【NestJS】06 AOP：用“切面思维”把通用逻辑从业务代码里“刨”出来

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import { Injectable, NestMiddleware } from '@nestjs/common'
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import { Request, Response, NextFunction } from 'express'
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@Injectable()
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export class LogMiddleware implements NestMiddleware {
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  use(req: Request, res: Response, next: NextFunction) {
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    console.log(`[${new Date().toLocaleString()}] ${req.method} ${req.url}`)
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    next() // 必须调用next()，否则请求会被拦截
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  }
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}

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import { NestFactory } from '@nestjs/core'
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import { AppModule } from './app.module'
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import { LogMiddleware } from './log.middleware'
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async function bootstrap() {
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  const app = await NestFactory.create(AppModule)
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  app.use(new LogMiddleware()) // 全局启用日志中间件
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  await app.listen(3000)
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}
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bootstrap()

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import { Module, NestModule, MiddlewareConsumer } from '@nestjs/common'
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import { LogMiddleware } from './log.middleware'
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import { AppController } from './app.controller'
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@Module({
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  controllers: [AppController],
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})
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export class AppModule implements NestModule {
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  configure(consumer: MiddlewareConsumer) {
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    consumer
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      .apply(LogMiddleware) // 应用中间件
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      .forRoutes('api/admin*') // 作用于所有/api/admin开头的路由
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  }
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}

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import { CanActivate, ExecutionContext, Injectable } from '@nestjs/common'
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import { JwtService } from '@nestjs/jwt'
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import { Request } from 'express'
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@Injectable()
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export class AuthGuard implements CanActivate {
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  constructor(private jwtService: JwtService) {} // 注入JWT服务
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  canActivate(context: ExecutionContext): boolean {
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    const req = context.switchToHttp().getRequest<Request>()
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    const token = req.headers.authorization?.split(' ')[1] // 从请求头拿token
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    if (!token) return false // 没有token，拦截
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    try {
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      this.jwtService.verify(token) // 校验token有效性
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      return true // 校验通过，放行
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    } catch (e) {
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      return false // 校验失败，拦截
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    }
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  }
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}

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import { Module } from '@nestjs/common'
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import { APP_GUARD } from '@nestjs/core'
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import { AuthGuard } from './auth.guard'
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@Module({
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  providers: [
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    {
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      provide: APP_GUARD,
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      useClass: AuthGuard, // 全局启用AuthGuard
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    },
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  ],
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})
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export class AppModule {}

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import {
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  Injectable,
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  NestInterceptor,
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  ExecutionContext,
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  CallHandler,
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} from '@nestjs/common'
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import { Observable } from 'rxjs'
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import { tap } from 'rxjs/operators'
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@Injectable()
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export class TimeInterceptor implements NestInterceptor {
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  intercept(context: ExecutionContext, next: CallHandler): Observable<any> {
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    const startTime = Date.now() // 记录开始时间
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    return next.handle().pipe(
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      tap(() => {
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        const endTime = Date.now()
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        console.log(`接口耗时：${endTime - startTime}ms`) // 打印耗时
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      })
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    )
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  }
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}

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import { PipeTransform, Injectable, BadRequestException } from '@nestjs/common'
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import { ArgumentMetadata } from '@nestjs/common/interfaces'
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@Injectable()
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export class ValidatePipe implements PipeTransform {
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  transform(value: any, metadata: ArgumentMetadata) {
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    // metadata.data：参数名（比如@Query('num')中的'num'）
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    if (isNaN(Number(value))) {
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      throw new BadRequestException(`参数${metadata.data}必须是数字`)
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    }
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    return Number(value) * 10 // 转换参数（乘10）
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  }
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}

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import { Controller, Get, Query, UsePipes } from '@nestjs/common'
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import { ValidatePipe } from './validate.pipe'
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@Controller('api')
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export class AppController {
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  @Get('calc')
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  // 对num参数应用ValidatePipe
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  calc(@Query('num', ValidatePipe) num: number) {
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    return num + 1 // 接收的num已经是乘10后的值
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  }
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}

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import { NestFactory } from '@nestjs/core'
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import { AppModule } from './app.module'
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import { ValidationPipe } from '@nestjs/common'
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async function bootstrap() {
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  const app = await NestFactory.create(AppModule)
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  // 全局启用ValidationPipe（自动校验DTO）
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  app.useGlobalPipes(
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    new ValidationPipe({
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      whitelist: true, // 过滤掉DTO中没有的属性
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      forbidNonWhitelisted: true, // 有非DTO属性时抛异常
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      transform: true, // 自动转换参数类型
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    })
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  )
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  await app.listen(3000)
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}

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import {
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  ExceptionFilter,
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  Catch,
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  ArgumentsHost,
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  BadRequestException,
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} from '@nestjs/common'
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import { Response } from 'express'
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@Catch(BadRequestException) // 捕获BadRequestException
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export class BadRequestFilter implements ExceptionFilter {
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  catch(exception: BadRequestException, host: ArgumentsHost) {
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    const ctx = host.switchToHttp()
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    const res = ctx.getResponse<Response>()
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    const status = exception.getStatus() // 异常的HTTP状态码（400）
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    res.status(status).json({
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      code: status,
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      message: `参数错误：${exception.message}`, // 自定义错误信息
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      data: null,
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    })
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  }
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}

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import { Controller, Get, UseFilters } from '@nestjs/common'
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import { BadRequestFilter } from './bad-request.filter'
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@Controller('api')
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@UseFilters(BadRequestFilter) // 该Controller的异常用自定义Filter处理
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export class AppController {
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  @Get('calc')
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  calc(@Query('num') num: number) {
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    if (isNaN(num)) throw new BadRequestException('num必须是数字')
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    return num + 1
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  }
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}

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import { NestFactory } from '@nestjs/core'
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import { AppModule } from './app.module'
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import { BadRequestFilter } from './bad-request.filter'
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async function bootstrap() {
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  const app = await NestFactory.create(AppModule)
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  app.useGlobalFilters(new BadRequestFilter()) // 全局启用自定义异常Filter
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  await app.listen(3000)
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}

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import { Injectable, NestMiddleware } from '@nestjs/common'
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import { Request, Response, NextFunction } from 'express'
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@Injectable()
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export class LogMiddleware implements NestMiddleware {
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  use(req: Request, res: Response, next: NextFunction) {
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    console.log(`[${new Date().toLocaleString()}] ${req.method} ${req.url}`)
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    next()
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  }
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}

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import { CanActivate, ExecutionContext, Injectable } from '@nestjs/common'
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import { JwtService } from '@nestjs/jwt'
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import { Request } from 'express'
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@Injectable()
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export class AuthGuard implements CanActivate {
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  constructor(private jwtService: JwtService) {}
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  canActivate(context: ExecutionContext): boolean {
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    const req = context.switchToHttp().getRequest<Request>()
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    const token = req.headers.authorization?.split(' ')[1]
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    if (!token) throw new Error('缺少token') // 会被ExceptionFilter捕获
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    try {
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      this.jwtService.verify(token, { secret: 'your-secret-key' }) // 替换成你的JWT密钥
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      return true
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    } catch (e) {
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      throw new Error('无效的token')
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    }
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  }
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}

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import {
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  Injectable,
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  NestInterceptor,
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  ExecutionContext,
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  CallHandler,
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} from '@nestjs/common'
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import { Observable } from 'rxjs'
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import { tap } from 'rxjs/operators'
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@Injectable()
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export class TimeInterceptor implements NestInterceptor {
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  intercept(context: ExecutionContext, next: CallHandler): Observable<any> {
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    const startTime = Date.now()
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    return next.handle().pipe(
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      tap(() => {
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        console.log(
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          `[${context.getHandler().name}] 耗时：${Date.now() - startTime}ms`
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        )
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      })
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    )
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  }
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}

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import { IsString, IsEmail, MinLength } from 'class-validator'
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export class CreateUserDto {
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  @IsString({ message: '姓名必须是字符串' }) // 校验类型
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  name: string
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  @IsEmail({}, { message: '邮箱格式错误' }) // 校验邮箱格式
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  email: string
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  @MinLength(6, { message: '密码至少6位' }) // 校验长度
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  password: string
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}

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import {
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  ExceptionFilter,
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  Catch,
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  ArgumentsHost,
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  HttpException,
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} from '@nestjs/common'
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import { Response } from 'express'
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@Catch() // 捕获所有异常（包括HttpException和自定义异常）
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export class GlobalExceptionFilter implements ExceptionFilter {
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  catch(exception: unknown, host: ArgumentsHost) {
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    const ctx = host.switchToHttp()
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    const res = ctx.getResponse<Response>()
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    const req = ctx.getRequest<Request>()
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    // 判断异常类型
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    const status =
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      exception instanceof HttpException ? exception.getStatus() : 500
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    const message =
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      exception instanceof Error ? exception.message : '服务器内部错误'
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    res.status(status).json({
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      code: status,
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      message,
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      path: req.url,
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      timestamp: new Date().toLocaleString(),
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    })
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  }
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}

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app.useGlobalFilters(new GlobalExceptionFilter())