SOAP Web Services Overview

SOAP (Simple Object Access Protocol) involves a client-server architecture where clients make state transitions through actions, and servers process the requests and return resources. The data exchanged can be in various formats, such as JSON, XML, or plain text, all of which are transmitted over the TCP/IP stack.

SOAP (Simple Object Access Protocol)

Contract-First Design

• WSDL (Web Services Definition Language):
  • Verbose XML document defining:
    • Location of the web service.
    • Structure of XML documents sent to and received from the SOAP endpoint.
  • Written in XSD (XML Schema Definition).
  • Contract created first, then the web service.

Challenges

• Complexity:
  • SOAP Protocol has a root SOAP Envelope XML with complicated nested XML elements.
  • Cumbersome and error-prone process.
  • Less suitable for agile development and business analysis preferring iterative discovery of business rules.

Key Differences from REST

1. Predefined WSDL Envelope: SOAP uses a predefined WSDL (Web Services Description Language) envelope to define the structure and format of messages.
2. Protocol Dependence: SOAP relies on XML for message format and follows strict protocols.
3. Complexity: SOAP’s use of WSDL and extensive standards can make it more cumbersome and less flexible than REST.
4. Action Mapping: SOAP actions are defined within the WSDL, whereas REST uses standard HTTP verbs.

Advantages of SOAP

• Standards and Security: SOAP provides robust standards and security features, making it suitable for enterprise-level applications.
• Formal Contracts: WSDL serves as a formal contract between client and server.

Summary

• SOAP Web Services are defined by extensive and detailed contracts, promoting strict structure but facing challenges in agility and simplicity.