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Editor to share with you what the return types of resultType and resultMap in MyBatis are, I believe most people do not know much about it, so share this article for your reference, I hope you will learn a lot after reading this article, let's go to know it!

First, return the collection 1. Returns the JavaBean collection public List selectMyUserByNameLike (String name); select * from myuser where name like # {name}

Testing method

Public static void main (String [] args) {SqlSession session = null; try {InputStream inputStream = Resources.getResourceAsStream ("mybatis-config.xml"); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder () .build (inputStream); session = sqlSessionFactory.openSession (); MyUserMapper mapper = session.getMapper (MyUserMapper.class); List myUsers = mapper.selectMyUserByNameLike ("% a%"); System.out.println (myUsers) } catch (IOException e) {e.printStackTrace ();} finally {if (session! = null) {session.close ();}

two。 Returns the Map collection select * from myuser

Second, return Map1. A record public Map selectMyUserById (Integer id); select * from myuser where id = # {id}

two。 Multiple records, need to specify the Key of Map and the type of Value / / specify the Key of Map to get @ MapKey ("id") public Map selectMyUserByGtId (Integer id) from the id column in the record; select * from myuser where id > # {id}

3. Return resultMap custom result set encapsulation

About the configuration of automatic mapping encapsulation

If the default database field does not correspond to JavaBean, you can turn on hump naming or use alias http://www.mybatis.org/mybatis-3/zh/sqlmap-xml.html when querying.

1. Custom JavaBean encapsulation

Confirm whether the automatic mapping of MyBatis can be turned off.

Public MyUser selectMyUserById (Integer id); select * from myuser where id = # {id}

two。 Encapsulation of associated queries, one-to-one, the JavaBean attribute contains JavaBean

Public MyUser selectMyUserById (Integer id)

Directly call attribute assignment

SELECT m.id, m.name, m.age, m.did, d.name AS dname FROM myuser mfocus dept d WHERE m.did = d.id AND m.id = # {id}

Use association

SELECT m.id, m.name, m.age, m.did, d.name AS dname FROM myuser mfocus dept d WHERE m.did = d.id AND m.id = # {id}

Use association for a second query, that is, there are two SQL

SELECT * FROM myuser WHERE id = # {id} select * from dept where id = # {id}

Turn on lazy loading: when the properties of Dept are not used, only the properties of MyUser are loaded. That is, only one SQL statement will be sent, and the second SQL will only be sent when the Dept attribute is used. Will not send two SQL at once

3. Encapsulation of associated queries, one-to-many, the JavaBean attribute contains a collection of JavaBean

Use association

Public Dept getDeptById (Integer id); SELECT m.idrect m.namememe m.agerecoverym.didnoted.name AS dname FROM myuser mdept d WHERE m.did = d.id AND d.id = # {id}

Turn off lazy loading and use secondary query

Public Dept getDeptByIdStep (Integer did); select * from dept where id = # {id} public List selectMyUserByDid (Integer dId); select * from myuser where dId = # {did}

4. Discriminator discriminator SELECT * FROM myuser WHERE id = # {id} select * from dept where id = # {id}

Entity classes and data used in the above test

Public class Dept {private Integer id; private String name; private List myUsers;public class MyUser {private Integer id; private String name; private Integer age; private Dept dept

The above is all the content of the article "what are the return types of resultType and resultMap in MyBatis". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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