SpringBoot整合Mybatis Plus实现基本CRUD的示例代码

目录

• 一、引入相应的依赖
• 二、进行配置
• 三、新建数据库表
• 四、配置 Mybatis Plus 自动填充
• 五、实现User实体类、UserMapper、UserService
• 六、使用Restful风格实现CRUD功能

对数据库的操作是我们公司中必不可少的功能，Mybatis Plus是在Mybatis的基础上的增强，使得我们对一些基本的CRUD使用起来更方便等，这篇文章主要讲讲SpringBoot如何去整合Mybatis Plus，并实现基本的CRUD功能。

一、引入相应的依赖

<dependency>
  <groupId>com.baomidou</groupId>
  <artifactId>mybatis-plus-boot-starter</artifactId>
  <version>3.5.3.1</version>
</dependency>
<dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <version>8.0.32</version>
</dependency>

引入mybatis-plus的依赖和mysql驱动的依赖。

二、进行配置

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/mydb?characterEncoding=utf-8&serverTimeZone=UTC
    username: root
    password: 123456
    driver-class-name: com.mysql.cj.jdbc.Driver
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  global-config:
    db-config:
      id-type: auto
      logic-delete-field: deleted
      logic-delete-value: 1
      logic-not-delete-value: 0

spring.datasource是对数据库的链接信息的配置

mybatis-plus:

• configuration.log-impl: 配置打印sql日志
• id-type: id主键生成策略，auto为自增
• logic-delete-field: 逻辑删除的字段，线上数据库一般要配置逻辑删除
• logic-delete-value: 逻辑删除已删除的值
• logic-not-delete-value: 逻辑删除未删除的值

三、新建数据库表

这里我新建一张简单的user表

sql如下：

DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `username` varchar(255) NOT NULL,
  `age` int(3) NOT NULL,
  `create_time` datetime DEFAULT NULL,
  `update_time` datetime DEFAULT NULL,
  `deleted` int(1) DEFAULT \'0\',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

可以看到表中有一些建表必须的字段create_time、update_time、deleted，前两个字段我们需要在项目中配置一下Mybatis Plus让他在我们新增数据，更新数据时自动插入值，deleted逻辑删除字段因为我们已经在yml中配置了，后续我们都不需要再处理。

四、配置 Mybatis Plus 自动填充

配置 Mybatis Plus 自动填充来实现对create_time、update_time的值自动插入和更新。

• 新建handler.mybatisplus.MyMetaObjectHandler类
• 该类实现MetaObjectHandler接口
• 并重写insertFille和updateFill方法

具体代码实现如下:

handler.mybatisplus.MyMetaObjectHandler:

import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;
import org.apache.ibatis.reflection.MetaObject;
import java.util.Date;
@Component
public class MyMetaObjectHandler implements MetaObjectHandler {
    @Override
    public void insertFill(MetaObject metaObject) {
        setFieldValByName(\"createTime\", new Date(), metaObject);
        setFieldValByName(\"updateTime\", new Date(), metaObject);
    }
    @Override
    public void updateFill(MetaObject metaObject) {
        setFieldValByName(\"updateTime\", new Date(), metaObject);
    }
}

五、实现User实体类、UserMapper、UserService

• User实体类

domain.entity.User：

import com.baomidou.mybatisplus.annotation.FieldFill;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.experimental.Accessors;
import java.util.Date;
@Data
@AllArgsConstructor
@NoArgsConstructor
@Accessors(chain = true)
@TableName(\"user\")
public class User {
    @TableId
    private Long id;
    private String username;
    private Integer age;
    @TableField(fill = FieldFill.INSERT)
    private Date createTime;
    @TableField(fill = FieldFill.INSERT_UPDATE)
    private Date updateTime;
    private Integer deleted;
}

@TableName：指定实体类对应的表名

@TableId：指定为主键，我们配置的是auto，即主键自增策略

@TableField：指定该值使用我们的自动填充策略，INSERT为插入时填充，INSERT_UPDATE为插入和更新时填充

• UserMapper

mapper.UserMapper:

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.jk.domain.entity.User;
import org.apache.ibatis.annotations.Mapper;
@Mapper
public interface UserMapper extends BaseMapper<User> {
}

继承Mybatis Plus提供的BaseMapper，已经实现了一些基本的CRUD接口

• UserService

service.UserService:

public interface UserService {
}

service.impl.UserServiceImpl:

import com.jk.service.UserService;
import org.springframework.stereotype.Service;
@Service
public class UserServiceImpl implements UserService {
}

先把对应的service建好，后面实现controller时再一并实现。

六、使用Restful风格实现CRUD功能

• 前期准备

因为我们需要在查列表时需要使用分页功能，需要配置一下Mybatis Plus分页插件

config.MybatisPlus:

import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class MybatisPlus {
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor mybatisPlusInterceptor = new MybatisPlusInterceptor();
        mybatisPlusInterceptor.addInnerInterceptor(new PaginationInnerInterceptor());
        return mybatisPlusInterceptor;
    }
}

另外因为我们需要在新增和更新时是不需要全部的实体字段，需要创建对应的DTO来接收前端数据，返回时也不需要全部字段，需要对应的Vo对返回前端所需字段

domain.dto.AddUserDto:

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@AllArgsConstructor
@NoArgsConstructor
public class AddUserDto {
    private String username;
    private Integer age;
}

domain.dto.UpdateUserDto:

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@AllArgsConstructor
@NoArgsConstructor
public class UpdateUserDto {
    private Long id;
    private String username;
    private Integer age;
}

domain.vo.UserVo:

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.util.Date;
@Data
@AllArgsConstructor
@NoArgsConstructor
public class UserVo {
    private Long id;
    private String username;
    private Integer age;
    private Date createTime;
}

domain.vo.PageVo:

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.util.List;
@Data
@AllArgsConstructor
@NoArgsConstructor
public class PageVo {
    private List result;
    private Long total;
}

PageVo用来处理所有需要分页数据的响应

关于统一响应大家可以看 SpringBoot 中统一响应格式及统一异常处理，你应该这样做

关于Bean拷贝大家可以看SpringBoot 项目中 Bean 拷贝及工具类封装

• CRUD 对应的controller

controller.UserController:

import com.jk.domain.dto.AddUserDto;
import com.jk.domain.dto.UpdateUserDto;
import com.jk.service.UserService;
import com.jk.domain.vo.ResponseResult;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
@RestController
@RequestMapping(\"/user\")
public class UserController {
    @Autowired
    private UserService userService;
    @PostMapping
    public ResponseResult addUser(@RequestBody AddUserDto addUserDto) {
        return userService.addUser(addUserDto);
    }
    @PutMapping
    public ResponseResult updateUser(@RequestBody UpdateUserDto updateUserDto) {
        return userService.updateUser(updateUserDto);
    }
    @DeleteMapping(\"/{id}\")
    public ResponseResult deleteUser(@PathVariable(\"id\") Long id) {
        return userService.deleteUser(id);
    }
    @GetMapping
    public ResponseResult getUser(@RequestParam(defaultValue = \"1\") Integer pageNum,
                                  @RequestParam(defaultValue = \"10\") Integer pageSize) {
        return userService.getUser(pageNum, pageSize);
    }
}

• CRUD 对应的 service

service.UserService:

import com.jk.domain.dto.AddUserDto;
import com.jk.domain.dto.UpdateUserDto;
import com.jk.domain.vo.ResponseResult;
public interface UserService {
    ResponseResult addUser(AddUserDto addUserDto);
    ResponseResult updateUser(UpdateUserDto updateUserDto);
    ResponseResult deleteUser(Long id);
    ResponseResult getUser(Integer pageNum, Integer pageSize);
}

• CRUD 都应 service实现类

service.impl.UserServiceImpl:

import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.jk.domain.dto.AddUserDto;
import com.jk.domain.dto.UpdateUserDto;
import com.jk.domain.entity.User;
import com.jk.domain.vo.UserVo;
import com.jk.mapper.UserMapper;
import com.jk.service.UserService;
import com.jk.domain.vo.PageVo;
import com.jk.domain.vo.ResponseResult;
import com.jk.utils.BeanCopyUtils;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;
@Service
public class UserServiceImpl implements UserService {
    @Autowired
    private UserMapper userMapper;
    @Override
    public ResponseResult addUser(AddUserDto addUserDto) {
        User user = BeanCopyUtils.copyBean(addUserDto, User.class);
        userMapper.insert(user);
        return ResponseResult.okResult();
    }
    @Override
    public ResponseResult updateUser(UpdateUserDto updateUserDto) {
        User user = new User();
        BeanUtils.copyProperties(updateUserDto, user);
        userMapper.updateById(user);
        return ResponseResult.okResult();
    }
    @Override
    public ResponseResult deleteUser(Long id) {
        userMapper.deleteById(id);
        return ResponseResult.okResult();
    }
    @Override
    public ResponseResult getUser(Integer pageNum, Integer pageSize) {
        Page<User> userPage = new Page<>(pageNum, pageSize);
        userMapper.selectPage(userPage, null);
        List<UserVo> userVos = BeanCopyUtils.copyBeanList(userPage.getRecords(), UserVo.class);
        PageVo pageVo = new PageVo(userVos, userPage.getTotal());
        return ResponseResult.okResult(pageVo);
    }
}