I have an HTTP request that retrieves an image from a database. When image retrieval happens, a view counter is incremented by one. Should this HTTP request be a GET request, or a POST request (given some state is modified by the request)?
Thanks!
>Solution :
It depends on the significance of incrementing the counter.
If increasing the counter is the point (or one of the points since you are also retrieving an image) of the request, then POST makes sense.
It is fine to use GET for retrieving data when there are changes on the server which are side effects (such as logging).
The working in the spec says:
Request methods are considered "safe" if their defined semantics are essentially read-only; i.e., the client does not request, and does not expect, any state change on the origin server as a result of applying a safe method to a target resource. Likewise, reasonable use of a safe method is not expected to cause any harm, loss of property, or unusual burden on the origin server.
This definition of safe methods does not prevent an implementation from including behavior that is potentially harmful, that is not entirely read-only, or that causes side effects while invoking a safe method. What is important, however, is that the client did not request that additional behavior and cannot be held accountable for it. For example, most servers append request information to access log files at the completion of every response, regardless of the method, and that is considered safe even though the log storage might become full and crash the server. Likewise, a safe request initiated by selecting an advertisement on the Web will often have the side effect of charging an advertising account.