ExceptionResolver class abstract interface

Strategy interface for resolving exceptions that occur during HTTP request processing.

Overview

The ExceptionResolver defines a contract for components that handle exceptions thrown during the execution of HTTP request handlers. Implementations of this interface provide specialized exception resolution strategies that can transform exceptions into appropriate HTTP responses.

Key Responsibilities

  • Exception Handling: Catch and process exceptions from handler method execution
  • Response Generation: Create appropriate HTTP responses for different exception types
  • Error Transformation: Convert technical exceptions to user-friendly error responses
  • Resolution Coordination: Work with other resolvers in a chain of responsibility pattern

Resolution Process

When an exception occurs during request processing:

  1. Framework Detection: The framework catches exceptions from handler methods
  2. Resolver Chain: Invokes registered ExceptionResolver instances in order
  3. Resolution Attempt: Each resolver attempts to handle the exception
  4. First Match Wins: The first resolver that returns true stops the chain
  5. Fallback Handling: If no resolver handles the exception, default error handling applies

Implementation Patterns

Common resolver implementations include:

  • ControllerAdviceExceptionResolver: Uses @ControllerAdvice annotated pods
  • ResponseStatusExceptionResolver: Handles @ResponseStatus annotated exceptions
  • DefaultExceptionResolver: Provides fallback exception handling
  • Custom Business Exception Resolvers: Application-specific exception handling

Return Value Semantics

  • true: The exception was successfully resolved and an HTTP response was generated
  • false: The resolver could not handle this exception type, continue to next resolver

Example: Custom Exception Resolver

@Pod
class BusinessExceptionResolver implements ExceptionResolver {
  @override
  Future<bool> resolve(
    ServerHttpRequest request,
    ServerHttpResponse response,
    HandlerMethod handler,
    Object ex,
  ) async {
    if (ex is BusinessException) {
      response.setStatus(HttpStatus.BAD_REQUEST);
      response.getBody().writeString('Business error: ${ex.message}');
      return true;
    }
    return false;
  }
}

Integration with Handler Pipeline

Exception resolvers integrate with the handler execution pipeline:

  • Pre-handler: Exceptions from argument resolution
  • During-handler: Exceptions from handler method execution
  • Post-handler: Exceptions from return value handling

Thread Safety

Implementations should be thread-safe as they may be invoked concurrently by multiple request processing threads.

Error Page Integration

Resolvers can work with the ErrorPages registry to:

  • Map exceptions to specific HTTP status codes
  • Render appropriate error page templates
  • Handle redirects for error scenarios

Best Practices

  • Specificity: Handle specific exception types rather than generic exceptions
  • Composition: Chain multiple specialized resolvers for comprehensive coverage
  • Performance: Cache resolution logic for common exception types when possible
  • Logging: Log exceptions appropriately before transforming to user responses
  • Security: Avoid exposing sensitive exception details in production responses
  • HandlerMethod: The handler method that generated the exception
  • ServerHttpRequest: The current HTTP request being processed
  • ServerHttpResponse: The HTTP response to populate with error details
  • ControllerAdviceExceptionResolver: Resolver using controller advice pods
  • ErrorPages: Registry for error page configurations

Summary

The ExceptionResolver interface enables a flexible, extensible approach to exception handling in Jetleaf applications, supporting both framework-provided strategies and custom application-specific error handling logic.

Implementers

Properties

hashCode → int
The hash code for this object.
no setterinherited
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited

Methods

getSupportedMediaTypes() → List<MediaType>
Returns the list of media types this handler supports by default.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
resolve(ServerHttpRequest request, ServerHttpResponse response, HandlerMethod? handler, Object ex, StackTrace st) → Future<bool>
Attempts to resolve an exception by generating an appropriate HTTP response.
toString() → String
A string representation of this object.
inherited

Operators

operator ==(Object other) → bool
The equality operator.
inherited