Spring Data-页面请求-按功能排序

Question

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!

Answer 1

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 .

Answer 2

You can use @Formula and define a custom field for the CHAR_LENGTH(name) expression and use it for ordering

See for example here