JsonInclude.ALWAYS not honored by ObjectMapper.convertValue(...)

A JSON property of type Map with annotation @JsonInclude(JsonInclude.Include.ALWAYS) gets populated wrongly (missing entries with null values) when using ObjectMapper.convertValue from a Map to the type containing the JsonProperty.

Here is a full reproduction scenario where Pojo is the type containing the JsonProperty:

import java.util.LinkedHashMap;
import java.util.Map;

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class Example {

    private static class Pojo {
        @JsonProperty("name1")
        String name1;

        @JsonProperty("name2")
        String name2;

        @JsonProperty("other")
        @JsonInclude(JsonInclude.Include.ALWAYS)
        Map<String, Object> otherInfo;
    }

    public static void main(String[] args) throws Exception {
        final Pojo pojo1 = new Pojo();
        pojo1.name1 = "hello";
        pojo1.name2 = null;
        pojo1.otherInfo = new LinkedHashMap<>();
        pojo1.otherInfo.put("foo", "bar");
        pojo1.otherInfo.put("baz", null);
        
        System.out.println("pojo1:\t" + pojo1.otherInfo);

        final ObjectMapper mapper = new ObjectMapper();
        mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);

        final String str = mapper.writeValueAsString(pojo1);
        final Map<?, ?> map = mapper.readValue(str, Map.class);
        System.out.println("map:\t" + map);
        
        final Pojo pojo2 = mapper.convertValue(map, Pojo.class);
        
        System.out.println("pojo2:\t" + pojo2.otherInfo);
    }
}

Expected output:

pojo1:	{foo=bar, baz=null}
map:	{name1=hello, other={foo=bar, baz=null}}
pojo2:	{foo=bar, baz=null}

Actual output:

pojo1:	{foo=bar, baz=null}
map:	{name1=hello, other={foo=bar, baz=null}}
pojo2:	{foo=bar}\

I am using Jackson databind version 2.9.4.

[cowtowncoder]

It is not a work-around but expected behavior.

Ine additional note, your earlier setting was equivalent to:

mapper.setDefaultPropertyInclusion(JsonInclude.Value.construct(Include.NON_NULL,
    Include.NON_NULL);

which indicates that all null property values are to be excluded (first) as well as all content values (values of Map entries). If you do not want latter, it has to be changed.

Also note that @JsonInclude actually accepts two properties as well:

@JsonInclude(value = Include.NON_NULL, contents = Include.ALWAYS)

but if one (or both) are omitted, that value defaults to global inclusion base (one set with setDefaultPropertyInclusion).

[kaspersorensen]

OK it seems that your suggested change works well for my scenario:

mapper.setDefaultPropertyInclusion(JsonInclude.Value.construct(Include.NON_NULL,
    Include.ALWAYS);

So I’m fine with closing this issue. It just seemed counter-intuitive to me, would be nice to have an annotation specifically for Map objects maybe. So that this different behavior can be controlled on the Pojo member level.