JavaSpringDataJPA：使用联接表进行排序和分页

Question

我有一个场景，我想过滤、排序和分页一个结果，其中有3个表参与

目前，我使用SpringDataJPA的规范特性在单个实体上实现：repository.findAll(specification, pageRequest)

这很好，但现在我有另一个场景，排序/筛选属性分布在3个表上，这些表通过一对多关系连接

以下是我的设想：

@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和Specification，其中customerNumber、itemNumber和validDate同时用于过滤、排序和分页

Answer 1

我发现您可以使用使用自定义查询创建的联接别名，按OneToMany列的内容进行排序。在我的代码库中，它是：

@Query("select p from Person p join p.roles r")
Page<Person> search(Pageable pageable);

因此，我能够使用以下方法进行排序：

r.role

使用以下命令从控制器传递：

@PageableDefault(size = 15, sort = "r.role") Pageable pageable

Answer 2

试着这样做：

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这里

您可以使相同的操作更简单：

@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，因为你的三个实体有顺序的一对多关联。在这种情况下，您只能使用最后一个条件，而不是三个条件：where d.validDate = ?1。然后，查询方法变得更加简单：

@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);

更新

要按连接实体的字段添加排序，我们可以使用query的orderBy方法：

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));

要按多个参数进行排序，可以将它们传递给用逗号或List分隔的方法：

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