126-java-exception-handling

# 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 ## 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](references/126-java-exception-handling.md).