mybatis-plus如何实现

根据提供的引用内容，MyBatis-Plus的实现流程如下：

1. 引入MyBatis-Plus依赖，可以通过Maven方式引入，例如：

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.4.3.1</version>
</dependency>

2. 配置MyBatis-Plus，可以在application.yml或application.properties文件中添加如下配置：

mybatis-plus:
  # mapper文件位置
  mapper-locations: classpath:/mapper/*.xml
  # 实体类包名
  typeAliasesPackage: com.example.entity

3. 创建实体类，可以使用Lombok注解简化代码，例如：

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private Long id;
    private String name;
    private Integer age;
    private String email;
}

4. 创建Mapper接口，可以继承MyBatis-Plus提供的BaseMapper接口，例如：

public interface UserMapper extends BaseMapper<User> {
}

5. 创建Mapper.xml文件，可以使用MyBatis-Plus提供的自动填充功能，例如：

<mapper namespace="com.example.mapper.UserMapper">
    <resultMap id="BaseResultMap" type="com.example.entity.User">
        <id column="id" property="id" />
        <result column="name" property="name" />
        <result column="age" property="age" />
        <result column="email" property="email" />
    </resultMap>

    <sql id="Base_Column_List">
        id, name, age, email
    </sql>

    <insert id="insert" parameterType="com.example.entity.User">
        <selectKey keyProperty="id" resultType="java.lang.Long" order="BEFORE">
            SELECT IFNULL(MAX(id), 0) + 1 FROM user
        </selectKey>
        INSERT INTO user (id, name, age, email)
        VALUES (#{id}, #{name}, #{age}, #{email})
    </insert>

    <update id="updateById" parameterType="com.example.entity.User">
        UPDATE user
        SET name = #{name}, age = #{age}, email = #{email}
        WHERE id = #{id}
    </update>

    <select id="selectById" resultMap="BaseResultMap" parameterType="java.lang.Long">
        SELECT <include refid="Base_Column_List" />
        FROM user
        WHERE id = #{id}
    </select>

    <delete id="deleteById" parameterType="java.lang.Long">
        DELETE FROM user
        WHERE id = #{id}
    </delete>

    <select id="selectList" resultMap="BaseResultMap">
        SELECT <include refid="Base_Column_List" />
        FROM user
    </select>
</mapper>

6. 在Service中调用Mapper接口，例如：

@Service
public class UserServiceImpl implements UserService {
    @Autowired
    private UserMapper userMapper;

    @Override
    public User getById(Long id) {
        return userMapper.selectById(id);
    }

    @Override
    public List<User> list() {
        return userMapper.selectList(null);
    }

    @Override
    public boolean save(User user) {
        return userMapper.insert(user) > 0;
    }

    @Override
    public boolean updateById(User user) {
        return userMapper.updateById(user) > 0;
    }

    @Override
    public boolean removeById(Long id) {
        return userMapper.deleteById(id) > 0;
    }
}