Exception for REST services for invalid input requests

Question

I am currently developing REST services and throwing BadRequestException for all of the following,

1. Path parameter is invalid
2. Query parameter is invalid
4. Input request object has missing attributes 

Is there any specific exceptions for each case like InvalidParameterException or so..? Is there any documentation available to learn which exceptions should be thrown on what situations?

Answer 1

All 3 errors sound like client errors, as the client fails to abide by the contract - so I would return a HTTP 400 Bad Request - perhaps with an explanation in the body of the response.

Answer 2

I believe usually you would create separate cases depending on how you would like to handle these errors. For example, you will have 3 different exceptions to represent your errors.

Most frameworks then allow you to install ExceptionMappers. These map your exceptions to an HTTP response code. These are documented and you should follow them:

For example: http://www.restapitutorial.com/httpstatuscodes.html

In your case for example, I would throw IllegalArgumentExceptions for all those 3 cases and install a mapper, mapping this to a 400 response code with potentially some info. This can be for example important since the client consuming your service will not receive your exceptions anyway, but rather analyse the response code of the request. With a 400, a user will then know that the request was invalid and won't be retried. You can have similar cases for all sorts.

To read about exception mappers, for example with the help of jersey:

https://jersey.java.net/documentation/latest/representations.html

So to your question: No, I don't believe there is any best-practise on what Exceptions are thrown from your application. Usually REST frameworks don't have specific exception mappers other than a catch-all mapper that will return a 500 (Internal Server Error)

There is however documentation for REST and the HTTP with regards to which responses should be returned for specific use cases. You should try and design your REST endpoint to conform to those standards for maximum reusability and understandability.

I hope that helps,

Artur