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Jpa entity inheritance. JPA supports the inheritance in the entity classes.
Jpa entity inheritance. The JPA module of Spring Data contains a custom namespace that allows defining repository beans. Generally, the JPA repositories can be set up by using the repositories element, as shown in the following example: May 8, 2025 · If you have this type of a JPA entity setup with a super class and a few child classes (see below), how do you write a JPA Query that would select say first 3 (ordered by created date) of each child class? Writing two separate queries and asking for specific subclass works fine, but I'd like to get it down to one query if possible. It is required to specify this annotation on the root entity class only. Entity Inheritance Mapping Strategies You can configure how the Java Persistence provider maps inherited entities to the underlying datastore by decorating the root class of the hierarchy with the annotation javax. In this article, we will discuss the first mapped superclass strategy, which is the simplest approach to mapping an inheritance structure to database tables. Moreover, JPA comes with two languages to manage data in relational databases. Introduction Inheritance is a fundamental concept in object-oriented programming, enabling you to create a hierarchy of classes to model real-world entities. With joined table inheritance, each class gets it's own table so no discriminator column is needed. It is a separate table that is created for the shared attributes. Take a step into the advanced world of JPA - caching, performance tuning (n + 1 queries), mapping inheritance hierarchies. 0 specification: Both abstract and concrete classes can be entities. Till now we are done with the basics of object relational mapping. 6. A JPA 2 XML descriptor syntax for overriding is defined as well). Their mappings are defined through JDK 5. Step 1: Create the new JPA project using the IntelliJ Idea named table-strategy-demo. Oct 3, 2023 · In this article, we'll dive into Inheritance Mapping with JPA and Hibernate in Java. This feature is supported since Hibernate version 6. In this article, we will explore how to use @MappedSuperclass to create an inheritable Jan 22, 2019 · Introduction As previously explained, the SINGLE_TABLE inheritance is the most efficient entity inheritance strategy. This column is registered by the @DiscriminatorColumn if omitted no default is used. Since Hibernate is a JPA implementation, it contains all of the above as well as a few Hibernate-specific features related to inheritance. Nov 24, 2010 · Use: @Entity @Inheritance(strategy = InheritanceType. Pour décrire la relation d’héritage avec JPA, on utilise l’annotation @Inheritance ou @MappedSuperclass. Using Jpa, it is possible to create entities by using the inheritance feature. May 8, 2024 · This annotation tells JPA to map the Subclass entity to a separate table, along with any properties inherited from its superclass (Superclass). Inheritance Strategies Inheritance is the core concept of object oriented language, therefore we Mar 1, 2023 · In TABLE_PER_CLASS inheritance strategy, we map only the concrete classes of an inheritance hierarchy to tables. In the previous article, we have discussed mapped superclass inheritance strategy. Nov 8, 2017 · @MappedSuperclass The JPA standard specification defines the @MappedSuperclass annotation to allow an entity to inherit properties from a base class. In the Joined strategy, each entity class in the hierarchy is mapped to its database table. The Apr 28, 2024 · 在JPA中，实体的继承策略定义了如何将 继承关系映射 到数据库中的表结构。常见的继承策略包括 Single Table （单表继承）、 Joined （连接表继承）和 Table Per Class （每个类对应一个表）。 1. However Learn about JPA @Entity inheritance types and how to implement them for seamless object-relational mapping in Java applications. Our goal is to have the DAO work with the base object through its extension so that we can have mutations of the same application by using a different entity extension, pointcuts and overrides without having to change providers and managers. The inheritance strategy is defined on the abstract superclass, using the @Inheritance annotation. Our data flow looks something like this: Receive GraphQL request May 30, 2022 · 単一テーブル戦略 (InheritanceType. Mar 31, 2010 · I'm having some problems with inheritance and the @PrePersist annotation. Pour ce faire, JPA utilise un mécanisme permettant de faire cette différence en créant une colomne appelée discriminator qui ne fait pas partie des attributs de l’entité mappée. Mar 19, 2024 · Hibernate is its support for inheritance, and the @MappedSuperclass annotation plays a central role in this. Unlike the @Inheritance annotation which maps the Java Object inheritance to a relational database model which emulates inheritance, @MappedSuperclass only models inheritance in the OOP world. The Java Persistence API (JPA) offers a powerful and flexible solution for persisting these entities in a relational database. Annotations can be split in two categories, the logical mapping annotations (describing the object model, the Entity inheritance is a key approach for structuring domain models with shared attributes and specialized behavior. 출처그렇다 이런 관계를 가진 경우 객체에서는 상속 관계를 맺으면 되지만 테이블과 JPA는 어떻게 설계해야할까?이런식으로 설계할 수 있고, 이를 JPA에서는 @Inheritance라는 어노테이션을 통해 지원한다. Apr 21, 2018 · JPA entity inheritance: which instance to create for lazy initialization? For example, Single table mapping strategy: Teacher(abstract) / \ FullTimeTeacher PartTimeTeacher Entity School referencing Teacher: @Entity public class School { @ManyToOne(fetch=FetchType. e. Feb 20, 2023 · On this page, we will lean using JPA @MappedSuperclass annotation in Hibernate inheritance application. This strategy has the disadvantage of repeating same attributes in the tables. Oct 12, 2015 · The following is an example for the mapping I'm trying to achieve. When @MappedSuperclass class is inherited by a class, all mapping information of this class, are applied to its subclass. Which Mar 2, 2015 · May be applied to an entity that extends a mapped superclass or to an embedded field or property to override a basic mapping or id mapping defined by the mapped superclass or embeddable class (or embeddable class of one of its attributes). 슈퍼타입 서브타입 논리 모델 May 6, 2024 · 2. Single Table（单表继承） 所有子类共享一个数据库表，使用一个类型字段来区分不同的子类。 @Entity @Inheritance . JPA is a library which is released with java specification. Check the documentation for more details. Aug 26, 2019 · 상속관계 매핑객체는 상속관계가 존재하지만, 관계형 데이터베이스는 상속 관계가 없다. xml files. You have specific constructs/annotations to define for table inheritance. JPA/Hibernate support 4 inheritance strategies which map the domain objects to different table structures. The @Inheritance annotation specifies the inheritance strategy to be used for an entity class hierarchy. persistence annotation @Entity indicates this is a persistent entity bean, and JPA would pick it up during classpath scanning. 상속관계 매핑이라는 것은 객체의 상속 구조와 DB의 슈퍼타입 서브타입 관계를 매핑하는 것이다. I have found Cosium / spring-data-jpa-entity-graph irreplaceable. There will be more than one entity inheriting a root class and they will persist data in same table. In this example, we used InheritanceType. Here's some example code: @Entity @Inheritance( strategy = InheritanceType. g. That means applications that use this mapping strategy might not be portable. However, for JPQL query such as this one: Hibernate generates a SQL query which filters by the associated discriminator column (e. There you can specify the database representation of the hierarchy. Aug 30, 2020 · I have created two entites (RegularEmployee and ContactEntity) that extends the Employee entity. Polymorphism can be used here. Hibernate provides several strategies to map an inheritance hierarchy of classes to a relational database. You can then build dynamic entity graphs at runtime to add in left joins for only the data you need. Each table defines all persistent states of the class, including the inherited state. This tutorial will delve into one of Spring Data JPA's key features, inheritance. JOINED) @DiscriminatorColumn public abstract class Item extends BaseEntity { @Id @GeneratedValue @Column(name = "ITEM_ID") private Long id; private String name; private int price; } Nov 21, 2024 · Jpa inheritance single table: Learn how to query JPA repository with single table inheritance and subtypes in Spring Boot. JPA, coupled with the power Object-oriented programming thrives on inheritance, allowing code reuse and hierarchical relationships between classes. Mar 17, 2022 · Learn the best way to use entity inheritance with JPA and Hibernate. The reason is I want model classes to be independent, so if I want to use JPA I can extend the same model classes and create JPA entities and get the job done. Apr 4, 2023 · You can learn about entity relationships and entity inheritance in a detailed way in this tutorial. Jul 13, 2023 · JPA and Hibernate support different inheritance strategies which allow you to map the entities to different table structures. The downside is that all properties from the subclass must be nullable. @DiscriminatorColumn is used on the root entity class to specify the discriminator column attributes. SINGLE_TABLE) @DiscriminatorColumn(name = "DTYPE") public abstract class Item { @GeneratedValue @Id private Long id; @Entity @Getter @Setter @Inheritance(strategy = InheritanceType. Entities can extend non-entity classes and non-entity classes can extend entity classes. Inheritance is useful when implementing behavioral patterns like strategy or visitor. JPA offers several strategies to model inheritance relationships between our entities and their corresponding database tables. An abstract class may be declared an entity by decorating the class with @Entity. JPA supports the inheritance in the entity classes. JOINED ) public abstract class A implements Serializable { @Id private String id; // other mapped properties Apr 5, 2024 · In Java, JPA is defined as JavaServer Pages, and JPA Joined Strategy is one of the inheritance mapping strategies, and it can be used to map the inheritance to the database tables. SINGLE_TABLE. persistence. You can optionally specify a discriminator column name. If an abstract entity is the target of a query, the query operates on all the concrete subclasses of the abstract entity: Apr 3, 2024 · Project to Implement Single Table Strategy in JPA We can develop the simple JPA project that can Animal entity, Cat entity and Dog Entity mapped both of the entities that can save the single table strategy into the MYSQL database. Inheritance in JPA Inheritance represents an “is-a” relationship, where a subclass inherits properties and behaviors from a superclass. TABLE_PER_CLASS) to the Answer class, and probably a @Table annotation to AnswerA and AnswerB. My problem is that I want to define an UniqueConstraint with two columns: One MemberField and the Discriminator May 12, 2014 · Blow, you should keep performance issues when choosing some kind of inheritance strategy. Nov 2, 2018 · I'm working with this tutorial to handle entities inheritance. May 11, 2024 · Entity inheritance means that we can use polymorphic queries for retrieving all the subclass entities when querying for a superclass. May 6, 2024 · Explore the fundamental differences between inheritance and composition in JPA entity modeling. In this article, we'll look at how JPA handles inheritance and explore different strategies for mapping class @Entity @Inheritance(strategy = InheritanceType. In JPA (Java Persistence API), you can define an abstract base entity with Sep 12, 2009 · 4 JPA knows two different ways to apply inheritance: Joined table inheritance Single table inheritance With single table inheritance you will need a discriminator column to distinguish between the rows in the table. The inheritance strategy can be JOINED, SINGLE_TABLE and TABLE_PER_CLASS. Abstract entities are like concrete entities but cannot be instantiated. @Entity @Inheritance(strategy = InheritanceType. Abstract entities can be queried just like concrete entities. 2. Mapping with JPA (Java Persistence Annotations) JPA entities are plain POJOs. Jun 22, 2023 · Spring is a platform designed to simplify the life of Java developers. There are three inheritance strategies defined from the InheritanceType enum, SINGLE_TABLE, TABLE_PER_CLASS and JOINED. The @MappedSuperclass annotation is annotated at a class level in which we configure mappings of columns that may be common for some database tables. This promotes code reuse by allowing subclasses to inherit attributes and methods from a superclass. Just define a discriminator Jan 30, 2021 · JPA allows us to easily create tables in the database with the @Entity annotation. LAZY) private Teacher manager; } When retrieving a School entity from database, the school's manager is lazy, not initialized. In the next sections, we’ll go over available strategies in more detail. Similarly, visits to the clinic can vary in type, requiring distinct data fields. Mar 24, 2024 · JPA’s inheritance capabilities can help simplify this process by allowing developers to define hierarchical relationships between entities and map them to the appropriate database tables. In terms of performance and easy implementation, this is the best strategy. Dec 18, 2014 · We want to write three Repository classes (aka DAO), one for each entity, following the hierarchy structure so all repository’s methods referring the base class User (for example a method findByEmail) are available on all repositories but written only once. Each subclass in the hierarchy annotated with @Entity and @Inheritance will be mapped to its own table in the database, as per the specified inheritance strategy. 1 and I want to define an entity with two sub entities. There are several strategies and annotations available for mapping and managing inheritance relationships: Single Table Inheritance: In this strategy, all subclasses share the same database table. If your child classes define only transient fields (not methods) (i. Discriminator is a way to differentiate rows belonging to different classes in the hierarchy. This means all concrete subclasses and superclasses will be stored in their own table. In JOINED inheritance strategy, the fields that are specific to a subclass are mapped to a May 21, 2024 · 1、简介 继承（Inheritance）和组合（Composition）是面向对象编程（OOP）中的两个基本概念，我们也可以在 JPA 中利用它们进行数据建模。 在 JPA 中，继承和组合都是对实体间关系进行建模的技术，但它们代表的是不同类型的关系。 本文将带你了解这两种方法及其 Should you use composition or inheritance when you design your entities? Do the general recommendations also apply to entities? And which mapping options do JPA and Hibernate offer for such an entity? Find out more in this article. It extends JpaRepository and adds methods to pass in an entity graph to the query. Inheritance. Actually, they are Hibernate persistent entities. I thought about a generic UserEntity but want to avoid creating additional tables as well as tables with fields of the "other" project. You can tell if you need one or the other by answering this questions: is there some other entity in the model which could have an association with the base class? If yes, then the base class is in fact an entity, and you should use entity inheritance. Like in Spring Data JPA, what are the equivalent annotations for @Inheritance and @ Aug 16, 2018 · You can create the entities using inheritance strategy @Entity @Inheritance(strategy = InheritanceType. not saved in the db), then perhaps a discriminator column is the best option. It maps each concrete class to its own table. Jun 10, 2016 · I am trying to use IdClass composite primary keys giving the following scenarios: Primary keys involve object reference (entity objects) Entity object in primary key are foreign keys to other entit Java Persistence consists of four areas: The Java Persistence API The query language The Java Persistence Criteria API Object/relational mapping metadata The following topics are addressed here: Entities Entity Inheritance Managing Entities Querying Entities Database Schema Creation Further Information about Persistence Apr 15, 2017 · 注：这里所说的实体指的是@Entity注解的类 继承映射使用@Inheritance来注解，它的strategy属性的取值由枚举InheritanceType来定义（包含SINGLE_TABLE、TABLE_PER_CLASS、JOINED，分别相应三种继承策略）。@Inheritance注解仅仅能 Apr 28, 2025 · The @DiscriminatorColumn annotation in JPA is used to differentiate one entity from another entity class from an inheritance hierarchy. En Jul 20, 2014 · 注：这里所说的实体指的是@Entity注解的类 继承映射使用@Inheritance来注解，它的strategy属性的取值由枚举InheritanceType来定义（包括SINGLE_TABLE、TABLE_PER_CLASS、JOINED，分别对应三种继承策略）。@Inheritance注解只能作用于继承结构的超类上。如果不指定继承策略，默认使用SINGLE_TABLE。 JPA提供了三种继承映射 Dec 6, 2013 · Additionally, you will have 2 entity classes, named AnswerA and AnswerB which will only hold the "extra" fields. SINGLE_TABLE) @Inheritance のみ宣言すると SINGLE_TABLE 戦略を使用する、JPAの基本戦略であります。 本当に単純で拡張の可能性が低い時に SINGLE_TABLE 戦略を使用することが良いです。 区分カラムは必須です。 @DiscriminatorColumn を宣言しなくてもHibernateが自動的に指定する Sep 10, 2024 · Learn how to map embeddable inheritance when using JPA and Hibernate. Nov 3, 2016 · Inheritance in JPA is specified on the root entity using the @Inheritance annotation. When you use: @MappedSuperclass AbstractLegalEntity @Entity ConcretePersonEntity extends Oct 15, 2015 · The Message Entity has @OneToMany relationship to one of the UserEntities in each project. 在父类实体的@Entity注解下添加如下的注解： @Inheritance 데이터 베이스를 설계할 때 다음과 같은 경우를 맞이 한다. I want to implement entities inheritance in Spring Data MongoDB. So add @Inheritance(strategy=InheritanceType. Dec 18, 2014 · I've three JPA entity classes A, B and C with the following hierarchy: A | +---+---+ | | C B That is: @Entity @Inheritance public abstract class A { /* */ } @Entity public class B extends A { /* */ } @Entity public class C extends A { /* */ } Using Spring Data JPA, what is the best way to write repositories classes for such entities? I know that I can write these: public interface Dec 11, 2023 · In SINGLE_TABLE inheritance, more than one @Entity classes can persist data into single table of database. As you want a single table, you should use Single Table inheritance. JPA Entity Configuration Example 1. Hibernate and JPA support 4 inheritance strategies which map the entities to different table models. Table-per-class Strategy Implementation Jan 7, 2018 · The annotation @Inheritance is used on the root entity class with strategy = InheritanceType. I‘m a software enginner. In Java JPA, you can use inheritance to model relationships between entities. (대부분)그나마 슈퍼타입 서브타입 관계라는 모델링 기법이 객체 상속과 유사하다. Do not forget a inheritance can be re-writen as a association as follows instead of public class A {} public class B extends A {} you can use public class B { private A a; } Or you can use MapedSuperClass To map all of your inherited Apr 13, 2017 · If repositories need to be created for each concrete entity, how to get the right repository for the specific equipment call? (store the table name and repository class in a map that gets created on startup of the application perhaps?) Aug 10, 2023 · In the world of modern software development, efficient design and implementation of entity classes play a crucial role in building robust and maintainable applications. But how do you model inheritance in relational databases, which lack this concept inherently? JPA bridges this gap by providing various Java inheritance strategies to map your object hierarchies to database tables effectively. Entity inheritance must be used when you have an entity, and several sub-entities. Jun 29, 2018 · 6 I'm trying to create JPA entities by using inheritance , I am not using any JPA polymorphic mechanism to do this. We will explore these inheritance mapping. L’héritage avec JPA ¶ JPA offre plusieurs stratégies pour associer une relation d’héritage dans le modèle objet avec une représentation dans le modèle relationnel de données. The Java Persistence API (JPA) is the persistence standard of the Java ec From JPA 1. In this article, we will discuss The single table strategy which maps all entities of the inheritance structure to the same database table. Therefore, it supports all object oriented concepts for entity persistence. Excerpt from Person The javax. @Entity @Table (name="employees") @Inheritance (strategy = InheritanceType. Configuring Inheritance for a JPA Entity OC4J supports the following inheritance strategies for mapping a class or class hierarchy to a relational database schema: Joined Subclass Single Table for Each Class Hierarchy You can configure either approach using annotations (see "Using Annotations"). Jun 9, 2018 · Your base classe is not annotated with @Entity so hibernate doesn't know of its existance. But it may be the case that you don't actually need Mar 18, 2024 · Hibernate supports inheritance, allowing the mapping of a Java class hierarchy to a database structure. This approach makes polymorphic queries very efficient and provides the best performance. In the Petclinic application, for example, pets share common fields like name and birthdate, but specific types such as cats or birds have unique properties. I have person and company entities that extends the User entity. 1. JOINED. Here you can see a good insight about available inheritance strategies. Learn the basics of JPA - entities, relationships, entity manager, annotations, JPQL and Criteria API. My source code looks like the following: _the 'base' class with the annotated updateDates() method: @javax. Master JPA using Hibernate as the implementation. Oct 9, 2024 · Learn how to implement JPA entity inheritance using a single table with a discriminator column for subtypes. TABLE_PER_CLASS) public abstract class Vehicle { @ManyToOne public VehicleReport report; } @Entity public class Car extends Vehicle { //Specific "Car" columns } And in the report class @OneToMany private Collection<Vehicle> vehicles; will work as expected - collection of vehicles each being Jan 25, 2025 · Unlock the secrets of JPA's Single Table Inheritance! Discover its hidden pitfalls and master powerful solutions to elevate your data management skills. Aug 29, 2024 · Following are the most frequently used JPA inheritance annotations: - @Inheritence - This annotation is applied on the root entity class to define the inheritance strategy. Inheritance in ORM is not implemented as inheritance in Java. It is used to define how the data of the entities in the hierarchy should be stored in the database. Apr 25, 2019 · Databases have no notion of inheritance between entities, so JPA providers like Hibernate must provide special features for defining object-oriented inheritance relationships in the database. [JPA] Inheritance 전략상속 SQL (데이터베이스)와 객체지향언어가 갖는 큰 차이점 중 하나가 바로 상속의 유무 여부이다. 나 Any mapping or relationship annotations in non-entity superclasses are ignored. The @Inheritance annotation is applied Mar 18, 2020 · Learn how to map the single table inheritance strategy with JPA and Hibernate so that you gain both performance and consistency. Dec 25, 2019 · 前面学习过@MappedSuperclass，可以把一些公共的属性提取到添加该注解的类里，如id，creteTime，updateTime等。该类不会生成表，该类中相应的字段都会生成在子类中。该类没有被@Entity注释，不是一个实体。 @Inheritance JPA为我们提供了@Inherita Jan 7, 2018 · The annotation @Inheritance is used on the root entity class with strategy = InheritanceType. If you’ve ever wondered about the optimal way to implement inheritance mapping in your code, and how it might affect performance. The @Inheritance annotation provides us with benefits to reduce code complexity by creating a base class and inheriting other classes from the base class. 객체지향언어에서는 상속을 지원하지만, 데이터베이스에서는 상속을 지원하지 않는다. Nov 20, 2013 · i see you are using single table inheritance strategy, thus you have to modify the descriminator field manulay (by using SQL queries) and set appropirate fields on child table. This article will examine in detail… L’héritage avec JPA ¶ JPA offre plusieurs stratégies pour associer une relation d’héritage dans le modèle objet avec une représentation dans le modèle relationnel de données. @Entity @Inheritance public abstract class User { @Id private long Jan 7, 2018 · For JPA implementations, support for the table per concrete class inheritance mapping strategy is optional. If you have 2 tables, then you need to use the TABLE_PER_CLASS inheritance type. Both abstract and concrete classes can be annotated with the Entity annotation, mapped as entities, and queried for as entities. Although in this configuration, JPA scanning for entity beans is turned off. Jul 7, 2020 · There are four different ways to use inheritance with entity classes. Sep 6, 2024 · Inheritance allows us to define common fields and behaviors in a base class, which can be extended by other entities. JOINED) AbstractLegalEntity In the database you will have one table for AbstractLegalEntity, and tables for classes, which extend AbstractLegalEntity class. I’ve got Feb 27, 2023 · On this page, we will learn to use JPA @Inheritance annotation with JOINED strategy in our Hibernate application. 3. But which one is the best for your use case? Jul 4, 2024 · JPA Inheritance Inheritance is the fundamental concept in object-oriented programming that allows the class to inherit properties and methods from another class. This chapter takes you through the advanced mappings between objects and relational entities. I'd like to use table-per-subclass mapping near the root of the hierarchy, but change to table-per-class-hierarchy mapping near the leaves. 스프링에서는 JPA를 이용하여 ORM 기술을 사용하는데, 클래스 간 상속 관계에 대해서는 어떻게 Aug 7, 2019 · 在JPA中，实体继承关系的映射策略共有三种：单表继承策略 (SINGLE_TABLE)、Joined策略和Table_PER_Class策略。 1、单表继承策略 单表继承策略，父类实体和子类实体共用一张数据库表，在表中通过一列辨别字段来区别不同类别的实体。具体做法如下： a. 0 annotations instead of hbm. Discriminator column differentiates between different types of entities. 继承 是面向对象编程中的一种常见模式，但是它不容易在数据库中复制。这个Java技巧向您展示了如何使用Hibernate在JPA中为继承关系建模。 了解四种不同的ORM继承策略的优缺点，并获得选择最能满足您的应用程序需求的技巧。 我假设您已经通过JPA和Hibernate入门到Java持久性，包括如何 建模 实体和 Nov 14, 2011 · 1 I am trying to set up Entity Inheritance using JPA annotations and abstract classes. It also contains certain features and element attributes that are special to JPA. Oct 12, 2023 · My name is Yassir ACAF. Apr 28, 2025 · The @Inheritance annotation in JPA is used to specify the inheritance relation between two entities. Mar 24, 2016 · Im using Hibernate with JPA 2. This annotation is used to provide the name of the discriminator column. You won't have instances of AbstractLegalEntity if it's abstract. It allows the developers to model the real-world inheritance hierarchies in the relational database. 2. Feb 17, 2024 · JPA defines several inheritance mechanisms, mainly defined though the @Inheritance annotation or the <inheritance> element. SINGLE_TABLE) @ Apr 26, 2017 · I've two entities Person, Employee and Employee1. DTYPE by default): So, because we are filtering by the discriminator column, we might want to index it or include it to speed up queries. Those are single table, table per class, joined or to use a MappedSuperclass. SINGLE_TABLE) @DiscriminatorColumn(name = "TYPE_PERSONNE") public class Personne { @Id protected long Id; Mar 26, 2025 · Learn how to define entities and customize them using the Java Persistence API. Oct 7, 2019 · JPA supports the following inheritance models: - SINGLE_TABLE – One table per class hierarchy. This strategy also uses SQL UNION queries (or a separate SQL query per subclass). The SingleTable strategy is one of them and maps an inheritance hierarchy of entities to a single database table. Apr 21, 2020 · SpringDataJPA笔记 (14)-Inheritance注解详解之SINGLE_TABLE 在JPA中使用映射注解Inheritance，有三种策略属性 SINGLE_TABLE – 将所有父类和子类集合在一张表 TABLE_PER_CLASS – 每个子类会生成一张单独的表，父类可以查询所有子类的表数据，参考上一篇笔记Union查询 JOINED – 每个类分别生成一张单独的表，但是每张表 2. Discriminator is a way to differentiate rows belonging to different subclasses in the root table. vujowlbrrqtyxluzwrlxbleexbvsqseuffpcsigsjupktppbgh