JACKSON: How to ignore the POJO name while converting a POJO to JSON using Jackson?

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I am using Jackson 2.10.1 library to convert my Java POJOs to JSON and I am getting the below output, I require the output without the POJO name(MyTestPojo here), I have tried various jackson annotations like @JsonIgnoreProperties but those are mostly for the members present in the POJO and not the POJO class name.

{
    "MyTestPojo": [
        {
            "CreatedBy": "user1",
            "Name": "testABC",
            "UpdatedBy": null,
            "UpdatedDate": null,
            "IsActive": true,
            "Value": "testABC1",
            "CreatedDate": "2017-03-13 15:41:54.0",
            "Description": "testABC"
        },
        {
            "CreatedBy": "user2",
            "Name": "testABC",
            "UpdatedBy": null,
            "UpdatedDate": null,
            "IsActive": false,
            "Value": "testABC2",
            "CreatedDate": "2017-03-13 15:41:54.0",
            "Description": "testABC"
        }
    ]
}

whereas what I require is -

[
        {
            "CreatedBy": "user1",
            "Name": "testABC",
            "UpdatedBy": null,
            "UpdatedDate": null,
            "IsActive": true,
            "Value": "testABC1",
            "CreatedDate": "2019-03-13 15:41:54.0",
            "Description": "testABC"
        },
        {
            "CreatedBy": "user2",
            "Name": "testABC",
            "UpdatedBy": null,
            "UpdatedDate": null,
            "IsActive": false,
            "Value": "testABC2",
            "CreatedDate": "2020-03-10 15:41:54.0",
            "Description": "testABC"
        }
    ]
}

Is there a way to handle this with Jackson annotations?

The POJOs that I have used are-

@JacksonXmlRootElement(localName = "ArrayOfTestPojos")
public class GetResponseVO {

    @JsonProperty("MyTestPojo")
    @JacksonXmlProperty(localName = "MyTestPojo")
    @JacksonXmlElementWrapper(useWrapping = false)
    private ArrayList<MyTestPojo> MyTestPojoList;

    public ArrayList<MyTestPojo> getMyTestPojoList() {
        return MyTestPojoList;
    }

    public void setMyTestPojoList(ArrayList<MyTestPojo> MyTestPojoList) {
        this.MyTestPojoList = MyTestPojoList;
    }

// standard getters and setters

}

and

@JacksonXmlRootElement(localName = "MyTestPojo")
public class MyTestPojo {

    @JsonProperty("Name")
    private String name;

    @JsonProperty("Description")
    private String description;

    @JsonProperty("IsActive")
    private int isActive;

    @JsonProperty("Value")
    private String value = null;

    @JsonProperty("CreatedBy")
    private String createdBy;

    @JsonProperty("CreatedDate")
    private String createdDate;

    @JsonProperty("UpdatedBy")
    private String updatedBy;

    @JsonProperty("UpdatedDate")
    private String updatedDate;

// standard getters and setters.    
}
```````````
I am also generating the XML out of this so you can ignore the annotations relevant to XML.
jackson2 jackson-databind marshalling json java
1 Answers

you can use JsonValue annotation for that purpose which basically "use-value of this property instead of serializing the container object". it can be used on getters also

@JsonValue indicates that results of the annotated "getter" method (which means signature must be that of getters; non-void return type, no args) is to be used as the single value to serialize for the instance. Usually value will be of a simple scalar type (String or Number), but it can be any serializable type (Collection, Map or Bean).

@JsonValue
@JacksonXmlProperty(localName = "MyTestPojo")
@JacksonXmlElementWrapper(useWrapping = false)
private ArrayList<MyTestPojo> MyTestPojoList;

But that would wrong practice as it will generate JSON like this, which would not be legal JSON.

{[{"x":"value"}, ...]}

If you want to alter only JSON structure (without affecting xml), you can use MixIn for that purpose.

public interface JsonMixin {

   @JsonValue
   List<MyTestPojo> getMyTestPojoList();   
}

And register it with your object mapper and remove @JsonValue from the main Class.

objectMapper.addMixIn(GetResponseVO.class, JsonMixin.class);
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