六、MybatisPlus快速上手    数据库操作

注意！注意！注意！springboot版本选择2.7.2

1.ORM介绍（对象关系映射）

既包含存储，又包含映射。将java类映射到数据库

2.MybatisPlus介绍

ORM框架

数据库操作来啦！注意欧

1.添加依赖到pom。xmlwen文件中

<dependency>
			<groupId>com.baomidou</groupId>
			<artifactId>mybatis-plus-boot-starter</artifactId>
			<version>3.4.2</version>
		</dependency>

		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>5.1.47</version>
		</dependency>

		<dependency>
			<groupId>com.alibaba</groupId>
			<artifactId>druid-spring-boot-starter</artifactId>
			<version>1.1.20</version>
		</dependency>

2.在properties中加入配置

spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.driverClassName=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/Englishword?useSSL=false
spring.datasource.username=root
spring.datasource.password="youpassword"

3.在mysql中添加数据库和表单，我添加了Englisword  database 和user table

有关MYSQL的具体操作大家可以参考

CREATE TABLE user (
  id VARCHAR(50) PRIMARY KEY,
  username VARCHAR(50) NOT NULL,
  password VARCHAR(50) NOT NULL,
  birth VARCHAR(50) NOT NULL
);

INSERT INTO user (id, username, password, birthday)
VALUES ('1', 'Alice', 'password123', '1990-01-01'), 
       ('2', 'Bob', '123password', '1995-05-10');

4.在启动类里面添加@MapperScan（“mapper文件夹路径”）

5.package mapper 添加usermapper （记得导入user类）

package com.example.sql2.mapper;
import com.example.sql2.entity.user;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;
import org.springframework.stereotype.Repository;

import java.util.List;
@Repository
@Mapper
public interface UserMapper {
    //根据ID查找用户
 /*   @Select("select * from user where id=#{id})
    public int findbyid(int id);*/
    //查询所有用户
    @Select("select * from user")
    public List<user> find();
    //增加用户
    @Insert("insert into user values(#{id},#{username},#{password},#{birthday})")
    public int insert(user user);
    //更新用户
    @Update("update user set username=#{username},password=#{password},#{birthday}) where id=#{id}")
    public int update(user user);

}

6.package entity添加实体user、

package com.example.sql2.entity;

public class user {
    private String id;
    private String username;
    private String password;
    private String birthday;

    @Override
    public String toString() {
        return "user{" +
                "id='" + id + '\'' +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", birthday='" + birthday + '\'' +
                '}';
    }

    public String getId() {
        return id;
    }

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

    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;
    }

    public String getBirthday() {
        return birthday;
    }

    public void setBirthday(String birthday) {
        this.birthday = birthday;
    }

    public user(String id, String username, String password, String birthday) {
        this.id = id;
        this.username = username;
        this.password = password;
        this.birthday = birthday;
    }
}

7.package controller添加控制器usercontroller

@RestController
public class usercontroller {
    @Autowired
    private UserMapper usermapper;

    @GetMapping("/user")
    public List query(){

       List <user>list=usermapper.find();
        System.out.println(list);
        return list;
    }

    @PostMapping("/user")
    public  String save(user user ){
       int i=usermapper.insert(user);
        if (i == 0) {
            return "创建失败";
        }
        else return  "创建成功";

    }
}

3.MybatisPlus CRUO操作