Java Spring JPA在关节表上使用规范和标准查询

我使用JPA规范和CriteriaQuery将where子句添加到实体中

域类：

public class Domain {

  @Id
  @Column(name = "id")
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;

  @Column(name = "account_id")
  private Long accountId;

  @OneToMany(cascade = CascadeType.ALL)
  @JoinColumn(name = "domain_id")
  private List<Notification> notification;
}

然后，我使用以下类创建规范：

public class DomainSpecification implements Specification<Domain> {

  final private SearchCriteria criteria;

  public DomainSpecification(SearchCriteria searchCriteria) {
    this.criteria = searchCriteria;
  }

  @Override
  public Predicate toPredicate(
          Root<Domain> root, CriteriaQuery<?> query, CriteriaBuilder builder) {

     switch (criteria.getOperation()) {
      case ":":
        if (root.get(criteria.getKey()).getJavaType() == String.class) {
          return builder.like(
                  root.<String>get(criteria.getKey()),
                  "%" + criteria.getValue() + "%");
        } else {
          return builder.equal(root.get(criteria.getKey()),
                  criteria.getValue());
        }
      case "=":
        return builder.equal(root.get(criteria.getKey()),
                criteria.getValue());
      default:
        return null;
    }
  }

}

然后，每当我想创建where子句时，我都会执行以下操作：

DomainSpecification idSpecification
        = new DomainSpecification(
                new SearchCriteria("id", "=", domainId));

Specifications<Domain> specifications = Specifications.where(idSpecification);

final Domain domain = this.domainRepository.findOne(specifications);

DomainSpecification ID规范
=新域规范(
新的搜索条件（“id”，“=”，domainId））；
规格规格=规格。其中（idSpecification）；
最终域=this.domainRepository.findOne（规范）；

这将通过域实体中名为

id

的字段进行搜索

现在，我怎样才能根据我加入的实体进行筛选？例如，我想筛选Domain.id=10和Notification.contact=“abc”的位置

---

感谢您的帮助

您可以将

规范

的定义包装到helper类中：

public class DelegationSpecificationsHelper {

    public static Specification<Domain> notificationContactSpec(String contact) {
        return (root, query, cb) -> cb.equal(root.join("notification").get("contact"), contact);
    }

    public static Specification<Domain> idSpec(SearchCriteria searchCriteria) {
        switch (criteria.getOperation()) {
          case ":":
            if (root.get(criteria.getKey()).getJavaType() == String.class) {
              return builder.like(
                      root.<String>get(criteria.getKey()),
                      "%" + criteria.getValue() + "%");
            } else {
              return builder.equal(root.get(criteria.getKey()),
                      criteria.getValue());
            }
          case "=":
            return builder.equal(root.get(criteria.getKey()),
                    criteria.getValue());
          default:
            return null;
        }
    }
}

有关元模型生成的详细信息：

---

成功了！！感谢MATCOOL：考虑使用元模型生成器，这是非常有用的工具同意！再次感谢

DomainSpecification idSpecification
        = new DomainSpecification(
                new SearchCriteria("id", "=", domainId));

Specifications<Domain> specifications = Specifications.where(idSpecification);

final Domain domain = this.domainRepository.findOne(specifications);

public class DelegationSpecificationsHelper {

    public static Specification<Domain> notificationContactSpec(String contact) {
        return (root, query, cb) -> cb.equal(root.join("notification").get("contact"), contact);
    }

    public static Specification<Domain> idSpec(SearchCriteria searchCriteria) {
        switch (criteria.getOperation()) {
          case ":":
            if (root.get(criteria.getKey()).getJavaType() == String.class) {
              return builder.like(
                      root.<String>get(criteria.getKey()),
                      "%" + criteria.getValue() + "%");
            } else {
              return builder.equal(root.get(criteria.getKey()),
                      criteria.getValue());
            }
          case "=":
            return builder.equal(root.get(criteria.getKey()),
                    criteria.getValue());
          default:
            return null;
        }
    }
}

Specifications<Domain> specifications = Specifications.where(DelegationSpecificationsHelper.idSpec(new SearchCriteria("id", "=", domainId))
                                                      .and(DelegationSpecificationsHelper.notificationContactSpec("someSearchString"));

SearchCriteria idCriteria = new SearchCriteria("id", "=", domainId)
Specifications<Domain> specifications = 
                 Specifications.where(idSpec(idCriteria)
                               .and(notificationContactSpec("someSearchString"));

 public static Specification<Domain> notificationContactSpec(String contactValue) {
        return (root, query, cb) -> cb.equal(root.join(Domain_.notification).get(Notification_.contact), contactValue);
 }