Error Handling

Glass Box maps exceptions to standard HTTP error responses. When any stage of request processing throws an exception, HTTPErrorHandler catches it, sends the appropriate error response, and logs the error.

Error Responses

All error responses follow the same format:

HTTP/1.1 {code} {message}
Content-Type: text/html; charset=utf-8
Connection: close

<h1>{code} {message}</h1>

Status Codes

Status Code	Message	Exception	Cause
400	Bad Request	BadRequestException	Malformed request line, missing method/path/version, invalid headers
404	Not Found	NotFoundException	No matching route, requested file does not exist, ToDo ID not found
405	Method Not Allowed	—	Sent directly by HTTPErrorHandler (not exception-mapped)
500	Internal Server Error	InternalServerErrorException	File read failures, unhandled exceptions
501	Not Implemented	NotImplementedException	Unsupported HTTP method, handler method not overridden

note

Any exception that doesn't match a specific type (i.e., is not one of the four custom exceptions) is treated as a 500 Internal Server Error.

Exception Classes

All custom exceptions extend Exception and live in the com.ns.tcpframework.exceptions package:

com.ns.tcpframework.exceptions
├── BadRequestException
├── NotFoundException
├── InternalServerErrorException
└── NotImplementedException

Usage in Handlers

Throw the appropriate exception from any handler and it will be automatically converted to an HTTP error response:

@Override
protected HTTPResponse handleGetRequest(HTTPRequest request) throws Exception {
    Path filePath = Paths.get(rootPath, request.getPath());

    if (!Files.exists(filePath)) {
        throw new NotFoundException("File not found: " + filePath);
    }

    // ... serve file
}

Usage in MethodeBasedHandler

If a handler extends MethodeBasedHandler but does not override a specific method (e.g., handlePostRequest), calling that method throws NotImplementedException, resulting in a 501 response.

Error Logging

All errors handled by HTTPErrorHandler are logged via ServerLogger at the ERROR level with destination EVERYWHERE, meaning they appear on both the server console and connected SSE clients:

[ERROR] Exception handled: File not found: /nonexistent.html