Soap Interview Questions

SOAP (Simple Object Access Protocol) is a communication protocol that facilitates the exchange of data over different networks. It is based on XML language that enables communication over different applications of Windows, Linux, etc. via the Internet. SOAP defines XML and HTTP messaging protocols and also uses the range of other protocols like FTP (File transfer protocol), SMTP (Simple Mail Transfer Protocol), POP3 (Post office protocol 3), etc. SOAP provides data transportation between web services and is used for broadcasting a message. It is a way to structure data prior to transmitting it.

The following are the differences between SOAP and other remote web services such as DCOM, COBRA :

SOAP WEB SERVICES	OTHER REMOTE WEB SERVICES
SOAP is the acronym for Simple Object Access Protocol.	DCOM is the acronym for Distributed Component Object Model.
It is a platform for transportation of data and language independence.	DCOM or COBRA doesn’t provide language independence.
It is user-friendly and easy to handle.	Web services like DCOM or COBRA are complex to handle.
SOAP uses HTTP protocols and data uses XML formats.	DCOM and COBRA have their own binary formats for transporting data in complexity.
It is hard to maintain.	It is easy to maintain as compared with SOAP’s.

Following is the syntax rule for SOAP message-

• A SOAP message should use XML that is encoded.
• A SOAP message MUST use the SOAP Envelope namespace.
• A SOAP message must NOT contain DTD reference.
• A SOAP message must NOT have an XML processing instruction.

SOAP is messaging based Web service that has been around for a while and enjoys almost all the benefits of long-term use. The following are few notable advantages of using SOAP web services:

• It is a language independent platform.
• It works well in a distributed runtime environment.
• SOAP payload can be received or obtained by web services and the platform information is entirely unrecognizable.
• SOAP uses XML structures for data transmission.
• It is very simple as compared with the COBRA, RMI, etc.
• It eliminates firewall problems as it uses HTTP.
• SOAP can also be used in combination with other protocols as well.
• It is the vendor neutral.

The SOAP envelope indicates the start and end of the message so that the receiver knows when the entire message has been received. The important characteristics of SOAP envelop are:

• It has a root Envelop element, which is a mandatory part of the SOAP.
• SOAP element should not contain more than one header. Also, it should appear as the first part of the envelope.
• Envelop version changes with the upgradations in SOAP version.
• We add ENV as a prefix and envelop element to SOAP envelops.
• The optional SOAP encoding is also specified using a namespace.

As every good thing comes with some cost, SOAP also has few disadvantages attached to it. Below are few disadvantages:

• SOAP only uses XML. It doesn’t take other formats like JSON into consideration.
• There is a high possibility of coupling between client and server as SOAP is based on contract.
• Since it uses XML format, SOAP is considered to be a slow platform because the payload is large for a simple string message.
• Any change in server contract is reflected in client stub classes.
• SOAP is hard to test in browsers.
• SOAP clients do not hold any stateful references to remote objects.

SOAP web services are usually created using JAX-WS API. However, there are some other frameworks available in Java that can be used to implement SOAP web services. These are Apache Axis, Apache CXF, Jersey, CodeIgniter, etc. These frameworks are totally different from JAX-WS API and work on Servlet model to highlight the business logic as SOAP web services.

The following are the facilities that are offered by SOAP to its users-

• PutAddress() : This function is used for putting address in web pages. It carries address instance on SOAP call.
• PutListing() : It facilitates insertion of XML file into the webpage. This function reads the XML file, which is received as an argument and transports it to XML parser liaison. It then puts it as a parameter in the SOAP call.
• GetAddress(): It is a form of string text which determines a query name and sends the result that is synonymous with the query. The name is then sent to the SOAP call.
• GetAllListing() : This function transfers the complete list in XML format and then returns the same.