The project will implement comprehensive error and exception handling to ensure robustness and reliability. Different types of errors will be handled appropriately through different mechanisms.
Programming errors caused by mistakes in the code logic, such as null pointer exceptions, index out of bounds exceptions, type mismatch exceptions etc. will be caught using try-catch blocks and handled gracefully. For all checked exceptions, the code will either catch and handle the exception, or specify that it throws the exception. Unchecked exceptions will be caught and managed carefully. For any unexpected exceptions, detailed exception objects will be created containing information about the reason, location and stack trace of the error to help with debugging.
Custom exception classes will be defined for all expected application-level exceptions like invalid user input, database connection failures, network errors etc. These custom exceptions will allow capturing additional contextual information specific to that error type. For example, a custom ‘InvalidInputException’ can contain the invalid value that caused the exception. Standardized error handling code will process these custom exceptions and return appropriate user-friendly error responses.
Configuration and initialization errors will be detected early during the application startup phase. Detailed validation of external configuration files and databases will be done to check for any issues with credentials, file permissions, schema mismatches etc. and throw descriptive exceptions specifying the problem. This prevents failures later during normal execution.
Infrastructure and environmental errors outside the application’s control like network failures, disk errors, timeouts will be gracefully handled without crashing the application. For network requests, timeouts will be set and connection reset/failures will throw specific exceptions that backend error handling can interpret. File I/O will have try-with-resources blocks and timeout settings to avoid locks in case of issues accessing resources.
Logging of errors and exceptions will follow industry best practices to aid troubleshooting. A central logger will be configured to write to files and databases with contextual details. Each log will capture the full exception/error object, thread details, stack trace etc. Log levels can be configured and different log appenders used based on severity to balance between noise and silence. Periodic health checks will monitor disk space, log sizes to ensure logs don’t fill up during prolonged errors.
For known application errors that may occur frequently, specific error codes mapped to user-friendly messages will be returned instead of full exceptions for client-facing APIs. 4xx and 5xx HTTP status codes will classify client and server errors as per REST guidelines. Non-critical errors may be gracefully ignored/logged based on configuration to avoid frequent crashing.
A centralized error handling framework based on dependency injection will process exceptions/errors across the application layers. It will parse exceptions, log details to files/databases, and return consistent machine-readable or user-friendly responses. Common class hierarchies for errors, logging and configurations will promote separation of concerns and testability.
Comprehensive automated unit and integration testing of error paths will be part of the initial development and ongoing quality assurance. Error scenarios and exceptions will be simulated to validate graceful handling without crashes. Tests will validate logged details, responses are as expected for different error types. Performance tests will evaluate the handling under varying load conditions.
Monitoring and instrumentation of the deployed system will continuously watch for emerging exceptions/errors. Metrics will show rates of known and unknown exceptions. Alerts will notify on changes in failure volumes compared to historical baselines. Distributed tracing can help troubleshoot specific problematic requests generating errors. Over time, previously unknown errors may be categorized, or the underlying issues resolved based on evidence from monitoring.
Together, these techniques will ensure a robust and resilient application architecture. Careful error handling prevents failures from impacting users while aiding debugging through structured logging, monitoring, and testing. The practices adopted will deliver high service reliability and improve user experience of the system even during exceptional conditions.