Base Entity and Audit entity with JPA

Introduction:

When creating any web application and wanting to connect it with DB, we will add id a column inside each class and createionDate updatedDate in all entity classes, and it is not a clean code. So in this article, I will cover how can we avoid these practices and write clean code when creating our entities.

Setup the project:

When creating a new project to practice it, we need to use the spring boot framework and, we will use MAVEN to manage our dependency.

<dependencies>
 <dependency>
  <groupId>org.projectlombok</groupId>
  <artifactId>lombok</artifactId>
  <optional>true</optional>
 </dependency>
 <dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId>
 </dependency>
 <dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-data-jpa</artifactId>
 </dependency>
 <dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <version>8.0.28</version>
 </dependency>
 <dependency>
  <groupId>org.hibernate</groupId>
  <artifactId>hibernate-core</artifactId>
  <version>5.6.9.Final</version>
 </dependency>
</dependencies>

After preparing our Pom.xml file and put the major dependency, We need to create a new Class called BasedEntity.class , inside It, we will put inside it the major filed inside the database like id and other common filed inside your application.

@Getter
@Setter
@MappedSuperclass
public abstract class BaseEntity implements Serializable {

    @Id
    @GeneratedValue
    @Column(columnDefinition = "BINARY(16)", updatable = false, nullable = false)
    private UUID id;
}

I think you have some ambiguous points about the above class I will explain each line:

• MappedSuperclass : is used to ensure that the BaseEntity class will not have a separate representation as the table of the extending class.
• public abstract class BaseEntity : to prevent developers from instantiating an instance of this class. Only extending classes can instantiate an instance.
• @getter and @setter : to generate getter and setter methods with losly code.

And now I will create a new class to represent the Audit class, And I will define createdAt and updatedAt.

@Getter
@Setter
@MappedSuperclass
public abstract class BaseEntityAudit extends BaseEntity implements Serializable {
    private String createdBy;
    private String updatedBy;

    @CreationTimestamp
    @Column(name = "created_at", updatable = false)
    private Date createdAt;

    @UpdateTimestamp
    @Column(name = "updated_at")
    private Date updatedAt;
}

So in the above Class, I extend the class from BaseEntity class. And I defined two fields to represent audit data.

So I will create a new entity class to define and use the above classes with it.

@Entity
@Getter
@Setter
@Table(name = "users")
public class User extends BaseEntityAudit {

    @Column(name = "name")
    private String name;

    @Column(name = "email")
    private String email;
}

And now like what you saw, I create a new class called User and the class extend data from BaseEntityAudit , so the User class will have 5 fields in the database id , createdAt , updatedAt , name , and email . And if we need to create another class we will avoid defining id and createAt in each entity class.

Conclusion:

I think the above approach is a good approach to creating an entity class with readable code, is not redundant, and you will not define the same field more than one time.

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