第一步,在实体中标记你的业务字段为@NaturalId:
@Entity public class Product implements Serializable {
private static final long serialVersionUID = 1L;
@Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id;
private String name;
@NaturalId(mutable = false) @Column(nullable = false, updatable = false, unique = true, length = 50) private String code;
@Override public boolean equals(Object o) { if (this == o) { return true; } if (!(o instanceof Product)) { return false; } Product naturalIdProduct = (Product) o; return Objects.equals(getCode(), naturalIdProduct.getCode()); // including sku // return Objects.equals(getCode(), naturalIdProduct.getCode()) // && Objects.equals(getSku(), naturalIdProduct.getSku()); }
@Override public int hashCode() { return Objects.hash(getCode()); // including sku // return Objects.hash(getCode(), getSku()); }
@Override public String toString() { return "Product{" + "id=" + id + ", name=" + name + ", code=" + code + '}'; // including sku // return "Product{" + "id=" + id + ", name=" + name + ", code=" + code + ", sku=" + sku + '}'; }
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这里的code字段标记为@NaturalId,注意点:
对于非可变id,将列标记为@NaturalId(mutable = false)和@Column(nullable = false, updatable = false, unique = true, ...)
对于可变id,将列标记为@NaturalId(mutable = true)和@Column(nullable = false, updatable = true, unique = true, ...)
使用NaturalId重写覆盖equals()并hashCode()方法
第二步,需要定义@NoRepositoryBean接口(NaturalRepository),在其中定义两个方法,命名findBySimpleNaturalId()和findByNaturalId()
@NoRepositoryBean public interface NaturalRepository<T, ID extends Serializable> extends JpaRepository<T, ID> {
// use this method when your entity has a single field annotated with @NaturalId Optional<T> findBySimpleNaturalId(ID naturalId); // use this method when your entity has more than one field annotated with @NaturalId Optional<T> findByNaturalId(Map<String, Object> naturalIds); }
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第三步, 实现此接口(NaturalRepositoryImpl),其中依赖使用Hibernate, Session, bySimpleNaturalId()和 byNaturalId() 方法。
@Transactional(readOnly = true) public class NaturalRepositoryImpl<T, ID extends Serializable> extends SimpleJpaRepository<T, ID> implements NaturalRepository<T, ID> {
private final EntityManager entityManager;
public NaturalRepositoryImpl(JpaEntityInformation entityInformation, EntityManager entityManager) { super(entityInformation, entityManager);
this.entityManager = entityManager; }
@Override public Optional<T> findBySimpleNaturalId(ID naturalId) {
Optional<T> entity = entityManager.unwrap(Session.class) .bySimpleNaturalId(this.getDomainClass()) .loadOptional(naturalId);
return entity; }
@Override public Optional<T> findByNaturalId(Map<String, Object> naturalIds) {
NaturalIdLoadAccess<T> loadAccess = entityManager.unwrap(Session.class).byNaturalId(this.getDomainClass()); naturalIds.forEach(loadAccess::using);
return loadAccess.loadOptional(); }
}
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第四步:在SpringBoot入口类中使用@EnableJpaRepositories(repositoryBaseClass = NaturalRepositoryImpl.class)注册此实施为基类
@SpringBootApplication @EnableJpaRepositories(repositoryBaseClass = NaturalRepositoryImpl.class) public class NaturalIdApplication {
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第五步:对于实体,编写一个经典的存储库:
@Repository public interface ProductRepository<T, ID> extends NaturalRepository<Product, Long>{ }
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第六步:在您的服务中注入此类并调用findBySimpleNaturalId()或findByNaturalId()
@SpringBootApplication @EnableJpaRepositories(repositoryBaseClass = NaturalRepositoryImpl.class) public class NaturalIdApplication {
private static final Logger logger = Logger.getLogger(NaturalIdApplication.class.getName());
private final ProductRepository productRepository;
public NaturalIdApplication(ProductRepository productRepository) { this.productRepository = productRepository; }
public static void main(String[] args) { SpringApplication.run(NaturalIdApplication.class, args); }
@Bean public ApplicationRunner init() { return args -> {
// persist two products Product tshirt = new Product(); tshirt.setName("T-Shirt"); tshirt.setCode("014-tshirt-2019"); // tshirt.setSku(1L);
Product socks = new Product(); socks.setName("Socks"); socks.setCode("012-socks-2018"); // socks.setSku(2L);
productRepository.save(tshirt); productRepository.save(socks);
Optional<Product> p1 = productRepository.findById(tshirt.getId()); // find by ID Optional<Product> p2 = productRepository.findBySimpleNaturalId(tshirt.getCode()); // find by natural ID
if (p1.isPresent() && p2.isPresent()) { System.out.println("p1: " + p1.get()); System.out.println("p2: " + p2.get()); } else { System.out.println("Not found!"); } }; } }
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点击标题见原文