How to validate request in typeorm controller

Question

I have created a sample application to save data for a user. I wanted to know how to validate it before saving and showing the response in JSON. I have got a reference link but its not using a controller.

Please suggest a solution using a controller. Below is my code

Entity file:

import {Entity, PrimaryGeneratedColumn, Column} from "typeorm"; 

@Entity() 
export class User { 

   @PrimaryGeneratedColumn() 
   id: number; 

   @Column() 
   firstName: string; 
 
   @Column() 
   lastName: string; 
       
   @Column() 
   age: number; 
}

Controller file:

import {getRepository} from "typeorm"; import {NextFunction, Request, Response} from "express"; import {User} from "../entity/User"; 
    
export class UserController {
    
   private userRepository = getRepository(User); 
       
   async all(request: Request, response: Response, next: NextFunction) { 
      return this.userRepository.find(); 
   } 
       
   async one(request: Request, response: Response, next: NextFunction) { 
      return this.userRepository.findOne(request.params.id); 
   } 
       
   async save(request: Request, response: Response, next: NextFunction) { 
      return this.userRepository.save(request.body); 
   } 

   async remove(request: Request, response: Response, next: NextFunction) { 
     let userToRemove = await this.userRepository.findOne(request.params.id); 
     await this.userRepository.remove(userToRemove); 
   } 
}

I wanted to validate firstname and lastname as mandatory i.e. no blank value should be accepted and age should take no blank values and numbers only.

Answer 1

Yes you can by using validate function in model class:

import {Entity, PrimaryGeneratedColumn, Column} from "typeorm"; 

@Entity() 
export class User { 

    @PrimaryGeneratedColumn() 
    id: number; 

    @Column() 
    firstName: string; 
     
    @Column() 
    lastName: string; 
           
    @Column() 
    age: number; 
     
    @BeforeInsert()
    @BeforeUpdate()
    async validate() {
      await validateOrReject(this);
    }

}

Answer 2

You can use the class-validator and class-transformer package. Define the structure of JSON as a typescript class and add decorators from class-validator package.

export class UserStructure { 

   @IsString()
   firstName: string; 
 
   @IsString()
   lastName: string; 
       

   age: number; 
}

Use class transformer to convert plain object to UserStructure Class and then pass the class to validate function which is imported from class-validator package for performing validation

import { plainToClass } from 'class-transformer';
import {validate} from 'class-validator';

//Place the following code inside your controller
let userStructureClass = plainToClass(UserStructure , req.body); //convert req.body plain object to UserStructure Class
let errors = await validate(userStructureClass);
if(errors.length > 0) req.json(errors)

• class-validator : https://www.npmjs.com/package/class-validator
• class-transformer : https://www.npmjs.com/package/class-transformer

NOTE : validate method only works for classes that is why we converted req.body plain object to class using class-transformer and then performed validation. These packages uses decorators so make sure to place the following in tsconfig.json

 "emitDecoratorMetadata": true,
 "experimentalDecorators": true,