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一、mybtis-plus配置下载
MyBatis-Plus 是一个 Mybatis 增强版工具，在 MyBatis 上扩充了其他功能没有改变其基本功能，为了简化开发提交效率而存在。
具体的介绍请参见官方文档。
官网文档地址：mybatis-plus

1. 添加mybatis-plus依赖

<dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-boot-starter</artifactId><version>3.5.1</version>
</dependency>

2. 添加MyBatisPlusConfig配置文件

config包中添加MyBatisPlusConfig配置文件，将原来在mapper中的@mapper注解取消，继承上BaseMapper泛型接口即可。
Mybatis-Plus里的BaseMapper接口，自带crud功能，继承了BaseMapper接口的接口.。

代码如下：

package com.example.demo.config;import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;@Configuration
@MapperScan("com.example.demo.demos.web.demo.mapper")
public class MyBatisPlusConfig {//配置分页插件@Beanpublic MybatisPlusInterceptor mybatisPlusInterceptor(){MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();//数据库类型是MySql，因此参数填写DbType.MYSQLinterceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));return interceptor;}}

mapper 中如下配置
3. yml 中写如下配置

mybatis-plus:configuration:log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

二、mybtis-plus实现增删改查

1. 数据增加或修改

在这里插入图片描述

结果：
修改：


注意映射表不要瞎加字段否则容易出现异常
Error querying database. Cause: java.sql.SQLSyntaxErrorException: Unknown column ‘page_num’ in ‘field list’

所有代码
config

package com.example.demo.config;import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;@Configuration
@MapperScan("com.example.demo.demos.web.demo.mapper")
public class MyBatisPlusConfig {//配置分页插件@Beanpublic MybatisPlusInterceptor mybatisPlusInterceptor(){MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();//数据库类型是MySql，因此参数填写DbType.MYSQLinterceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));return interceptor;}}

controller

package com.example.demo.demos.web.demo.controller;import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.example.demo.demos.web.demo.entity.UserEntity;
import com.example.demo.demos.web.demo.mapper.UserMapper;
import com.example.demo.demos.web.demo.service.UserService;
import org.apache.ibatis.annotations.Param;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.*;import java.util.HashMap;
import java.util.List;
import java.util.Map;@RestController
@RequestMapping("user")
public class UserController {// @Autowired// private UserMapper userMapper;@Autowiredpublic UserService userService;
/*        @GetMapping("/")public List<UserEntity> index(){return userMapper.findAll();}*///使用mybtis-plus实现查询所有数据@GetMapping("/")public List<UserEntity> findAll(){return userService.list();}/* @PostMapping("/add")//这里做了一个单纯的添加的示例，使用的是mapper中的insert方法public Integer save(@RequestBody UserEntity userEntity){return userService.save(userEntity);}*//*        @DeleteMapping("/{id}")public Integer deleteById(@PathVariable Integer id){return  userService.deleteById(id);}*///使用mybtis-plus实现删除@DeleteMapping("/{id}")public boolean deleteById(@PathVariable Integer id){return  userService.removeById(id);}@PostMapping("/add")//使用mybtis-plus,注意这里返回的是boolean型public Boolean save(@RequestBody UserEntity user) {return userService.saveUser(user);}//分页查询//接口路径user/page?pageNum=1&pageSize=10//RequestParam接受前台传过来的第几页，每页显示数
/*    @GetMapping("/page")public Map<String,Object> findPage(@RequestParam Integer pageNum,@RequestParam Integer pageSize){pageNum=(pageNum-1)*pageSize;List<UserEntity> data=userService.selectPage(pageNum,pageSize);Integer total=userMapper.selectTotal();Map<String,Object> res=new HashMap<>();res.put("data",data);res.put("total",total);return res;}*///使用mybtis-plus实现根据ID查找记录@GetMapping("/{id}")public UserEntity findOne(@PathVariable Integer id){return userService.getById(id);}//使用mybtis-plus实现模糊查询并分页@GetMapping("/page")public IPage<UserEntity> findPage(@RequestParam Integer pageNum,@RequestParam Integer pageSize,@RequestParam(defaultValue = "") String username,@RequestParam(defaultValue = "") String nickname,@RequestParam(defaultValue = "") String address){IPage<UserEntity> page=new Page<>(pageNum,pageSize);QueryWrapper<UserEntity> queryWrapper=new QueryWrapper<>();queryWrapper.like("username",username);queryWrapper.like("nickname",nickname);queryWrapper.like("address",address);return userService.page(page,queryWrapper);}}

entity

package com.example.demo.demos.web.demo.entity;import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;@Data
@NoArgsConstructor
@AllArgsConstructor
@TableName(value="sys_user")
public class UserEntity {@TableId(value = "id",type = IdType.AUTO)private Integer id;
/*    private Integer pageNum;private Integer pageSize;*/private String username;private String password;private String email;private String phone;private String nickname;private String address;private String create_time;private String avatar;private String role;}

mapper

package com.example.demo.demos.web.demo.mapper;import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.demo.demos.web.demo.entity.UserEntity;
import org.apache.ibatis.annotations.*;import java.util.List;//@Mapper 前面配置文件中已经配置 这个注解可以注销但是要继承接口
public interface UserMapper extends BaseMapper<UserEntity> {/*   @Select("select * from sys_user limit #{pageNum},#{pageSize}")List<UserEntity> selectPage(@Param("pageNum") Integer pageNum,@Param("pageSize")  Integer pageSize);//@Select("select * from sys_user limit #{pageNum},#{pageSize}")@Select("select * from sys_user")List<UserEntity> findAll();@Insert("insert into sys_user(username,password,email,phone,nickname,address,avatar,role) " +"VALUES(#{username},#{password},#{email},#{phone},#{nickname},#{address},#{avatar},#{role});")//这里只是做测试使用int insert(UserEntity userEntity);int update(UserEntity userEntity);@Delete("delete from sys_user where id=#{id}")int deleteById(@Param("id") Integer id);*/// 记录总数/* @Select("select count(*) from sys_user")Integer selectTotal();
*/}

service

package com.example.demo.demos.web.demo.service;import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.example.demo.demos.web.demo.entity.UserEntity;
import com.example.demo.demos.web.demo.mapper.UserMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;import java.util.List;@Service
public class UserService extends ServiceImpl<UserMapper, UserEntity> {// @Autowired// private UserMapper userMapper;/* public int save(UserEntity userEntity){//如果user没有id则表明是新增if(userEntity.getId()==null){return userMapper.insert(userEntity);}//否则就是更新else {return userMapper.update(userEntity);}}*/public Boolean saveUser(UserEntity userEntity){return saveOrUpdate(userEntity);}/* public Integer deleteById(Integer id) {return userMapper.deleteById(id);}*/// 分页查找/* public List selectPage(Integer pageNum, Integer pageSize) {return userMapper.selectPage(pageNum,pageSize);}*/}

项目架构