1.添加依赖

        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.1</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.18</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/c3p0/c3p0 -->
        <dependency>
            <groupId>c3p0</groupId>
            <artifactId>c3p0</artifactId>
            <version>0.9.1.2</version>
        </dependency>

2.在src/main/resources目录下创建mybatis-config.xml

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE configuration
    PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!-- 配置全局属性 -->
    <settings>
        <!-- 使用jdbc的getGeneratedKeys获取数据库自增主键值 -->
        <setting name="useGeneratedKeys" value="true" />

        <!-- 使用列标签替换列别名 默认:true -->
        <setting name="useColumnLabel" value="true" />

        <!-- 开启驼峰命名转换:Table{create_time} -> Entity{createTime} -->
        <setting name="mapUnderscoreToCamelCase" value="true" />
    </settings>
</configuration>

3.在application.properties文件中添加如下配置

#配置数据源
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.url=jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf8&useSSL=false&&serverTimezone=UTC
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
#配置mybatis
mybatis.config-location=classpath:mybatis-config.xml
mybatis.mapper-locations=classpath:/mapper/**/*.xml
mybatis.type-aliases-package=com.demo.entity