休眠悲观锁定不适用于 Oracle 数据库？答案

【问题标题】：Hibernate Pessimistic Locking not working for Oracle Database?休眠悲观锁定不适用于 Oracle 数据库？
【发布时间】：2014-11-12 04:00:12
【问题描述】：

我有一个可以被多个线程调用的事务方法。

为了避免发生并发调用时出现StaleStateException，我在hibernate 中使用了悲观锁定，但它没有按预期工作，我仍然得到StaleStateException。然后我查看了日志，发现对象没有正确锁定，这是我的日志：

2014-09-17_19:12:19.078 INFO  c.c.p.a.w.m.ImportExportManagerImpl - ************************Test Name: Requirement Coverage Test
2014-09-17_19:12:19.079 INFO  c.c.p.a.w.m.ImportExportManagerImpl - ************************Test folder ID: 9312
2014-09-17_19:12:19.525 INFO  c.c.p.a.w.m.ImportExportManagerImpl - Test Case Id: P072051933
2014-09-17_19:12:19.615 WARN  org.hibernate.loader.Loader - HHH000444: Encountered request for locking however dialect reports that database prefers locking be done in a separate select (follow-on locking); results will be locked after initial query executes
Hibernate: 
    select
        requiremen0_."RC_ITEM_ID" as RC_ITEM_ID1_1_,
        requiremen0_."RC_ENTITY_ID" as RC_ENTITY_ID2_1_,
        requiremen0_."RC_ENTITY_TYPE" as RC_ENTITY_TYPE3_1_,
        requiremen0_.RC_REQ_ID as RC_REQ_ID4_1_ 
    from
        "OME6500_OM65_OME6500_R9_2_DB"."REQ_COVER" requiremen0_ 
    where
        requiremen0_."RC_ENTITY_ID"=?
Hibernate: 
    select
        requiremen0_."RQ_REQ_ID" as RQ_REQ_ID1_2_0_,
        requiremen0_."RQ_USER_03" as RQ_USER_2_2_0_ 
    from
        "OME6500_OM65_OME6500_R9_2_DB"."REQ" requiremen0_ 
    where
        requiremen0_."RQ_REQ_ID"=?
Hibernate: 
    select
        "RC_ITEM_ID" 
    from
        "OME6500_OM65_OME6500_R9_2_DB"."REQ_COVER" 
    where
        "RC_ITEM_ID" =? for update

2014-09-17_19:12:19.631 INFO  c.c.p.a.w.m.ImportExportManagerImpl - Requirement Coverages Size:1
2014-09-17_19:12:19.631 INFO  c.c.p.a.w.m.ImportExportManagerImpl - Deleting requirement coverage id: 130967
2014-09-17_19:12:19.634 INFO  c.c.p.a.w.m.ImportExportManagerImpl - Requirement in testcase table Size:1
2014-09-17_19:12:19.669 INFO  c.c.p.a.w.m.ImportExportManagerImpl - Checking if requirement coverage exists: test case id: 51933, req id:  7760
Hibernate: 
    delete 
    from
        "OME6500_OM65_OME6500_R9_2_DB"."REQ_COVER" 
    where
        "RC_ITEM_ID"=?

我的交易方式在这里：

@Transactional(readOnly = false)
    public void importTestCases(String domain, String project, List<TestCase> testCases,
                                Boolean onlyUpdateReqCover, Boolean foldersExist)
            throws RequestFailureException, RESTAPIException, InvalidDataException,
            UnAuthorizedOperationException {

        setDBSchema(domain, project);

        for (TestCase testCase : testCases) {
            TestFolder testFolder = retrieveTestFolderFromPath(domain, project, testCase.getFolderPath(),
                                                               foldersExist, testCase);
            Test test = new Test(testCase, testFolder);
            ALMEntity almEntity = null;
            LOGGER.info("************************Test Name: " + test.getName());
            LOGGER.info("************************Test folder ID: " + test.getParent_id());
            ...
            ...
            LOGGER.info("Test Case Id: " + existingTest.getQc_tcid());

            List<RequirementCoverage> requirementCoverages = requirementCoverageDao.findAllFromTestId(Integer
                    .parseInt(existingTest.getId()));

            LOGGER.info("Requirement Coverages Size:" + requirementCoverages.size());

            for (RequirementCoverage requirementCoverage : requirementCoverages) {
                LOGGER.info("Deleting requirement coverage id: " + requirementCoverage.getId());
                requirementCoverageDao.delete(requirementCoverage);
            }

           ...
           ...
           }
}

这是我的带有锁定的 DAO 方法：

@Override
    public List<RequirementCoverage> findAllFromTestId(int testId) {
        List<RequirementCoverage> list = sessionFactory.getCurrentSession()
                .createQuery("from RequirementCoverage where entityId = :testId")
                .setLockOptions(new LockOptions(LockMode.PESSIMISTIC_WRITE)).setParameter("testId", testId)
                .list();
        return list;
    }

从日志可以看出，findAllFromTestId 返回的requirementCoverages 没有被锁定。只有在for (RequirementCoverage requirementCoverage : requirementCoverages) 启动之后，才会为每个requirementCoverage 获得锁。

所以我认为StaleStateException的原因是一个线程获取列表requirementCoverages并试图访问每个对象，但同时requirementCoverages已被另一个线程修改。

我说的对吗？有没有办法锁定列表requirementCoverages 阻止另一个线程访问它？任何帮助表示赞赏。

【问题讨论】：

标签： oracle hibernate transactions pessimistic-locking

【解决方案1】：

我通过重组代码解决了这个问题。

我没有对一些实体的命名查询使用悲观锁定，而是对这些实体的父实体应用悲观锁定并在读取时锁定它。

然后对这些子实体进行更新。

最后，释放父实体。

【讨论】：

【解决方案2】：

还有另一个使用 LockMode.PESSIMISTIC_FORCE_INCREMENT 的选项，请查看 this solution。

【讨论】：