SOA (Service Oriented Architecture) is a collection of loosely-coupled services that communicate with each other over a network. Web services are a common implementation of SOA that use XML-based open standards like SOAP, WSDL, and UDDI. A WSDL file defines the operations and parameters of a web service, acting as a contract between the service and its clients. SOAP is an XML-based messaging protocol used to invoke operations defined in a WSDL over various transports like HTTP.

1. SOA and Web Services Sreekanth Narayanan Code samples in Java

5. Quick Comparison Tight Agnostic (Visual C++, VB, PowerBuilder, Delhi, etc.) Windows Registry IDL ORPC (Object RPC) Binary (Unlike WCP which encourages XML-based SOAP) NDR DCOM (Enables - but does not guarantee) loose coupling Tight Tight Coupling Java RMI registry or JNDI Java Interface JRMP or IIOP Stream Serialized Java Java RMI Java RMI Agnostic COS Naming Service OMG IDL IIOP (Inter-ORB Protocol) GIOP CDR CORBA RMI CORBA Agnostic Programming language & platform WSDL Interface description UDDI Discovery mechanism HTTP, SMTP, FTP, JMS… Transport protocol SOAP Wire format Web services XML Data format JAX-RPC, .NET.. Invocation Mechanism

9. Anatomy of a XML based WS

15. SOAP Error Response Sample HTTP/1.1 500 Internal Server Error Host: www.borland.com Content-Type: text/xml; charset=&quot;utf-8&quot; Content-Length: nnnn <SOAP-ENV:Envelope xmlns:SOAP-ENV=&quot;http://schemas.xmlsoap.org/soap/envelope/&quot; <SOAP-ENV:Body> <SOAP-ENV:Fault> <faultcode>SOAP-ENV:Server</faultcode> <faultstring>Server Error</faultstring> <detail> <d:message xmlns:d=&quot;some URI&quot;> No Symbol found </d:message> </detail> </SOAP-ENV:Fault> </SOAP-ENV:Body> SOAP Envelope SOAP Fault Code Detailed Error Message from the Server Shows the HTTP Response Status – ERROR

19. More on the Contract

21. WSDL - Structure

30. WSDL 1.1 – Summary

40. REST Vs SOAP Better chance of loose coupling due to the non existence of the contract. The Resource processing might be dependent on Parameters, even of they change, it is easier to default them on Server side without the Client changing anything. Strict adherence to contract. The Contract needs to be established first. Tightly couples the Client due to the Contract. Ease of Development/Change Management REST not being a standard, all the advantages mentioned in SOAP do not come by default. Most cases the implementation has to take care of the Security needs as well as the Error handling. This becomes difficult as Out of the Box Solutions for the same are not available and all is left to the Coder to implement. SOAP based WS have extensive support within all the application containers. As SOAP provides for extensive storage of metadata within the message, a lot of infrastructure support can be built making use of the data which is sent. SOAP provides inherent support for Security and Error Handling Infrastructure Support/Security/Error Handling REST is not defined in any of the standards. It is just an architectural style. It is tightly coupled to the HTTP transport. Rest is suited for mostly Web Driven Architectures where the base mode of transport is HTTP Standards based/Defined in all the WS standards. SOAP becomes heavy because of the amount of metadata it carries. SOAP is transport Agnostic. If you have a heterogeneous messaging infrastructure to integrate, SOAP is a better solution. Environment/Standards/Transport Rest enables sending smaller messages as response. As the technology is not tied to the use of SOAP for messaging, the designer can use XML, JSON or TEXT. This enables lightweight messaging. SOAP message has a header and a body. In most cases, the need for sending the data as soap is not needed. Sending a SOAP message has considerable overhead due to the stringent structure Size of the message REST SOAP