Introducing SOAP and REST web services

SOAP has been the traditional method for developing a web service, but it has many drawbacks, and applications are now moving over to REST or RESTful web service. XML is the only data exchange format available when using a SOAP web service, whereas REST web services can work with JSON and other data formats. Although SOAP-based web services are still recommended in some cases due to the extra security specifications, the lightweight REST web service is the preferred method of many web service developers due to its simplicity. SOAP is a protocol, whereas REST is an architectural style. Amazon, Facebook, Google, and Yahoo! have already moved over to REST web services.

Some of the features of REST web services are as follows:

• They work really well with CRUD operations
• They have better performance and scalability
• They can handle multiple input and output formats
• The smaller learning curve for developers connecting to web services
• The REST design philosophy is similar to web applications

The major advantage that SOAP has over REST is that SOAP is transport independent, whereas REST works only over HTTP. REST is based on HTTP, and therefore the same vulnerabilities that affect a standard web application could be used against it. Fortunately, the same security best practices can be applied to secure the REST web service.

The complexity inherent in developing SOAP services where the XML data is wrapped in a SOAP request and then sent using HTTP forced many organizations to move to REST services. It also needed a Web Service Definition Language (WSDL) file, which provided information related to the service. A UDDI directory had to be maintained where the WSDL file is published.

The basic idea of a REST service is, rather than using a complicated mechanism such as SOAP, it directly communicates with the service provider over HTTP without the need for any additional protocol. It uses HTTP to create, read, update, and delete data.

A request sent by the consumer of a SOAP-based web service is as follows:

<?xml version="1.0"?> 
<soap:Envelope 
xmlns:soap="http://www.w3.org/2001/12/soap-envelope" soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding">
  <soap:body sp="http://www.stockexchange.com/stockprice"> 
    <sp:GetStockPrice> 
      <sp:Stockname>xyz</sp:Stockname> 
    </sp:GetStockPrice> 
  </soap:Body> 
</soap:Envelope> 

On the other hand, a request sent to a REST web service could be as simple as this:

http://www.stockexchange.com/stockprice/Stockname/xyz 

The application uses a GET request to read data from the web service, which has low overhead and, unlike a long and complicated SOAP request, is easy for developers to code. While REST web services can also return data using XML, it is the rarely used-JSON that is the preferred method for returning data.