What is Entity?

In Java (especially in JPA/Hibernate), an Entity is a Java class that represents a table in a database.

Each object of the entity class corresponds to a row in that table, and each field in the class maps to a column.

Simple Definition

👉 An Entity is a POJO (Plain Old Java Object) that is mapped to a database table using annotations.

Example of an Entity

java id="y9e5c2"
import jakarta.persistence.Entity;
import jakarta.persistence.Id;

@ Entity
public class User {

@Id
private int id;
private String name;
private String email;

}

How Mapping Works

Java Class	Database
Class (User)	Table (user)
Object	Row
Field (name)	Column
@ Id	Primary Key

Important Annotations

@ Entity

Marks the class as a database entity.

@ Id

Specifies the primary key.

@ Table

Used to define table name (optional).

java id="lgbl66"
@entity
@Table(name = "users")
public class User {
}

@ Column

Maps field to a specific column.

Key Characteristics of an Entity

• Must have a primary key (@ Id)
• Should have a no-argument constructor
• Should be a POJO class
• Can include getters and setters

Example Scenario

In a banking application:

• Customer → Entity → Customer table
• Account → Entity → Account table

Each entity represents real-world data stored in the database.

Why Entities are Important

• Simplifies database interaction
• Enables ORM (Object-Relational Mapping)
• Reduces SQL usage
• Improves code readability

Conclusion

An Entity is a core concept in JPA/Hibernate that allows Java developers to map objects to database tables easily. It plays a key role in building database-driven applications using modern frameworks like Spring Boot.

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