Handling HTTPExceptions with a Custom Exception Handler

In FastAPI, HTTPExceptions are used to represent specific HTTP status codes and error messages. By creating a custom exception handler, you can customize the way these exceptions are handled and provide more informative responses to clients.

Creating a Custom Exception Handler

Create a Function:

Python

from fastapi import FastAPI, Request, Response, status

app = FastAPI()

@app.exception_handler(HTTPException)
async def http_exception_handler(request: Request, exc: HTTPException) -> Response:
# Custom exception handling logic
return Response(content=”An error occurred”, status_code=exc.status_code)

Customize the Response:

You can customize the response content, status code, or headers based on the specific exception. For example:

Python

@app.exception_handler(HTTPException)
async def http_exception_handler(request: Request, exc: HTTPException) -> Response:
if exc.status_code == 404:
return Response(content=”Resource not found”, status_code=404)
else:
return Response(content=”An error occurred”, status_code=exc.status_code)

Handling Specific Exceptions

You can create separate exception handlers for specific types of HTTPExceptions:

Python

@app.exception_handler(HTTPException)
async def http_exception_handler(request: Request, exc: HTTPException) -> Response:
    if isinstance(exc, HTTPException):
        if exc.status_code == 404:
            # Handle 404 exceptions
        elif exc.status_code == 401:
            # Handle 401 exceptions
        else:
            # Handle other exceptions
    else:
        # Handle other types of exceptions

By creating custom exception handlers, you can provide a more planned and informative error response to your clients, improving the overall user experience of your FastAPI application.