public static void main(String[] args) throws Exception {
    System.out.println(test(-99));
    System.out.println(test(0));
    System.out.println(test(99));
}

private static int test(int errorCode) {
    UserData u1 = new UserData();
    u1.setErrorCode(errorCode);

    byte[] bytes = JSONB.toBytes(
            u1,
            JSONWriter.Feature.WriteClassName,
            JSONWriter.Feature.FieldBased,
            JSONWriter.Feature.ReferenceDetection,
            JSONWriter.Feature.WriteNulls,
            JSONWriter.Feature.NotWriteDefaultValue,
            JSONWriter.Feature.NotWriteHashMapArrayListClassName,
            JSONWriter.Feature.WriteNameAsSymbol);

    UserData u2 = JSONB.parseObject(
            bytes,
            UserData.class,
            JSONReader.Feature.UseDefaultConstructorAsPossible,
            JSONReader.Feature.IgnoreAutoTypeNotMatch,
            JSONReader.Feature.UseNativeObject,
            JSONReader.Feature.FieldBased
    );
    return u2.getErrorCode();
}


public static class UserData implements Serializable {

    private static final long serialVersionUID = 8521716552408936209L;

    private int errorCode = -1;
    // private int errorCode;

    public int getErrorCode() {
        return errorCode;
    }

    public void setErrorCode(int errorCode) {
        this.errorCode = errorCode;
    }
}