嵌套单表继承

Question

我正面临对象模型和Hibernate的问题。我希望将整个模型存储为一个表格。

我尝试了以下方法，但是当我要求Hibernate生成SQL创建文件时，它会创建3个表格而不是1个。类层次结构可能看起来很奇怪，但是它取材于当然的上下文:)

尝试1：

@MappedSuperclass 
@Inheritance(strategy = InheritanceType.SINGLE_TABLE) 
@DiscriminatorColumn(name = "CATEGORY", discriminatorType = DiscriminatorType.STRING, length = 10) 
@Table(name = "the_table") 
public abstract class A {} 

@MappedSuperclass 
@DiscriminatorValue(value = "B") 
@Inheritance(strategy = InheritanceType.SINGLE_TABLE) 
@DiscriminatorColumn(name = "TYPE", discriminatorType = DiscriminatorType.STRING, length = 20) 
public abstract class B extends A {} 

@Entity 
@DiscriminatorValue(value = "X") 
public class X extends B {} 

@Entity 
@DiscriminatorValue(value = "Y") 
public class Y extends B {} 

@Entity 
@DiscriminatorValue(value = "Z") 
public class Z extends B {} 

尝试2： 就快了，没有它创建1台，但不会产生鉴别列。任何人都可以发现错误？

@Entity 
@Inheritance(strategy = InheritanceType.SINGLE_TABLE) 
@DiscriminatorColumn(name = "CATEGORY", discriminatorType = DiscriminatorType.STRING, length = 10) 
@DiscriminatorFormula(value = "CATEGORY || '_' || TYPE") 
@Table(name = "the_table") 
public abstract class A {} 

@Entity 
@DiscriminatorColumn(name = "TYPE", discriminatorType = DiscriminatorType.STRING, length = 20) 
public abstract class B extends A {} 

@Entity 
@DiscriminatorValue(value = "B_X") 
public class X extends B {} 

@Entity 
@DiscriminatorValue(value = "B_Y") 
public class Y extends B {} 

@Entity 
@DiscriminatorValue(value = "B_Z") 
public class Z extends B {} 

Answer 1

删除@MappedSuperclass并尝试。你也不能在一个层次中有两次@Inheritance标签 - 只会使用一个。

如果你想使用多列作为鉴别使用@DiscriminatorFormula

@Entity 
@Inheritance(strategy = InheritanceType.SINGLE_TABLE) 
@DiscriminatorForumula("CATEGORY || '_' || TYPE") 
public abstract class A 

@Entity 
@DiscriminatorValue(value = "B_X") 
public class X extends A {} 

@Entity 
@DiscriminatorValue(value = "B_Y") 
public class Y extends A {} 

@Entity 
@DiscriminatorValue(value = "B_Z") 
public class Z extends A {}