What is SOAP API and does it still work?


SOAP, which stands for Simple Object Access Protocol, is another type of API used by larger companies. But it’s not so popular anymore, as its use seems to be decreasing in modern applications. Want to learn more about this classic API architecture, even though you’re a fan of REST?

Sit down tight as we explain what SOAP is and see if it’s still in use today.

What is SOAP API and how does it work?

Code scattered with pile of soap in the background

SOAP is based on the Web Service Description Language (WSDL), an extensible markup language (XML) for sending data between software.

And given the rigid structure of XML, the data transmitted by the SOAP API is verbose and seems more complex than the more popular Representational State Transfer (REST) ​​architecture.

When sending or receiving data from a SOAP API, you are passing tightly packaged items wrapped in individual identification labels. The arrangement of data in SOAP follows a rigid access model and structure in a dedicated file. This makes SOAP highly protocol-oriented.

In addition to transferring data using Hypertext Transfer Protocol (HTTP), SOAP also supports more primitive protocols, including File Transfer Protocol (FTP), Transmission Control Protocol (TCP), and Data Transfer Protocol (TCP). simple mail transfer (SMTP). Thus, it offers flexibility of transfer over various networks and platforms.


However, while other transfer protocols allow primitive data exchange, it is more convenient to serve SOAP over an HTTPS network.

SOAP uses Web Services (WS) Security, an extension dedicated to message encryption. Thus, it fills the gap when sending data using data transfer protocols other than HTTPS.

It also combines this with Secure Socket Layer (SSL), a security token that serves websites over HTTPS. So, from a security perspective, SOAP has an advantage over REST, which relies solely on HTTPS for security.

Related: What Is an XML File and How Do I Open and Use It?

In addition, the format of the data returned by a SOAP API is easily programmed. This makes it easily integrated into several programming technologies.

Thus, the SOAP API is extensible, agnostic, and protocol neutral.

SOAP architecture

SOAP, like any API framework, has a generic structure. However, the architecture of a SOAP API is similar to that of an HTML DOM.

A SOAP API has the following structure:

  • Envelope: This tells you that an incoming or outgoing XML is SOAP data. You can think of this as the head of an HTML DOM.
  • On your mind: It contains more header information about XML.
  • Body: This is the payload or the main content of a SOAP message.
  • Fault: Handles errors and request statuses in the SOAP API.

Is SOAP API still in use today and why?

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Originally designed and first used by Microsoft in 1998, SOAP is considered old and complex. And it has been radically replaced by the more flexible REST architecture, which serves over 70% of public APIs today.

However, some large companies still use SOAP, especially as a transfer agent between internal services.

The SOAP API supports stateless and stateful communications. This biphasic capacity is another reason why it remains the framework of choice in certain cases.

When used in a stateful data exchange, it enables efficient tracking of information across multiple requests. While this complex operation can clog the server, it still makes SOAP a preferred option when building complex applications that require an additional layer of security and chaining.

A stateless transfer, on the other hand, does not overload server memory. So, this feature is just as handy if the goal is to reduce runtime and get better server performance.

But rather than using SOAP to handle stateless communications, web services now prefer to use the REST framework, which is more flexible and completely stateless.

The Microsoft Dynamics program, for example, uses the SOAP API to provide business-to-business solutions to large enterprises.

Because SOAP is ACID compliant, stateful, offers WS security encryption, and ships with SSL, it is a popular API architecture for banking and financial applications transactions.

The stateful nature of the SOAP API maintains database integrity during transactions. Even when an error occurs in a query, it tracks it and reverses the compromised data.

Related: What Does API Mean? Examples of API usage

Invariably, this explains the meaning of its conformity with the ACID concept (Atomicity, Coherence, Integrity and Durability):

  • Atomicity: assigns relevance to each process in a request. In this way, the failure of a demand unit cancels an entire process.
  • Consistency: Ensures that database queries and methods follow defined rules.
  • Integrity: Maintains the state of the database even when the queries are simultaneous.
  • Durability: Keeps a successful request in its state even when the server fails.

Should you use the SOAP API in your programs?

SOAP reigns in the API realm as one of the most secure messaging channels between software. Although it is complex, slow, old and heavy, it is still indispensable in many companies today. While modern APIs are easy to use, SOAP API may be your best bet in some situations after all.

And besides creating one yourself, you might find yourself in a scenario where this is the only applicable option that can provide a solution in your software. Learning more about SOAP is therefore a valuable addition to your API knowledge.

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