Parsing JSON message to Java Pojo with Gson library whilst mapping JSON to String field

Question

I am using the Gson library to parse JSON messages into Java POJOs before persisting to a PostgreSQL database. The PostgreSQL database schema cannot be changed.

An example POJO Message.java is below:

@TypeDef(name = "jsonb", typeClass = JsonBinaryType.class)
public class Message {

    @Column(nullable = false, columnDefinition = "jsonb")
    @Type(type = "jsonb")
    private String messageDetail;

    @Column(nullable = false)
    private String messageType;

    @Column(nullable = false, unique = true)
    private String messageId;

}

An example JSON message is below:

{
    "messageId": "ae97d31b-c63e-42fd-b619-f3cdcb169f58",
    "messageDetail": {
        "count": 5
    },
    "messageType":"AdminUserSearch"
}

I want to the messageDetail which is a JSON object to be parsed (kept) as a String. Gson is failing as it seems to recognise that it is a JSON object and hence not allowing me to keep it as a string. For database integration reasons I would prefer this field on my POJO to be a string rather than anything else e.g. Object, JSONNode, Map<String,Object>.

The following code fails:

String messageString = gson.toJson(kafkaMessage);
JsonObject messageObject = gson.fromJson(messageString, JsonObject.class);
Message messagePojo = gson.fromJson(messageObject, Message.class);