Spring Data JPA：使用连接表进行排序和分页

我有一个场景，我想要对包含 3 个表的结果进行过滤、排序和分页。

目前，我使用 Spring Data JPA 的规范功能在单个实体上执行此操作：repository.findAll(specification, pageRequest).

这很好用，但现在我有另一种情况，其中排序/过滤属性分布在 3 个表上，这些表通过一对多关系连接。

这是我的场景：

@Entity
public class CustomerEntity ... {
  ...

  @Column(nullable = false)
  public String                                 customerNumber;

  @OneToMany(mappedBy = "customer", cascade = CascadeType.ALL, orphanRemoval = true)
  public List<CustomerItemEntity> items;
}


@Entity
public class CustomerItemEntity ... {
  ...

  @Column(nullable = false)
  public String                                 itemNumber;

  @ManyToOne(optional = false)
  @JoinColumn(name = "customerId")
  public CustomerEntity customer;

  @OneToMany(mappedBy = "item", cascade = CascadeType.ALL, orphanRemoval = true)
  public List<DocumentEntity> documents;
}


@Entity
public class DocumentEntity ... {
  ...

  @Column(nullable = false)
  public LocalDate                                 validDate;

  @ManyToOne(optional = false)
  @JoinColumn(name = "itemId")
  public CustomerItemEntity item;
}

有没有办法使用PageRequest and Specification where customerNumber, itemNumber and validDate同时用于过滤、排序和分页？

尝试这样的事情：

Specification<CustomerEntity> joins = (customer, query, cb) ->  {
    // from CustomerEntity c
    // join c.items i
    Join<CustomerEntity, CustomerItemEntity> items = customer.join("items");

    // join i.documents d
    Join<CustomerItemEntity, DocumentEntity> documents = items.join("documents");

    // // where c.customerNumber = ?1 and i.itemNumber = ?2 and d.validDate = ?3 
    return cb.and( 
            customer.equal(customer.get("customerNumber", customerNumber)),
            items.equal(items.get("itemNumber", itemNumber)), 
            documents.equal(documents.get("validDate", validDate))
    );
};

// sort by c.customerNumber asc
PageRequest pageRequest = new PageRequest(0, 2, new Sort(Sort.Direction.ASC, "customerNumber"));

Page<CustomerEntity> customerPage = CustomerRepo.findAll(joins, pageRequest);

但我不知道你为什么需要Specification here?

您可以使同样的事情变得更简单：

@Query("select c from CustomerEntity c join c.items i join i.documents d where c.customerNumber = ?1 and i.itemNumber = ?2 and d.validDate = ?3")
Page<CustomerEntity> getCustomers(String customerNumber, String itemNumber, LocaleDate validDate, Pageable pageable);  

但所有这些都没有意义，因为您的三个实体具有连续的一对多关联。在这种情况下，您可以只使用最后一个条件，而不是三个条件：where d.validDate = ?1。那么查询方法就变得更加简单了：

@Query("select c from CustomerEntity c join c.items i join i.documents d where d.validDate = ?1")
Page<CustomerEntity> getCustomers(LocaleDate validDate, Pageable pageable);

UPDATE

要按连接实体的字段添加排序，我们可以使用orderBy的方法query:

Specification<CustomerEntity> joins = (customer, query, cb) ->  {

    Join<CustomerEntity, CustomerItemEntity> items = customer.join("items");
    Join<CustomerItemEntity, DocumentEntity> documents = items.join("documents");

    // Ascending order by 'Document.itemNumber'
    query.orderBy(cb.asc(documents.get("itemNumber")));

    return cb.and( 
            customer.equal(customer.get("customerNumber", customerNumber)),
            items.equal(items.get("itemNumber", itemNumber)), 
            documents.equal(documents.get("validDate", validDate))
    );
};

Page<CustomerEntity> customerPage = CustomerRepo.findAll(joins, new PageRequest(0, 2));

要按多个参数排序，您可以将它们传递给以逗号或List:

query.orderBy(cb.asc(items.get("customerNumber")), cb.desc(documents.get("itemNumber")));