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This article mainly explains "Hibernate inheritance mapping contains three different strategies", the explanation in the article is simple and clear, easy to learn and understand, please follow the idea of Xiaobian slowly in-depth, together to study and learn "Hibernate inheritance mapping contains three different strategies"!

Hibernate inheritance mapping involves three different strategies:

Use one table per cluster class;

one table per subclass;

A table (with limits) within each concrete.

Suppose we have four classes Animal, Dog, Cat, filename: Animal.java,

The code is as follows:

Program Code:

class Animal { private String identifier; private String name; private String category; // setter and getter }

File name: Dog.java

class Dog extends Animal { private String // setter and getter }

File name: Cat.java

class Cat extends Animal { private String // setter and getter }

Use one table per cluster class. When using the policy of using one table per cluster class, there is a restriction that subclasses cannot have NOT NULL. The mapping file is filename: Animal.hbm.xml

Program Code:

"identifier" type="string" column="IDENTIFIER"> class="uuid.hex"/> "ANIMAL_TYPE" type="string"/> "name" column="NAME" type="string"/> "Dog" discriminator-value="DOG"> "Cat" discriminator-value="CAT"> class>

One table for each subclass. When using the policy of one table for each subclass, it can be implemented by using one mapping file or divided into multiple mapping files. One mapping file per subclass:

Filename: Animal.hbm.xml

Program Code:

"identifier" column="IDENTIFIER" type="string"> class="uuid.hex"/> class>

Filename: Dog.hbm.xml

Program Code:

"Dog" table="DOG" extends="Animal"> "DOG_ID"/>

Filename: Cat.hbm.xml

Program Code:

"Cat" table="CAT" extends="Cat"> "CAT_ID"/>

The one-table-per-subclass strategy is essentially a one-to-one mapping.

One table per instance (with restrictions). When using the one table per instance (with restrictions) policy, the mapping file for each subclass will contain attributes from all parent classes. Mapping file filename: Dog.hbm.xml

Program Code:

"identifier" column="IDENTIFIER" type="string"> class="uuid.hex"/> "name" column="NAME" type="string"/> class>

Filename: Cat.hbm.xml

Program Code:

"identifier" column="IDENTIFIER" type="string"> class="uuid.hex"/> "name" column="NAME" type="string"/> class> Thank you for reading, the above is the "Hibernate inheritance mapping contains three different strategies" of the content, after the study of this article, I believe that everyone on Hibernate inheritance mapping contains three different strategies of the introduction of this problem has a deeper understanding, the specific use of the situation also needs to be verified by practice. Here is, Xiaobian will push more articles related to knowledge points for everyone, welcome to pay attention!

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