Question

Hibernate用于实现JPA的getResultList（）的排序机制是什么？它是由id还是不保证正确的顺序？我在JPA javadoc中没有看到任何关于此的细节。

/**
     * Execute a SELECT query and return the query results
     * as an untyped List.
     *
     * @return a list of the results
     *
     * @throws IllegalStateException if called for a Java
     * Persistence query language UPDATE or DELETE statement
     * @throws QueryTimeoutException if the query execution exceeds
     * the query timeout value set and only the statement is
     * rolled back
     * @throws TransactionRequiredException if a lock mode has
     * been set and there is no transaction
     * @throws PessimisticLockException if pessimistic locking
     * fails and the transaction is rolled back
     * @throws LockTimeoutException if pessimistic locking
     * fails and only the statement is rolled back
     * @throws PersistenceException if the query execution exceeds
     * the query timeout value set and the transaction
     * is rolled back
     */
    List getResultList();

但每次我运行并测试结果时，它都会给我按id排序的列表。这就是我仍然感到困惑，虽然天才已经投票支持这个问题

我只是将show_sql设为true并检查生成的sql。它没有任何排序。

Answer 1

它是数据库返回的元素的顺序。

您永远不会知道它是哪个顺序，因为数据库可以按任意顺序自由返回ResultSet（特别是在表格中插入和删除时）。

要确保某个订单，您必须自己定义。

Answer 2

来自getResultList的方法javax.persistence.Query返回DB返回的默认顺序。但是，您可以在查询中指定顺序

    List customerList = em.createQuery("SELECT r FROM Customer r").getResultList();
    List customerList1 = em.createQuery("SELECT r FROM Customer r order by r.lastUpdatedDate").getResultList();
    List customerList2 = em.createQuery("SELECT r FROM Customer r order by r.lastUpdatedDate desc").getResultList();

getResultList（）hibernate的默认排序顺序

2 个答案: