Springboot 2.x has been released for some time, where bloggers use Springboot 2.1.7 to integrate mybatis 3.5.2 and use MySQL 8.0.13 as the database.

1. Import dependency

<!--mysql-->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.13</version>
</dependency>    
<!--mybatis-spring-boot-starter-->
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.1.0</version>
</dependency>

2. Configure the data source in application.properties (this file will be automatically scanned by spring boot)

spring.datasource.url=jdbc:mysql://localhost:3306/test?useSSL=false&serverTimezone=UTC&characterEncoding=utf8
spring.datasource.username=root
spring.datasource.password=*********
#This is used in versions above MySQL 8
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
#mybatis reads all files ending in. xml under the mapper folder in the root directory
mybatis.mapper-locations=classpath:/mapper/*.xml

3. Write controller,service,dao,mapper.xml

AdminController:

package com.gl.pin.web.controller;

import com.gl.pin.service.api.system.entity.AdminEntity;
import com.gl.pin.service.api.system.res.DubboRes;
import com.gl.pin.service.api.system.service.AdminServiceI;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiImplicitParam;
import io.swagger.annotations.ApiOperation;
import io.swagger.annotations.ApiParam;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.MediaType;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

import java.util.ArrayList;
import java.util.List;

/**
 * @Auther: zjk
 * @Date: 2019/9/3
 * @Description:
 */

@ResponseBody
@Controller
@RequestMapping(value = "/admin")
public class AdminController {

    @Autowired
    AdminServiceI adminServiceI;

    @PostMapping(value = "/login")
    public AdminEntity login(@RequestParam(value = "userName") String userName , @RequestParam (value = "password") String password){
         return adminServiceI.login(userName,password);
    }

}

AdminService: (AdminService I self-brain-filling)

package com.gl.pin.service.system.service;

import com.gl.pin.service.api.system.entity.AdminEntity;
import com.gl.pin.service.api.system.res.DubboRes;
import com.gl.pin.service.api.system.service.AdminServiceI;
import com.gl.pin.service.system.dao.AdminDao;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

/**
 * @Auther: zjk
 * @Date: 2019/9/4
 * @Description:
 */
@Service
public class AdminService implements AdminServiceI {

    @Autowired
    AdminDao adminDao;

    @Override
    public AdminEntity login(String userName , String password) {
        return adminDao.login(userName,password);
    }
}

 AdminDao:

package com.gl.pin.service.system.dao;

import com.gl.pin.service.api.system.entity.AdminEntity;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Repository;

/**
 * @Auther: zjk
 * @Date: 2019/9/4
 * @Description:
 */
@Repository
@Mapper
public interface AdminDao {

    /**
     * Administrator login
     * @param userName
     * @param password
     * @return AdminEntity
     */
    AdminEntity login(String userName,String password);
}

Resoures/mapper/AdminDao.xml (mapping file):

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC
        "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.gl.pin.service.system.dao.AdminDao">
    <!--AdminEntity Mapping with columns in the database-->
    <resultMap id="adminDao" type="com.gl.pin.service.api.system.entity.AdminEntity">
        <id property="id" column="a_id"/>
        <result property="userName" column="a_userName"/>
        <result property="password" column="a_password"/>
    </resultMap>

    <!--admin login -->
    <select id="login1" parameterType="java.lang.String" resultMap="adminDao">
        SELECT a_id,a_userName,a_password FROM sys_admin WHERE a_userName=#{userName} AND a_password=#{password}
    </select>
</mapper>

4. How to assemble dao in spring container?

Method 1: Add an annotation @Mapper to the dao interface class

@Repository
@Mapper
public interface AdminDao {

    /**
     * Administrator login
     * @param userName
     * @param password
     * @return AdminEntity
     */
    AdminEntity login(String userName,String password);

}

Method 2: Annotate @MapperScan on spring boot startup class

@SpringBootApplication
@MapperScan("com.gl.pin.service.system.dao")
public class PinServiceSystemApplication {

    public static void main(String[] args) {
        SpringApplication.run(PinServiceSystemApplication.class, args);
    }

}

5. Summary of Error Reporting

1.springboot startup failed - - no interface class was found

Error details:

Description:

Field adminDao in com.gl.pin.service.system.service.AdminService required a bean of type 'com.gl.pin.service.system.dao.AdminDao' that could not be found.

The injection point has the following annotations:
	- @org.springframework.beans.factory.annotation.Autowired(required=true)


Action:

Consider defining a bean of type 'com.gl.pin.service.system.dao.AdminDao' in your configuration.

Solution: Not using @Mapper or @MapperScan, or using it incorrectly (@MapperScan scans the package with the wrong path, etc.)

2. springboot starts successfully and sends an error message - - dao and mapper.xml bindings fail and no corresponding method can be found

Error details:

org.apache.ibatis.binding.BindingException: Invalid bound statement (not found): com.gl.pin.service.system.dao.AdminDao.login

Solutions:

2.1 The package where the Dao interface resides is inconsistent with the namespace in the mapper.xml Mapping File

<mapper namespace="com.gl.pin.service.system.dao.AdminDao">

2.2 There are methods in dao, but not in mapper.xml
2.3 The method name in Dao is different from the id in mapper.xml

<select id="login" parameterType="java.lang.String" resultMap="adminDao">

2.4 mapper.xml file is not parsed at all and needs to be configured in application.properties

#It's better to use "/" and "." in case of multi-level files, there may be problems.
mybatis.mapper-locations=classpath:/mapper/*.xml

springboot integration mybatis is bound to have such and such problems, these errors are summarized as bloggers stepped on the pit, especially posted for your reference.