When is it appropriate to respond with a HTTP 412 error?
If you look at RFC 2616 you’ll see a number of request headers that can be used to apply conditions to a request: If-Match If-Modified-Since If-None-Match If-Range If-Unmodified-Since These headers contain ‘preconditions’, allowing the client to tell the server to only complete the request if certain conditions are met. For example, you use a PUT … Read more