官方网站：https://mybatis.org/mybatis-3/zh_CN/index.html

依赖：

<!-- MyBatis 持久层框架 -->
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>3.0.5</version>
</dependency>

配置：

## MyBatis配置与xml映射
mybatis:
  ## 映射xml
  mapper-locations: classpath:mapper/*.xml 
  configuration:
    ## 日志配置
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
    ## 映射格式转换
    map-underscore-to-camel-case: true

自动映射：

Java：驼峰命名：departmentId

数据库：下划线：department_id

mapper包扫描：

启动类注解：

@MapperScan("com.chang.mapper")

XML基础模版：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="对应mapper接口引用">
    
</mapper>

XML格式：

<select id="selectAll" resultType="com.chang.entity.Employee"> <!--id对应方法名 resultType：结果类型 对应实体类引用-->
    select * from employee
    <where>
        <if test="name!=null">name like concat('%',#{name},'%')</if>
    </where>
</select>
​
<insert id="insert" parameterType="com.chang.entity.Employee"> <!--parameterType：参数类型-->
    insert into `employee` (name,sex,no,age,description,department_id) <!--下划线命名法-->
    values (#{name},#{sex},#{no},#{age},#{description},#{departmentId}) <!--驼峰命名-->
</insert>

注解查询：

@Select("select * from employee where id = #{id}")
Employee selectById(Integer id);

代码模版：

Mapper:

package com.chang.mapper;
​
public interface EmployeeMapper {
}

Service:

package com.chang.service;
​
import org.springframework.stereotype.Service;
​
@Service
public class EmployeeService {
}

分页插件-分页查询：

依赖：

<!--PageHelper 分页插件-->
<dependency>
    <groupId>com.github.pagehelper</groupId>
    <artifactId>pagehelper-spring-boot-starter</artifactId>
    <version>1.4.6</version>
    <exclusions>
       <exclusion>
          <groupId>org.mybatis</groupId>
          <artifactId>mybatis</artifactId>
       </exclusion>
    </exclusions>
</dependency>

代码：

controller：

/**
 * 分页查询数据
 * pageNum: 当前页码
 * pageSize: 每页的个数
 */
@GetMapping("/selectPage")
public Result selectPage(@RequestParam(defaultValue = "1") Integer pageNum,
                         @RequestParam(defaultValue = "10") Integer pageSize){
    PageInfo<Employee> pageInfo = employeeService.selectPage(pageNum, pageSize);
    return Result.success(pageInfo);
}

service：

@Override
public PageInfo<Employee> selectPage(Integer pageNum, Integer pageSize) {
    PageHelper.startPage(pageNum, pageSize);
    List<Employee> list = employeeMapper.selectAll();
    return PageInfo.of(list) ;
}

CRUD：

Controller层：

package com.chang.controller;
​
import com.chang.common.Result;
import com.chang.entity.Employee;
import com.chang.service.EmployeeService;
import com.github.pagehelper.PageInfo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
​
import java.util.List;
​
@RestController
@RequestMapping("/employee")
public class EmployeeController {
​
    @Autowired
    private EmployeeService employeeService;
​
    /**
     * 查询单个数据
     */
    @GetMapping("/selectById/{id}")
    public Result selectById(@PathVariable Integer id){
        Employee employee = employeeService.selectById(id);
        return Result.success(employee);
    }
​
    /**
     * 查询所有的数据
     */
    @GetMapping("/selectAll")
    public Result selectAll(){
        List<Employee> list = employeeService.selectAll();
        return Result.success(list);
    }
​
    /**
     * 分页查询数据
     * pageNum: 当前页码
     * pageSize: 每页的个数
     */
    @GetMapping("/selectPage")
    public Result selectPage(@RequestParam(defaultValue = "1") Integer pageNum,
                             @RequestParam(defaultValue = "10") Integer pageSize){
        PageInfo<Employee> pageInfo = employeeService.selectPage(pageNum, pageSize);
        return Result.success(pageInfo);
    }
​
    /**
     * 新增数据
     */
    @PostMapping("/add")
    public Result add(@RequestBody Employee employee){
        employeeService.add(employee);
        return Result.success();
    }
​
    /**
     * 跟新数据
     */
    @PutMapping("/update")
    public Result update(@RequestBody Employee employee){
        employeeService.update(employee);
        return Result.success();
    }
​
    /**
     * 删除单个数据
     */
    @DeleteMapping("/deleteById/{id}")
    public Result update(@PathVariable Integer id){
        employeeService.deleteById(id);
        return Result.success();
    }
}

ServiceImpl接口：

package com.chang.service.impl;
​
import com.chang.entity.Employee;
import com.github.pagehelper.PageInfo;
​
import java.util.List;
​
public interface EmployeeServiceImpl {
​
    Employee selectById(Integer id);
​
    List<Employee> selectAll();
​
    PageInfo<Employee> selectPage(Integer pageNum, Integer pageSize);
​
    void add(Employee employee);
​
    void update(Employee employee);
​
    void deleteById(Integer id);
}

Service层：

package com.chang.service;
​
import com.chang.entity.Employee;
import com.chang.mapper.EmployeeMapper;
import com.chang.service.impl.EmployeeServiceImpl;
import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
​
import java.util.List;
​
@Service
public class EmployeeService implements EmployeeServiceImpl {
​
    @Autowired
    private EmployeeMapper employeeMapper;
​
    @Override
    public Employee selectById(Integer id) {
        return employeeMapper.selectById(id);
    }
​
    @Override
    public List<Employee> selectAll() {
        //额外业务操作
        return employeeMapper.selectAll();
    }
​
    @Override
    public PageInfo<Employee> selectPage(Integer pageNum, Integer pageSize) {
        PageHelper.startPage(pageNum, pageSize);
        List<Employee> list = employeeMapper.selectAll();
        return PageInfo.of(list) ;
    }
​
    @Override
    public void add(Employee employee) {
        employeeMapper.insert(employee);
    }
​
    @Override
    public void update(Employee employee) {
        employeeMapper.updateById(employee);
    }
​
    @Override
    public void deleteById(Integer id) {
        employeeMapper.deleteById(id);
    }
​
}

Mapper层：

package com.chang.mapper;
​
import com.chang.entity.Employee;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Select;
​
import java.util.List;
​
public interface EmployeeMapper {
​
    List<Employee> selectAll();
​
    @Select("select * from `employee` where id = #{id}")
    Employee selectById(Integer id);
​
    void insert(Employee employee);
​
    void updateById(Employee employee);
​
    @Delete("delete from `employee` where id = #{id}")
    void deleteById(Integer id);
}

XML文件：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.chang.mapper.EmployeeMapper">
​
    <select id="selectAll" resultType="com.chang.entity.Employee">
        select * from employee
    </select>
​
    <insert id="insert" parameterType="com.chang.entity.Employee">
        insert into `employee` (name,sex,no,age,description,department_id)
        values (#{name},#{sex},#{no},#{age},#{description},#{departmentId})
    </insert>
​
    <update id="updateById" parameterType="com.chang.entity.Employee">
        update `employee` set name = #{name},sex = #{sex},no=#{no},age=#{age},
        description=#{description},department_id=#{departmentId}
        where id=#{id}
    </update>
​
</mapper>