Custom Validation with class-validator
Sometimes the built-in tsoa-next validator is not enough for an application-specific workflow. In that case you can attach your own validation middleware, for example with class-validator. Relevant API reference: @Middlewares, ValidateError, @Body, @Post, and @SuccessResponse.
This chapter shows a middleware-based class-validator approach for Express.
The @Middlewares decorator accepts middleware functions as positional arguments:
@Middlewares(validateBody(RequestClass))Install class-validator package
Install class-validator and class-transformer as described in their repos:
https://github.com/typestack/class-transformer
https://github.com/typestack/class-validator
Write custom middleware
The example validation middleware using class-validator:
import { ClassConstructor, plainToInstance } from 'class-transformer';
import { validateSync } from 'class-validator';
import { NextFunction, Request, Response } from 'express';
import { ValidateError } from 'tsoa-next';
export function validateBody<T extends object>(targetClass: ClassConstructor<T>) {
return async (req: Request, _res: Response, next: NextFunction) => {
const instance = plainToInstance(targetClass, req.body);
const errors = validateSync(instance, {
forbidUnknownValues: true,
validationError: {
target: false
}
});
const fieldsErrors: { [name: string]: { message: string; value: string } } = {};
if (errors.length > 0) {
errors.forEach(error => {
if (error.constraints) {
fieldsErrors[error.property] = {
message: Object.values(error.constraints).join(', '),
value: error.value
};
}
if (error.children) {
error.children.forEach(errorNested => {
if (errorNested.constraints) {
fieldsErrors[errorNested.property] = {
message: Object.values(errorNested.constraints!).join(', '),
value: errorNested.value
};
}
})
}
});
next(new ValidateError(fieldsErrors, 'Validation failed'));
return;
}
next();
};
}Annotate a request class with class-validator
import { Length } from 'class-validator'
class RequestClass {
@Length(1, 2000)
public text!: string
}Usage in a controller
import {
Body,
Controller,
Middlewares,
Post,
Route,
SuccessResponse,
} from 'tsoa-next'
import { validateBody } from '../middleware/ValidationMiddleware'
@Route('post')
export class PostController extends Controller {
@SuccessResponse('200', 'Post created')
@Post()
@Middlewares(validateBody(RequestClass))
public async create(@Body() request: RequestClass): Promise<void> {
console.log(`validated request: ${request.text}`)
}
}class-validator and class-transformer may need emitDecoratorMetadata depending on the decorators and transformation features you use. That requirement comes from those libraries, not from @Middlewares(...) itself.
Contributors
Vanna DiCatania