How to hide the internal structure of a Java API to the rest of the world

Question

i am developing a Java Api to do things (secret, uhhhh ;).

Is there a way to hide classes, and the internal structure of my API?

What i found until now:

Using inner classes (ugly way, i do not want to put all in on class file)
All classes in one package so that i can use the "package"-visibilty (also ugly, i need more packages)

Example:

---
package net.my.app;
//this is the Public Access
class MyPublicClass{
    public void somePublicFunction(){ 
        //access to not visibil classes
    }
}

---
package net.my.app.notvisible:
//this is what i want to hide
class MyNOTPublicClass{
    ...
}
---

Any ideas? Thank you!

Does this SO post help you? http://stackoverflow.com/questions/3857895/hide-public-classes-in-jar — Chris Thompson, May 03 '11 at 15:50

score 9 · Answer 1 · edited May 23 '17 at 12:17

9

There are two solutions to your question that don't involve keeping all classes in the same package.

The first is to use the Friend Accessor/Friend Package pattern described in (Practical API Design, Tulach 2008).

The second is to use OSGi.

Related Questions: 1, 2, 3, and 4.

edited May 23 '17 at 12:17

Community

1
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answered May 27 '11 at 15:20

Jeff Axelrod

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score 5 · Accepted Answer · edited May 22 '14 at 07:03

5

Use interfaces to define what your app does
Create a main entry point to accesses services, returning interfaces only
I wouldn't bother about actually hiding the implementation classes. You can never really hide them in Java, and those who are technically interested might just start your app with a debugger. Just provide no public constructors, for example

Regarding this comment:

Sean, would you elaborate a little more on your answer? ...

One way to implement my second bullet point I mean using a Service Lookup class, e.g.

public class Lookup {
    private static final Foo foo = new FooImpl();
    public static Foo getFoo() { 
        return foo; 
    }
}

Foo is an interface, FooImpl an implementation class (which can be package private if you want to enforce that it can't be instantiated by clients)

edited May 22 '14 at 07:03

Mark Pazon

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answered May 03 '11 at 15:50

Sean Patrick Floyd

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Thanks for your answere, i was looking for a design approche like you provided. – CoffeJunky May 04 '11 at 09:00
1

@CoffeJunky you should read [Effective Java by Josh Bloch](http://java.sun.com/docs/books/effective/). You will learn many more goodies there. – Sean Patrick Floyd May 04 '11 at 09:18
@Sean OK, but then aren't we back to where we started with the question that prompted all of this--all classes in the same package? – Jeff Axelrod May 26 '11 at 22:03
@glen if you want to enforce that classes can't be instantiated, that is the easiest way, yes – Sean Patrick Floyd May 27 '11 at 09:17
What this gives us so the user still can go into `Lookup` class and thanks to this check the implementation of `FooImpl`? – shurrok Oct 06 '17 at 09:43
1

@soommy12 Java is an open language, everybody can decompile your code. The only thing you can do against that is obfuscate (e.g. with ProGuard). – Sean Patrick Floyd Oct 09 '17 at 16:27

score 0 · Answer 3 · answered May 03 '11 at 15:54

0

What do you mean by 'hide'?

You can use the final modifier to stop people from extending methods and classes you don't want them to extend. If you want to stop people from decompiling your code, you can use code obfuscation and if you want to take it even further, you can use anonymous inner classes that implement interfaces.

answered May 03 '11 at 15:54

spot35

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Hi, ty for your answer. By hide i mean "not accessable with eclipse". I do not want to expose the internal structer of my API to any development tool to access the inner (maybe chaning) structer of the API. – CoffeJunky May 04 '11 at 08:47
How about removing Java from the equation altogether and using native methods and JNI? – spot35 May 04 '11 at 08:53

score 0 · Answer 4 · answered May 03 '11 at 15:58

You can try and make only your interfaces public. Have a look at the Factory Pattern.
Alternatively, you can implement you're application in OSGI.

Neither of these methods would allow you to hide the implementation completely to someone who really wanted to see it. Someone could still use a decompiler to examine you .class files, or even examine the code in memory.

If you really need to protect your implementation in this way, then a good approach would be to only allow access to your application as a remote service and host it on a secure machine.

Ok thank you for your answer! i was looking for a design approche. Thank you for your tip! — CoffeJunky, May 04 '11 at 09:02

How to hide the internal structure of a Java API to the rest of the world

What i found until now:

Example:

4 Answers4

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