Question

I have a bunch of classes with a unique set of methods.

class1 {
    method1(dbconn, args...);
    method2(dbconn, args...);
}

class2 {
    method3(dbconn, args...);
    method4(dbconn, args...);
}

class3 {
    method5(dbconn, args...);
}

We need to expose all the methods via a flat library:

class library {
    init () {
        //create instance of all helper classes
    }
    method1(args...) {
        return class1Instance.method1(getDbconn(), args...);
    }
    method2(args...) {
        return class1Instance.method2(getDbconn(), args...);
    }
    method3(args...) {
        return class2Instance.method3(getDbconn(), args...);
    }
    method4(args...) {
        return class2Instance.method4(getDbconn(), args...);
    }
    method5(args...) {
        return class3Instance.method5(getDbconn(), args...);
    }
}

But it is very time consuming, and there is a lot of repetitive code to move each method into the library. Is there a better way to do this?

Note that each method name is unique. The arguments and return value are of different types.

Answer 1

define an interface:

interface library {
    method1();
    ...
    methodN();
}

then use dynamic proxy to reflectively invoke methods of your service implementations. you will also have to find a solution on how to choose on which service particular method should be invoked. but this is not very hard.

you can implement a class:

class ServiceDemultiplexer implements InvocationHandler {

     ServiceDemultiplexer(Object services[]) {
       ... 
     }

     public Object invoke(Object proxy, Method m, Object[] args)
    throws Throwable
     {
        ...
     }
}