Mybatis SpringBoot integration

Create a SpringBoot project

Here, I choose Spring Initializr in Idea for creation, which can also be created inIO and download it.

Fill in the project name

Check dependencies, Web, JDBC, MyBatis, MySQL

Project created successfully!

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Create a user table

Here, for simplicity, I create the user table in a database named Demo:

Insert three pieces of data:

id	username	age	address
1	Zhang SAN	22	hangzhou
2	Li si	19	Beijing
3	Cathy	33	Shanghai

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The configuration file

Open the application.properties file and do the following:

# port
server.port=8080
# MySQL configuration
spring.datasource.url=jdbc:mysql:///demo? serverTimezone=Asia/Shanghai
spring.datasource.username=root
spring.datasource.password=123456
# MyBatis configuration
mybatis.mapper-locations=classpath:mapper/*.xml
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Or you can configure it with yml, and the effect is the same.

server:
  port: 8080

spring:
  datasource:
    url: jdbc:mysql:///demo? serverTimezone=Asia/Shanghai
    username: root
    password: 123456

mybatis:
  mapper-locations: classpath:mapper/*.xml
  type-aliases-package: com.korilweb.demo_mybatis.entity
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Write the User class

Create an Entity folder and create class user.java:

package com.korilweb.demo_mybatis.entity;

public class User {

    public Integer id;
    public String username;
    public Integer age;
    public String address;


    public Integer getId(a) {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername(a) {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public Integer getAge(a) {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getAddress(a) {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString(a) {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\' ' +
                ", age=" + age +
                ", address='" + address + '\' ' +
                '} '; }}Copy the code

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Write Mapper XML files

Under the Resources folder, create a new folder named mapper that will hold all the XML files

In the mapper folder, create a new file named user-mapper. XML:

      
<! DOCTYPEmapper
        PUBLIC "- / / mybatis.org//DTD Mapper / 3.0 / EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.korilweb.demo_mybatis.dao.UserMapper">

    <select id="selectUserById" resultType="com.korilweb.demo_mybatis.entity.User">
        select id, username, age, address
        from user
        where id = #{id}
    </select>
</mapper>
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Here, the resultType can be shortened to User, but you need to configure one more entry in application.properties:

mybatis.type-aliases-package=com.korilweb.demo_springcloud.entity
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Write the dao layer

Create a new DAO folder and create the interface usermapper.java:

package com.korilweb.demo_mybatis.dao;

import com.korilweb.demo_mybatis.entity.User;
import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface UserMapper {

    User selectUserById(int id);
}
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We annotate the UserMapper with @mapper, but if we add @mapper to each written Mapper, we can instead annotate the startup class with @mapperscan and specify the package path of the Mapper to be scanned in parentheses:

package com.korilweb.demo_mybatis;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@MapperScan("com.korilweb.demo_mybatis.dao") // With this annotation, we don't need to write @mapper for every Mapper
public class DemoMybatisApplication {

    public static void main(String[] args) { SpringApplication.run(DemoMybatisApplication.class, args); }}Copy the code

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Write the service layer

Create a new service folder and create the class userService.java:

package com.korilweb.demo_mybatis.service;

import com.korilweb.demo_mybatis.dao.UserMapper;
import com.korilweb.demo_mybatis.entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserService {

    @Autowired
    private UserMapper userMapper;

    public User findUserById(int id) {
        returnuserMapper.selectUserById(id); }}Copy the code

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Write the test

@Autowired
private UserService userService;

@Test
void findUserByIdTest(a) {
    User userById = userService.findUserById(1);
    System.out.println(userById);
}
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Test results:

User{id=1, username=' zhang3 ', age=22, address=' zhang3 '}Copy the code

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Some other simple function implementation (add, delete, change and check)

Find all Users

Add a method to UserMapper first:

List<User> selectAllUsers(a);
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Then, write the corresponding SQL statement in user-mapper. XML:

<select id="selectAllUsers" resultType="com.korilweb.demo_mybatis.entity.User">
    select id, username, age, address
    from user
</select>
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Finally, call the UserMapper method inside the UserService:

public List<User> findAllUsers(a) {
    return userMapper.selectAllUsers();
}
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Testing:

@Test
void findAllUsersTest(a) {
    List<User> users = userService.findAllUsers();
    for(User user : users) { System.out.println(user); }}Copy the code

Test results:

User{id=1, username=' zhang ', age=22, address=' wang '} User{id=2, username=' li ', age=19, address=' Beijing '} User{id=1, username=' zhang ', age=22, address=' wang '} Username =' wang5 ', age=33, address=' wang5 '}Copy the code

Add a user

UserMapper. Java:

int insertUser(User user);
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user-mapper.xml

<insert id="insertUser" parameterType="com.korilweb.demo_mybatis.entity.User">
    insert into user (username, age, address)
    values (#{username}, #{age}, #{address})
</insert>
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UserService.java

public int addUser(User user) {
    return userMapper.insertUser(user);
}
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Testing:

@Test
void addUserTest(a) {
    User user = new User();
    user.setUsername("Daisy");
    user.setAge(18);
    user.setAddress("Guangzhou");
    int result = userService.addUser(user);
    System.out.println(result);
}
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Test results:

Returns 1, and you can see that the new user has been added to the database

Update a user’s information

UserMapper. Java:

int updateUserInfo(User user);
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User – mapper. XML:

<update id="updateUserInfo" parameterType="com.korilweb.demo_mybatis.entity.User">
    update user
    set username = #{username}, age = #{age}, address = #{address}
    where id = #{id}
</update>
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UserService. Java:

public int changeUserInfo(User user) {
    return userMapper.updateUserInfo(user);
}
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Testing:

@Test
void changeUserInfoTest(a) {
    User user = new User();
    user.setId(1);
    user.setUsername("Zhang Sanfeng");
    user.setAge(88);
    user.setAddress("Fujian");
    int result = userService.changeUserInfo(user);
    System.out.println(result);
}
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Test results:

Returns 1, and you can see in the database that the user information with ID =1 has changed

Deleting a User

UserMapper. Java:

int deleteUserById(int id);
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User – mapper. XML:

<delete id="deleteUserById">
    delete from user
    where id = #{id}
</delete>
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UserService. Java:

public int deleteUserById(int id) {
    return userMapper.deleteUserById(id);
}
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Testing:

@Test
void deleteUserByIdTest(a) {
    int result = userService.deleteUserById(1);
    System.out.println(result);
}
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Test results:

Return 1, and you can see that the data with id=1 is deleted

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code

Code has been uploaded to Gitee:

Gitee.com/ding_jing_h…