Spring Boot Tutorial 0/110 lessons ~6 min read Lesson 29“Production-grade backends”

Entity Mapping

Entities are Java classes annotated with @Entity that map 1-to-1 to database tables.

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Focus

3 guided sections

Practice signal

Examples included

Career prep

Foundation builder

Introduction

Entities are Java classes annotated with @Entity that map 1-to-1 to database tables. Get the mapping right and JPA stays out of your way.

Informative example

@Entity
@Table(name = "orders", indexes = {
    @Index(name = "ix_orders_user", columnList = "user_id"),
    @Index(name = "ix_orders_status", columnList = "status")
})
public class Order {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;

  @Column(name = "user_id", nullable = false)
  private Long userId;

  @Enumerated(EnumType.STRING)
  @Column(nullable = false, length = 16)
  private OrderStatus status;

  @Column(name = "total_cents", nullable = false)
  private int totalCents;

  @Column(name = "created_at", nullable = false, updatable = false)
  private Instant createdAt = Instant.now();

  // getters / setters or @Getter @Setter from Lombok
}

Best practices

@Enumerated(EnumType.STRING) — never ORDINAL (renaming/reordering breaks data).
Index FK columns and frequent filters explicitly with @Index.
updatable = false for created_at — protect against accidental writes.

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