DROP TABLE IF EXISTS user;

CREATE TABLE user
(
    id BIGINT(20) NOT NULL COMMENT '主键ID',
    name VARCHAR(30) NULL DEFAULT NULL COMMENT '姓名',
    age INT(11) NULL DEFAULT NULL COMMENT '年龄',
    email VARCHAR(50) NULL DEFAULT NULL COMMENT '邮箱',
    PRIMARY KEY (id)
);

DELETE FROM user;

INSERT INTO user (id, name, age, email) VALUES
(1, 'Jone', 18, 'test1@baomidou.com'),
(2, 'Jack', 20, 'test2@baomidou.com'),
(3, 'Tom', 28, 'test3@baomidou.com'),
(4, 'Sandy', 21, 'test4@baomidou.com'),
(5, 'Billie', 24, 'test5@baomidou.com');

3.2 创建一个springboot工程并引入相关的依赖

<dependencies>

        <!--mp依赖-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.5.0</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

3.3 修改配置文件

#数据源
spring.datasource.password=root
spring.datasource.username=wjk351066
spring.datasource.driver-classname=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/mydb?serverTimezone=Asia/Shanghai

#显示sql语句
mybatis-plus.configuration.logimpl=org.apache.ibatis.logging.stdout.StdOutImpl

3.4 创建实体类

/**
 * Created by Intellij IDEA
 *
 * @author 王俊凯
 * @Date: 2022/11/19 11:57
 * @Version 1.0
 */
package com.wjk.entity;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {

    private Long id;
    private String name;
    private Integer age;
    private String email;

}

3.5 创建dao接口

public interface UserDao extends BaseMapper<User> {

}

3.6 为dao接口生成带来实现类

3.7 测试

@SpringBootTest
class SpringbootMybatisplusApplicationTests {


    @Resource
    private UserDao userDao;
    /**
     * 根据id查询信息
     */
    @Test
    void testById() {
        User user = userDao.selectById(1);
        System.out.println(user);
    }

四、使用mp完成crud操作

4.1 添加操作

    /**
     * 添加操作
     */
    @Test
    public void testInsert(){
        User user=new User();
        user.setName("姚远");
        user.setAge(24);
        user.setEmail("850551147.@qqcom");
        userDao.insert(user);
    }

4.2 删除操作

/**
     * 删除操作
     */
    @Test
    public void testDelete(){
        //根据主键删除
        int delete = userDao.deleteById(1593824504754245634L);
        System.out.println("删除影响的行数:"+delete);

        //根据主键批量删除
        List<Long> ids= Arrays.asList(1593817503689134083l,5l);
        int row = userDao.deleteBatchIds(ids);
        System.out.println("影响的行数："+row);

        /**
         * 上面的操作都是根据id删除
         */
        //该方法需要一个Wrapper抽象对象 mp把所有的条件封装到该抽象类中了
        //子类有updateWrapper--->针对修改封装的子类
        //子类有queryWrapper-->针对查询封装的子类
        //子类有LambdaQueryWrapper和LambdaUpdateWrapper
        /**
         * UpdateWrapper<User> wrapper=new UpdateWrapper<>();
         * wrapper.eq("name","姚远");
         * wrapper.or();  //添加wrapper.or就是或  不添加就是且
         * wrapper.ge("age",30);
         * userDao.delete(wrapper);
         */
        /**
         * LambdaUpdateWrapper的操作  必须得用类名
         */
        LambdaUpdateWrapper<User> lambdaUpdateWrapper=new LambdaUpdateWrapper<>();
        lambdaUpdateWrapper.like(User::getName,"姚栎晗");
        userDao.delete(lambdaUpdateWrapper);
    }

4.3 修改操作

    /**
     * 修改操作
     */
    @Test
    public void testUpdate(){
        //根据主键修改

          User user=new User();
                  user.setId(5l);
                  user.setName("卜佩园");
                  user.setAge(18);
                  user.setEmail("13213213210");
                  userDao.updateById(user);

        /**
         * 根据条件修改
         */
        User user=new User();
        user.setName("王俊凯");

        LambdaUpdateWrapper<User> lambdaUpdateWrapper=new LambdaUpdateWrapper();
        //根据年龄大于23的修改
        lambdaUpdateWrapper.ge(User::getAge,23);
        userDao.update(user,lambdaUpdateWrapper);
    }

4.4 查询操作

    /**
     * 查询操作
     */
    @Test
    public void testFind(){
        /**
         * 查询多条记录  如果没有条件可以直接传入一个null 就是查询所有
         */
        List<User> users = userDao.selectList(null);
        System.out.println(users);

        /**
         * 条件查询
         */
        QueryWrapper wrapper=new QueryWrapper();
        wrapper.like("name", "卜佩园");
        List<User> list = userDao.selectList(wrapper);
        System.out.println(list);

        /**
         * 根据条件查询一条记录
         */
        QueryWrapper wrapper=new QueryWrapper();
        wrapper.like("name", "卜佩园");
        wrapper.eq("age",18);
        User user = userDao.selectOne(wrapper);
        System.out.println(user);

    }

4.5 分页查询

   /**
     * 分页查询
     * 这里的分页需要配置分页拦截器
     */
    @Test
    public void testFindPage(){
        //需要两个参数Page接口对象  第二个条件对象
        Page<User> page=new Page<>(1,3);
        //把查询的结果封装到page类中
        Page<User> selectPage = userDao.selectPage(page, null);

        System.out.println("总条数:"+selectPage.getTotal());
        System.out.println("总页数:"+selectPage.getPages());
        System.out.println("当前页的记录:"+selectPage.getRecords());
    }

/**
 * Created by Intellij IDEA
 *
 * @author 王俊凯
 * @Date: 2022/11/19 13:34
 * @Version 1.0
 */
package com.wjk.config;

import com.baomidou.mybatisplus.annotation.DbType;
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 MpConfig {

    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        return interceptor;
    }

}

五、零散的说明

@Data
@NoArgsConstructor
@AllArgsConstructor
@TableName(value = "user") //标记表名和实体明的对应关系
public class User {

    @TableId(type = IdType.ASSIGN_ID)
    private Long id;
    @TableField(value = "name")
    private String name;
    private Integer age;
    private String email;

    @TableField(exist = false) //表示该属性不在数据库
    private Integer status;



    public User(String name, Integer age, String email) {
        this.name = name;
        this.age = age;
        this.email = email;
    }
}