简单的代码设计问题

Question

I have a 3 layer app. The second layer is receiving and object from the 3rd layer and there are two attributes from this object that I need to pass on to the 1st layer (UI). Should I make this object's class visible in the 1st layer (by importing it's package/namespace, which I'm trying to avoid) or should I pass on these attributes as an string array (I'd rather have an Object array, but they're a string and an int types in Java 1.4) and cast them to their proper types in compilation time (Their types are fixed, so thankfully this is an option)?

Answer 1

That's what DTOs (Data Transfer Objects) are for. So in short: use Objects in your top-level interface.

Answer 2

I'm no java expert, but I can offer some general advice from a .NET perspective. Since that's your background it should be relevant to you.

Should I make this object's class visible in the 1st layer (by importing it's package/namespace, which I'm trying to avoid

Its OK to import the namespace. While it may feel like you decrease coupling, this is better than a string array as it does not require expensive boxing .

Do not forget that readability is always a serious consideration. I recommend you take a look at the MVC pattern.

Answer 3

Sounds like JavaBeans are your friend, although you'll probably not profit from reusability/serializabiliy.

JavaBeans are classic DTOs ( Data Transfer Objects ), used to pass along information in your program.

Answer 4

What kind of UI do you have? Swing? Then DTOs is probably the way to go. Consider to put the DTO classes in a project of its own, which then can be shared by the client side and the server side.