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我正在尝试使用 ScrollableCursor 将系统的所有用户加载到内存中。我有这样的代码：

    Query findUsersQuery
            = entityManager.createNamedQuery(UserEntity.QUERY_ALL_USERS, UserEntity.class);
    findUsersQuery.setHint(QueryHints.SCROLLABLE_CURSOR, Boolean.TRUE);
    findUsersQuery.setHint(QueryHints.CURSOR_PAGE_SIZE, bulkSize);
    findUsersQuery.setMaxResults(maxInitialCacheSize);

    ScrollableCursor scrollableCursor = (ScrollableCursor) findUsersQuery.getSingleResult();
    int leftSize = scrollableCursor.size();
    while (scrollableCursor.hasNext()) {

        int nextSize = leftSize > bulkSize ? bulkSize : leftSize;
        List subscriberPrefs = scrollableCursor.next(nextSize);
        leftSize -= nextSize;
        //... Result list processing

    }

查询是：SELECT s FROM UserEntity u order by u.userId

结果表的大小为 100，当 scrollableCursor.next(nextSize); 调用，我得到以下异常：

org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: java.sql.SQLRecoverableException: Closed Resultset
Error Code: 17010
    at org.eclipse.persistence.exceptions.DatabaseException.sqlException(DatabaseException.java:324)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.cursorRetrieveNextRow(DatabaseAccessor.java:447)[215:org.eclipse.persistence.core:2.4.1.v20121003-ad44345]
    at org.eclipse.persistence.queries.ScrollableCursor.retrieveNextObject(ScrollableCursor.java:563)[215:org.eclipse.persistence.core:2.4.1.v20121003-ad44345]
    at org.eclipse.persistence.queries.ScrollableCursor.loadNext(ScrollableCursor.java:411)[215:org.eclipse.persistence.core:2.4.1.v20121003-ad44345]
    at org.eclipse.persistence.queries.ScrollableCursor.next(ScrollableCursor.java:437)[215:org.eclipse.persistence.core:2.4.1.v20121003-ad44345]
    at org.eclipse.persistence.queries.ScrollableCursor.next(ScrollableCursor.java:459)[215:org.eclipse.persistence.core:2.4.1.v20121003-ad44345]

在调用 next(10) 时，第一行正常加载，异常发生在第二行。我不知道为什么。谁能说我如何避免这个错误？

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