JsonParser.readTree () returns null after using JsonParser for default deserializer in jackson

The title doesn't define the problem, so here's the prblem description.

I have used the native deserializer in jackson for my purpose. I need to use defaul in my custom deserializer and change some of the fields in it. I did it based on This approach and here is my method:

public Test deserialize(JsonParser p, DeserializationContext ctxt)
        throws IOException, JsonProcessingException{

    Test test = (Test)this.defaultDeserializer.deserialize(p, ctxt); 

    JsonNode node = p.getCodec().readTree(p);

    // The rest of the code use node to change is some fields.

}

      

        
        
        
      

    

My problem is when the default deserializer is used, the node object will be null and I cannot use it to retrieve other fields from the json object. do you know how i can fix this problem?