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Json array map position to java property with jackson

Is there a way in Jackson to map json array’s positions to different class properties?

For example if we have an api that returns person properties as array (0 is the id, 1 is the name,2 is the age, etc.) how to map this to an object that has properties id, name and age?

"person": [
1,
"Evgeni",
35
]


record Person(Long id, String name, Integer age)

Looking for something like:

@JsonProperty("<get the item at position 1>") String name
Tags:

2

Answers


  1. 0

    You can create a custom deserializer using the JsonDeserializer interface and map the contents of a JSON array to the corresponding properties by overriding the class deserialize(JsonParser p, DeserializationContext ctxt).

    Create a custom deserializer:

    public class FooBarDeserializer extends JsonDeserializer<FooBar> {
@Override
public FooBar deserialize(JsonParser p, DeserializationContext ctxt) 
        throws IOException, JsonProcessingException {
    JsonNode node = p.getCodec().readTree(p);
    int foo = node.get(0).asInt();
    String bar = node.get(1).asText();

    return new FooBar(foo, bar);
  }
}

    Annotate the class with the custom deserializer:

    @JsonDeserialize(using = FooBarDeserializer.class)
public class FooBar {
  private int foo;
  private String bar;
}

    Deserialize the JSON:

    public static void main(String[] args) throws Exception {
  String json = "[42, "hello"]";

  ObjectMapper mapper = new ObjectMapper();
  FooBar fooBar = mapper.readValue(json, FooBar.class);

  ...
}
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  2. 0

    You may try to use JSON library Josson to transform the JSON array into object.

    https://github.com/octomix/josson

    POJO Person

    public static class Person {
    @JsonProperty("0")
    private Long id;

    @JsonProperty("1")
    private String name;

    @JsonProperty("2")
    private Integer age;

    @Override
    public String toString() {
        return "Person{" +
                "id=" + id +
                ", name='" + name + ''' +
                ", age=" + age +
                '}';
    }
}

    Deserialize, Transform and Convert

    Josson josson = Josson.fromJsonString("{"person":[1,"Evgeni",35]}");

JsonNode node = josson.getNode("person.map(#::?).mergeObjects()");
System.out.println("nJsonNode:n" + node.toPrettyString());

Person person = Josson.readValueFor(node, Person.class);
System.out.println("nPerson:n" + person);

    Transformation expression:

    • map() : Construct an object.
      • # denote the zero based array index.
      • :: extract the field value to become the key name.
      • ? denote the current node value.
    • mergeObjects() : Merge multiple objects into one object.

    Output

    JsonNode:
{
  "0" : 1,
  "1" : "Evgeni",
  "2" : 35
}

Person:
Person{id=1, name='Evgeni', age=35}
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