126-java-exception-handling

name	126-java-exception-handling
description	Use when you need to apply Java exception handling best practices — including using specific exception types, managing resources with try-with-resources, securing exception messages, preserving error context via exception chaining, validating inputs early with fail-fast principles, handling thread interruption correctly, documenting exceptions with @throws, enforcing logging policy, translating exceptions at API boundaries, managing retries and idempotency, enforcing timeouts, attaching suppressed exceptions, and propagating failures in async/reactive code. This should trigger for requests such as Exception handling; Use try-with-resources in Java code; Create exception chaining in Java code; Apply fail-fast validation in Java code; Review Java exception taxonomy and propagation. Part of Plinth Toolkit
license	Apache-2.0
metadata	{"author":"Juan Antonio Breña Moral","version":"0.18.0"}

Java Exception Handling Guidelines

Identify and apply robust Java exception handling practices to improve error clarity, security, debuggability, and system reliability.

What is covered in this Skill?

• Specific exception types instead of generic Exception/RuntimeException
• try-with-resources for automatic resource cleanup
• Secure exception messages that avoid information leakage
• Exception chaining to preserve full error context
• Early input validation with IllegalArgumentException/NullPointerException
• InterruptedException handling with interrupted-status restoration
• @throws JavaDoc documentation, fail-fast principle
• Structured logging with correlation IDs, avoiding log-and-throw duplication
• API boundary translation via centralized exception mappers
• Bounded retry with backoff for idempotent operations only
• Timeout enforcement with deadline propagation
• Throwable#addSuppressed for secondary cleanup failures
• Never catching Throwable/Error
• Observability via error metrics
• Failure propagation in async CompletionStage code

Scope: The reference is organized by examples (good/bad code patterns) for each core area. Apply recommendations based on applicable examples.

Constraints

Before applying any exception handling changes, ensure the project compiles. If compilation fails, stop immediately — do not proceed until resolved. After applying improvements, run full verification.

• MANDATORY: Run ./mvnw compile or mvn compile before applying any changes
• SAFETY: If compilation fails, stop immediately — do not proceed until the project is in a valid state
• VERIFY: Run ./mvnw clean verify or mvn clean verify after applying improvements
• BEFORE APPLYING: Read the reference for detailed good/bad examples, constraints, and safeguards for each exception handling pattern

When to use this skill

• Exception handling
• Use try-with-resources in Java code
• Create exception chaining in Java code
• Apply fail-fast validation in Java code
• Review Java exception taxonomy and propagation

Workflow

1. Compile project before exception-handling changes

Run ./mvnw compile or mvn compile and stop immediately if compilation fails.

2. Read exception-handling reference

Read references/126-java-exception-handling.md and identify applicable failure-handling and observability improvements.

3. Apply exception-handling improvements

Refactor to specific exceptions, safe resource handling, error translation, and consistent logging patterns.

4. Verify with full build

Run ./mvnw clean verify or mvn clean verify after applying improvements.

Reference

For detailed guidance, examples, and constraints, see references/126-java-exception-handling.md.