Setting default values to null fields when mapping with Jackson

Question

I am trying to map some JSON objects to Java objects with Jackson. Some of the fields in the JSON object are mandatory(which I can mark with @NotNull) and some are optional.

After the mapping with Jackson, all the fields that are not set in the JSON object will have a null value in Java. Is there a similar annotation to @NotNull that can tell Jackson to set a default value to a Java class member, in case it is null?

Edit: To make the question more clear here is some code example.

The Java object:

class JavaObject {     @NotNull     public String notNullMember;      @DefaultValue("Value")     public String optionalMember; } 

The JSON object can be either:

{     "notNullMember" : "notNull" } 

or:

{     "notNullMember" : "notNull",     "optionalMember" : "optional" } 

The @DefaultValue annotations is just to show what I am asking. It's not a real annotation. If the JSON object is like in the first example I want the value of the optionalMember to be "Value" and not null. Is there an annotation that does such a thing?

Answer 1

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"; } 

Answer 2

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;      } }