What is SOAP API?
Simple Object Access Protocol (SOAP) is an API request and response message protocol used by application developers to establish communications between distributed elements of different applications. It relies on an XML schema to impose its structure of request and response messaging.
SOAP APIs are used in enterprises to create, delete, and update an outsourced account, a passcode, and any custom object. SOAP APIs are useful for businesses that require security, and safe transactions and are based on a complex environment.
How does SOAP API work?
REST APIs rule the modern web due to their efficiency and less bandwidth usage. SOAP APIs, however, offer some unique features as this approach provides security, and uses XML data transmission format for declaration of Request/Respond messages.
Most enterprises, including Macrometa, are dependent on REST APIs, whereas SOAP, initially developed by Microsoft, was designed as an expansion of applications based on Web services. Some of the standards include WS-Policy, WS-Atomic Transaction, WS-Remote Portlets, and a bunch of other WS standards.
SOAP APIs depend on data format i.e., Extensible Markup Language (XML). When the client sends a request message to the Web server, SOAP utilizes XML code. After receiving the request from the web server, SOAP demands the response back in XML format. This request is made via HyperText Transfer Protocol (HTTP) to a request handler that maintains the requests over a web server. The XML document received by the handler gets forwarded to the web server awaiting a response from it. The response message is then received by SOAP using standard XML payload format.
How is SOAP API different from RESTful API?
The message structure of SOAP comprises elements such as the Envelope, which provides encapsulation to SOAP messages whereas the Body is the one containing the details of a message, Header, and Fault. This layered structure is what differentiates it from REST API. Header, however, is responsible for authentication or uniqueness of the message and Fault covers the information about the possibility of potential errors that could occur in the Request/response procedure.
The flow of SOAP client-server interactions:
Source: IAN J.H REYNOLDS (HTTPS://WWW.ZIBTEK.COM/BLOG/REST-VS-SOAP/)
What are the benefits of SOAP API?
The most favourable benefit of SOAP API is its built-in Web service security which makes this protocol robust. Moreover, it is independent of Language, transmission, and platform due to its dependence on XML protocol. There exists a built-in error detection layer to cope with potential errors. Secure functioning makes it useful in sensitive data transmission and provides legacy systems with an edge. There are some drawbacks of SOAP that include complex architecture, higher bandwidth usage, and uncacheable API calls.
Despite the dominance of RESTful APIs, SOAP API protocols are still being used by some enterprises that depend on security procedures like transactions, sensitive information such as login credentials, etc.
Let us consider a practical application to get a better conception of SOAP API.
SOAP API call:
<?xml version="1.0"?> <soap:Envelope xmlns:soap="http://www.Examplewebsite.org/"> <soap:Header> </soap:Header> <soap:Body> <m:GetUser> <m:UserId>Monty</m:UserId> </m:GetUser> </soap:Body> </soap:Envelope>
By using such API call, the server is requested to respond and below is the response received:
<?xml version="1.0"?> <soap:Envelope xmlns:soap="http://www.Examplewebsite.org/" soap:encodingStyle=" http://www.Examplewebsite.org/"> <soap:Body> <m:GetUserResponse> <m:Username>Monty</m:Username> </m:GetUserResponse> </soap:Body> </soap:Envelope>
SOAP APIs still have an impact on technological advancements are preferred by organizations requiring datatype control, relying on complex functions, highly secure, and extensible platforms. RESTful APIs, however, continue to dominate due to their flexibility and better performance.