REST ideas mandate to make use of HTTP standing to speak. For errors, HTTP defines two ranges: shopper errors, 4xx, and server errors, 5xx.
Think about a banking API that lets you make transfers. It ought to fail for those who attempt to switch extra funds to your account. A few HTTP standing codes can match:
400 Dangerous Request: The server can’t or is not going to course of the request because of one thing that’s perceived to be a shopper error402 Cost Required: The request can’t be processed till the shopper makes a cost. Nonetheless, no customary use conference exists, and completely different entities use it in different contexts.409 Battle: The request battle with the present state of the goal useful resource
Right here’s the primary downside: HTTP standing codes had been specified for human-to-machine interactions through browsers, not for machine-to-machine interactions through APIs. Therefore, choosing a standing code that maps one-to-one to the use case isn’t easy. For the report, Martin Fowler appears to favor 409 in our case.
Regardless of the standing code, the second downside issues the error payload or, extra exactly, its construction. The construction is unimportant if a single group manages the shopper and the API supplier. Even when a devoted staff develops every of them, they’ll align. For instance, think about a cell app that calls its personal API.
Nonetheless, points come up when a staff decides to make use of a third-party API. The selection of the response construction is important on this case as a result of it’s now thought of a part of a contract: any change from the supplier might break the purchasers. Worse, the construction is probably going completely different from supplier to supplier.
Therefore, a standardized error reporting construction:
- Gives uniformity throughout suppliers
- Will increase API stability
