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Thread: API Hell

  1. April 6th, 2014, 11:47 PM #1
    sci4me
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    Default API Hell

    Hey guys. So, I am working in an environment where certain API's may or may not exist depending on the scenario. I have classes that implement certain interfaces from API's which might not always exist. The thing is: my classes don't DEPEND on those interfaces. I just want to implement them if I can. Sounds like an easy fix: java.lang.reflect.Proxy. Problem with that.. heres some example code:

    class MyClass
{
    public void methodFromTheInterface();
}
 
MyClass c = (MyClass) ReflectionHelper.createProxy("someInterface", new MyClass())
 
//so far so good...
 
SomeAPIThatUsesReflection.registerMyClass((someInterface) c); //NoClassDefFoundError because of the cast.. referencing the interface...

    Since "registerMyClass" takes a "someInterface", I have to cast it...
    And distributing the api in my jar is not (afaik) a viable solution... because what happens if there are 2 of the same class (interface in this case)...

    What I have learned so far: API's suck (dynamic, runtime API's).

    I will keep on this and try to find a solution...
    If anyone can help, please let me know! Thanks!

    Edit: I just realized something... I could call the method with reflection to avoid casting. hmm... should work. Will try later.
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  3. April 7th, 2014, 12:33 PM #2
    aussiemcgr
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    Default Re: API Hell

    The thing is: my classes don't DEPEND on those interfaces. I just want to implement them if I can.
    That sounds counter-intuitive. If you want to implement an interface, the class implementing the interface is dependent on the interface, otherwise: how does it know what it is implementing?
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  4. April 7th, 2014, 02:33 PM #3
    sci4me
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    Default Re: API Hell

    Perhaps I should word this better... My code will work with or without the interface, the interface is simply a way to add an "extra feature" to the class. It is not required for the class to function properly.
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  5. April 7th, 2014, 02:43 PM #4
    Norm
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    Default Re: API Hell

    Having a class implement an interface has little to do with a class functioning properly. It has to do with telling a method in another class what the class can do so that the compiler can validate that contract between the method and the instance of the class that is being passed to it.
    If you don't understand my answer, don't ignore it, ask a question.
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  6. April 7th, 2014, 02:57 PM #5
    aussiemcgr
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    Default Re: API Hell

    Ok... I feel you are confusing the English definition of "depend" with what it means in java when we talk about "dependencies". Let me try to explain this the best I can.
    In java, when you say that Class A depends on Class B, you are creating the relationship where Class A is aware of the existence of Class B, and that it has access to Class B's compiled code. Class A depending on Class B does not guarantee Class A inherits from Class B or anything, but rather that Class A uses Class B for some reason (could be inheritance, or Class A might simply have a variable of type B ).
    So you say that MyClass works without SomeInterface, which would mean MyClass makes no reference to anything SomeInterface related. Nothing wrong with that. Then you say you are adding some extra feature, which is coming from SomeInterface (am I correct?). When you add the extra feature to MyClass, MyClass becomes "dependent on" SomeInterface.
    You may get this to work with reflection, but reflection should always be considered a last-resort option, since it is an inconsistent means of breaking normal java convention. There is absolutely no guarantee that reflected code will be portable, which oracle even warns about. For example, there are some security restrictions which may prevent reflection from even working. These security restrictions will result in client-dependent errors and crashes. The lack of stable portability (which is arguably the entire purpose of java) is the main reason reflection is discouraged.
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