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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）：

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.driver

spring.datasource.url=jdbc:mysql://192.168.133.139/db_mybatisplus?useunicode=true&characterencoding=utf8&autoreconnect=true&allowmultiqueries=true

spring.datasource.username=root

spring.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;

@repository
public 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;

@service
public 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;

@springboottest
class 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：

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;

@component
public 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;

@springboottest
class 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;

@component
public 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;

@springboottest
class 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

数据库中id为1的老师信息依然存在

四、实现分页功能

1.创建一个配置类，通过方法返回一个paginationinterceptor

package cn.byuan.conf;

import com.baomidou.mybatisplus.extension.plugins.paginationinterceptor;
import org.mybatis.spring.annotation.mapperscan;
import org.springframework.context.annotation.bean;
import org.springframework.context.annotation.configuration;

@configuration
@mapperscan("cn.byuan.dao")
public class pageconfig {
    @bean
    public paginationinterceptor paginationinterceptor(){
        return new paginationinterceptor();
    }
}

2.在service中根据selectpage方法进行分页

这里展示两种分页方式，对表中所有数据进行分页以及根据条件进行分页

接口：

package cn.byuan.service;

import cn.byuan.entity.teacher;
import com.baomidou.mybatisplus.extension.plugins.pagination.page;

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();

//    该部分增加的方法
//    对表中所有信息进行分页, 传入参数为要查询的页数
    page<teacher> getallteacherpage(integer pagenumber);

//    按条件(性别)进行分页
    page<teacher> getallteacherbyteachersexpage(integer pagenumber, string teachersex);
}

实现类：

package cn.byuan.service;

import cn.byuan.dao.teacherdao;
import cn.byuan.entity.teacher;
import com.baomidou.mybatisplus.core.conditions.query.querywrapper;
import com.baomidou.mybatisplus.extension.plugins.pagination.page;
import org.springframework.beans.factory.annotation.autowired;
import org.springframework.stereotype.service;

import java.util.list;

@service
public 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);
    }
    
    //    该部分增加的方法
    //    对表中所有信息进行分页, 传入参数为要查询的页数
    public page<teacher> getallteacherpage(integer pagenumber){
        querywrapper<teacher> teacherquerywrapper = new querywrapper<>();

        page<teacher> teacherpage = new page<>(pagenumber, 5);// 每页大小为5

        teacherdao.selectpage(teacherpage, teacherquerywrapper);

        return teacherpage;
    }

    //    按条件(性别)进行分页
    public page<teacher> getallteacherbyteachersexpage(integer pagenumber, string teachersex){
        querywrapper<teacher> teacherquerywrapper = new querywrapper<>();

        teacherquerywrapper.eq("teacher_sex", teachersex);// 根据条件进行分页, 这里填写的是表中的列名

        page<teacher> teacherpage = new page<>(pagenumber, 5);

        teacherdao.selectpage(teacherpage, teacherquerywrapper);
        return teacherpage;
    }
}

3.进行测试

package cn.byuan;

import cn.byuan.entity.teacher;
import cn.byuan.service.teacherservice;
import com.baomidou.mybatisplus.extension.plugins.pagination.page;
import org.junit.jupiter.api.test;
import org.springframework.beans.factory.annotation.autowired;
import org.springframework.boot.test.context.springboottest;

@springboottest
class teacherdaofourtests {
    @autowired
    private teacherservice teacherservice;

    @test
    void getallteacherpagetest(){
        //    查看第三页
        page<teacher> teacherpage = teacherservice.getallteacherpage(3);

        teacherpage.getrecords().foreach(system.out::println);
    }

    @test
    void getallteacherbyteachersexpagetest(){
        //    查询男生第1页的内容
        page<teacher> teacherpage = teacherservice.getallteacherbyteachersexpage(1, "男");

        teacherpage.getrecords().foreach(system.out::println);
    }
}

测试结果

附：page对象的一些常用方法

page<object> page = new page<>(1, 6);// 指定当前页, 每页记录数
page.getcurrent();// 获取当前页
page.gettotal();// 获取总记录数
page.getsize();// 获取每页的记录数
page.getrecords();// 获取当前页数据的集合
page.getpages();// 获取总页数
page.hasnext();// 是否存在下一页
page.hasprevious();// 是否存在上一页

源码地址：

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