Setting default values to null fields when mapping with Jackson

There is no annotation to set default value.
You can set default value only on java class level:

public class JavaObject 
{
    public String notNullMember;

    public String optionalMember = "Value";
}

Use the JsonSetter annotation with the value Nulls.SKIP

If you want to assign a default value to any param which is not set in json request then you can simply assign that in the POJO itself.

If you don't use @JsonSetter(nulls = Nulls.SKIP) then the default value will be initialised only if there is no value coming in JSON, but if someone explicitly put a null then it can lead to a problem. Using @JsonSetter(nulls = Nulls.SKIP) will tell the Json de-searilizer to avoid null initialisation.

Value that indicates that an input null value should be skipped and the default assignment is to be made; this usually means that the property will have its default value.

as follow:

public class User {
    @JsonSetter(nulls = Nulls.SKIP)
    private Integer Score = 1000;
    ...
}

Only one proposed solution keeps the default-value when some-value:null was set explicitly (POJO readability is lost there and it's clumsy)

Here's how one can keep the default-value and never set it to null

@JsonProperty("some-value")
public String someValue = "default-value";

@JsonSetter("some-value")
public void setSomeValue(String s) {
    if (s != null) { 
        someValue = s; 
    }
}

You can create your own JsonDeserializer and annotate that property with @JsonDeserialize(as = DefaultZero.class)

For example: To configure BigDecimal to default to ZERO:

public static class DefaultZero extends JsonDeserializer<BigDecimal> {
    private final JsonDeserializer<BigDecimal> delegate;

    public DefaultZero(JsonDeserializer<BigDecimal> delegate) {
        this.delegate = delegate;
    }

    @Override
    public BigDecimal deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException, JsonProcessingException {
        return jsonParser.getDecimalValue();
    }

    @Override
    public BigDecimal getNullValue(DeserializationContext ctxt) throws JsonMappingException {
        return BigDecimal.ZERO;
    }
}

And usage:

class Sth {

   @JsonDeserialize(as = DefaultZero.class)
   BigDecimal property;
 }