'Java + JSON: list of anonymous objects (key + value) with different key names

Maybe it's simple, but I'm stuck... I have an app using Spring Boot and springframework.web.client.RestTemplate, so there's Jackson on backseat doing JSON job automatically.

I want to deserialize REST input with JSON like this:

{
    "serial_no": 12345678,
    "last_dt": [
        {
            "lp": "2022-04-22T15:00:00"
        },
        {
            "bp": null
        },
        {
            "dp": "2022-04-22T00:00:00"
        },
        {
            "iv": "2022-04-22T00:05:11"
        }
    ]
}

Please, help me to create POJO for this model... If I created following classes (simplified with lombok):

@Data
public class LastDt {

    @JsonProperty("lp")
    private String lp;
    @JsonProperty("bp")
    private String bp;
    @JsonProperty("dp")
    private String dp;
    @JsonProperty("iv")
    private String iv;

}

@Data
public class Device {

    @JsonProperty("serial_no")
    private Long serialNo;
    @JsonProperty("last_dt")
    private List<LastDt> lastDt;

}

deserialization is technically ok - I got an object with serialNo Long value and unfortunatelly list of 4 instances of class LastDt: first instance (lastDt[0]) had field "lp" with value and "bp", "dp", "iv" null; second (lastDt[1]): "bp" with value and "lp", "dp", "iv" null and so on - only one value was set and others are not. That's far from what I want to get. As you can see, there's four pair-like anonymous objects with different key names, so my model is bad, and I know this, but got stuck trying to create other ones... Can anyone help me?

javajsonjackson


Solution 1:[1]

You can use @JsonAlias. The idea is to have a single field in LastDt, with all possible names of the property mapped to that field.

public class LastDt {

  @JsonAlias({"lp", "bp", "dp", "iv"})
  private String value;

  //getter and setters

  @Override
  public String toString() {
    return "LastDt{" +
            "value='" + value + '\'' +
            '}';
  }
}

No changes are required to Device.

And a simple test:

public class Temp {

  public static void main(String[] args) throws Exception {
    ObjectMapper mapper = new ObjectMapper();
    InputStream dataStream = getTheStream();
    Device device = mapper.readValue(dataStream, Device.class);
    System.out.println(device);
  }
}

Solution 2:[2]

You should use @JsonInclude(JsonInclude.Include.NON_NULL) in your class:

@Data
@JsonInclude(JsonInclude.Include.NON_NULL)
public class LastDt {
    @JsonProperty("lp")
    private String lp;
    @JsonProperty("bp")
    private String bp;
    @JsonProperty("dp")
    private String dp;
    @JsonProperty("iv")
    private String iv;
}

Sources

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Source: Stack Overflow

Solution Source
Solution 1 Chaosfire
Solution 2

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