虛擬視圖

多表關(guān)聯(lián)常常通過創(chuàng)建數(shù)據(jù)庫視圖的方式來解決，其實(shí)也可以使用虛擬視圖，維護(hù)更為方便。

表person和表id_card通過外鍵id_card_id關(guān)聯(lián)。

創(chuàng)建虛擬視圖PersonIdCard類：

@Entity
@Immutable
@Subselect("SELECT p.id id, p.name name, p.age age, ic.number number " +
           "FROM person p " +
           "LEFT JOIN id_card ic " +
           "ON p.id_card_id=ic.id")
public class PersonIdCard {
    @Id
    private Long id;
    private String name;
    private Integer age;
    private String number;

    // getter and setter}

public interface PersonIdCardRepository extends JpaRepository<PersonIdCard, Long>, JpaSpecificationExecutor<PersonIdCard> {
}

public List<PersonIdCard> findAll(SearchRequest request) {
    Specification<PersonIdCard> specification = new Specifications<PersonIdCard>()
            .gt(Object.nonNull(request.getAge()), "age", 20)
            .build();

    return personRepository.findAll(specification); 
}