CREATE TABLE user_info
(
	id BIGINT(20) NOT NULL COMMENT '主键ID',
	name VARCHAR(30) NULL DEFAULT NULL COMMENT '姓名',
	age INT(11) NULL DEFAULT NULL COMMENT '年龄',
	email VARCHAR(50) NULL DEFAULT NULL COMMENT '邮箱',
	PRIMARY KEY (id)
);

插入数据

INSERT INTO user_info (id, name, age, email) VALUES
(1, 'Jone', 18, '[email protected]'),
(2, 'Jack', 20, '[email protected]'),
(3, 'Tom', 28, '[email protected]'),
(4, 'Sandy', 21, '[email protected]'),
(5, 'Billie', 24, '[email protected]');

步骤：
1.创建一个springboot项目：

完成后未改动的pom文件如下

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>mybatis_demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>mybatis_demo</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.7.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.2</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>


</project>

2 修改pom文件

1 首先咱们建立工程用的sping boot为2.0.7 .从我的截图和pom文件上看出

因为笔者建立工程时spring boot包一直拉不下来所以版本改为2.0.3.RELEASE

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

2 因为我用的mysql为8的版本，所以修改一下mysql的依赖版本

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.13</version>
            <scope>runtime</scope>
        </dependency>

3 mybatis.generator 插件

依赖

        <dependency>
            <groupId>org.mybatis.generator</groupId>
            <artifactId>mybatis-generator-core</artifactId>
            <version>1.3.7</version>
        </dependency>

插件

           <!-- mybatis generator 自动生成代码插件 -->
            <plugin>
                <groupId>org.mybatis.generator</groupId>
                <artifactId>mybatis-generator-maven-plugin</artifactId>
                <version>1.3.2</version>
                <configuration>
                    <configurationFile>${basedir}/src/main/resources/generator/generatorConfig.xml</configurationFile>
                    <overwrite>true</overwrite>
                    <verbose>true</verbose>
                </configuration>
            </plugin>

完成后刷新一下pom

工程目录如下

3、application添加相关配置

本案例不使用application.properties文件而使用更加简洁的application.yml文件。
将resource文件夹下原有的application.properties文件改为application.yml
（备注：其实SpringBoot底层会把application.yml文件解析为application.properties），文件的内容如下(此处只配置最基本的)

server:
  port: 8080

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT
    username: root
    password: 12345678
mybatis:
  mapper-locations: classpath:mapping/*Mapper.xml
  type-aliases-package: com.example.mybatis_demo.po

springboot会自动加载spring.datasource.*相关配置，数据源就会自动注入到sqlSessionFactory中，sqlSessionFactory会自动注入到Mapper中，对于开发人员不用管，直接拿来使用即可。

4 配置mybatis generator 自动生成代码插件

配置pom.xml中generator 插件所对应的配置文件

${basedir}/src/main/resources/generator/generatorConfig.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration
        PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
<generatorConfiguration>
    <!-- 数据库驱动:选择你的本地硬盘上面的数据库驱动包-->
    <classPathEntry  location="F:\repository\mysql\mysql-connector-java\8.0.13\mysql-connector-java-8.0.13.jar"/>
    <context id="DB2Tables"  targetRuntime="MyBatis3">
        <commentGenerator>
            <property name="suppressDate" value="true"/>
            <!-- 是否去除自动生成的注释 true：是 ： false:否 -->
            <property name="suppressAllComments" value="true"/>
        </commentGenerator>
        <!--数据库链接URL，用户名、密码 -->
        <jdbcConnection driverClass="com.mysql.cj.jdbc.Driver" connectionURL="jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&amp;characterEncoding=utf8&amp;serverTimezone=GMT" userId="root" password="12345678">
        </jdbcConnection>
        <javaTypeResolver>
            <property name="forceBigDecimals" value="false"/>
        </javaTypeResolver>
        <!-- 生成模型的包名和位置-->
        <javaModelGenerator targetPackage="com.example.mybatis_demo.po" targetProject="src/main/java">
            <property name="enableSubPackages" value="true"/>
            <property name="trimStrings" value="true"/>
        </javaModelGenerator>
        <!-- 生成映射文件的包名和位置-->
        <sqlMapGenerator targetPackage="mapping" targetProject="src/main/resources">
            <property name="enableSubPackages" value="true"/>
        </sqlMapGenerator>
        <!-- 生成DAO的包名和位置-->
        <javaClientGenerator type="XMLMAPPER" targetPackage="com.example.mybatis_demo.mapper" targetProject="src/main/java">
            <property name="enableSubPackages" value="true"/>
        </javaClientGenerator>
        <!-- 要生成的表 tableName是数据库中的表名或视图名 domainObjectName是实体类名-->
        <table tableName="user_info" domainObjectName="User" enableCountByExample="false" enableUpdateByExample="false" enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false"></table>
    </context>
</generatorConfiguration>

注意 1

generatorConfig.xml的头文件http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd标红原因：缺少mybatis-generator-core.jar

https://blog.csdn.net/qq_36688143/article/details/82014889

MyBatis Generator http://www.mybatis.org/generator/index.html

MyBatis GeneratorXML Configuration File Referencehttp://www.mybatis.org/generator/configreference/xmlconfig.html

Dependency Information http://www.mybatis.org/generator/dependency-info.html

注意2

这里jdbc连接处的connectionURL为

而不是

mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT

主要是因为XML中&为转义符的原因

下面是五个在XML文件中预定义好的实体：

<	<	小于号
>	>	大于号
&	&	和
'	’	单引号
"	"	双引号

实体必须以符号"&"开头，以符号";"结尾。

注意: 只有"<" 字符和"&"字符对于XML来说是严格禁止使用的。剩下的都是合法的，为了减少出错，使用实体是个好习惯。

https://blog.csdn.net/teedry/article/details/5816687

自动生成代码

点击run----> Edit Configurations

从上往下我依次贴一下自动生成的代码

public interface UserMapper {
    int deleteByPrimaryKey(Long id);

    int insert(User record);

    int insertSelective(User record);

    User selectByPrimaryKey(Long id);

    int updateByPrimaryKeySelective(User record);

    int updateByPrimaryKey(User record);
}

public class User {
    private Long id;

    private String name;

    private Integer age;

    private String email;

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name == null ? null : name.trim();
    }

    public Integer getAge() {
        return age;
    }

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

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email == null ? null : email.trim();
    }
}

<?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.example.mybatis_demo.mapper.UserMapper" >
  <resultMap id="BaseResultMap" type="com.example.mybatis_demo.po.User" >
    <id column="id" property="id" jdbcType="BIGINT" />
    <result column="name" property="name" jdbcType="VARCHAR" />
    <result column="age" property="age" jdbcType="INTEGER" />
    <result column="email" property="email" jdbcType="VARCHAR" />
  </resultMap>
  <sql id="Base_Column_List" >
    id, name, age, email
  </sql>
  <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Long" >
    select 
    <include refid="Base_Column_List" />
    from user_info
    where id = #{id,jdbcType=BIGINT}
  </select>
  <delete id="deleteByPrimaryKey" parameterType="java.lang.Long" >
    delete from user_info
    where id = #{id,jdbcType=BIGINT}
  </delete>
  <insert id="insert" parameterType="com.example.mybatis_demo.po.User" >
    insert into user_info (id, name, age, 
      email)
    values (#{id,jdbcType=BIGINT}, #{name,jdbcType=VARCHAR}, #{age,jdbcType=INTEGER}, 
      #{email,jdbcType=VARCHAR})
  </insert>
  <insert id="insertSelective" parameterType="com.example.mybatis_demo.po.User" >
    insert into user_info
    <trim prefix="(" suffix=")" suffixOverrides="," >
      <if test="id != null" >
        id,
      </if>
      <if test="name != null" >
        name,
      </if>
      <if test="age != null" >
        age,
      </if>
      <if test="email != null" >
        email,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides="," >
      <if test="id != null" >
        #{id,jdbcType=BIGINT},
      </if>
      <if test="name != null" >
        #{name,jdbcType=VARCHAR},
      </if>
      <if test="age != null" >
        #{age,jdbcType=INTEGER},
      </if>
      <if test="email != null" >
        #{email,jdbcType=VARCHAR},
      </if>
    </trim>
  </insert>
  <update id="updateByPrimaryKeySelective" parameterType="com.example.mybatis_demo.po.User" >
    update user_info
    <set >
      <if test="name != null" >
        name = #{name,jdbcType=VARCHAR},
      </if>
      <if test="age != null" >
        age = #{age,jdbcType=INTEGER},
      </if>
      <if test="email != null" >
        email = #{email,jdbcType=VARCHAR},
      </if>
    </set>
    where id = #{id,jdbcType=BIGINT}
  </update>
  <update id="updateByPrimaryKey" parameterType="com.example.mybatis_demo.po.User" >
    update user_info
    set name = #{name,jdbcType=VARCHAR},
      age = #{age,jdbcType=INTEGER},
      email = #{email,jdbcType=VARCHAR}
    where id = #{id,jdbcType=BIGINT}
  </update>
</mapper>

5. SpringBoot启动类加注解@MapperScan

@SpringBootApplication
@MapperScan("com.example.mybatis_demo.mapper")
public class MybatisDemoApplication {

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

6 测试

就测试一下删除

@RunWith(SpringRunner.class)
@SpringBootTest
public class MybatisDemoApplicationTests {

    @Autowired
    private UserMapper userMapper;
    @Test
    public void contextLoads() {
    }

    @Test
    public void testDelete(){
        int i = userMapper.deleteByPrimaryKey((long) 1);
        System.out.println(i);
        assert(i==1);
    }

}