Jackson deserializing Array inside an array

Question

I have Json response as

"Test1": {
        "Test2": [
            [
                0,
                "US TV",
                []
            ]
        ]
}

I have created a Test2 class like

    @JsonProperty("Test2")
    @JsonFormat(with = JsonFormat.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY)
    Test2[] arrayObjects; 

And not sure how to give [] in Test2 class, can anyone suggest how to create Pojo for the mentioned Json response in Java?

Answer 1

Declare the field like this:

@JsonProperty("Test2")
Object[][] test2;

or like this:

@JsonProperty("Test2")
List<List<Object>> test2;

The type is Object since the inner array contains a mix of number, string, and array.

The name of the field doesn't matter, since you have @JsonProperty naming it for the JSON.

You can of course also do List<Object[]> or List<Object>[], but those seem a bit weird.

---

UPDATE: Proof that above code works:

Foo.java

@JsonRootName("Test1")
class Foo {
    @JsonProperty("Test2")
    List<List<Object>> bar;

    public static void main(String[] args) throws Exception {
        Foo foo = new ObjectMapper()
                .configure(DeserializationFeature.UNWRAP_ROOT_VALUE, true)
                .readValue(new File("test.json"), Foo.class);
        System.out.println(foo.bar);
    }
}

test.json

{
    "Test1": {
        "Test2": [
            [
                0,
                "US TV",
                []
            ]
        ]
    }
}

Output

[[0, US TV, []]]