JBridge: Certification Question Of The Day

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Last updated: Saturday 3rd May 2003

Which of the following are HTTP methods that can be described as idempotent?
Choose all that apply (3)

A GET
B POST
C PUSH
D OPTIONS
E TRACE
F PUT
G POP

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The Answer

Idempotent means that the method acts as if applied once even if applied multiple times.
GET, OPTIONS and TRACE are (or should be written to be!) idempotent; hence answers A, D & E are correct.
PUSH & POP are not HTTP methods.
POST gives no guarantee of idempotency.
PUT doesn't either. Often, PUT acts idempotently - if you send the same file and URL request over and over again, all that happens is that the file is replaced in the same part of the server over and over again. However, the point is that PUT offers no guarantees; the placing of the file on the server may trigger a process which can't be repeated.

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