MyBatis Plus最底层的就是封装工具代码，具有以下功能：

1.根据数据库的表动态生成对应mapper层、service层、controller层代码

2.mapper层代码自动带有对应的表单的接口方法，并且底层根据实体类来逆向生成对应的基本sql语句，除了复杂的sql歪，无需声明mapper配置文件

3.service层的代码自动带有对应的基本业务操作

4.controller层的代码创建对应的控制器类

5.pojo层自动生成表对应的实体类

开发环境的搭建：

1.导包：在原有SSM的jar包的基础上增加了MyBatisPlus的jar即可

2.开发：结构大概是这样的：

  例子：查看数据

entity：
package com.bornwon.iot.web.modules.acs.entity;

import com.baomidou.mybatisplus.annotation.TableName;
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;

import java.time.LocalDateTime;
import java.io.Serializable;

import com.baomidou.mybatisplus.extension.activerecord.Model;
import lombok.Data;
import io.swagger.annotations.ApiModel;
import io.swagger.annotations.ApiModelProperty;

/**
 * 实体类
 *
 * @author Fw
 * @since 2020-07-17
 */
@Data
@TableName("t_gate_user")
@ApiModel(value = "GateUser对象", description = "GateUser对象")
public class GateUser extends Model<GateUser> implements Serializable{

    private static final long serialVersionUID = 1L;

    /**
     * 主键
     */
    @ApiModelProperty(value = "主键")
    @TableId(value = "id", type = IdType.AUTO)
    private Integer id;
   
    /**
     * 用户id
     */
    @ApiModelProperty(value = "用户id")
    private Integer userId;
    /**
     * 用户名
     */
    @ApiModelProperty(value = "用户名")
    private String name;
    /**
     * 用户角色 0普通用户 3超级管理员
     */
    @ApiModelProperty(value = "用户角色 0普通用户 3超级管理员")
    private Integer role;
    /**
     * 指纹数据
     */
    @ApiModelProperty(value = "指纹数据")
    private byte[] fingerData;

    /**
     * 是否已删除
     */
    @ApiModelProperty(value = "是否已删除")
    private Integer isDeleted;

    @Override
    protected Serializable pkVal() {
        return this.id;
    }

    public static long getSerialVersionUID() {
        return serialVersionUID;
    }

    public Integer getId() {
        return id;
    }

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

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }


    public byte[] getFingerData() {
        return fingerData;
    }

    public void setFingerData(byte[] fingerData) {
        this.fingerData = fingerData;
    }

    public Integer getIsDeleted() {
        return isDeleted;
    }

    public void setIsDeleted(Integer isDeleted) {
        this.isDeleted = isDeleted;
    }
}

mapper目录中有两个文件：mapper.xml ,mapper接口

<?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.bornwon.iot.web.modules.acs.mapper.GateUserMapper">

    <!-- 通用查询映射结果 -->
    <resultMap id="gateUserResultMap" type="com.bornwon.iot.web.modules.acs.entity.GateUser">
        <id column="id" property="id"/>
        <result column="user_id" property="userId"/>
        <result column="name" property="name"/>
        <!-- 数据库中字段类型为Blob,所以这里必须加上BlobTypeHandler进行处理 -->
        <result column="finger_data" property="fingerData" typeHandler="org.apache.ibatis.type.BlobTypeHandler"/>
        <result column="is_deleted" property="isDeleted"/>
    </resultMap>

    <!-- 查询 -->
    <select id="selectGateUserPage" resultMap="gateUserResultMap">
        select id,user_id,`name`,finger_data from t_gate_user where is_deleted = 0
    <!-- 如果需要参数 -->        
    <if test="id != null">
            and id = #{id}
        </if>
    </select>

    <!-- 添加,类型为Blob =》 添加typeHandler -->
    <insert id="addGateUser" parameterType="com.bornwon.iot.web.modules.acs.entity.GateUser">
        insert into t_gate_user(`name`,user_id,finger_data)
        values (#{name},#{userId},{fingerData,typeHandler=org.apache.ibatis.type.BlobTypeHandler})
    </insert>
</mapper>

----------------------------------------------------------------------------------------

mapper接口：
public interface GateUserMapper extends BaseMapper<GateUser> {

	List<GateUserVO> selectGateUserPage(IPage page, GateUserVO gateUser,Integer equipId);

	boolean addGateUser(GateUser user);

}

service也是分为service与service接口：

public interface IGateUserService extends IService<GateUser> {

	IPage<GateUserVO> selectGateUserPage(IPage<GateUserVO> page, GateUserVO gateUser,Integer id);

    boolean addGateUser(String userArray,String siteKey,Integer equipId);

}

-------------------------------------------------------------------------------------

public class UserServiceImpl extends ServiceImpl<GateUserMapper, GateUser> implements IGateUserService {

    @Override
	public IPage<GateUserVO> selectGateUserPage(IPage<GateUserVO> page, GateUserVO gateUser,Integer equipId) {
		return page.setRecords(baseMapper.selectGateUserPage(page, gateUser,id));
	}

    @Override
	public boolean addGateUser(GateUser user) {
        //返回添加的状态
		return R.status(baseMapper.addGateUser(gateUser));
	}
}

最后是controller：

@RestController
@AllArgsConstructor
@RequestMapping("/devops/acs")
@Api(value = "", tags = "接口")
public class GateUserController extends BaseController {

    private IGateUserService gateUserService;

    /**
     * 详情
     */
    @GetMapping("/detail")
    @ApiOperationSupport(order = 1)
    @ApiOperation(value = "详情", notes = "传入gateUser")
    public R<GateUserVO> detail(GateUser gateUser) {
        GateUser detail = gateUserService.getOne(Condition.getQueryWrapper(gateUser));
        return R.data(GateUserWrapper.build().entityVO(detail));
    }

    @GetMapping("/list")
    @ApiOperationSupport(order = 2)
    @ApiOperation(value = "分页", notes = "传入gateUser")
    public R<IPage<GateUserVO>> list(GateUserVO gateUser, Query query) {
        return R.data(gateUserService.selectGateUserPage(Condition.getPage(query), gateUser,id));
    }


    /**
     * 新增
     */
    @PostMapping("/save")
    @ApiOperationSupport(order = 4)
    @ApiOperation(value = "新增", notes = "传入gateUser")
    public R save(@Valid @RequestBody GateUser gateUser) {
        return R.status(gateUserService.addGateUser(gateUser));
    }

    /**
     * 修改
     */
    @PostMapping("/update")
    @ApiOperationSupport(order = 5)
    @ApiOperation(value = "修改", notes = "传入gateUser")
    public R update(@Valid @RequestBody GateUser gateUser) {
        return R.status(gateUserService.updateById(gateUser));
    }

    /**
     * 新增或修改
     */
    @PostMapping("/submit")
    @ApiOperationSupport(order = 6)
    @ApiOperation(value = "新增或修改", notes = "传入gateUser")
    public R submit(@Valid @RequestBody GateUser gateUser) {
        return R.status(gateUserService.saveOrUpdate(gateUser));
    }


    /**
     * 删除
     */
    @PostMapping("/remove")
    @ApiOperationSupport(order = 8)
    @ApiOperation(value = "删除", notes = "传入ids")
    public R remove(@ApiParam(value = "主键集合", required = true) @RequestParam String ids) {
        return R.status(gateUserService.removeByIds(Func.toIntList(ids)));
    }

}

其中遇到的问题：

数据类型为Blob时，在声明实体类是类型为 byte[]

       插入：fingerData.getBytes();

       取出：(如果需要转换为Blob)  =》fingerData = new String(gateUser.getFingerData(), "UTF-8");