java - HibernateTransactionManager @Transactional(propagation=REQUIRES_NEW) 无法打开 2 个 session

Question

有一个批处理作业如下所示:

@Transactional
public void myBatchJob() {
    // retrieves thousands of entries and locks them 
    // to prevent other jobs from touthing this dataset
    entries = getEntriesToProcessWithLock(); 
    additional = doPrepWork(); // interacts with DB
    processor = applicationContext.getBean(getClass());
    while (!entries.isEmpty()) {
        result = doActualProcessing(entries, additional); // takes as many entries as it needs; removes them from collection afterwards
        resultDao.save(result);
    }
}

但是，如果 entries 集合足够大，我偶尔会收到以下错误。

ORA-01000: maximum open cursors exceeded

我决定责怪 doActualProcessing() 和 save() 方法，因为它们最终可能会在一个事务中创建数百个 blob。

明显的出路似乎是将处理分成多个事务:一个用于获取和锁定条目，多个其他事务用于处理和持久化。像这样:

@Transactional
public void myBatchJob() {
    // retrieves thousands of entries and locks them 
    // to prevent other jobs from touthing this dataset
    entries = getEntriesToProcessWithLock(); 
    additional = doPrepWork(); // interacts with DB
    processor = applicationContext.getBean(getClass());
    while (!entries.isEmpty()) {
        processor.doProcess(entries, additional);
    }
}

@Transactional(propagation=REQUIRES_NEW)
public void doProcess(entries, additional) {
    result = doActualProcessing(entries, additional); // takes as many entries as it needs; removes them from collection afterwards
    resultDao.save(result);
}

现在每当调用 doProcess 时我都会得到:

Caused by: org.hibernate.HibernateException: illegally attempted to associate a proxy with two open Sessions

如何让 HibernateTransactionManager 执行 REQUIRES_NEW javadoc 建议的操作:暂停当前事务并启动新事务？

Answer 1

在我看来，问题在于您已经检索了顶部事务中的实体，并且当它们仍然与该事务相关联时，您尝试将它们(代理)传递给将在单独的事务中处理的方法。

我认为你可以尝试两种选择:

1) 在调用之前分离实体 processor.doProcess(entries, extra);:

session.evict(entity); // loop through the list and do this

然后在内部事务中尝试合并:

session.merge(entity);

2) 第二个选项是检索 id，而不是 getEntriesToProcessWithLock 中的实体。然后您将传递不会导致代理问题的普通原始字段。然后，您将检索内部事务内的正确实体。