An entity in Java is usually a simple Java class (a POJO) that represents a table row in a database when you use JPA or another ORM framework.

Quick Scoop: Core Idea

  • An entity is a Java class whose instances map to records (rows) in a database table.
  • It is used in persistence frameworks like JPA/Hibernate to bridge Java objects and relational data.
  • The class is typically annotated with @Entity and has an @Id field as the primary key.

Example:

java

import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String username;
    private String email;

    // getters and setters
}

In this example, each User object corresponds to one row in a user (or similar) table in the database, and JPA handles saving, updating, and loading these entities for you.

Mini Sections

1. What makes a class an entity?

  • Annotated with @Entity.
  • Has a primary key field annotated with @Id (optionally @GeneratedValue).
  • Uses normal fields plus getters/setters to represent columns.
  • Must be a regular, non-abstract (in most cases) Java class, often implementing Serializable in enterprise apps.

2. How entities relate to the database

  • Class ↔ table.
  • Field ↔ column.
  • Object instance ↔ row.

Relationships between entities (like @OneToMany, @ManyToOne, @OneToOne) represent foreign keys and joins in the database.

Quick bullet recap

  • Entity = persistent domain object.
  • Used by JPA/Hibernate and managed by an entity manager.
  • Annotated with @Entity, has @Id primary key.
  • Maps Java world to database world (OO ↔ relational).

If you’re thinking “what is entity in Java” in 2026, most folks mean exactly this JPA-style persistent class that maps your Java model to a database table.

TL;DR: An entity in Java is a POJO marked with @Entity that represents a database table row and is managed by a persistence framework like JPA/Hibernate.

Information gathered from public forums or data available on the internet and portrayed here.