Java Hibernate 中的枚举
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Enumerations in Hibernate
提问by Georgios Gousios
It is often useful to have a field in a DAO whose value comes from a Java enumeration. A typical example is a login DAO where you usually have a field that characterises the user as "NORMAL" or "ADMIN". In Hibernate, I would use the following 2 objects to represent this relationship in a (semi-)typesafe way:
在 DAO 中有一个字段的值来自 Java 枚举通常很有用。一个典型的例子是登录 DAO，其中通常有一个字段将用户描述为“NORMAL”或“ADMIN”。在 Hibernate 中，我将使用以下 2 个对象以（半）类型安全的方式表示这种关系：
class User {
String username;
String passwd;
UserType type;
}
class UserType {
private enum Type {ADMIN, NORMAL};
private String type;
//Setters/Getters for Hibernate
public void setType(String type);
public String getType();
//Setters/Getters for user
public void setUserType(UserType.Type t);
public UserType.Type getUserType();
public static UserType fromType(UserType.Type t);
}
This works, but I find the UserType class ungly and requiring too much bureaucracy just to store a couple of values. Ideally, Hibernate should support enum fields directly and would create an extra table to store the enumeration values.
这是有效的，但我发现 UserType 类很丑陋，并且需要太多的官僚作风来存储几个值。理想情况下，Hibernate 应该直接支持枚举字段，并会创建一个额外的表来存储枚举值。
My question is: Is there any way to directly map an enumeration class in Hibernate? If not, is my pattern for representing enumerations good enough or am I missing something? What other patterns do people use?
我的问题是：有没有办法在 Hibernate 中直接映射枚举类？如果不是，我代表枚举的模式是否足够好或者我错过了什么？人们还使用哪些其他模式？
采纳答案by Gareth Davis
using hibernate or JPA annotations:
使用休眠或 JPA 注释：
class User {
@Enumerated(EnumType.STRING)
UserType type
}
UserType is just a standard java 5 enum.
UserType 只是一个标准的 java 5 枚举。
I can't imagine this is just limited to just annotations but I don't actually know how to do this with hbm files. It may be very version dependant, I'm guessing but I'm pretty sure that hibernate 3.2+ is required.
我无法想象这仅限于注释，但我实际上不知道如何使用 hbm 文件来做到这一点。它可能非常依赖于版本，我猜但我很确定需要 hibernate 3.2+。
edit: it is possible in a hbm, but is a little messy, have a look at this forum thread
编辑：在 hbm 中是可能的，但有点乱，看看这个论坛帖子
回答by Craig
From the Hibernate documentation: http://www.hibernate.org/272.html
来自 Hibernate 文档：http: //www.hibernate.org/272.html
You can create a new typedef for each of your enums and reference the typedefs in the property tag.
您可以为每个枚举创建一个新的 typedef，并在 property 标记中引用 typedef。
Example Mapping - inline <type>tag
示例映射 - 内联<type>标记
<property name='suit'>
<type name="EnumUserType">
<param name="enumClassName">com.company.project.Suit</param>
</type>
</property>
Example Mapping - using <typedef>
示例映射 - 使用 <typedef>
<typedef name="suit" class='EnumUserType'>
<param name="enumClassName">com.company.project.Suit</param>
</typedef>
<class ...>
<property name='suit' type='suit'/>
</class>
