getting "NULL" instead of null in Json response in java

Question

I have my own object when there is no value it is coming as "NULL" in a string from downstream and it is failing while converting to java object in ObjectMapper

class Test 
private String value1; 
private String value2; 
.... getters and setters.

Json Response is

{"Test": "NULL"}

How I can handle this in java Error message is :

** error : com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of com.test.Test (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('NULL') **

This is how I am converting json to java

ResponseEntity<String> responseEntity = getDownstreamResponse(id);
ObjectMapper mapper = new ObjectMapper();
Test test =  mapper.readValue(responseEntity.getBody(), Test.class);

Answer 1

Inside the body of:

ResponseEntity<String> responseEntity = getDownstreamResponse(id);

... you will have:

{"Test": "NULL"}

... but that's not a Test.class. The Test.class, eventually, it's only the value of the key "Test", so the following line of code would fail anyway even if the response was correct:

Test test =  mapper.readValue(responseEntity.getBody(), Test.class);

To make it simpler, I'd do this:

ObjectMapper mapper = new ObjectMapper();
JsonNode fullResponse = mapper.readTree(responseEntity.getBody());
JsonNode testNode = fullResponse.get("Test");
if ("NULL".equals(testNode.asText())) {
    //you won't be able to parse the response into class Test.class. 
    //do what you wish to do here (throw an exception, return null etc.)
}
Test test =  mapper.readValue(testNode, Test.class);
//here you should have parsed test, so do what you want with it