作用：可以將單表的增刪改查操作省去

一、新增依賴

 <!--mybatis通用mapper的依賴-->
        <dependency>
            <groupId>tk.mybatis</groupId>
            <artifactId>mapper-spring-boot-starter</artifactId>
            <version>1.2.3</version>
            <exclusions>
                <
 
exclusion>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-jdbc</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

二、讓mapper介面繼承Mapper<T>介面

　　注意:是該包的Mapper介面（package tk.mybatis.mapper.common）,其泛型是對應的實體類

package com.atguigu.gmall.user.mapper;

import com.atguigu.gmall.user.domain.Users;
import tk.mybatis.mapper.common.Mapper;

import java.util.List;

public interface UserMapper extends Mapper<Users> {


//無需寫方法，直接在service實現類呼叫方法
}

三、在實現類呼叫方法

package com.atguigu.gmall.user.service.impl;

import com.atguigu.gmall.user.domain.Users;
import com.atguigu.gmall.user.mapper.UserMapper;
import com.atguigu.gmall.user.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    UserMapper userMapper;

    public  List<Users> getAllUser(){
        //該selectAll方法是通用mapper制定好的，直接呼叫。其中還有好多方法
        List<Users> userList = userMapper.selectAll();
        return userList;
    }
}
    

四、在實體類中添加註解如下

　　@Id指定主鍵

　　@GenneratedValue(strategy=GennerationType.IDENTITY)指定主鍵返回策略

package com.atguigu.gmall.user.domain;

import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

public class Users {

    @Id//指定主鍵
    @GeneratedValue(strategy = GenerationType.IDENTITY)//指定主鍵返回策略
    private Integer id;
    private String name;
    private String sex;
    private String address;

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}

五、在啟動類上配置通用mapper的掃描器

　　@MapperScan(basePackages="com.atguigu.gmall.user.mapper")注意是該包下的（tk.mybatis.spring.annotation.MapperScan）

package com.atguigu.gmall.user;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import tk.mybatis.spring.annotation.MapperScan;

@SpringBootApplication
//@MapperScan(basePackages = "com.atguigu.gmall.user.mapper")
@MapperScan(basePackages = "com.atguigu.gmall.user.mapper")
public class GmallUser01Application {

    public static void main(String[] args) {
        SpringApplication.run(GmallUser01Application.class, args);
    }

}