# 🛑 Standardize API Error Handling with Global Middleware

[KhairnarLokesh]

🛑 Standardize API Error Handling with Global Middleware

📌 Title

Refactor Controllers to Use Centralized Global Error Handling Middleware

---

🚨 The Issue

Currently, controllers use:

• Individual try-catch blocks
• Inconsistent error response formats
• Mixed status codes
• Unpredictable error structures

This causes:

• ❌ Frontend parsing issues
• ❌ Inconsistent error UX
• ❌ Hard-to-maintain controllers
• ❌ Duplicated error logic
• ❌ Reduced debugging clarity

The API is not predictable for frontend consumption.

---

🎯 Goal

Implement a global error-handling middleware and refactor all controllers to:

• Remove redundant try-catch blocks
• Use next(error) pattern
• Standardize error response format
• Ensure consistent status codes
• Improve maintainability

---

🧱 Implementation Plan

---

1️⃣ Create Global Error Middleware

📁 Create:

middlewares/errorHandler.js

Example Structure:

function errorHandler(err, req, res, next) {
  console.error(err);

  const statusCode = err.statusCode || 500;

  res.status(statusCode).json({
    success: false,
    message: err.message || 'Internal Server Error',
    errorCode: err.code || 'SERVER_ERROR',
    timestamp: new Date().toISOString()
  });
}

module.exports = errorHandler;

---

2️⃣ Create Custom Error Utility

📁 Create:

utils/ApiError.js

Example:

class ApiError extends Error {
  constructor(statusCode, message, code = null) {
    super(message);
    this.statusCode = statusCode;
    this.code = code;
  }
}

module.exports = ApiError;

---

3️⃣ Refactor Controllers

Replace:

try {
  ...
} catch (error) {
  res.status(500).json({ error: error.message });
}

With:

if (!evidence) {
  return next(new ApiError(404, 'Evidence not found', 'EVIDENCE_NOT_FOUND'));
}

Let middleware handle the response.

---

4️⃣ Register Middleware in App

In:

app.js

Add at bottom:

app.use(errorHandler);

⚠ Must be after all routes.

---

📦 Standard Error Response Format

All errors should follow:

{
  "success": false,
  "message": "Evidence not found",
  "errorCode": "EVIDENCE_NOT_FOUND",
  "timestamp": "2026-02-25T14:00:00Z"
}

---

🧪 Refactor Scope

Apply to all controllers:

• evidenceUploadController
• evidenceIntegrityController
• evidenceBlockchainController
• evidenceJudicialController
• evidenceQueryController
• Any remaining legacy controllers

---

🧠 Error Categories to Standardize

Category	Status Code
Validation Error	400
Unauthorized	401
Forbidden	403
Not Found	404
Conflict	409
Blockchain Failure	502
Internal Server Error	500

---

🔐 Benefits

This change will:

• Improve frontend predictability
• Reduce controller boilerplate
• Enforce clean architecture
• Simplify debugging
• Enable centralized logging
• Allow future integration with monitoring tools (e.g., Sentry)

---

🧪 Testing Requirements

• Simulate validation error
• Simulate DB failure
• Simulate blockchain failure
• Simulate missing record
• Confirm consistent JSON response
• Confirm no controller sends manual error responses

---

📊 Acceptance Criteria

• errorHandler middleware created
• ApiError utility created
• Controllers refactored
• No manual res.status(...).json error responses
• All errors use consistent format
• Status codes standardized
• Middleware registered correctly
• API remains fully functional

---

🏁 Expected Outcome

A clean, predictable, and production-grade API error system that:

• Centralizes error handling
• Standardizes responses
• Improves frontend integration
• Enhances long-term maintainability

---

Priority: High
Type: Architectural Refactor
Impact: API Stability & Frontend Predictability

[Gooichand]

Good architectural improvement! This will standardize error responses across the API.

Task: Create global error middleware and refactor all controllers to use centralized error handling.

Priority: High - Improves API consistency and frontend predictability.

Looking for an experienced backend contributor. Please comment if interested!