Question

我有一些Json，看起来像：

{
  "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
      }
    }
  ]
}

我对“ foo”和“ foo2”不感兴趣，只想反序列化“ dishes”。为此，我创建了两个类：

public class Dish {

    @JsonProperty("name")
    private String name;

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

和

public class Detail {

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

    @JsonProperty("price")
    private int price;

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

我找到了this方法，并尝试了以下方法：

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);

但是，如果运行此命令，我会得到

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]

如何在不映射我不感兴趣的字段的情况下使用嵌套数组反序列化嵌套Json？

Answer 1

您应该将details映射为POJO而不是List<Details>

public class Dish {

@JsonProperty("name")
private String name;

@JsonProperty("details")
private Detail details;

}

Answer 2

您可以尝试以下方法：

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

反序列化嵌套的Json数组

2 个答案: