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

This article mainly introduces "what is the role of selectKey tags". In daily operation, I believe that many people have doubts about the role of selectKey tags. The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful for you to answer the doubts of "what is the role of selectKey tags?" Next, please follow the editor to study!

1. Why use selectKey

Database primary keys include self-increment and non-self-increment. Sometimes adding a piece of data not only needs to know the success, but may also need this new primary key for the logic behind. At this time, querying the database will be a bit time-consuming and time-consuming. We can use selectKey to help us get the new primary key.

two。 Specific implementation of demo

The easiest steps to query a database

2.1 controller

@ Controller

Public class SelectKeyController {

@ Autowired

SelectKeyServiceImpl selectKeyService

Public Integer String () {

Goods goods = new Goods ()

Goods.setAmount ("100")

Goods.setGname ("braised pork")

Goods.setMid ("666666")

Goods.setPrice ("25")

Int insert = selectKeyService.insert (goods)

System.out.println ("number of successful execution:" + insert)

System.out.println (goods.getId ())

Return goods.getId ()

}

}

2.2 service

@ Service

Public class SelectKeyServiceImpl implements SelectKeyService {

@ Autowired

SelectKeyMapper selectKeyMapper

@ Override

Public int insert (Goods goods) {

Int insert = selectKeyMapper.insert (goods)

Return insert

}

}

2.3 mapper

Public interface SelectKeyMapper {

Int insert (Goods goods)

}

2.4 entity classes (written according to your own database tables)

@ Data

Public class Goods {

/ / self-increasing primary key

Private Integer id

Private String mid

Private String gname

Private String price

Private String amount

Private String imageName

}

3.mapper.xml file

SELECT LAST_INSERT_ID ()

INSERT INTO Goods (MID,GNAME,PRICE,AMOUNT,imageName)

VALUES (# {mid}, # {gname}, # {price}, # {amount}, # {imageName})

SelectKey will put the result of SELECT LASTINSERTID () into the primary key of the incoming model. The attribute name of the primary key in the model corresponding to keyProperty, here is the id in Goods, because it corresponds to the primary key of the database order AFTER means that SELECT LASTINSERTID () executes after insert execution, and BEFORE means that SELECT LASTINSERTID () executes before insert execution, so you can't get the primary key. This is suitable for the type of primary key that is not self-increasing.

At this point, the study of "what is the role of selectKey tags" is over. I hope to be able to 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.