Jackson deserialize JSON that intermittently has an array

Question

I'm retrieving JSON back from a web service. Sometimes the property in the JSON would return as an object, and other times it's an array of the object. How can I write the Java class that I'm deserializing into to deserialize properly this property with Jackson's ObjectMapper? Can I do with the ObjectMapper to help with this?

JSON with object:

"results": {
  "account": {
     "expiration": "2012-11-16"
  }
}

JSON with collection

"results": {
  "account": [{
    "expiration": "2012-11-16"
  }]
}

See [this](http://stackoverflow.com/q/12450404/823393) question of mine where I had to deal with polymorphic objects. Essentially you must enhance the deserializer with your own code. — OldCurmudgeon, Oct 11 '12 at 21:06
In this particular case one should not have to add custom deserializers; although IMO such non-OO JSON structure is bit bad. — StaxMan, Oct 12 '12 at 05:49

score 5 · Accepted Answer · answered Oct 11 '12 at 23:19

5

You need to mark the property as a Java array or Collection, and enable feature ACCEPT_SINGLE_VALUE_AS_ARRAY:

ObjectMapper mapper = new ObjectMapper();
mapper.enable(DeserializationFeature. ACCEPT_SINGLE_VALUE_AS_ARRAY);
ResultOb ob = mapper.readValue(jsonInput, ResultOb.class);

and if a single JSON Object is encountered, it gets treated like it was a single-element JSON Array.

answered Oct 11 '12 at 23:19

StaxMan

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Doh. I looked through the java docs for jackson 1.7.9 for a config like that but didn't see any. I should always look at the latest docs. Thanks! – Glide Oct 12 '12 at 21:51
True, this is relatively new feature. – StaxMan Oct 12 '12 at 21:55

Jackson deserialize JSON that intermittently has an array

1 Answers1