I've been using the JSON-RPC library for some time now to write the server for my game, thus far I've only had a need to transport simple objects back to the client, but recently I've had a need send a collection of objects back. This is where I found that JSON-RPC falls short if you try to use the standard Java collections.

I've tried several things, first I used a Collection, which resulted in the following exception:


Then I thought if I used a concrete class, it would fix that, but alas, the following exception is thrown:




So what's a parametrized class? Well that's to do with Java Generics, the ArrayList I had was actually something like an ArrayList and the JSON-RPC library doesn't know how to handle that.

It looks like all of the Java collections now are parametrized, so using them will not work. The only thing I found that would work was to send an array of my objects instead. This is a bit messy since it means I have to allocate my array on the server side with a known size, with a collection I was just using lazy loading, which saved me some hassle.

So to sum up, my object that was being returned to the client had to change from this:

public class MyClass {

private List<MyOtherClass> otherClass;

public MyClass() {}

...

}

to this:

public class MyClass {

private MyOtherClass[] otherClass;

public MyClass() {}

...

}

-i