Shulou(Shulou.com)06/02 Report--

This article mainly introduces "how to use SpringJPA to achieve count (*)". In daily operation, I believe many people have doubts about how to use SpringJPA to achieve count (*). The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful to answer the doubts of "how to use SpringJPA to achieve count (*)"! Next, please follow the editor to study!

SpringJPA directly implements count (*)

When you start using JPA, you basically rely on @ query (SQL) annotations to be implemented through native sql

Count the number according to the number:

Method one @ Query ("select count (t) from FollowerInfo t where investUserId =: invUserId") Integer findFollowerNumberByInvUserId (@ Param ("invUserId") Long invUserId)

This native way is no different from writing SQL directly. Although it can achieve the function, it wastes the advantages of JPA's simplicity and simplification of code design.

See another method on the Internet:

List findAll (Specification spec)

FindAll in the repository layer, and then encapsulated in the service layer, get list.size () to deal with the total number of entries.

This avoids writing SQL statements.

After looking at the source code of CrudRepository today, we found that there is a function in the source code of this API:

Method 2 / Returns the number of entities available. * * @ return the number of entities * / long count ()

So he inherited CrudRepository and wrote a demo:

Method 3 Long countByInvestUserId (Long investUserId)

It's all done with one line of code! The effect is the same as method 1.

Use the count counting method in (spring data jpa) jpa

It is very simple to use count counting method in spring data jpa

You can write the method directly in the dao layer.

Int countByUidAndTenementId (String parentUid, String tenementId); at this point, the study on "how to use SpringJPA to implement count (*)" is over. I hope I can solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.