1.需要的依赖包

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatisplus-spring-boot-starter</artifactId>
    <version>1.0.5</version>
</dependency>
<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus</artifactId>
    <version>2.3</version>
</dependency>
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>1.3.1</version>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-devtools</artifactId>
    <scope>runtime</scope>
</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>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

2.数据源配置

##端口号
server.port=8888

##数据库url
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/mybatisplus?useUnicode=true&allowMultiQueries=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&serverTimezone=UTC
##数据库用户名
spring.datasource.username=root
##数据库密码
spring.datasource.password=123456
##数据库驱动
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

3.数据库脚本

DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `id` bigint(20) NOT NULL COMMENT '主键ID',
  `name` varchar(30) DEFAULT NULL COMMENT '姓名',
  `age` int(11) DEFAULT NULL COMMENT '年龄',
  `email` varchar(50) DEFAULT NULL COMMENT '邮箱',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO `user` VALUES ('1', 'Jone', '25', '[email protected]');
INSERT INTO `user` VALUES ('2', 'Jack', '20', '[email protected]');
INSERT INTO `user` VALUES ('3', 'Tom', '28', '[email protected]');
INSERT INTO `user` VALUES ('4', 'Sandy', '21', '[email protected]');
INSERT INTO `user` VALUES ('5', 'Billie', '24', '[email protected]');

4.实体类User

public class User {
    private Long id;
    private String name;
    private Integer age;
    private String email;

    public User() {
    }

    public User(Long id, String name, Integer age, String email) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.email = 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;
    }

    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;
    }
}

5.创建UserMapper，继承BaseMapper<User>

import com.baomidou.mybatisplus.mapper.BaseMapper;
import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface UserMapper extends BaseMapper<User> {

}

6.写测试类

@RunWith(SpringRunner.class)
@SpringBootTest(classes = DemoApplication.class,webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class DemoApplicationTests {
    @Autowired(required = false)
    private UserMapper userMapper;
    @Test
    public void contextLoads() {
        List<User> users = userMapper.selectList(null);
        for (User user : users) {
            System.out.println(user);
        }
    }

    @Test
    public void testQuery() {
        Map<String,Object> map = new HashMap();
        map.put("name","Jone");
        List<User> users = userMapper.selectByMap(map);
        for (User user : users) {
            System.out.println(user.getName());
        }
    }

    @Test
    public void testInsert() {
        User user = new User(19l, "test", 23, "qq.com");
        Integer insert = userMapper.insert(user);
        System.out.println(insert);
    }

    @Test
    public void testWrapper() {
        EntityWrapper<User> wrapper = new EntityWrapper<>();
        wrapper.eq("name", "Jone");
        wrapper.or();
        wrapper.like("name", "J");
        List<User> users = userMapper.selectList(wrapper);
        for (User user : users) {
            System.out.println(user.getName());
        }
    }

    @Test
    public void testUpdate() {
        EntityWrapper<User> userEntityWrapper = new EntityWrapper<>();
        userEntityWrapper.eq("name", "Jone");
        User user = new User(15l, "test01", 20, "[email protected]");
        Integer update = userMapper.update(user, userEntityWrapper);
        System.out.println(update);
    }

    @Test
    public void testUpdate2() {
        User user = new User(1l, "Jone", 25, "[email protected]");
        Integer integer = userMapper.updateById(user);
        System.out.println(integer);
    }

    @Test
    public void testDelete() {
        Integer integer = userMapper.deleteById(19l);
        System.out.println(integer);
    }
}

运行测试例子就可以进行CRUD操作了