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Service Locator pattern

 
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In the JSF, I want to use service locator pattern, then I have two choices, one is use singleton + synchronizedMap, another choice is to inject a service locator instance in the DAO class . these two choices , what is pros and cons ?

thanks
 
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What do you think? List out some and we can provide feedback.
 
Edward Chen
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Singleton approach can cache data, one object across system, easy to use. the bad part is the testing. but singleton is good enough for Service Locator pattern.
 
Jeanne Boyarsky
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I agree. Good analysis.

There are some techniques to make a Singleton more unit testable. First you give it in interface. Then other classes can pass in a mock instead of the real Singleton. You can also change the static variable of the Singleton to another implementation of the interface, but that is hacky since it is global.
 
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What is the use case for you to think about the DAO is injected with Service Locator instance?
 
Edward Chen
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it is possible, for example, cache manager in DAO class.
 
naresh kumar nand
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But couldn't it be the violation of layer structure. Service Locator falls in Business layer but DAO comes in Integration layer.
 
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