class JavaObject {
    @NotNull
    public String notNullMember;

    @DefaultValue("Value")
    public String optionalMember;
}

{
    "notNullMember" : "notNull"
}

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

public class JavaObject
{
    public String notNullMember;

    public String optionalMember = "Value";
}

class JavaObject {

    public JavaObject() {

        optionalMember = "Value";
    }

    @NotNull
    public String notNullMember;

    public String optionalMember;
}

class JavaObject {
    private static final String DEFAULT="Default Value";

    public JavaObject() {
    }

    @NotNull
    private String notNullMember;
    public void setNotNullMember(String value){
            if (value==null) { notNullMember=DEFAULT; return; }
            notNullMember=value;
            return;
    }

    public String getNotNullMember(){
            if (notNullMember==null) { return DEFAULT;}
            return notNullMember;
    }

    public String optionalMember;
}

public Value someValue = new Value("default-value");

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