blocks|key|2759614|text|Hibernate文档的Chapter+8.+Inheritance+Mapping可能会有所帮助。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2759615|否则，我认为有多个“什么都不做”的ApprovalItem派生类没有问题，就像你说的，因为它确实区分了批准，这就像拥有一种类型的批准。看到您的模型是这样的，我建议您使用多个类，即使它们只继承自您的ApprovalItem基类。|2759616|我是否很好地理解了你的问题，或者我漏掉了一些更微妙的东西？|2759617|entityMap|0|LINK|mutability|MUTABLE|url|https://www.hibernate.org/hib_docs/nhibernate/html/inheritance.html^0|C|U|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|U|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]]]

<a href="https://www.hibernate.org/hib_docs/nhibernate/html/inheritance.html" rel="nofollow noreferrer">Chapter 8. Inheritance Mapping</a> of Hibernate Documentation might help.

Otherwise, I see no problem having multiple ApprovalItem derived class that "do nothing", like you say, since it does differentiate the Approval, it's like having a type of approval. Seeing your model like so, I would recommend using multiple classes, even if they only inherit from your base ApprovalItem class.

Have I well understood your question or am I missing something else more subtle?

blocks|key|2759680|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2759681|我可以为每种实体类型(例如A_ApprovalItem、B_ApprovalItem等)创建一个ApprovalItem表。在数据库端，这似乎是一个很好的模式|blockquote|2759682|2759683|2759684|而不是|offset|length|style|BOLD|2759685|似乎我需要在|2759686|中为每个实体审批创建一个单独的域类(例如AAprrovalItem类、BApprovalItem类等)。|2759687|2759688|2759689|你不需要它。您可以创建一个ApprovalItem类，并在父类和ApprovalItem之间创建@OneToMany关系。Hibernate+负责为每个关系创建链接表。|2759690|@Entity
public+class+ClassA+{

++++@Id
++++@GeneratedValue+
++++private+Integer+id;

++++//+Hibernate+will+create+CLASSA_APPROVALITEM+to+link+both+class
++++@OneToMany
++++private+List<ApprovalItem>+approvalItemList;

}

@Entity
public+class+ClassB+{

++++@Id
++++@GeneratedValue+
++++private+Integer+id;

++++//+Hibernate+will+create+CLASSB_APPROVALITEM+to+link+both+class
++++@OneToMany
++++private+List<ApprovalItem>+approvalItemList;

}|code-block|syntax|javascript|2759691|和你的ApprovalItem类|2759692|@Entity
public+class+ApprovalItem+{

++++@Id
++++@GeneratedValue+
++++private+Integer+id;

++++//+Nothing+else

}|2759693|但是让我们看看Java+Persistence+with+Hibernate这本书是怎么谈到它的|2759694|2759695|您可以拥有对Bid对象的共享引用。如前所述，用户可以拥有对他们制作的Bid实例的引用的集合。如果不先删除这些引用，则不能删除项目及其所有出价。如果您尝试提交此事务，则可能会得到异常，因为可能会违反的外键约束。|2759696|2759697|2759698|因此，在处理共享引用时请牢记这一点。|2759699|为了查看目标模式的外观，您可以使用以下命令|2759700|AnnotationConfiguration+configuration+=+new+AnnotationConfiguration();

configuration
++++.addAnnotatedClass(ClassA.class)
++++.addAnnotatedClass(ClassB.class)
++++.addAnnotatedClass(ApprovalItem.class)
++++.setProperty(Environment.USER,+<TYPE_YOUR_USER>)
++++.setProperty(Environment.PASS,+<TYPE_YOUR_PASSWORD>)
++++.setProperty(Environment.URL,+<TYPE_YOUR_URL>)
++++.setProperty(Environment.DIALECT,+<TYPE_YOUR_DIALECT>)
++++.setProperty(Environment.DRIVER,+<TYPE_YOUR_DRIVER>);

SchemaExport+schema+=+new+SchemaExport(configuration);
schema.setOutputFile("schema.sql");

schema.create(<DO_YOU_WANT_TO_PRINT_TO_THE_CONSOLE>,+<DO_YOU_WANT_TO_EXPORT_THE_SCRIPT_TO_THE_DATABASE>);|2759701|它将生成一个名为schema.sql的文件，其中包含您的目标模式|2759702|致以敬意，|2759703|entityMap^0|0|0|0|0|0|3|0|0|0|0|0|1Z|9|0|0|0|0|0|0|C|4|2V|1|0|0|0|0|I|0|0|L|0|0|0|W|0|0|5|0^^$0|@$1|2|3|-4|4|5|6|1L|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|1M|7|@]|8|@]|9|$]]|$1|D|3|-4|4|5|6|1N|7|@]|8|@]|9|$]]|$1|E|3|-4|4|5|6|1O|7|@]|8|@]|9|$]]|$1|F|3|G|4|5|6|1P|7|@$H|1Q|I|1R|J|K]]|8|@]|9|$]]|$1|L|3|M|4|5|6|1S|7|@]|8|@]|9|$]]|$1|N|3|O|4|C|6|1T|7|@]|8|@]|9|$]]|$1|P|3|-4|4|5|6|1U|7|@]|8|@]|9|$]]|$1|Q|3|-4|4|5|6|1V|7|@]|8|@]|9|$]]|$1|R|3|S|4|5|6|1W|7|@$H|1X|I|1Y|J|K]]|8|@]|9|$]]|$1|T|3|U|4|V|6|1Z|7|@]|8|@]|9|$W|X]]|$1|Y|3|Z|4|5|6|20|7|@]|8|@]|9|$]]|$1|10|3|11|4|V|6|21|7|@]|8|@]|9|$W|X]]|$1|12|3|13|4|5|6|22|7|@]|8|@]|9|$]]|$1|14|3|-4|4|5|6|23|7|@]|8|@]|9|$]]|$1|15|3|16|4|C|6|24|7|@$H|25|I|26|J|K]|$H|27|I|28|J|K]]|8|@]|9|$]]|$1|17|3|-4|4|5|6|29|7|@]|8|@]|9|$]]|$1|18|3|-4|4|5|6|2A|7|@]|8|@]|9|$]]|$1|19|3|1A|4|5|6|2B|7|@$H|2C|I|2D|J|K]]|8|@]|9|$]]|$1|1B|3|1C|4|5|6|2E|7|@$H|2F|I|2G|J|K]]|8|@]|9|$]]|$1|1D|3|1E|4|V|6|2H|7|@]|8|@]|9|$W|X]]|$1|1F|3|1G|4|5|6|2I|7|@$H|2J|I|2K|J|K]]|8|@]|9|$]]|$1|1H|3|1I|4|5|6|2L|7|@$H|2M|I|2N|J|K]]|8|@]|9|$]]|$1|1J|3|-4|4|5|6|2O|7|@]|8|@]|9|$]]]|1K|$]]

<blockquote>
 I could create an ApprovalItem table for each entity type (e.g. A_ApprovalItem, B_ApprovalItem, etc.). This seems like a good schema on the database side
</blockquote>

But

<blockquote>
 It seems i need to create a separate domain classes in Java for each entity approval (e.g. AAprrovalItem class, BApprovalItem class, etc.).
</blockquote>

You do not need it. you can create a single ApprovalItem class and create a @OneToMany relationship between your parent classes and your ApprovalItem. Hibernate takes care to create a linked table for each relationship. 

<pre><code>@Entity
public class ClassA {

 @Id
 @GeneratedValue 
 private Integer id;

 // Hibernate will create CLASSA_APPROVALITEM to link both class
 @OneToMany
 private List&lt;ApprovalItem&gt; approvalItemList;

}

@Entity
public class ClassB {

 @Id
 @GeneratedValue 
 private Integer id;

 // Hibernate will create CLASSB_APPROVALITEM to link both class
 @OneToMany
 private List&lt;ApprovalItem&gt; approvalItemList;

}
</code></pre>

And your ApprovalItem class

<pre><code>@Entity
public class ApprovalItem {

 @Id
 @GeneratedValue 
 private Integer id;

 // Nothing else

}
</code></pre>

But Let's see what Java Persistence with Hibernate book talks about it

<blockquote>
 You may have shared references to the Bid objects. As suggested earlier, a User may have a collection of references to the Bid instances they made. You can’t delete an item and all its bids without removing these references first. You may get an exception if you try to commit this transaction, because a foreign key constraint may be violated.
</blockquote>

So keep it in mind when dealing with shared references.

In order to see how the target schema looks like, you can use the following

<pre><code>AnnotationConfiguration configuration = new AnnotationConfiguration();

configuration
 .addAnnotatedClass(ClassA.class)
 .addAnnotatedClass(ClassB.class)
 .addAnnotatedClass(ApprovalItem.class)
 .setProperty(Environment.USER, &lt;TYPE_YOUR_USER&gt;)
 .setProperty(Environment.PASS, &lt;TYPE_YOUR_PASSWORD&gt;)
 .setProperty(Environment.URL, &lt;TYPE_YOUR_URL&gt;)
 .setProperty(Environment.DIALECT, &lt;TYPE_YOUR_DIALECT&gt;)
 .setProperty(Environment.DRIVER, &lt;TYPE_YOUR_DRIVER&gt;);

SchemaExport schema = new SchemaExport(configuration);
schema.setOutputFile("schema.sql");

schema.create(&lt;DO_YOU_WANT_TO_PRINT_TO_THE_CONSOLE&gt;, &lt;DO_YOU_WANT_TO_EXPORT_THE_SCRIPT_TO_THE_DATABASE&gt;);
</code></pre>

It will generate a file called schema.sql, which contains your target schema

regards,

Put another way: How do you model/map a heavily reused child class/table to many different parent entities?

I have several entity types each being persisted into its own table:

class A --> table A
class B --> table B
....

Now I need to make each of these classes the parent of a 1:M unidirectional child collection. The collection is a history of approvals the entity has gained over time. The Child domain class is called "ApprovalItem". The Approval class is exactly the same for all types of parents.

What is the best way to map this? If I create a single table to hold all ApprovalItems, then I can't enforce a FK relation to the PK of the entity and/or I am left with a bad database design.

On the other hand, I could create an ApprovalIems table for each entity type (e.g. A_ApprovalItems, B_ApprovalItems, etc.). This seems like a good schema on the database side, but then it seems I need to create a separate domain classes in Java for each entity approval (e.g. AAprrovalItem class, BApprovalItem class, etc.). This seems like a lot of hassle and complexity to create so many new classes in Java that do nothing other than allow me to put in different JPA mapping annotations.

Is there a mapping technique in Hibernate that will allow me to have one class in Java map to several different tables depending on who the parent owner of the collection is?

Hibernate best approach for one Java class and multiple tables?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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换句话说:如何对一个被大量重用的子类/表进行建模/映射到许多不同的父实体？我有几个实体类型，每个实体类型都持久化到自己的表中：A类-->表A类B -->表B....现在，我需要使这些类中的每个类都成为1:M单向子集的父类。集合是实体随着时间的推移而获得的批准的历史记录。子域类称为"ApprovalItem“。审批类对于...

问Hibernate是一个Java类和多个表的最佳方法吗？
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