#Data annotations composite key how to

Here you need to mention the table’s column names if they are different from Java field name using annotation.

The composite primary key class can be marked with annotation to use this class as a key in the entity class.

To build a composite primary key class in Java using Hibernate (JPA), you need to have the no-argument constructor and you need to override equals() and hashCode() methods for building the logic to check equality. (2, 'Liton', 'Sarkar') Composite Primary Key Class I am also inserting few rows to test the application right away: INSERT INTO `user` (`id`, `first_name`, `last_name`) VALUES

#Data annotations composite key how to

Now I will show you how to map the composite primary key in the entity class. Let’s say you want to make first_name and last_name as a composite primary key in the above user table. )ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci Last_name varchar(30) COLLATE utf8mb4_unicode_ci NOT NULL, Id int unsigned COLLATE utf8mb4_unicode_ci NOT NULL,įirst_name varchar(30) COLLATE utf8mb4_unicode_ci NOT NULL, Let’s say you have created the following user table under roytuts database in MySQL server. So JPA is a specification and Hibernate is one of the implementation frameworks for JPA (Java Persistence API). As you can see in the following build file I have added only Hibernate dependency. The following pom.xml file can be used for your application. Physical ER models show all table structures, including column name, column data type, column constraints, primary key, foreign key, and relationships between. The name of the project is jpa-hibernate-composite-primary-key. You can create a maven based project in your favorite IDE or tool. Java at least 8, Hibernate 6.0.0.Alpha7, JPA 2.1 Project Setup You can also use the same entity class in your Spring Boot application. In this example I am going to show you only Hibernate (JPA) standalone application. Here email and name fields make together a composite primary key. So you don’t want to make the id column as a primary key but name and email together will be a unique and primary key. Let’s say you have created a table called user in your database and the user table has three columns – id, name and email. Therefore the combination of column values will be as a unique instead of having a single column value as unique.

Composite primary key is a combination of two or more columns made together as a primary key. Essentially, it allows you to create reusable, composite value types that can be embedded within multiple entity classes.Īs you can see, the compound key fields are not included in the Entity class.In this example I am going to tell you how to map composite primary key to entity class in your JPA Hibernate entity class. The attributes of the embeddable class are mapped to the columns of the entity's table. When you mark a class with it means that instances of that class will be stored as part of the owning entity's table in the database. It indicates that the annotated class is intended to be a value type and can be used as a component of another entity. In Java Persistence API (JPA), the annotation is used to define a class that can be embedded within an entity class. Mapping a Composite key with an name of the class is indicated as the value of the class attribute of the IdClass element, as shown in this example: class Person surname Īs you can see, the Compound keys are annotated with and we need to provide an public class PersonId implements Serializable What is the Embeddable annotation in JPA ? When using Hibernate or JPA applications there are two main strategies to map a Composite Primary Key. Composite keys are a group of columns in the database, whose values together make a unique value.