使用nestjs连接mysql并进行增删改查 - 糊涂

如何使用nestjs连接mysql，并进行增删改查，首先创建nestjs项目
### 一、准备nestjs项目
```
npm i -g @nestjs/cli
nest new project-name
```
### 二、目录结构
```
src
 ├── app.controller.spec.ts
 ├── app.controller.ts
 ├── app.module.ts
 ├── app.service.ts
 └── main.ts
```
### 三、创建cats数据库表
| name  | type  |  length |
| ------------ | ------------ | ------------ |
|  id | int  | 11  |
|title   |  varchar | 20  |
| age  | int  | 11  |
### 四、创建对应文件
1、 创建 `cats/cats.entities.ts` 文件

```javascript
import { Entity, Column, PrimaryGeneratedColumn } from 'typeorm';

@Entity({ name: 'cats' })
export class Cats {
    @PrimaryGeneratedColumn()
    id: number;

@Column({ name: 'title' })
    title: string;

@Column({ name: 'age' })
    age: number;
}
```
2、 创建 `cats/cats.service.ts` 文件

```javascript
import { Injectable } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { Cats } from './cats.entities';

@Injectable()
export class CatsService {
  constructor(
    @InjectRepository(Cats)
    private catsRepository: Repository,
  ) { }

findAll(): Promise {
    return this.catsRepository.find();
  }

findOne(id: number): Promise {
    return this.catsRepository.findOne(id);
  }

async remove(id: number): Promise {
    await this.catsRepository.delete(id);
  }

async create(cats: Cats): Promise {
    await this.catsRepository.save(cats);
  }
}
```
3、创建 `cats/cats.controller.ts` 文件

```javascript
import { Controller, Get, Param } from '@nestjs/common';
import { CatsService } from './cats.service';
import { Cats } from './cats.entities';
@Controller('cats')
export class CatsController {
    constructor(private readonly catsService: CatsService) { }
    /**
     * 获取一条数据
     * @param params 
     * @returns 
     */
    @Get('/get/:id')
    async get(@Param() params) {
        return await this.catsService.findOne(params.id);
    }
    /**
     * 获取所有数据
     * @returns 
     */
    @Get("/all")
    async findAll() {
        return await this.catsService.findAll()
    }
    /**
     * 创建数据
     * @param params 
     * @returns 
     */
    @Get('/create/:title/:age')
    async findOne(@Param() params) {
        let cats = new Cats();
        cats.title = params.title;
        cats.age = params.age;
        return await this.catsService.create(cats);
    }
    /**
     * 删除一条数据
     * @param params 
     * @returns 
     */
    @Get('/remove/:id')
    async remove(@Param() params) {
        return await this.catsService.remove(params.id);
    }
}

```
4、创建 `cats/cats.module.ts` 文件

```javascript
import { Module } from '@nestjs/common';
import { TypeOrmModule } from '@nestjs/typeorm';
import { CatsController } from './cats.controller';
import { Cats } from './cats.entities';
import { CatsService } from './cats.service';

@Module({
    imports: [TypeOrmModule.forFeature([Cats])],
    controllers: [CatsController],
    providers: [CatsService],
})
export class CatsModule { }
```
5、修改`app.module.ts` ，使用 `npm install --save save @nestjs/typeorm typeorm mysql` 安装mysql模板，并连接数据库
```javascript
import { Module } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { TypeOrmModule } from '@nestjs/typeorm';
import { Cats } from './cats/cats.entities';
import { CatsModule } from './cats/cats.module';
import { Connection } from 'typeorm';
@Module({
  imports: [
    TypeOrmModule.forRoot({
      type: 'mysql',
      host: '127.0.0.1',
      port: 3306,
      username: 'hutu',
      password: 'aa2248',
      database: 'demo',
      entities: [Cats],
      synchronize: true,
    }),
    CatsModule,
  ],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {
  constructor(private connection: Connection) { }
}
```
### 五、请求对应的路由
get http://localhost:3000/cats/create/name/19
get http://localhost:3000/cats/get/1
get http://localhost:3000/cats/all
get http://localhost:3000/cats/remove/1