nestjs学习（四）

nestjs学习（四）

1. Guards

   确定请求是否应由路由处理程序处理,在每个中间件之后执行，但在任何pipe之前执行。

   • Authorization guard

       import { Injectable, CanActivate, ExecutionContext } from '@nestjs/common';
       import { Observable } from 'rxjs';
     
       @Injectable()
       export class AuthGuard implements CanActivate {
           canActivate(
               context: ExecutionContext,
           ): boolean | Promise | Observable {
               const request = context.switchToHttp().getRequest();
               return validateRequest(request);
           }
       }
     

   • Role-based authentication

       import { Injectable, CanActivate, ExecutionContext } from '@nestjs/common';
       import { Observable } from 'rxjs';
     
       @Injectable()
       export class RolesGuard implements CanActivate {
           canActivate(
               context: ExecutionContext,
           ): boolean | Promise | Observable {
               return true;
           }
       }
     
       // 绑定
       @Controller('cats')
       @UseGuards(RolesGuard)
       export class CatsController {}
     
       // 全局 绑定
       app.useGlobalGuards(new RolesGuard());
     
       // 模块绑定
       import { Module } from '@nestjs/common';
       import { APP_GUARD } from '@nestjs/core';
     
       @Module({
           providers: [
               {
                   provide: APP_GUARD,
                   useClass: RolesGuard,
               },
           ],
       })
       export class ApplicationModule {}
     

   • Reflector

       @Post()
       @ReflectMetadata('roles', ['admin']) //使用ReflectMetadata装饰器
       async create(@Body() createCatDto: CreateCatDto) {
           this.catsService.create(createCatDto);
       }
       // 直接使用不太好， 建立自己的decorator  
       // roles.decorator.ts
       import { ReflectMetadata } from '@nestjs/common';
       export const Roles = (...roles: string[]) => ReflectMetadata('roles', roles);
       // 这样就可以直接使用  @Roles('admin')
     
       // roles.guard.ts 示例
       import { Injectable, CanActivate, ExecutionContext } from '@nestjs/common';
       import { Observable } from 'rxjs';
       import { Reflector } from '@nestjs/core';
     
       @Injectable()
       export class RolesGuard implements CanActivate {
           constructor(private readonly reflector: Reflector) {}
     
           canActivate(context: ExecutionContext): boolean {
               const roles = this.reflector.get('roles', context.getHandler());
               if (!roles) {
                   return true;
               }
               const request = context.switchToHttp().getRequest();
               const user = request.user;
               const hasRole = () => user.roles.some((role) => roles.includes(role));
               return user && user.roles && hasRole();
           }
       }
     

2. Interceptors 拦截器

   • 功能

     • 在方法执行之前/之后绑定额外的逻辑
     • 转换函数返回的结果
     • 转换从函数抛出的异常
     • 扩展基本函数行为
     • 根据所选条件完全覆盖函数（例如缓存目的）

   • 拦截示例

       import { Injectable, NestInterceptor, ExecutionContext } from '@nestjs/common';
       import { Observable } from 'rxjs';
       import { tap, map } from 'rxjs/operators';
     
       @Injectable()
       export class LoggingInterceptor implements NestInterceptor {
           intercept(
               context: ExecutionContext,
               call$: Observable,
           ): Observable {
               console.log('Before...');
     
               const now = Date.now();
               return call$.pipe(
                   tap(() => console.log(`After... ${Date.now() - now}ms`)),
               );
               // return call$.pipe(map(data => ({ data }))); 返回一个map
           }
       }
     
       // 类绑定，方法绑定，全局绑定useGlobalInterceptors()
       @UseInterceptors(LoggingInterceptor)
     
       // 模块绑定
       import { Module } from '@nestjs/common';
       import { APP_INTERCEPTOR } from '@nestjs/core';
     
       @Module({
           providers: [
               {
                   provide: APP_INTERCEPTOR,
                   useClass: LoggingInterceptor,
               },
           ],
       })
       export class ApplicationModule {}
     

3. 自定义路由装饰器

    // 自定义装饰器
    import { createParamDecorator } from '@nestjs/common';
   
    export const User = createParamDecorator((data, req) => {
        return req.user;
    });
   
    // data 可以接收string， 也可以接受pipe
    @Get()
    async findOne(@User(new ValidationPipe()) user: UserEntity) {
        console.log(user);
    }
   

大致流程图