Custom Parsers

The plugin includes a built-in request body parser that automatically handles common content types such as JSON and URL-encoded data.

However, in advanced scenarios you may need to:

• Integrate existing Express parsers
• Support multipart file uploads
• Apply custom body transformations
• Add validation or sanitization layers
• Support proprietary or non-standard formats

For these cases, the plugin allows full parser customization.

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Default Parser Behavior

When the parser option is enabled (default behavior):

• JSON bodies are automatically parsed
• Query parameters are extracted
• Uploaded files (multipart) are parsed if supported

universalApi({
  endpointPrefix: '/api',
  parser: true
})

---

Disabling the Parser

You can disable parsing entirely:

universalApi({
  endpointPrefix: '/api',
  parser: false
})

---

Custom Parser Configuration

parser: {
  parser: ParserFunction | ParserFunction[],
  transform: (req: IncomingMessage) => ({
    body?: any
    files?: UploadedFile[]
    query?: URLSearchParams
  })
}

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Example: Express Integration

import express from 'express'
import multer from 'multer'

const upload = multer()

universalApi({
  endpointPrefix: '/api',
  parser: {
    parser: [
      express.json(),
      express.urlencoded({ extended: true }),
      upload.any()
    ],
    transform: (req: any) => ({
      body: req.body,
      files: req.files?.map((file: any) => ({
        name: file.originalname,
        content: file.buffer,
        contentType: file.mimetype
      })),
      query: new URLSearchParams(req.url.split('?')[1])
    })
  }
})

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Best Practices

✔ Keep parser logic minimal
✔ Validate input early
✔ Avoid blocking operations
✔ Use streaming for large data

Next Steps

• REST Handlers - Add custom logic
• Pagination & Filters - Detailed configuration
• HTTP Methods - Complete reference