JSON.Feature.READ_JSON_ARRAYS_AS_JAVA_ARRAYS does not work

[gpiancastelli]

The following code, called on Jackson Jr. 2.6.3

JSON.std.with(JSON.Feature.READ_JSON_ARRAYS_AS_JAVA_ARRAYS)
        .arrayOfFrom(Object.class, "[]");

crashes with the following exception

java.lang.ClassCastException: java.util.ArrayList cannot be cast to java.lang.Object[]
    at com.fasterxml.jackson.jr.ob.impl.JSONReader.readArrayOf(JSONReader.java)
    at com.fasterxml.jackson.jr.ob.JSON.arrayOfFrom(JSON.java)

However, if I remove the feature and ask Jackson Jr. to read a list from the JSON array by using listOfFrom, everything works fine.

Since even calling arrayOfFrom without the feature does not work (which I presume is due to JSON arrays indeed being read as Java Lists... but, then, what's the purpose of the arrayOfFrom method?), how else I am supposed to make Jackson Jr. return me a Java array from a JSON array?

[cowtowncoder]

Thank you for reporting this: it sounds like a bug and your code should work as you expect.

[cowtowncoder]

Ok, looking at the unit test, usage that is tested is:

    ob = JSON.std.with(Feature.READ_JSON_ARRAYS_AS_JAVA_ARRAYS).anyFrom(INPUT);
    // gives Object[]

so a possible short-term work-around would be to use anyFrom().

This just as a sidenote; will try to resolve the actual problem next.

[cowtowncoder]

Hmmh. Interesting. Code works just fine with non-empty JSON Array -- problem only occurs with empty one.

[gpiancastelli]

Well, I had the same problem with a non-empty JSON array, but since it was filled with some model objects specific to the application I was working on (rather, their JSON representation, of course) I guessed it was easier to report the bug with an empty array example.

[cowtowncoder]

Turned out to be a copy+paste error for array reader; interestingly enough, only special cases of 0 and 1 elements were affected, but not larger arrays. And this is why unit tests passed; they had 2 elements in the JSON Array....

Fixed for 2.6.4.

[cowtowncoder]

@gpiancastelli no that's completely fine, I was just hunting down the bug, trying to see why unit test was not catching the problem. :)

[gpiancastelli]

@cowtowncoder but now that you pointed out the specifics of the bug, I double checked my "real" example, and indeed the array contained only one of those model objects I said it was filled with! Everything comes together.