Can not deserialize instance of java.util.ArrayList out of START_OBJECT token

The problem is the JSON - this cannot, by default, be deserialized into a Collection because it's not actually a JSON Array - that would look like this:

[    {        "name": "Test order1",        "detail": "ahk ks"    },    {        "name": "Test order2",        "detail": "Fisteku"    }]

Since you're not controlling the exact process of deserialization (RestEasy does) - a first option would be to simply inject the JSON as a String and then take control of the deserialization process:

Collection<COrder> readValues = new ObjectMapper().readValue(    jsonAsString, new TypeReference<Collection<COrder>>() { });

You would loose a bit of the convenience of not having to do that yourself, but you would easily sort out the problem.

Another option - if you cannot change the JSON - would be to construct a wrapper to fit the structure of your JSON input - and use that instead of Collection<COrder>.

Hope this helps.

Instead of the JSON document, you can update the ObjectMapper object like below :

ObjectMapper mapper = new ObjectMapper();mapper.configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true);

This will work:

The problem may happen when you're trying to read a list with a single element as a JsonArray rather than a JsonNode or vice versa.

Since you can't know for sure if the returned list contains a single element (so the json looks like this {...}) or multiple elements (and the json looks like this [{...},{...}]) - you'll have to check in runtime the type of the element.

It should look like this:

(Note: in this code sample I'm using com.fasterxml.jackson)

String jsonStr = response.readEntity(String.class);ObjectMapper mapper = new ObjectMapper();JsonNode rootNode = mapper.readTree(jsonStr);// Start by checking if this is a list -> the order is important here:                      if (rootNode instanceof ArrayNode) {    // Read the json as a list:    myObjClass[] objects = mapper.readValue(rootNode.toString(), myObjClass[].class);    ...} else if (rootNode instanceof JsonNode) {    // Read the json as a single object:    myObjClass object = mapper.readValue(rootNode.toString(), myObjClass.class);    ...} else {    ...}