Simple way to get an array class type of a generic?

Asked Sep 16 '20 at 10:10

Active Sep 21 '20 at 10:58

Viewed 105 times

I've got a little code snippet that's supposed to make parsing JSON arrays simpler. My idea was originally as follows (pseudo-Java):

  public <T> T[] parseAsArray(String content, Class<T> valueType) {
    return objectMapper.readValue(content, T[].class); // doesn't work as you can't just go T[].class
  }

So then I fiddled around with the code. And then some more. And some more.

Eventually I landed at the following mess, which does work, but requires me to create a new array instance, just so I could fetch its array class type, not to mention all the casting.

  public <T> T[] parseAsArray(String content, Class<T> valueType) {
    Class<T[]> tArrClass = (Class<T[]>) Array.newInstance(valueType, 0).getClass();
    return (T[]) objectMapper.readValue(content, tArrClass);
  }

Isn't there a simpler way? All I'm really trying to do is, how can I go from T to T[] and with it to T[].class?

edited Sep 21 '20 at 10:58

asked Sep 16 '20 at 10:10

Selbi

I think that you can use TypeToken (or something like that) to specify that the result will be of List. – Antoniossss Sep 16 '20 at 10:16
i found it new TypeReference>() No idea how to deal with arrays., – Antoniossss Sep 16 '20 at 10:17
here you have some string->class hax https://stackoverflow.com/a/44720865/1527544 – Antoniossss Sep 16 '20 at 10:19
Pass in a `Class`? e.g. `parseAsArray(someContent, Integer[].class)`? – Andy Turner Sep 16 '20 at 10:26
`Class arrayClass = (Class) Class.forName("[L" + classOnWhichArrayIsDefined.getName() + ";");` seems even more messy, not really what I had in mind... – Selbi Sep 16 '20 at 10:26
@AndyTurner But that's the problem, the class type is passed in as singular object. I need to transform whatever was passed in into an array class. – Selbi Sep 16 '20 at 10:27
@Selbi then don't pass it in as a singular object? – Andy Turner Sep 16 '20 at 10:28
@AndyTurner I got no control over the other side, unfortunately. – Selbi Sep 16 '20 at 10:59

Simple way to get an array class type of a generic?

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