Jackson JSON反序列化列表

Question

I want to deserialize a JSON string using the same POJO for two kind of messages. Take a look at the message below

{
"success": true,
"data": [
    {
        "id": 2,
        "comments": null
    },
    {
        "id": 3,
        "comments": null
    }
]
}

The data is an array , but sometimes the data is a single object:

{
"success": true,
"data":
    {
        "id": 2,
        "comments": null
    }
}

My POJO looks like this:

public void setData(List<Object> data)
{
    this.data = data;
}

Is there any way to deserialize the second message (where data is not an array) using the same class?

Kind regards, Ricardo

Answer 1

I havent used it, but there is a deserialization feature that allows for this on deserialization:

ACCEPT_SINGLE_VALUE_AS_ARRAY (default: false)

Allows auto-conversion from non-JSON-array values to single-element arrays and Collections (adding implicit "array wrapper"): this is sometimes necessary for interoperability, as some libraries and frameworks omit JSON arrays when serializing single-element arrays.

also looks like there is the opposite for serialization as well (writing single element arrays to non-JSON array

UNWRAP_SINGLE_VALUE_ARRAYS (default: false) (since 2.4)

Allows auto-conversion from single-element arrays to non-JSON-array values : this is similar to the ACCEPT_SINGLE_VALUE_AS_ARRAY feature but works in the opposite manner (ie if you have a bound property that is not an array or collection, a single value array in JSON would be acceptable to bind to that property). If the JSON value contains more than one element in the array, deserialization will still fail.

see https://github.com/FasterXML/jackson-databind/wiki/Deserialization-Features

I am unsure if there is a way to do this for specific fields. Seems to be an all-or-nothing kind of thing.

Hope this helps!