数据层（CRUD操作）

1.先在pom里导坐标

</dependency>
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid-spring-boot-starter</artifactId>
    <version>1.2.15</version>
</dependency>
<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.4.3</version>
</dependency>



2.yml里配置

spring:
  datasource:
    druid:
      url: jdbc:mysql://localhost:3306/test?serverTimezone=UTC&useSSL=false&characterEncoding=UTF-8
      username: root
      password: root
server:
  port: 8080


3.bean

package com.dwe.bean;

import lombok.Data;

@Data
public class Book{
    private Integer id;
    private String type;
    private String name;
    private String description;
}


4.controller

@RestController
@RequestMapping("/book")
public class BookController {
    @Autowired
    BookMapper bookMapper;

    @RequestMapping("/ok")
    public String ok() {
        return "ok";
    }

    @RequestMapping("/all")
    public String queryAll() {
        return bookMapper.selectList(null).toString();
    }

    @RequestMapping("/queryById/{id}")
    public String queryById(@PathVariable("id") String id) {

        return bookMapper.selectById(id).toString();
    }
}
5.启动类里加mapperscan