5、SpringBoot整合之SpringBoot整合MybatisPlus

SpringBoot整合MybatisPlus

目录（可点击直接跳转，但还是建议按照顺序观看，四部分具有一定的关联性）：

实现基础的增删改查

实现自动填充功能

实现逻辑删除

实现分页

首先给出四部分完整的项目结构

一、实现基础的增删改查功能

1.创建项目、选择依赖

选择Spring Web、JDBC API、MyBatis Framework、MySQL Driver

2.在pom文件中引入相关依赖

<dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <!-- 修改jdbc版本 --> <version>5.1.47</version> <scope>runtime</scope></dependency><!-- 引入MybatisPlus的启动器 --><dependency> <groupId>com.baomidou</groupId> <artifactId>mybatis-plus-boot-starter</artifactId> <version>3.3.2</version></dependency><!-- 引入lombok --><dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId></dependency><!-- 引入druid连接池 --><dependency> <groupId>com.alibaba</groupId> <artifactId>druid</artifactId> <version>1.2.6</version></dependency><!-- 引入log4j --><dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>1.2.17</version></dependency>

3.建库、建表、插入数据

CREATE DATABASE db_mybatisplus;USE db_mybatisplus;CREATE TABLE tab_teacher( pk_teacher_id INT PRIMARY KEY AUTO_INCREMENT COMMENT '老师主键id,起始为1', teacher_name VARCHAR(10) COMMENT '老师姓名', teacher_sex CHAR(1) COMMENT '老师性别', teacher_salary DOUBLE(6,1) COMMENT '老师工资');-- 反复执行多次，随机插入多条数据INSERT INTO tab_teacher VALUES( NULL, SUBSTR(MD5(RAND()), 1, 5), IF(RAND()>0.5, '男', '女'), RAND()*10000+1000);SELECT * FROM tab_teacher;

4.配置核心配置文件

# 配置连接数据库的四大参数spring.datasource.driver-class-name=com.mysql.jdbc.Driverspring.datasource.url=jdbc:mysql://192.168.133.139/db_mybatisplus?useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=truespring.datasource.username=rootspring.datasource.password=root# 指定连接池的类型spring.datasource.type=com.alibaba.druid.pool.DruidDataSource# 显示SQL语句mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

5.创建实体类

package cn.byuan.entity;import com.baomidou.mybatisplus.annotation.IdType;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.io.Serializable;@NoArgsConstructor// 创建无参的构造方法@AllArgsConstructor// 创建满参的构造方法@Accessors(chain = true)// 使用链式方法@Data// 重写toString方法等方法@TableName("tab_teacher")// 对应表名public class Teacher implements Serializable { @TableId(value = "pk_teacher_id", type = IdType.AUTO)// 主键必须有TableId注解 private Integer teacherId; @TableField("teacher_name") private String teacherName; @TableField("teacher_sex") private String teacherSex; @TableField("teacher_salary") private Double teacherSalary;}

6.创建Teacher类的dao接口，继承BaseMapper接口，使用BaseMapper接口的方法

这里我省去了mapper层，直接让dao层接口继承BaseMapper

这里要牢记一个原则：在启动类对继承BaseMapper的类进行扫描，谁继承BaseMapper类就对它进行扫描

package cn.byuan.dao;import cn.byuan.entity.Teacher;import com.baomidou.mybatisplus.core.mapper.BaseMapper;import org.springframework.stereotype.Repository;@Repositorypublic interface TeacherDao extends BaseMapper<Teacher> {}

7.创建service接口及实现类

接口：

import cn.byuan.entity.Teacher;import java.util.List;public interface TeacherService {// 添加一位老师 Integer addOneTeacher(Teacher teacher);// 根据id删除一位老师 Integer deleteOneTeacherByTeacherId(Integer teacherId);// 修改一位老师的信息 Integer updateOneTeacher(Teacher teacher);// 根据id查询一位老师 Teacher getOneTeacherByTeacherId(Integer teacherId);// 获取所有老师 List<Teacher> getAllTeacher();}

实现类：

package cn.byuan.service;import cn.byuan.dao.TeacherDao;import cn.byuan.entity.Teacher;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service;import java.util.List;@Servicepublic class TeacherServiceImp implements TeacherService{ @Autowired private TeacherDao teacherDao; // 添加一位老师 public Integer addOneTeacher(Teacher teacher){  return teacherDao.insert(teacher); } // 根据id删除一位老师 public Integer deleteOneTeacherByTeacherId(Integer teacherId){  return teacherDao.deleteById(teacherId); } // 修改一位老师的信息 public Integer updateOneTeacher(Teacher teacher){  return teacherDao.updateById(teacher); } // 根据id查询一位老师 public Teacher getOneTeacherByTeacherId(Integer teacherId){  return teacherDao.selectById(teacherId); } // 获取所有老师 public List<Teacher> getAllTeacher(){  return teacherDao.selectList(null); }}

8.在启动类对继承BaseMapper的类配置扫描

谁继承了BaseMapper就对谁进行扫描，因为之前我省去了mapper层，直接让dao层接口继承BaseMapper，因此这里扫描的是dao包

package cn.byuan;import org.mybatis.spring.annotation.MapperScan;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplication@MapperScan("cn.byuan.dao")// 那一层继承了BaseMapper就对那一层进行扫描public class Test005SpringbootMybatisplusApplication { public static void main(String[] args) {  SpringApplication.run(Test005SpringbootMybatisplusApplication.class, args); }}

9.在测试类进行测试

package cn.byuan;import cn.byuan.entity.Teacher;import cn.byuan.service.TeacherService;import org.junit.jupiter.api.Test;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.test.context.SpringBootTest;@SpringBootTestclass TeacherDaoOneTests { @Autowired private TeacherService teacherService; @Test void addOneTeacherTest(){  Teacher teacher = new Teacher()    .setTeacherName("test2")    .setTeacherSex("女")    .setTeacherSalary(9876.5);  teacherService.addOneTeacher(teacher); } @Test void deleteOneTeacherByTeacherIdTest(){  teacherService.deleteOneTeacherByTeacherId(2); } @Test void updateOneTeacher(){  Teacher teacher = new Teacher()    .setTeacherId(1)    .setTeacherName("qwe12")    .setTeacherSex("女")    .setTeacherSalary(1234.5);  teacherService.updateOneTeacher(teacher); } @Test void getOneTeacherByTeacherId(){  teacherService.getOneTeacherByTeacherId(1); } @Test void getAllTeacher(){  teacherService.getAllTeacher(); }}

测试结果：

二、实现自动填充功能

自动填充功能一般可以用作记录操作发生时间，如某列的最后修改时间等，本部分代码基于第一部分：实现基础的增删改查、

1.修改数据库中的表结构

-- 修改数据库中表结构ALTER TABLE tab_teacher ADD create_time TIMESTAMP COMMENT '记录插入时间';ALTER TABLE tab_teacher ADD update_time TIMESTAMP COMMENT '记录修改时间';-- 更新所有表中数据UPDATE tab_teacher SET create_time=NOW();UPDATE tab_teacher SET update_time=NOW();SELECT * FROM tab_teacher;

2.修改实体类

这一步简单来说就是将增加的两列添加进Teacher类的属性中，其余与第一部分保持一致；

为实现自动填充还应在新加入的两个属性的TableField中增加"fill"属性

package cn.byuan.entity;import com.baomidou.mybatisplus.annotation.IdType;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.io.Serializable;import java.util.Date;@NoArgsConstructor// 创建无参的构造方法@AllArgsConstructor// 创建满参的构造方法@Accessors(chain = true)// 使用链式方法@Data// 重写toString方法等方法@TableName("tab_teacher")// 对应表名public class Teacher implements Serializable { @TableId(value = "pk_teacher_id", type = IdType.AUTO)// 主键必须有TableId注解 private Integer teacherId; @TableField("teacher_name") private String teacherName; @TableField("teacher_sex") private String teacherSex; @TableField("teacher_salary") private Double teacherSalary;// 增加的两列属性 @TableField(value = "create_time", fill = FieldFill.INSERT)// 插入时自动填充 private Date createTime; @TableField(value = "update_time", fill = FieldFill.INSERT_UPDATE)// 插入和修改时自动填充 private Date updateTime;}

3.创建handler层，实现MetaObjectHandler接口，重写insertFill与updateFill方法，指定填充的字段及属性值

package cn.byuan.handler;import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;import org.apache.ibatis.reflection.MetaObject;import org.springframework.stereotype.Component;import java.util.Date;@Componentpublic class TeacherHandler implements MetaObjectHandler { @Override public void insertFill(MetaObject metaObject) {  this.strictInsertFill(metaObject, "createTime", Date.class, new Date());  this.strictInsertFill(metaObject, "updateTime", Date.class, new Date());   } @Override public void updateFill(MetaObject metaObject) {  this.strictUpdateFill(metaObject, "updateTime", Date.class, new Date()); }}

4.进行测试

这里我们只测试增加和修改两个方法

package cn.byuan;import cn.byuan.entity.Teacher;import cn.byuan.service.TeacherService;import org.junit.jupiter.api.Test;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.test.context.SpringBootTest;@SpringBootTestclass TeacherDaoTwoTests { @Autowired private TeacherService teacherService; @Test void addOneTeacherTest(){  Teacher teacher = new Teacher()    .setTeacherName("test2")    .setTeacherSex("女")    .setTeacherSalary(9876.5);  teacherService.addOneTeacher(teacher); } @Test void updateOneTeacher(){  Teacher teacher = new Teacher()    .setTeacherId(1)    .setTeacherName("wer23")    .setTeacherSex("女")    .setTeacherSalary(1234.5);  teacherService.updateOneTeacher(teacher); }}

从SQL语句可以看出，在执行update方法时，已自动为我们填充字段

数据库中新插入数据也没有问题

三、实现逻辑删除功能

数据是无价的，因此一般而言我们不会直接删除数据。对于"删除"我们一般的做法是定义一个字段来记录本行数据的可见性

1.修改数据库中的表结构

添加一个字段作为标记

-- 修改数据库中表结构, 添加一个字段作为标记ALTER TABLE tab_teacher ADD visibility TINYINT COMMENT "0表示未删除，1表示删除";-- 更新表中所有数据, 全部设置为未删除UPDATE tab_teacher SET visibility=0;

2.在实体类中添加字段，并添加TableField和TableLogic两个注解

package cn.byuan.entity;import com.baomidou.mybatisplus.annotation.*;import lombok.AllArgsConstructor;import lombok.Data;import lombok.NoArgsConstructor;import lombok.experimental.Accessors;import java.io.Serializable;import java.util.Date;@NoArgsConstructor// 创建无参的构造方法@AllArgsConstructor// 创建满参的构造方法@Accessors(chain = true)// 使用链式方法@Data// 重写toString方法等方法@TableName("tab_teacher")// 对应表名public class Teacher implements Serializable { @TableId(value = "pk_teacher_id", type = IdType.AUTO)// 主键必须有TableId注解 private Integer teacherId; @TableField("teacher_name") private String teacherName; @TableField("teacher_sex") private String teacherSex; @TableField("teacher_salary") private Double teacherSalary; @TableField(value = "create_time", fill = FieldFill.INSERT)// 插入时自动填充 private Date createTime; @TableField(value = "update_time", fill = FieldFill.INSERT_UPDATE)// 插入和修改时自动填充 private Date updateTime; // 新添加进来的字段 @TableField(value = "visibility", fill = FieldFill.INSERT) @TableLogic(value = "0", delval = "1")// 指定次字段为逻辑删除字段, 默认0是未删除, 1是已删除 private Integer visibility;}

3.在TeacherHandler中指定visibility字段的初始值

package cn.byuan.handler;import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;import org.apache.ibatis.reflection.MetaObject;import org.springframework.stereotype.Component;import java.util.Date;@Componentpublic class TeacherHandler implements MetaObjectHandler { @Override public void insertFill(MetaObject metaObject) {  this.strictInsertFill(metaObject, "createTime", Date.class, new Date());  this.strictInsertFill(metaObject, "updateTime", Date.class, new Date());  //  新添加的字段  this.strictInsertFill(metaObject, "visibility", Integer.class, 0); } @Override public void updateFill(MetaObject metaObject) {  this.strictUpdateFill(metaObject, "updateTime", Date.class, new Date()); }}

4.进行测试

这里只测试两个方法，一个是删除指定id值的老师，一个是根据被删除的老师id查询该老师是否可以被查询

package cn.byuan;import cn.byuan.entity.Teacher;import cn.byuan.service.TeacherService;import org.junit.jupiter.api.Test;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.test.context.SpringBootTest;@SpringBootTestclass TeacherDaoThreeTests { @Autowired private TeacherService teacherService; @Test void deleteOneTeacherByTeacherIdTest(){//  删除id为1的老师  teacherService.deleteOneTeacherByTeacherId(1); } @Test void getOneTeacherByTeacherId(){//  查询id为1的老师  teacherService.getOneTeacherByTeacherId(1); }}

可以看到，当我们执行delete方法时，实际上执行的是update方法

而查询语句并没有查询到该老师

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