SOAP API

Hello dear reader. After explaining what API is, now I would like to talk about Architectural Styles for API. One of these styles is called SOAP.

SOAP stands for Simple Object Access Protocol. SOAP is a standard based Web services access protocol that enjoys the benefits of long-term use. SOAP is developed by Microsoft.
SOAP relies exclusively on XML to provide messaging services. Microsoft originally developed SOAP to take the place of older technologies that don’t work well on the Internet. These technologies are bad and fail because they rely on binary messaging; the XML messaging that SOAP employs works better over the Internet. SOAP is designed to support expansion, so it has all sorts of other acronyms and abbreviations associated with it, such as WS-Addressing, WS-ReliableMessaging, WS-Policy, WS-AtomicTransaction, WS-Federation, WS-Coordination, WS-Security, and WS-RemotePortlets. In SOAP you can only choose to use the pieces you need for a particular task.As we know, in some programming languages, you need to build requests manually, which becomes problematic because SOAP is intolerant of errors. However, SOAP provides shortcuts to help in this issue. The difficulty of using SOAP depends on the language you use.
One of the most important SOAP features is built-in error handling. If there’s a problem with your request, the response contains error information that you can use to fix the problem. An interesting SOAP feature is that you don’t necessarily have to use it with the HyperText Transfer Protocol (HTTP) transport. There’s an actual specification for using SOAP over Simple Mail Transfer Protocol (SMTP) and there isn’t any reason you can’t use it over other transports.
As SOAP is an ordinary XML file that consists of the following parts: 1. Envelope, which is the starting and the ending tags; 2. Header, which it allows you to extend the SOAP message in a modular way; 3. Body, which contains XML data that the server send to the receiver; 4. Fault, which carries the information about errors occurring during the process of sending the message.

SOAP is mostly used for enterprise-lever web service because that require high security. Some examples of SOAP that I found online were: financial services, payment gateways, identity management and telecommunication services. Also another feature of SOAP is that the API calls can not be cached. The biggest disadvantage is the poorer performance, more complexity and less flexibility.

I didn’t know SOAP existed until I searched for REST (the next blog). The reason why I choose to write about SOAP is that it is a wide used architectural style for API and it has its own place of use, places or situation where REST can not be used.