JSON: JsonMappingException while try to deserialize object with null values

Question

I try to deserialize object that contains null-properties and have the JsonMappingException.

What I do:

String actual = "{\"@class\" : \"PersonResponse\"," +                 "  \"id\" : \"PersonResponse\"," +                 "  \"result\" : \"Ok\"," +                 "  \"message\" : \"Send new person object to the client\"," +                 "  \"person\" : {" +                 "    \"id\" : 51," +                 "    \"firstName\" : null}}"; ObjectMapper mapper = new ObjectMapper(); mapper.readValue(new StringReader(json), PersonResponse.class); //EXCEPTION! 

BUT: if to throw away "firstName = null" property - all works fine! I mean pass the next string:

String test = "{\"@class\" : \"PersonResponse\"," +                 "  \"id\" : \"PersonResponse\"," +                 "  \"result\" : \"Ok\"," +                 "  \"message\" : \"Send new person object to the client\"," +                 "  \"person\" : {" +                 "    \"id\" : 51}}"; ObjectMapper mapper = new ObjectMapper(); mapper.readValue(new StringReader(json), PersonResponse.class); //ALL WORKS FINE! 

Question: How to avoid this exception or to pledge Jackson ignore null-values during serialization?

Throws:

Message:

com.fasterxml.jackson.databind.MessageJsonException:  com.fasterxml.jackson.databind.JsonMappingException:   N/A (through reference chain: person.Create["person"]->Person["firstName"]) 

cause:

com.fasterxml.jackson.databind.MessageJsonException:  com.fasterxml.jackson.databind.JsonMappingException:   N/A (through reference chain: prson.Create["person"]->Person["firstName"]) 

cause: java.lang.NullPointerException

Answer 1

Sometimes this problem occurs when accidentally using a primitive type as return type of the getter of a non-primitive field:

public class Item {     private Float value;      public float getValue()     {         return value;     }      public void setValue(Float value)     {         this.value = value;     }    } 

Notice the "float" instead of "Float" for the getValue()-method, this can lead to a Null Pointer Exception, even when you have added

objectMapper.setSerializationInclusion(Include.NON_NULL); 

Answer 2

If you don't want to serialize null values, you can use the following setting (during serialization):

objectMapper.setSerializationInclusion(Include.NON_NULL); 

Hope this solves your problem.

But the NullPointerException you get during deserialization seems suspicious to me (Jackson should ideally be able to handle null values in the serialized output). Could you post the code corresponding to the PersonResponse class?