Question 108994 in Json Question posted in
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How to convert a JSON Property to an Object using ObjectMapper

I use the following to convert a JSON into an Object:

JSON:

{
     "color": "blue"
}

Code:

somethingDto = objectMapper.readValue(myJson, SomethingDTO.class);

However, let’s say that the JSON comes at the following format:

{
    "something": {
         "color": "blue"
    }
}

What code can achieve the same result?

Edit: There may be more properties alongside "something"

Tags:

2

Answers


  1. 0

    You should create a root class for it for example

    public class RootDto {
     SomethingDTO somthing;

     public SomethingDTO getSomething() {
      return somthing;
     }
    
    
     public void setSomething(SomethingDTO somthing) {
      this.somthing = somthing;
     }
}

    Then map your JSON to it

    RootDto rootDto = objectMapper.readValue(myJson, RootDto.class);

    Or you can use JsonNode

    JsonNode rootNode = objectMapper.readTree(myJson);
JsonNode somethingNode = rootNode.get("something");
SomethingDTO somethingDto = objectMapper.convertValue(somethingNode, SomethingDTO.class);

    Also, you can handle both of them in this way

    JsonNode rootNode = objectMapper.readTree(myJson);
JsonNode somethingNode = rootNode.get("something");
SomethingDTO somethingDto;
if (somethingNode != null) {
    somethingDto = objectMapper.convertValue(somethingNode, SomethingDTO.class);
} else {
    somethingDto = objectMapper.convertValue(rootNode, SomethingDTO.class);
}
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  2. 0

    Threre is an annotation called @JsonRootName which is similar to @XmlRootElement. That annotation indicates the name of the "root" wrapping.

    @JsonRootName("something")
public class SomethingDto {

    String color;

    public String getColor() {
        return color;
    }

    public SomethingDto setColor(String color) {
        this.color = color;
        return this;
    }
}

    After that, the fearure must be enabled:

    ObjectMapper om = new ObjectMapper()
        .enable(SerializationFeature.WRAP_ROOT_VALUE)
        .enable(DeserializationFeature.UNWRAP_ROOT_VALUE);

    Now, it will wrap / unwrap objects to desired root element(s).

    class WrapTest {

    private static final ObjectMapper om = new ObjectMapper()
            .enable(SerializationFeature.WRAP_ROOT_VALUE)
            .enable(DeserializationFeature.UNWRAP_ROOT_VALUE);

    //language=json
    private static final String input = """
            {
                "something": {
                    "color" : "blue"
                }
            }
            """;

    @Test
    void wrappedTest() throws JsonProcessingException {
        var dto = om.readValue(input, SomethingDto.class);
        Assertions.assertAll(
                () -> assertNotNull(dto),
                () -> assertEquals("blue", dto.getColor(), "color field mismatch")
        );
    }
}
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