后端

springboot2
SpringBoot的学习记录
mybatis-plus
Gson

数据库

mysql

开发工具

社区版idea
vs code

实现后端增删改查

首先我们新建一个文件夹，通过cmd输入命令 vue create front(为前端项目命名为”front”)，选择vue2。在创建vue的同时，我们可以在这段时间创建数据库，登陆msql之后，source + 数据库的路径可以将之前设计好的数据库拖过来。

之后我们打开Idea,选择new project - > 点击next- > 选择Maven - > 选择新建的文件夹路径\back(为前端项目命名为”back”)

在maven的pom.xml文件中引入依赖后刷新maven

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>mybatis_plus01</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.7</version>
        <relativePath/>
    </parent>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <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-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.5.1</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.8.5</version>
        </dependency>
    </dependencies>
</project>

在source下创建一个文件（file）,重命名为”application.yaml”

spring:
  datasource:
    username: root
    password: '123456'
    url: jdbc:mysql://127.0.0.1:3306/demo3?characterEncoding=UTF-8&serverTimezone=UTC
    driver-class-name: com.mysql.cj.jdbc.Driver

写法很固定，username和password分别是用户名和密码（注意打上单引号），url中加上数据库。

接下来在java下新建一个包”org.example.Application”，最后就会创建出一个Application类作为启动类

package org.example;

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

@SpringBootApplication
@MapperScan("org.example.mapper")
public class Application {

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

新建一个Student类，通过Navicat的设计表查看（也可以在cmd中输入命令”desc+表名”查看）有哪些属性，类型需要一一匹配。通过lombok可以帮助我们快速生成构造方法、toString方法等等。

package org.example.pojo;

import lombok.Data;

@Data
public class Student {
    private Long id;
    private String date;
    private String content;
    private Integer num1;
    private Integer num2;
    private Integer num3;
    private Integer num4;
}

在mapper包下创建一个StudentMapper接口

package org.example.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import org.example.pojo.Student;

public interface StudentMapper extends BaseMapper<Student> {
}

创建Controller类配置路由规则，Gson可以将查出来的数据转成字符串，这个时候会有警告，在上方加上@SuppressWarnings(“all”)

package org.example;

import com.google.gson.Gson;
import org.example.mapper.StudentMapper;
import org.example.pojo.Student;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@SuppressWarnings("all")
@CrossOrigin(origins = {"*", "null"})
public class Controller {
    @Autowired
    private StudentMapper studentMapper;
    private Gson gson=new Gson();

    @GetMapping("/students")
    public String getStudents(){
        List<Student> students = studentMapper.selectList(null);
        return gson.toJson(students);
    }
    @PostMapping("/add")
    public  void addStudent(@RequestBody Student student){
        studentMapper.insert(student);
    }
    @PostMapping("delete")
    public void removeStudent(@RequestBody Student student){
        studentMapper.deleteById(student);
    }
    @PostMapping("update")
    public void updateStudent(@RequestBody Student student){
        studentMapper.updateById(student);
    }
}