Normalizers

🧪 Normalizers

What is a Normalizer?

A Normalizer is a component that transforms messages between different formats before sending and after receiving. It plays a crucial role in serialization and deserialization—ensuring that messages are properly encoded for transmission and correctly decoded when received.

This is especially helpful when integrating with systems that require specific data formats like Protobuf, Base64, or custom JSON structures.

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🧩 Why Use a Normalizer?

You may want to use a custom normalizer to:

• Work with binary formats like Protobuf

• Encode messages in Base64 or another custom format

• Encrypt/decrypt messages

• Support custom serialization logic not handled by default JSON

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⚙️ Defining a Normalizer

To create a normalizer, implement the MessageNormalizer interface and decorate the class with @MessagingNormalizer().

Example: Base64 Normalizer

import { Injectable } from '@nestjs/common';
import { MessagingNormalizer, MessageNormalizer } from '@nestjstools/messaging';
import { Buffer } from 'buffer';

@Injectable()
@MessagingNormalizer()
export class Base64Normalizer implements MessageNormalizer {
  denormalize(message: string | object, type: string): Promise<object> {
    if (typeof message === 'object') {
      throw new Error('Message must be a string!');
    }
    return Promise.resolve(
      JSON.parse(Buffer.from(message, 'base64').toString('utf-8')),
    );
  }

  normalize(message: object, type: string): Promise<string> {
    const jsonString = JSON.stringify(message);
    return Promise.resolve(
      Buffer.from(jsonString, 'utf-8').toString('base64'),
    );
  }
}

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🔄 How It Works

Phase	Description
Normalize	Called before sending. Converts a message object into a transport-safe string (e.g., Base64).
Denormalize	Called after receiving. Converts the raw string back into a message object.

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🎯 Usage Per Channel

You can assign a normalizer per channel in your messaging configuration. This allows different channels to use different formats as needed:

new InMemoryChannelConfig({
  name: 'my-channel',
  normalizer: Base64Normalizer, // Use custom normalizer for this channel
}),

💡 Each channel can use a different normalizer depending on the protocol or service it interacts with.

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Summary

Feature	Description
normalize()	Transforms message before it’s sent
denormalize()	Parses message after it’s received
Per-channel config	Apply specific format handling per communication channel