Deserialize nested Json Arrays

Question

I have some Json which looks like:

{
  "foo": [
    {
      "bar": "baz"
    }
  ],
  "foo2": [
    {
      "bar": "baz"
    }
  ],
  "dishes": [
    {
      "name": "tonno",
      "details": {
        "toppings": [
          "cheese",
          "tomato",
          "tuna"
        ],
        "price": 10
      }
    },
    {
      "name": "cheese",
      "details": {
        "toppings": [
          "cheese",
          "tomato"
        ],
        "price": 5
      }
    },
    {
      "name": "mexicana",
      "details": {
        "toppings": [
          "cheese",
          "tomato",
          "chicken"
        ],
        "price": 12,
        "inOffer": true
      }
    }
  ]
}

I'm not interested in "foo" and "foo2" but only want to deserialize "dishes". For this I created two classes:

public class Dish {

    @JsonProperty("name")
    private String name;

    @JsonProperty("details")
    private List<Detail> details;
}

and

public class Detail {

    @JsonProperty("toppings")
    private List<String> toppings;

    @JsonProperty("price")
    private int price;

    @JsonProperty("inOffer")
    private boolean inOffer;
}

I found this approach and tried the following:

ObjectMapper mapper = new ObjectMapper();
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
final JsonNode response = mapper.readTree(json).path("dishes");
final CollectionType collectionType = TypeFactory.defaultInstance().constructCollectionType(List.class, Dish.class);
List<Dish> dishes = mapper.readerFor(collectionType).readValue(response);

However, if I run this, I get

m.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.util.ArrayList` out of START_OBJECT token  at [Source: UNKNOWN; line: -1, column: -1]

How can I deserialize nested Json with a nested array without having to map fields I'm not interested in?

Ryuzaki L · Accepted Answer · 2019-08-09 08:44:13Z

2

You should map details as a POJO not as List<Details>

public class Dish {

@JsonProperty("name")
private String name;

@JsonProperty("details")
private Detail details;

}

answered Aug 9, 2019 at 8:44

Ryuzaki L

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Chaos Hodgson · Accepted Answer · 2019-08-09 08:38:59Z

0

you may try this:

JavaType javaType = mapper.getTypeFactory().constructParametricType(List.class, Dish.class);
List<Dish> dishes = mapper.readValue("jsonString", javaType);

answered Aug 9, 2019 at 8:38

Chaos Hodgson

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