
46 lines
1.7 KiB
Markdown
---
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layout: pattern
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title: Service Locator
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folder: service-locator
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permalink: /patterns/service-locator/
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pumlid: NSjB3iCm203HgxG7iDdtDeIWX0fZYqzo_MRTtUX9ynOZhPtBzNLchlW0EDxza3nhgs2dQScMdUO0qRenqU6B5xQTGmvh2pFPBM1WF07FSmbnqqcOqu6J_gsNZxvgw0y0
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categories: Structural
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tags:
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- Java
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- Difficulty-Beginner
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- Performance
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---
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## Intent
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Encapsulate the processes involved in obtaining a service with a
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strong abstraction layer.
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## Applicability
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The service locator pattern is applicable whenever we want
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to locate/fetch various services using JNDI which, typically, is a redundant
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and expensive lookup. The service Locator pattern addresses this expensive
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lookup by making use of caching techniques ie. for the very first time a
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particular service is requested, the service Locator looks up in JNDI, fetched
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the relevant service and then finally caches this service object. Now, further
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lookups of the same service via Service Locator is done in its cache which
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improves the performance of application to great extent.
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## Typical Use Case
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* when network hits are expensive and time consuming
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* lookups of services are done quite frequently
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* large number of services are being used
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## Consequences
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* Violates Interface Segregation Principle (ISP) by providing pattern consumers with an access
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to a number of services that they don't potentially need.
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* Creates hidden dependencies that can break the clients at runtime.
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* Limits object composability by stopping the clients to specify needed dependencies for different objects instantiation.
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## Credits
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* [J2EE Design Patterns](http://www.amazon.com/J2EE-Design-Patterns-William-Crawford/dp/0596004273/ref=sr_1_2)
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