ObjectMapper setSerializationInclusion(JsonInclude.Include.NON_NULL) setting is not reflected

Question

ObjectMapper still includes null values. I tried a lot of solutions found here, but nothing works. I cannot use json annotation, so my only solution is predefined setting of mapper, but this was not reflected. I thought this was due to caching of objectMapper. But my only modifies of mapper are made in Constructor. So caching would not be a problem

Dependencies:

Log4J2: 2.17.1
Fasterxml Jackson annotation: 2.13.2
Fasterxml Jackson databind: 2.13.2
Wildfly: 20.0.1
OpenJDK: 11.0.14.1

I have an objectMapper defined as global value which is instantiated in constructor. Then I have one method for building a JSON which accepts key and value. As value can by anything.

private final ObjectMapper jsonMapper;

public SomeConstructor() {
    this.jsonMapper = new ObjectMapper();
    this.jsonMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
    this.jsonMapper.setDefaultPropertyInclusion(JsonInclude.Include.NON_NULL);
}

@Override
public void setJsonVar(String jsonVar, String jsonKey, Object values) {

    // loads ObjectNode from memory if exists
    ObjectNode jsonNode = getJsonVar(jsonVar);

    // lazy init if ObjectNode not exists
    if (jsonNode == null) {
        jsonNode = jsonMapper.createObjectNode();
    }
    // add object
    jsonNode.putPOJO(jsonKey, values);
}

Usage:

setJsonVar("var-A", "key-A", 1);
setJsonVar("var-A", "key-B", null);
print("var-a");

Expectation:

I want to avoid null values in JSON.

Expected: var-A: { "key-A":1 } Got: var-A: { "key-A":1, "key-B":null }

Why does this happen and what can I do to work around this?

Why not `if (values != null) jsonNode.putPOJO(jsonKey, values);`? — Oboe, Mar 22 '22 at 15:44
To summarize the question linked above, it's easiest to either manually exclude null when working with json tree, or don't include them at all. The explanation why this is happening is in the accepted answer. — Chaosfire, Mar 22 '22 at 16:08
@Oboe I agree that this is one of the solutions I currently use, but I wanted a native solution when the ObjectMapper supports it. — XChobot, Mar 24 '22 at 09:10
@Chaosfire, Thanks you a lot for provided link. This clarifies me why the settings is ignored and filtering are not applied. What i don't understand is, why this options is allowed to set. Is it only applicable to specific scenario? like for example for primitive data types? — XChobot, Mar 24 '22 at 09:17

score 1 · Accepted Answer · answered Mar 24 '22 at 10:38

This option is applicable when serializing objects, custom objects or a Map for example, but not when working with json tree. Consider this Foo class:

public class Foo {

    private String id;
    private String name;

    //getters and setters
}

The option to exclude nulls will work as expected with it.

Main method to illustrate it:

public class Main {

    public static void main(String[] args) throws Exception {
        serializeNulls();
        System.out.println();
        doNotSerializeNulls();
    }

    private static void serializeNulls() throws Exception {
        ObjectMapper jsonMapper = new ObjectMapper();
        Foo foo = new Foo();
        foo.setId("id");
        System.out.println("Serialize nulls");
        System.out.println(jsonMapper.writeValueAsString(foo));

        Map<String, Object> map = new LinkedHashMap<>();
        map.put("key1", "val1");
        map.put("key2", null);
        System.out.println(jsonMapper.writeValueAsString(map));
    }

    private static void doNotSerializeNulls() throws Exception {
        ObjectMapper jsonMapper = new ObjectMapper();
        jsonMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
        jsonMapper.setDefaultPropertyInclusion(JsonInclude.Include.NON_NULL);

        Foo foo = new Foo();
        foo.setId("id");
        System.out.println("Do not serialize nulls");
        System.out.println(jsonMapper.writeValueAsString(foo));

        Map<String, Object> map = new LinkedHashMap<>();
        map.put("key1", "val1");
        map.put("key2", null);
        System.out.println(jsonMapper.writeValueAsString(map));
    }
}

thank you for explanation, i accepted this answer as well as provided link by you in comments above. — XChobot, Mar 28 '22 at 07:21

ObjectMapper setSerializationInclusion(JsonInclude.Include.NON_NULL) setting is not reflected

1 Answers1