CODEWITHSUNDEEP
javajsonjackson
Abbas
Abbas

Reputation: 3258

java and json jackson property - different types at run-time

I am calling an external web-service to get an object as json. This object has a property "value" which is sometimes a String and sometimes an array of Strings. 

public class MyClass {

    // ... other variables

    private String value;

    public String getValue() {
        return value;
    }

    @JsonProperty("value")
    public void setValue(String value) {
        this.value = value;
    }
}

Currently, I get an error org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of java.lang.String out of START_ARRAY token complaining about this field. I was wondering if some one could give me a hint on what is the correct way of defining value in my class.

This is a part of a sample json that I have to deal with:

    {
      "id": 12016907001,
      "type": "Create",
      "value": "normal",
      "field_name": "priority"
    },
    {
      "id": 12016907011,
      "type": "Create",
      "value": [
        "sample",
        "another"
      ],
      "field_name": "tags"
    }

Thanks.

-- EDIT

I changed the type of the value to Object and it solved my problem. However, I am still wondering if there is a better way to handle this case.

Upvotes: 2

Views: 3658

Answers (3)

HiJon89
HiJon89

Reputation: 911

A simple hack would be to enable DeserializationFeature#ACCEPT_SINGLE_VALUE_AS_ARRAY and then use Daniel's answer. If the web service returns a string, Jackson will turn it into a single-element collection.

EDIT:

If you can't upgrade to Jackson 1.8 or higher to use this feature, you could do something like:

private Collection<String> value;

public Collection<String> getValue() {
    return value;
}

public void setValue(Object value) {
    if (value instanceof Collection) {
        this.value = (Collection<String>) value;
    } else {
        this.value = Arrays.asList((String) value);
    }
}

Upvotes: 8

nutlike
nutlike

Reputation: 4975

You can use JsonNode as type for your value. Afterwards you can process your value dependent on the return values of isArray() (or isValueNode()). I think that JsonNodes are the most convenient way way to handle raw JSON because they offer a broad functionality beyond those simple checks.

if (value.isArray()) {

    // process your array

} else {

    // process your string

}

Upvotes: 0

Daniel Walton
Daniel Walton

Reputation: 228

value is an array so it can't be converted to a string.

You're java class should be something like the following:

class MyClass
{
   public int id;
   public String type;
   public Collection<String> value;
   public String field_name;
}

I'm using public fields for example (this will work fine).

Upvotes: 0

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