JPA实体中的枚举字段 [英] Enum field in JPA Entity

问题描述

问这个问题我有点傻，但是我找不到这个问题的简单答案.

I feel a little dumb asking this but I can't find any simple answer to the question.

以这个简单的实体为例:

Take this simple entity as example:

@Entity
@Table( name="clienti" )
public class Cliente implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Long id;

    private String nome;

    private String cognome;

//...
}

它代表一个人，所以我想添加一个"性别"属性.

It represents a person, so I want to add a "gender" property.

它将是男性"或女性".那又怎样呢?

It will be "male" or "female". So what?

我可以使用字符串，并记住"m"代表男性，"f"代表女性.

I can use a String, and keep in mind that "m" stands for male and "f" for female.

或者我可以使用布尔值"isMale"(是或否).

Or I can use a boolean "isMale", true or false.

但是，无论哪种情况，我都不认为Hibernate的纯粹主义者会很高兴:)

However, I don't think in either case Hibernate purists would be happy :)

谷歌搜索一点，我发现最佳实践是使用枚举.

Googling a little bit I found that the best practice is using an enum.

我对如何使用它有些困惑.你能帮我举个例子吗?

I am a little confused on how to use it. Can you help me with an example?

推荐答案

您可以将enum映射到String或序数.映射到String是更可移植的方法，因为映射将在更改枚举顺序后仍然存在.

You can map your enum to a String or to an ordinal number. Mapping to String is the more portable approach as the mapping will survive changing the enumeration order.

使用您的示例:

@Entity
@Table( name="clienti" )
public class Cliente implements Serializable {

...
    @Enumerated(EnumType.STRING)
    private Gender gender;
...
}

字符串映射将使用枚举类型的简单名称，因此数据库中将有两个可能的值-'Male'和'Female'

The string mapping will use the simple name of the enumeration type, so you would have two possible values in the DB - 'Male' and 'Female'

public enum Gender { MALE, FEMALE }

持久性提供程序负责映射，因此在您的代码中，您可以继续使用Gender枚举，而不必担心字符串或序数.

The persistence provider takes care of the mapping, so in your code, you can continue using the Gender enum and not worry about Strings or ordinals.

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