playframework hibernate不可变实体和通过合并更改的版本

Question

我想确保

1. 我可以使用/来使用不可变实体和Hibernate（使用play-framework）
2. 当我将实体保存/退回数据库时，这种乐观策略适用于我的实体（版本正在更改）

有测试：

 @Test
    public void test() {
        // create question->answer and save them to db
        QuestionUtil.createQuestion("question1", "answer1");

        // detaching question from the hibernate session, let user to think and play with entity
        Question question1 = Question.find("title", "question1").first();    
        Question.em().detach(question1);

        // user think/edit time ... [1 minute.. 2 minutes.. coffee.. break time.. ]

        // user makes some edits in detached question, create new fresh copy (since it's immutable)
        Question editingQuestion  = new Question.Builder().copy(question1).title("updated question1").build();

        editingQuestion.merge(); 

        // get updated Question
        Question updatedQuestion = Question.find("title", "question1").first();

        assertEquals(updatedQuestion.getTitle(), "updated question1");  // OK
        assertTrue(updatedQuestion .getVersion().intValue() == 1);     // FAILS here
    }

问题。为什么版本不会增加到1（而不是0）？是否有更好的方法来做到这一点？

问题类的负责人在这里：

@Entity
public class Question extends GenericModel {

    @Version
    private Integer version;
...