Data Validation

Validation is essential for correctness, security, and stable APIs.

Why validate?

Without validation, you can get:

Malicious payload injection
Type mismatches
Invalid business data
Downstream persistence errors

With validation, you get predictable and safer behavior.

Install validation component

npm install @midwayjs/validate

package.json:

{
  "dependencies": {
    "@midwayjs/validate": "^4.0.0"
  }
}

Optional Swagger support:

npm install @midwayjs/swagger

package.json:

{
  "dependencies": {
    "@midwayjs/swagger": "^4.0.0"
  }
}

Enable validate component

import { Configuration } from '@midwayjs/core';
import * as koa from '@midwayjs/koa';
import * as validate from '@midwayjs/validate';

@Configuration({
  imports: [koa, validate],
})
export class MainConfiguration {}

DTO + `@Validate()`

import { Rule, RuleType } from '@midwayjs/validate';

export class CreateUserDTO {
  @Rule(RuleType.string().required())
  name: string;

  @Rule(RuleType.string().email().required())
  email: string;

  @Rule(RuleType.number().min(0).max(150).optional())
  age?: number;
}

import { Controller, Post, Body, Inject } from '@midwayjs/core';
import { Validate } from '@midwayjs/validate';

@Post('/')
@Validate()
async create(@Body() dto: CreateUserDTO) {
  const user = await this.userService.createUser(dto.name, dto.email);
  return {
    success: true,
    message: 'User created successfully',
    data: user,
  };
}

Summary

Define validation in DTO classes
Use @Validate() on handlers
Keep validation close to API contract

Application Configuration

Best Practices Summary

Files

Preparing Environment