将JSONArray转换为适当类型的Java数组

Question

I'm struggling at integrating some existing pieces of code with a server that accepts inputs via JSON payload. I am handed a JSON object, and I need to construct a Map that represents the key-value pairs, where the values take on reasonable, expected types. The org.json parser seems adequate for every case except for the one around JSONArrays.

I can see that it's quite easy to build a String[] from a JSONArray ... provided you know that a String[] is what you need. However, I am also handed arrays of doubles, arrays of ints, with nothing to distinguish them. I need to figure out the type, and create an appropriately-typed array.

I've tried pulling the first element from the array and getting its type, in hopes of creating an array instance of that type, like so:

private Object[] decodeToArray(JSONArray list) throws JSONException { 

    if (list.length() > 0) {
        Class<? extends Object> type = list.get(0).getClass();
        type[] result = Array.newInstance(type, list.length());
    }

But of course, this doesn't compile -- type is an instance, not a class; it won't accept ? as a type; and if I try to give it a name, a la <T extends Object> , it requires the T to be declared in the method signature, which doesn't seem to be connected in any way to the unknown type obtained from the list element.

And this, of course, doesn't do anything at all for the int[] and double[] case. Integer[] and Double[] would be acceptable compromises, probably.

As an interim solution, I've been able to render the JSONArray as an Object[], and then change the server-side code that interacts with these arrays to cast them as needed, but it's ugly, and it allows some JSON-yuck to seep into our code base.

Are there any libraries or clever tricks for creating arrays of unknown type in Java? Is there a JSON convention I can ask to be used that would inform me what type is expected?

Answer 1

Assuming this is for the real world and not homework, just use Gson , a library that does exactly what you're looking for.

Also, read this thread thoroughly: https://stackoverflow.com/questions/338586/a-better-java-json-library?rq=1