SOAP

/soʊp/

What is SOAP?

• SOAP stands for Simple Object Access Protocol. It is a messaging protocol specification used for exchanging structured information in web services, primarily over HTTP/HTTPS, but it can also be used over other protocols such as SMTP.

History of SOAP

SOAP was developed by Microsoft, IBM, and other major companies in the late 1990s, with the first version of SOAP published as a W3C Note in 1999. It was created to facilitate communication between different systems, particularly in distributed computing environments, where systems and applications could be developed using different platforms or languages.

SOAP has its roots in XML-based messaging and was designed to be platform-agnostic, meaning it can be used in different programming environments. It became popular during the early 2000s as a standard for exchanging information in distributed systems, such as enterprise software, where reliability and robustness were required.

Key milestones in SOAP's history:

• 1998-1999: Initial development and release of SOAP 1.0 by Microsoft and its partners.
• 2000: SOAP 1.1 was submitted to the W3C (World Wide Web Consortium) for standardization.
• 2003: SOAP 1.2 became a W3C recommendation, enhancing the protocol to be more flexible and efficient.

Purpose of SOAP

SOAP’s primary purpose is to allow different systems to communicate with each other over a network, regardless of the platform, programming language, or architecture used.

Key aspects of SOAP:

1. Structured Messaging: SOAP messages are typically written in XML (Extensible Markup Language), a structured and human-readable format that can be processed by machines.
2. Interoperability: SOAP is designed to work across different platforms and programming languages. This allows systems built using different technologies to interact without compatibility issues.
3. Reliability: SOAP supports WS-Security, which provides encryption and authentication for secure communication, making it suitable for enterprise-level applications that require robust security.
4. Standardized Protocol: SOAP is a strict protocol with a well-defined standard. This ensures that all implementations of SOAP follow the same rules and guidelines, leading to predictable behavior and reliability.

Application of SOAP

SOAP is widely used in industries and organizations where data integrity, security, and reliability are paramount, such as finance, healthcare, and government systems.

1. Enterprise Software Integration: SOAP is used to link disparate systems within an organization. For example, integrating a Customer Relationship Management (CRM) system with an Enterprise Resource Planning (ERP) system.
2. Web Services: SOAP was one of the earliest protocols used for web services, enabling different web applications to communicate with each other. Many SOAP-based web services still operate, especially in sectors like banking and insurance.
3. Distributed Systems: SOAP allows distributed systems to communicate, even if they are built using different programming languages or hosted on different platforms. This makes SOAP a popular choice for service-oriented architecture (SOA) environments.
4. Messaging in Secure Environments: SOAP’s ability to handle encryption, authentication, and transactions makes it ideal for exchanging sensitive information, such as financial transactions and healthcare data.

SOAP vs. REST (Representational State Transfer)

Although SOAP was widely used in the 2000s, RESTful APIs have since become more popular due to their simplicity and lighter overhead. However, SOAP remains prevalent in scenarios where security, reliability, and stateful operations are more important than simplicity.

SOAP Message Structure

A SOAP message is composed of several key elements:

1. Envelope: This is the root element that defines the structure of the SOAP message.
2. Header (optional): Contains metadata and control information, such as security tokens.
3. Body: Contains the actual data or information being sent.
4. Fault (optional): Used to carry error and status information.

Here's an example of a simple SOAP message:

<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope">
  <soap:Header>
     <security>API_KEY</security>
  </soap:Header>
  <soap:Body>
     <getTemperature>
        <city>New York</city>
     </getTemperature>
  </soap:Body>
</soap:Envelope>

• The Envelope encapsulates the message.
• The Header contains security or routing information.
• The Body contains the actual message, which in this case is a request to get the temperature for New York.

How SOAP Works

1. Request: A client sends a SOAP message (formatted in XML) to the server. This request might contain information like an operation the client wants to perform, such as retrieving or updating data.
2. Processing: The server processes the SOAP request and performs the requested action (such as querying a database or performing calculations).
3. Response: The server sends back a SOAP response, which could contain the requested data or a status indicating success or failure.

Example of SOAP in Use

Let’s consider a scenario in which a banking system uses SOAP to process transactions.

Scenario:

A customer wants to check their bank balance. Here’s how SOAP can be used:

• SOAP Request: The client application sends a request in XML format to the bank’s server to get the customer’s balance:

<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope">
   <soap:Header>
       <authToken>ABC12345</authToken>
   </soap:Header>
   <soap:Body>
       <checkBalance>
           <accountNumber>123456789</accountNumber>
       </checkBalance>
   </soap:Body>
</soap:Envelope>

• SOAP Request: The client application sends a request in XML format to the bank’s server to get the customer’s balance:

<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope">
   <soap:Body>
       <checkBalanceResponse>
           <balance>5000.00</balance>
           <currency>USD</currency>
       </checkBalanceResponse>
   </soap:Body>
</soap:Envelope>

This secure exchange of information allows customers to access their data while ensuring that the communication between the client and server is protected.

Conclusion

SOAP is a robust, highly secure protocol designed for exchanging structured information in distributed computing environments. Despite the rise of simpler alternatives like REST, SOAP remains crucial for applications where reliability, security, and compliance with enterprise standards are essential, such as financial transactions, healthcare systems, and government services. Its strict protocol ensures compatibility and reliability across different platforms and systems, making it an enduring choice in various industries.