Ignore wrapper type when mapping JSON with RestTemplate

Question

I am trying to parse a JSON in the following format:

[
    {
        "wrapper": {
            "fieldA": "testA1",
            "fieldB": "testB1",
        }
    },
    {
        "wrapper": {
            "fieldA": "testA2",
            "fieldB": "testB2",
        }
    },
    {
        "wrapper": {
            "fieldA": "testA3",
            "fieldB": "testB3",
        }
    }
]

My Java code looks like this:

@JsonIgnoreProperties(ignoreUnknown = true)
public class Wrapper {
  @JsonProperty("wrapper")
  MyObject wrapper;
}

and

@JsonIgnoreProperties(ignoreUnknown = true)
public class MyObject {
  @JsonProperty("fieldA")
  String fieldA;

  @JsonProperty("fieldB")
  String fieldA;
}

This works but I don't want to use a separate class just for the wrapper element. How can I configure the MyObject class to map the JSON structure directly?

Answer 1

I stumbled over the same problem. To shorten the research for others I'll add the solution to the example the author has given.

It can be done with @JsonProperty and some simple logic.

Example:

@JsonIgnoreProperties(ignoreUnknown = true)
public class MyObject {
  String fieldA;
  String fieldA;

  @JsonProperty("wrapper")
  private void unpackNested(Map<String,Object> wrapper) {
    this.fieldA = (String) wrapper.get("fieldA");
    this.fieldB = (String) wrapper.get("fieldB");
}

}

Source: Jackson nested values