Global Error Handling

Consistent error responses are crucial for API usability. This article covers implementing RFC 7807 Problem Details, building a global exception handler, and creating a unified error handling strategy across your application.

📋 At a Glance

Aspect	Details
Standard	RFC 7807 Problem Details for HTTP APIs
Spring Support	ProblemDetail (Spring 6+), @ControllerAdvice
Content-Type	application/problem+json
Benefits	Consistent errors, machine-readable, self-documenting

🎯 What You'll Learn

RFC 7807 Problem Details standard
Spring Boot 3 native support
Global exception handler implementation
Error mapping strategies
Logging and monitoring integration

Production Story: The Inconsistent API

An API had inconsistent error responses across endpoints:

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Problems:

Frontend needed different parsing for each endpoint
No way to programmatically identify error type
Documentation was a nightmare
Third-party integrations constantly broke

The fix: RFC 7807 everywhere:

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Mental Model: RFC 7807 Structure

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🔬 Deep Dive

Pattern 1: Spring 6+ Native ProblemDetail

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Pattern 2: Custom Problem Detail with Builder

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Pattern 3: Comprehensive Exception Handler

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Pattern 4: Error Catalog

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Pattern 5: Logging and Monitoring

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Pattern 6: Client-Side Error Handling

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⚠️ Common Mistakes

Mistake 1: Exposing Internal Details

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Mistake 2: Inconsistent Error Codes

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🐛 Debug This: The Leaking Stack Trace

A security audit reveals: "API responses include full stack traces and SQL queries in production!"

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What sensitive information is being exposed and how would you fix it?

✅ Solution:

Multiple security issues:

Stack traces - Reveal internal class names, line numbers, library versions
Cause messages - Can expose database schema, table names
SQL queries - Can expose column names, sometimes even query parameters
Exception messages - May contain user data or system details

Secure implementation:

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The lesson: Never expose stack traces, causes, or internal details to clients. Log everything server-side with a correlation ID, return only sanitized messages to users.

💻 Exercises

Exercise 1: Basic RFC 7807 Response

⭐ Difficulty: Easy | ⏱️ Time: 15 minutes

Task: Create a simple RFC 7807 problem response.

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✅ Solution:

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Exercise 2: Exception Handler with Metrics

⭐⭐ Difficulty: Medium | ⏱️ Time: 20 minutes

Task: Create an exception handler that records error metrics.

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✅ Solution:

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Exercise 3: Error Catalog

⭐⭐ Difficulty: Medium | ⏱️ Time: 20 minutes

Task: Create a centralized error catalog with predefined error types.

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✅ Solution:

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Exercise 4: Validation Error Formatting

⭐⭐⭐ Difficulty: Medium-Hard | ⏱️ Time: 20 minutes

Task: Handle Spring validation errors with detailed field-level information.

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✅ Solution:

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Exercise 5: Client Error Handling

⭐⭐⭐⭐ Difficulty: Hard | ⏱️ Time: 25 minutes

Task: Create an API client that properly handles RFC 7807 error responses.

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✅ Solution:

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📝 Summary

Component	Purpose
type	URI identifying error type
title	Human-readable summary (same for all instances)
status	HTTP status code
detail	Specific explanation for this occurrence
instance	URI of the request
extensions	Custom fields (errorCode, traceId, errors[])

📅 Review Schedule for This Article

Day	Task	Time
Day 1	Review RFC 7807 structure diagram	5 min
Day 3	Redo Exercise 1 (Basic RFC 7807 Response)	15 min
Day 7	Answer interview questions without looking	10 min
Day 14	Redo Debug This (Leaking Stack Trace)	15 min
Day 30	Audit your API's error responses for RFC 7807 compliance	20 min

Next: [Part 17: Bean Validation]

📋 At a Glance

🎯 What You'll Learn

Production Story: The Inconsistent API

Mental Model: RFC 7807 Structure

🔬 Deep Dive

Pattern 1: Spring 6+ Native ProblemDetail

Pattern 2: Custom Problem Detail with Builder

Pattern 3: Comprehensive Exception Handler

Pattern 4: Error Catalog

Pattern 5: Logging and Monitoring

Pattern 6: Client-Side Error Handling

⚠️ Common Mistakes

Mistake 1: Exposing Internal Details

Mistake 2: Inconsistent Error Codes

🐛 Debug This: The Leaking Stack Trace

💻 Exercises

Exercise 1: Basic RFC 7807 Response

Exercise 2: Exception Handler with Metrics

Exercise 3: Error Catalog

Exercise 4: Validation Error Formatting

Exercise 5: Client Error Handling

📝 Summary

📅 Review Schedule for This Article

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