How to detect trailing garbage using Jackson ObjectMapper

Question

Say I have a class

class A {
    public int x;
}

Then a valid json can be parsed as follows:

ObjectMapper mapper = new Obje         


        

Answer 1

The main thing to do is to create a JsonParser first, separately, then call ObjectMapper.readValue() passing that parser, and THEN call nextToken() once more and verify it returns null (instead of non-null value, or throw exception).

So, something like

JsonParser jp = mapper.getFactory().createParser(jsonSource);
try {
    Value v = mapper.readValue(jp, Value.class);
    if (jp.nextToken() != null) {
        //throw some exception: trailing garbage detected
    }
    return v;
} finally {
    jp.close();
}

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Note: This is for Jackson 2.x. For Jackson 1.x, use getJsonFactory().createJsonParser() instead of getFactory().createParser().