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This article is about how MyBatis implements the function of adding, deleting, changing and querying a single table through xml configuration files. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

Introduction to Mybatis

Official website link: https://mybatis.org/mybatis-3/zh/index.html. More detailed information can be found on the official website.

MyBatis is an excellent persistence layer framework that supports custom SQL, stored procedures, and advanced mapping. MyBatis eliminates almost all the JDBC code and the work of setting parameters and getting result sets. MyBatis can configure and map primitive types, interfaces, and Java POJO (Plain Old Java Objects, plain old Java objects) to records in the database through simple XML or annotations.

To use MyBatis, simply place the mybatis-x.x.x.jar file in the classpath (classpath).

If you use Maven to build the project, you need to put the following dependent code in the pom.xml file:

Org.mybatis mybatis x.x.x configuration steps

1. Introducing the jar package of Mybatis

two。 Write entity class and DAO interface

3. Add main configuration file (configure mysql environment, transaction type, data source, basic information about connection database, location of mapping file)

4. Add a mapping file for the DAO interface (you need to specify the location of the DAO interface and make a mapping for each method) Note: the path is under the Resource folder, and the directory path needs the same hierarchical structure of DAO.

5. Use the mybatis framework

Use steps (all xml configurations have been configured)

1. Read the configuration file, using the Resources class encapsulated by mybatis.

two。 Create a SQLSessionFactory factory

3. Use a factory to produce SQLsession objects

4. Using SQLSession to create a proxy object for the DAO interface

5. Use proxy objects to execute methods

6. Commit transactions and release resources

Why should the basic data entity class public class User implements Serializable {/ * Java entity class implement Serializable interface * 1. For serialization and deserialization-- only if a class implements the Serializable interface can its objects be serialized. * 2.Serializable API is the mechanism that Java provides for efficient remote sharing of instance objects. You can implement this API. * / private Integer id; private String username; private Date birthday; private String sex; private String address; public Integer getId () {return id;} public void setId (Integer id) {this.id = id;} public String getUsername () {return username;} public void setUsername (String username) {this.username = username } public Date getBirthday () {return birthday;} public void setBirthday (Date birthday) {this.birthday = birthday;} public String getSex () {return sex;} public void setSex (String sex) {this.sex = sex;} public String getAddress () {return address;} public void setAddress (String address) {this.address = address } @ Override public String toString () {return "User {" + "id=" + id + ", username='" + username +''+ ", birthday=" + birthday + ", sex='" + sex +''+ ", address='" + address +''+'}' } DAO layer interface public interface IUserDao {/ * query all User information of * @ return * / / @ Select ("select * from User") List findAll (); / * * Save operation * @ param user * / / @ Insert ("insert into User (username,address,sex,birthday) values ()") void saveUser (User user) / * change operation * / void updateUser (User user); / * * delete operation * @ param I * / void deleteUser (Integer I); / * * query a single user according to id * @ param id * @ return * / User findById (Integer id) / * * Fuzzy query by name * @ param name * @ return * / List findByName (String name); / * * query total number of users * @ return * / int findTotal () } main profile subprofile Select * from user insert into user (username Address,sex,birthday) values (# {username}, # {address}, # {sex}, # {birthday}) Update user set username=# {username}, address=# {address}, sex=# {sex}, birthday=# {birthday} where id=# {id} delete from User where id=# {id} select * from user where id=# {id} select * from user where username like # {name} SELECT COUNT (id) FROM `user` Test class / * * @ Author: Promsing * @ Date: 2021-3-29-8:58 * @ Description: description * @ version: 1.0 * / public class MyBatisTest {private InputStream in; private SqlSession sqlSession; private IUserDao userDao; @ Before public void init () throws Exception {/ / 1. The read configuration file Resources is the class in= Resources.getResourceAsStream ("SqlMapConfig.xml") encapsulated by myBatis; / / 2. Create a SQLSessionFactory factory / / SqlSessionFactory factory=new SqlSessionFactoryBuilder (). Build (is); SqlSessionFactoryBuilder builder=new SqlSessionFactoryBuilder (); SqlSessionFactory factory=builder.build (in); / / 3. Use the factory to produce SQLSession objects sqlSession = factory.openSession (); / / 4. Use SQLSession to create a proxy object for the DAO interface userDao = sqlSession.getMapper (IUserDao.class);} @ After public void destory () throws Exception {/ / 6. Release resource / / commit transaction sqlSession.commit (); sqlSession.close (); in.close ();} / / getting started / * query operation * / @ Test public void selectUser () {/ / initialize the resource-use the note Before / / 5. Use the proxy object execution method List all = userDao.findAll (); for (User user: all) {System.out.println (user);} / / release resources-use annotations After} / * Test Save * / @ Test public void testSave () {User user=new User (); user.setUsername ("mybatis") User.setAddress ("Yanqing District of Beijing"); user.setSex ("female"); user.setBirthday (new Date ()); / / initialize resources-use note Before / / 5. Use proxy object execution method userDao.saveUser (user); / / release resources-use annotations After} / * test modification * / @ Test public void testUpdate () {User user=new User (); user.setId (50); user.setUsername ("mybatis_plus"); user.setAddress ("Beijing Anji") User.setSex ("male"); user.setBirthday (new Date ()); / / initialize resources-use note Before / / 5. Use the proxy object execution method userDao.updateUser (user); / / release resources-use note After} / * test delete * / @ Test public void testDelete () {/ / initialize resources-use note Before / / 5. Use proxy object to execute method userDao.deleteUser (50); / / release resources-use note After} / * query individual personnel information * / @ Test public void testFindById () {/ / initialize resources-use note Before / / 5. Use proxy object execution method User user=userDao.findById (49); System.out.println (user); / / release resources-use annotation After} / * fuzzy query * / @ Test public void testFindByName () {/ / initialize resources-use annotation Before / / 5. Use proxy object execution method List users=userDao.findByName ("% king%"); users.forEach (I-> System.out.println (I)); / / release resources-use annotation After} / * test query total number of records * / @ Test public void testFindTotal () {/ / initialize resources-use annotation Before / / 5. Use the proxy object execution method int total=userDao.findTotal (); System.out.println (total); / / release resources-use annotations After}} Thank you for reading! 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