[Java知识库]如何使用Mybtis-Plus创建项目？？？

1.建立项目

????????file->New->Project

?????????选择Maven项目

?

?

2.导入依赖

????????编写pom.xml文件

 <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.4.RELEASE</version>
        <relativePath/>    
</parent>


<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.4.3</version>
        </dependency>
        <!--web开发依赖-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>

        <!--分页依赖-->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
            <version>1.2.12</version>
        </dependency>
        <!--数据库驱动依赖-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.23</version>
        </dependency>
        <!--阿里巴巴连接池依赖-->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.1.21</version>
        </dependency>
        <!--测试框架依赖-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <!--Springboot测试框架依赖-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-validation</artifactId>
        </dependency>
        <!--JWT依赖-->
        <dependency>
            <groupId>com.auth0</groupId>
            <artifactId>java-jwt</artifactId>
            <version>3.13.0</version>
        </dependency>

3.书写配置文件，连接数据库

? ? ? ? 编写application.yml

spring:
  datasource:
    driverClassName: com.mysql.cj.jdbc.Driver
    #    3306为数据库端口号，demo4为数据库表名
    url: jdbc:mysql://localhost:3306/demo4?characterEncoding=utf-8
    username: root  #数据库用户名
    password: 123456  #数据库密码
    type: com.alibaba.druid.pool.DruidDataSource
    maxActive: 50
    maxWait: 2000
    minIdle: 10

mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  type-aliases-package: com.project.bean #对应项目结构


mybatis:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  type-aliases-package: com.project.bean #对应项目结构

? ? ? ? 数据库设计

?

4.构建项目

????????建立包com.project，在此包下建立bean、dao、service包，分别建立用户实体bean，持久层，业务层等，以及在resources目录下下创建映射文件 持久层名.xml

????????创建结束后的结构

?

4.1.各个包下的实现代码块（按自己数据库设计需求来编写，此处为本人数据库实列）

? ? ? ? bean包下用户实体类UserBean：

package com.project.bean;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;

@TableName("t_user")//当前实体对应的数据库表名称
public class UserBean {
    //@TableId注解，指定属性对应主键的列
    //type = IdType.AUTO使用数据库表主键自动高增长策略
    @TableId(value = "pk_userid",type = IdType.AUTO)
    private int userid;
    //@TableField普通属性，书写属性对应的数据表的列
    @TableField("f_username")
    private String username;
    @TableField("f_password")
    private String password;

    public UserBean() {
    }

    public UserBean(String username, String password) {
        this.username = username;
        this.password = password;
    }

    public int getUserid() {
        return userid;
    }

    public void setUserid(int userid) {
        this.userid = userid;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "UserBean{" +
                "userid=" + userid +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

? ? ? ? dao层(持久层)UserDao类：

package com.project.dao;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.project.bean.UserBean;
import org.springframework.stereotype.Repository;


/**
 * 持久接口
 * 1.需要继承BaseMapper接口
 * 2.在接口里书写对应的实体类类名
 * 3.加上注解@Repository，表示该接口为持久层组件
 */
@Repository
public interface UserDao extends BaseMapper<UserBean> {
    //此时持久接口中，已经包含基本单表的增删查改的实现
/**
     * 根据用户姓名、生日查询用户信息
     * @param name
     * @param start
     * @param end
     * @return
     */
    List<UserBean> findByItem(@Param("name")String name,
                              @Param("start")LocalDate start,
                              @Param("end") LocalDate end);


    /**
     * 根据姓名分页查询
     * @param page
     * @param name
     * @return
     */
    IPage<UserBean> pageByItem(Page<UserBean> page,
                               @Param("name")String name);



}

????????

? ? ? ? service层(业务层)UserService类：

????????

package com.project.service;

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.service.IService;
import com.project.bean.UserBean;

import java.time.LocalDate;
import java.util.List;


/**
 * 自定义业务层接口
 * 1.需要继承IService
 * 注意：通用service接口和通用mapper接口不一样，
 * 通用mapper接口不需要提供实现类，就已经包含所有数据的数据库操作方法
 * 通用service接口必须要提供实现类
 */
public interface UserService extends IService<UserBean> {


    /**
     * 根据用户姓名、生日查询用户信息
     * @param name
     * @param start
     * @param end
     * @return
     */
    List<UserBean> findByItem(String name, LocalDate start, LocalDate end);


    /**
     * 根据姓名分页查询
     * @param pageNo
     * @param pageSize
     * @param name
     * @return
     */
    IPage<UserBean> pageByItem(int pageNo,int pageSize,String name);
}

????????service层(业务层)下impl包UserServiceImpl类：

package com.project.service.impl;

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.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.project.bean.UserBean;
import com.project.dao.UserDao;
import com.project.service.UserService;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;
import java.time.LocalDate;
import java.util.ArrayList;
import java.util.List;


/**
 * 自定义接口实现类
 * 继承ServiceImpl
 * 注意：实现类必须继承mybatis-plus提供的ServiceImpl实现类，
 * 并加入泛型<持久层接口，实体bean>
 */

@Service
@Transactional
public class UserServiceImpl extends ServiceImpl<UserDao, UserBean> implements UserService {


    /**
     * 根据用户姓名、生日查询用户信息
     * @param name
     * @param start
     * @param end
     * @return
     */
    @Override
    public List<UserBean> findByItem(String name, LocalDate start, LocalDate end) {
//        //方案1，不写xml
        QueryWrapper<UserBean> wrapper = new QueryWrapper();
        if (name!=null&&!name.equals("")){
            wrapper.like("f_userName",name);
        }if (start!=null){
            wrapper.ge("userDate",start);
        }if (end!=null){
            wrapper.le("userDate",end);
        }
        List<UserBean> list = this.list(wrapper);
        return list;

        //方案2 书写持久层接口和xml文件
        //通过this.baseMapper
        List<UserBean> list = this.baseMapper.findByItem(name, start, end);
        return list;
    }

    /**
     * 根据姓名分页查询
     * @param pageNo
     * @param pageSize
     * @param name
     * @return
     */
    @Override
    public IPage<UserBean> pageByItem(int pageNo, int pageSize, String name) {
//        Page<UserBean> page = new Page<>(pageNo,pageSize);
//        QueryWrapper wrapper = new QueryWrapper();
//        if (name!=null&&!name.equals("")){
//            wrapper.like("f_userName",name);
//        }
//
//        IPage<UserBean> p = this.page(page,wrapper);
//        return p;
    }
}

4.2.在test/java目录下新建TestUserDao测试类，测试持久层代码

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.project.MainServer;
import com.project.bean.UserBean;
import com.project.dao.UserDao;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import javax.annotation.Resource;
import java.time.LocalDate;
import java.util.List;

@RunWith(SpringRunner.class)
@SpringBootTest(classes = MainServer.class)

public class TestUserDao {

    @Resource
    private UserDao userDao;

    @Test
    public void test(){
        //添加用户
        UserBean userBean = new UserBean("孙悟空", LocalDate.parse("1299-09-24"),"男","123456","用户");
        userDao.insert(userBean);
        //根据id查询用户信息
        userDao.selectById(2);
        //根据用户姓名和用户密码查询用户
        QueryWrapper<UserBean> wrapper = new QueryWrapper<>();
        wrapper.eq("f_userName","周公");
        wrapper.eq("f_userPwd","123");
        List<UserBean> list = userDao.selectList(wrapper);
        for (UserBean i:list){
            System.out.println(i);
        }
        //根据用户id修改用户
//        UserBean userBean2 = new UserBean();
        userBean2.setUserId(3);
        userBean2.setUserName("周瑜好帅哦");
        userBean2.setUserPwd("666");
        userDao.updateById(userBean2);
        //根据用户的姓名修改用户
        userBean2.setUserType("游客");
        userDao.update(userBean2,wrapper.eq("f_userName","孙悟空"));
        //根据用户id删除用户
        userDao.deleteById(4);
        //根据用户身份删除用户
        userDao.delete(wrapper.eq("f_userType","游客"));
        //查询所有用户集合
        List<UserBean> list = userDao.selectList(null);
        for (UserBean i:list){
            System.out.println(i);
        }
        //根据姓名和性别查询用户集合
        wrapper.eq("f_userName","李逵");
        wrapper.eq("f_userGender","男");
        List<UserBean> list = userDao.selectList(wrapper);
        for (UserBean i:list){
            System.out.println(i);
        }



        //分页
        Page<UserBean> page = new Page<>(1,3);
        wrapper.like("f_userName","好");
        wrapper.eq("f_userGender","男");
        wrapper.eq("f_userType","用户");
        IPage<UserBean> p = userDao.selectPage(page,wrapper);
        //获取总记录数
        long total = p.getTotal();
        System.out.println(total);
        //当前页码
       long num = p.getCurrent();
        System.out.println(num);
        //获取当前页数据
        List<UserBean> list =  p.getRecords();
        System.out.println(list);
        for (UserBean i:list){
            System.out.println(i);
        }


        //模糊查询，以生日范围查询用户信息
        //比较范围用ge（）--大于等于和le（）--小于等于
         //        gt（）--大于和lt（）--小于
        wrapper.gt("f_userDate","2022-09-01");//大于
        wrapper.lt("f_userDate","2022-09-15");
        List<UserBean> list = userDao.selectList(wrapper);
        for (UserBean i:list){
            System.out.println(i);
//        }


    }
}

5.编写MainServer准备测试

package com.project;


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

@SpringBootApplication
@MapperScan("com.project.dao")
public class MainServer {
    public static void main(String[] args) {
        SpringApplication.run(MainServer.class,args);
    }
}