春季数据 - 页面请求 - 按功能排序 [英] Spring Data - Page Request - order by function

问题描述

我试图在基于Spring 4.1.1.RELEASE和Hibernate 4.2.16.Final的Java应用程序中实现分页。

我有以下代码：

  PageRequest pageRequest = new PageRequest（pageNumber，pageSize，new Sort（new Order（Direction.DESC，name））
 Page page = myRepository.findAll（specification，pageRequest）; 
  

一切正常。我想通过sql函数值来命令，例如： ORDER BY CHAR_LENGTH（name）。

当我在 @ org.springframework.data.jpa.repository.Query 中输入这样的子句时，例如：

<$
$ public元素MyRepository {
@Query（从MyEntity e选择e由CHAR_LENGTH（e.name））
public List< MyEntity> findAllOrderedByNameLength（）;
}

不幸的是，我无法使用PageRequest完成它。 code> ORDER BY CHAR_LENGTH（

  PageRequest pageRequest = new PageRequest（pageNumber，pageSize，new） Sort（new Order（Direction.DESC，ORDER BY CHAR_LENGTH（name）））
 Page page = myRepository.findAll（specification，pageRequest）; 
  

引发以下异常：

 原因：org.springframework.data.mapping.PropertyReferenceException：找不到属性类型为MyEntity的CHAR！ 
  

解决方案

它不直接识别SQL，它不是JPA功能，因此它可能不适用于其他提供程序。

一个不错的选择是实现一个自定义的 Order 类，并使用它。您可以在这个博客。按照博客中的具体实现，您可以使用它作为 OrderBySqlFormula.sqlFormula（CHAR_LENGTH（name）desc）

UPDATE

建议的解决方案仅适用于Hibernate，不能用于Spring Data代码，该代码需要 org.springframework.data.domain.Sort.Order 而不是 org.hibernate.criterion.Order 。

I am trying to implement pagination in Java application based on Spring 4.1.1.RELEASE and Hibernate 4.2.16.Final.

I have a following code:

PageRequest pageRequest = new PageRequest(pageNumber, pageSize, new Sort(new Order(Direction.DESC, "name"))
Page page = myRepository.findAll(specification, pageRequest);

and everything works fine. However now I would like to order by sql function value, for example: ORDER BY CHAR_LENGTH(name).

It works perfectly when I input such clause in @org.springframework.data.jpa.repository.Query, for example:

public class MyRepository {
  @Query("select e from MyEntity e order by CHAR_LENGTH(e.name)")
  public List<MyEntity> findAllOrderedByNameLength();
}

unfortunately I am not able to do it with PageRequest. When I pass: ORDER BY CHAR_LENGTH(name) to PageRequest as a property:

PageRequest pageRequest = new PageRequest(pageNumber, pageSize, new Sort(new Order(Direction.DESC, "ORDER BY CHAR_LENGTH(name)"))
Page page = myRepository.findAll(specification, pageRequest);

the following exception is being thrown:

Caused by: org.springframework.data.mapping.PropertyReferenceException: No property CHAR found for type MyEntity!

解决方案

The reason it works in query is that Hibernate passes whatever it doesn't recognize directly into SQL, it isn't a JPA feature so it probably wouldn't work with some other provider.

One nice option is to implement a custom Order class, and use that instead. You can find detailed instructions in this blog. With the exact implementation as in the blog, you would use it as OrderBySqlFormula.sqlFormula("CHAR_LENGTH(name) desc")

UPDATE

The proposed solution is for Hibernate only, can't be used with Spring Data code, which expects org.springframework.data.domain.Sort.Order and not org.hibernate.criterion.Order.

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