jpa返回什么集合? [英] What collections does jpa return?

问题描述

JPA(在这种情况下为Eclipselink)是否总是在实体具有列表的情况下返回IndirectList? 该列表可以吗，还是应该将其转换为另一个列表(也许是链表)?

Does JPA ( Eclipselink in this case) always return IndirectList where Entity have a List? Is ok that list or It should be converted to another list( maybe linkedlist)?

推荐答案

分析

如果我们查看EclipseLink的 IndirectList的API ，它说:

要使用IndirectList，请使用IndirectList(jdk1.1)或Collection/List/Vector(jdk1.2)类型声明适当的实例变量.

To use an IndirectList: declare the appropriate instance variable with type IndirectList (jdk1.1) or Collection/List/Vector (jdk1.2).

TopLink将在实例变量中放置一个IndirectList. 包含域对象是从数据库中读取的.与第一 消息发送到IndirectList，内容从 数据库并恢复到正常的收集/列表/向量"行为.

TopLink will place an IndirectList in the instance variable when the containing domain object is read from the datatabase. With the first message sent to the IndirectList, the contents are fetched from the database and normal Collection/List/Vector behavior is resumed.

如果我们查看

If we view IndirectList sources, we will see, that all the work is delegated to it's original collection, just like API says.

JPA(在这种情况下为Eclipselink)是否总是在实体具有列表的情况下返回IndirectList?

Does JPA ( Eclipselink in this case) always return IndirectList where Entity have a List?

是的，它始终会返回用IndirectList包装的指定集合.由于它将所有内部工作委托给包装的集合，因此保留了工作方式.

Yes, it always does return your specified collection wrapped with IndirectList. Since it delegates all its internal work to the wrapped collection, it preserves the way it works.

该列表可以，还是应该将其转换为另一个列表(也许 链表)?

Is ok that list or It should be converted to another list( maybe linkedlist)?

是的，可以使用IndirectList.您无需进行转换，只需定义所需的任何类型的集合，不必担心IndirectList，因为它是透明管理的.

Yes, it is okay to use IndirectList. You don't convert, you just define any type of collection you want and don't worry about IndirectList, since it is managed transparently.

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