JPA Hibernate是否以任何可读格式持有任何枚举（地图键）？ [英] JPA Hibernate Persist any Enum (a Map key) in human readable format?

问题描述

假设你有一个类，需要保存一些映射的项，使用任何枚举的密钥。使用该映射 varbinary （SQL Server）具有十六进制值。

  @Entity 
 public abstract class X {
 @ElementCollection 
 private Map&布尔>值; 
} 
  

这是有效的，但主要问题是可读性。数据库中的数据不可读。尝试使用 @MapKeyEnumerated（EnumType.STRING）或EnumType.Ordinal不起作用，因为枚举可以是任何类型，并保存 MyEnum .SOME_VALUE 为SOME_VALUE。

是否可以截取保存/检索并保存完全限定名称（com.x.myenum .value）或清晰的东西可以用来恢复枚举而不是十六进制值？

解决方案

存储地图key是一个枚举，并且可以在db中得到一些可读的数据，可以尝试：

  @Entity 
 public class QuestionnaireDefinition { 
 ... 
 @OneToMany（mappedBy =questionnaireDefinition，fetch = FetchType.LAZY，cascade = CascadeType.ALL）
 @MapKeyEnumerated（EnumType.STRING）
 @MapKeyColumn name =language，insertable = false，updatable = false）
 private final Map< Language，QuestionnaireDefinitionTranslation> translations = new HashMap< Language，QuestionnaireDefinitionTranslation>（）; 
 ...} 
  

其中QuestionnaireDefinitionTranslation是将被赋予的实体或值，语言枚举
在此示例中，映射值为type：QuestionnaireDefinitionTranslation

  @Entity 
 public class QuestionnaireDefinitionTranslation {
 
 @Enumerated（EnumType.STRING）
 @Column（nullable = false，insertable = true，updatable = true）
 private语言; 
 
 @ManyToOne（fetch = FetchType.LAZY，optional = false）
 private QuestionnaireDefinition questionnaireDefinition; 
 
私有字符串文本; 
 ... 
} 
  

类语言是一个普通的枚举： / p>

  public enum Language {
 EN，ES，FI，FR; 
} 
  

这个工作的想法是：
1.首先持续所有者类：

 问卷定义问卷Def =新问卷定义（）; 
 em.persist（questionnaireDef）; 
  

然后使用您的枚举作为关键的聚合类。

  QuestionnaireDefinitionTranslation Translation = new QuestionnaireDefinitionTranslation（）; 
 translation.set（questionnaireDef）; 
 translation.setLanguage（Language.En）; 
 translation.setText（hello）; 
 em.persist（翻译）; 
  

voilá这就是所有，你可以通过你的枚举获取

  QuestionnaireDefinition qd = em.find（1，QuestionnaireDefinition.class）; 
 qd.getTranslations（）。get（Language.EN）; 
  

注意事务，LazyException和那些东西。

Say you have a class which needs to save some mapped items, using any Enum for the key. Using this mapping it generates e.g. varbinary (SQL Server) with a hexadecimal value.

@Entity
public abstract class X {
    @ElementCollection
    private Map<Enum, Boolean> values;
}

This works but the main issue is readability. The data in the database isn't human readable. trying to use @MapKeyEnumerated(EnumType.STRING) or with EnumType.Ordinal doesn't work since the Enum can be any type and that saves the MyEnum.SOME_VALUE as "SOME_VALUE".

Is it possible to intercept the save/retrieve and save a fully qualified name (com.x.myenum.value) or something legible which could be used to restore the enum instead of a hexadecimal value?

解决方案

To store a Map where key is an enum, and get something human readable in db you could try:

@Entity
public class QuestionnaireDefinition{
    ...
    @OneToMany(mappedBy = "questionnaireDefinition", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @MapKeyEnumerated(EnumType.STRING)
    @MapKeyColumn(name = "language", insertable = false, updatable = false)
    private final Map<Language, QuestionnaireDefinitionTranslation> translations = new HashMap<Language, QuestionnaireDefinitionTranslation>();
... }

where QuestionnaireDefinitionTranslation is the entity or value that will be fecthed given the Language enum. In this example the map value is type: QuestionnaireDefinitionTranslation

@Entity
public class QuestionnaireDefinitionTranslation {

    @Enumerated(EnumType.STRING)
    @Column(nullable = false, insertable = true, updatable = true)    
    private Language language;

    @ManyToOne(fetch = FetchType.LAZY, optional = false)
    private QuestionnaireDefinition questionnaireDefinition;

    private String text;
    ...
}

The class Language is an ordinary enum:

public enum Language {
    EN, ES, FI, FR;
}

The idea to make this work is: 1. First persist a the owner class:

QuestionnaireDefinition questionnaireDef = new QuestionnaireDefinition();
em.persist(questionnaireDef );

and then the aggregated class using your enum as key.

QuestionnaireDefinitionTranslation translation = new QuestionnaireDefinitionTranslation();
translation.set(questionnaireDef);
translation.setLanguage(Language.En);
translation.setText("hello");
em.persist(translation);

voilá that's all, you can fetch known by your enum

QuestionnaireDefinition qd = em.find(1,QuestionnaireDefinition.class);
qd.getTranslations().get(Language.EN);

Be aware with transactions, LazyException and that stuff.

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