JPA 애너테이션으로 엔터티 매핑

JPA 엔티티 매핑이란 무엇입니까

@Entity와 @Table

@Entity
@Table(name = "users", uniqueConstraints = @UniqueConstraint(columnNames = "email"))
public class User {
    // ...
    protected User() {} // required by JPA
}

@Id와 @GeneratedValue

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

@Column: 열 사용자 지정

@Column(name = "full_name", nullable = false, length = 100)
private String name;
@Column(name = "email", unique = true, nullable = false)
private String email;
@Column(name = "created_at", updatable = false)
private LocalDateTime createdAt;

@Embedded와 @Embeddable

@Embeddable
public class Address {
    private String street, city, country;
    @Column(name = "zip_code") private String zipCode;
}
@Entity
public class User {
    @Embedded private Address address;
}

@Enumerated: 열거형 저장

@Enumerated(EnumType.STRING)
@Column(nullable = false)
private UserStatus status; // stored as "ACTIVE", "INACTIVE", etc.

@CreationTimestamp와 @UpdateTimestamp

@CreationTimestamp
@Column(updatable = false)
private LocalDateTime createdAt;
@UpdateTimestamp
private LocalDateTime updatedAt;

@Transient: 필드 제외

@Transient
public String getFullName() { return firstName + " " + lastName; }

@Lob: 대형 객체

@Lob
@Column(name = "content")
private String content; // maps to TEXT in PostgreSQL

equals와 hashCode 계약

@Override public boolean equals(Object o) {
    if (this == o) return true;
    if (!(o instanceof User u)) return false;
    return email != null && email.equals(u.email);
}
@Override public int hashCode() { return getClass().hashCode(); }

낙관적 잠금을 위한 @Version

@Version
private Long version; // auto-managed by Hibernate

간단한 확인

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