UntypedObjectDeserializer.Vanilla not handling xml sequences (same tags) correctly

[Antibrumm]

(Moved from databinding as requested)

I don't know if this applies also for deserializing a json message, but by using the XmlMapper the resulting Map does only contain the last child node in case there are some `maxOccurence="unbounded" elements.

The reason seems to be that the Vanilla implementation just uses result.put(key,value) instead of checking if there already exists an entry.

I was able to get the expected result by modifying the method mapObject(JsonParser jp, DeserializationContext ctxt) and replacing all 'result.put' with an addValue delegate which looks like this:

private void addValue(Map<String, Object> result, String fieldName, Object value) {
            if (!result.containsKey(fieldName)) {
                result.put(fieldName, value);
            } else {
                Object existing = result.get(fieldName);
                if (existing instanceof List) {
                    ((List) existing).add(value);
                } else {
                    List list = new ArrayList();
                    list.add(existing);
                    list.add(value);
                    result.put(fieldName, list);
                }
            }
        }

I could provide a pull request if this is considered a bug/improvement and is desired, but for that i would need to know where to hook in, as the current solution is based on the databinding deserializer.

[cowtowncoder]

Note: similar to planned work for JsonNode with XML improvements: FasterXML/jackson-databind#2732 -- will tag with 2.12 to possibly address this in similar way, as suggested.

[cowtowncoder]

Just realized that there is #205 that is same thing (I think) -- and although usually I'd close newer issue as dup, there is bit more discussion on that one so will close this issue instead.