27 SOA Interview Questions (ANSWERED) Devs Need To Clarify

SOAP stands for Simple Object Access Protocol. SOAP is an XML based industry standard protocol for designing and developing web services. Since it’s XML based, it’s platform and language independent. So our server can be based on JAVA and client can be on .NET, PHP etc. and vice versa.

WSDL stands for Web Service Description Language. WSDL is an XML based document that provides technical details about the web service. Some of the useful information in WSDL document are:

• method name,
• port types,
• service end point,
• binding,
• method parameters etc.

WSDL stands for Web service Description Language. It is a simple XML document which comes under the Service Description layer of Web Service Protocol Stock and describes the technical details or locates the user interface to web service. Few of the important information present in WSDL document are

• Method name
• Port types
• Service end point
• Method parameters
• Header information
• Origin, etc

Web Services work on client-server model and when it comes to choose between SOAP and REST, it all depends on project requirements. Let’s look at some of the conditions affecting our choice:

• Do you know your web service clients beforehand? If Yes, then you can define a contract before implementation and SOAP seems better choice. But if you don’t then REST seems better choice because you can provide sample request/response and test cases easily for client applications to use later on.
• How much time you have? For quick implementation REST is the best choice. You can create web service easily, test it through browser/curl and get ready for your clients. What kind of data format are supported? If only XML then you can go with SOAP but if you think about supporting JSON also in future then go with REST.

In document style web services, we can transport an XML message as part of SOAP request which is not possible in RPC style web service. Document style web service is most appropriate in some application where XML message behaves as document and content of that document can alter and intention of web service does not rely on the content of XML message.

SOAP web services have all the advantages that web services has, some of the additional advantages are:

• WSDL document provides contract and technical details of the web services for client applications without exposing the underlying implementation technologies.
• SOAP uses XML data for payload as well as contract, so it can be easily read by any technology.
• SOAP protocol is universally accepted, so it's an industry standard approach with many easily available open source implementations.

Some of the disadvantages of SOAP protocol are:

• Only XML can be used, JSON and other lightweight formats are not supported.
• SOAP is based on the contract, so there is a tight coupling between client and server applications.
• SOAP is slow because payload is large for a simple string message, since it uses XML format.
• Anytime there is change in the server side contract, client stub classes need to be generated again. Can’t be tested easily in browser

As we start to model more and more complex logic, we have to deal with the problem of managing business processes that stretch across the boundary of individual services.

• With orchestration, we rely on a central brain to guide and drive the process, much like the conductor in an orchestra. The orchestration style corresponds more to the SOA idea of orchestration/task services. For example we could wrap the business flow in its own service. Where the proxy orchestrates the interaction between the microservices like shown in the below picture.

• With choreography, we inform each part of the system of its job, and let it work out the details, like dancers all find‐ ing their way and reacting to others around them in a ballet. The choreography style corresponds to the dumb pipes and smart endpoints mentioned by Martin Fowler's. That approach is also called the domain approach and is using domain events, where each service publish events regarding what have happened and other services can subscribe to those events.

There are basically 2 different approaches available for developing SOAP-based web services. These are explained as follows

• Contract-first approach: In this approach, the contract is defined first by XML and WSDL and then java classes are derived from the contract.
• Contract-last approach: In this approach, java classes are defined first and then the contract is generated which is usually the WSDL file from the java class.

“Contract-first” method is the most preferred approach.

UDDI is acronym for Universal Description, Discovery and Integration. UDDI is a directory of web services where client applications can lookup for web services. Web Services can register to the UDDI server and make them available to client applications.

• Monolithic Architecture is similar to a big container wherein all the software components of an application are assembled together and tightly packaged.
• A Service-Oriented Architecture is a collection of services which communicate with each other. The communication can involve either simple data passing or it could involve two or more services coordinating some activity.
• Microservice Architecture is an architectural style that structures an application as a collection of small autonomous services, modeled around a business domain.