SOAP based web services


One major category of web services is SOAP based web services. (Simple Object Access Protocol)

SOAP is a message format specification. (Which is also XML based)

SOAP WS can process over HTTP, FTP,SMTP etc.. (But HTTP is being the popular protocol)

SOAP has 2 major versions. See specs at http://www.w3.org/TR/soap/
  1. SOAP 1.1
  2. SOAP 1.2 (released in 2007 and W3 recommended)


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For serialization/ deserialization of messages we need to have 2 SOAP libraries.

  • One at client side (SOAP client library)
  • One at server side (SOAP server library) 
These SOAP library implementations are available for popular programming languages and OSs. But the SOAP library you are using should comply with your OS and programming language. So the serialization process is handled by the libraries not by the programmer.

In SOAP based WS, messages are XML based (They are called SOAP envelopes)

All the details about the WS are contained in XML message called WSDL (Web Service Description Language). If you have the WSDL you know how to call the web service.

SOAP advantages 

  • Many platform and programming languages support SOAP
  • Developers dont have create/read WS messages directly (SOAP libraries can do that)
  • When used with HTTP can work with existing internet resources   

SOAP disadvantages 

  • Serialization process takes some time(depends on SOAP library quality)
native data => xml data and xml data => native data conversion

  • SOAP messages (envelope) sizes are big
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