Top SOAP Interview Questions and Answers for Beginners

In this post, we see SOAP Interview Questions. Before we go any further, let’s look at some questions that every hiring manager will ask you during my Software Testing interview.

SOAP, or Simple Object Access Protocol, is a set of rules for how Web services should talk to other systems. Without it, Web services can’t work on different platforms and operating systems, and they often can’t talk to each other at all. Besides REST, SOAP has become increasingly popular for developers working on system integration based projects. Because of this, it would be helpful for both new professionals and experienced ones in the field to learn more about SOAP API in general.

We have put together a full list of common SOAP testing interview questions and answers to help you learn more about SOAP quickly, whether you need to prepare for a technical interview or a new job. You should take some time to read through the list if you want to do well in job interviews or get ready for new projects.

SOAP (Simple Object Access Protocol) is an XML-based protocol for accessing web services over HTTP. It provides a standard way for systems to communicate with each other and is commonly used for building web APIs. As SOAP is a popular technology for backend development, you can expect SOAP interview questions in many technical interviews, especially for web developer roles.

In this article, we will cover the most frequently asked SOAP interview questions and sample answers to help you prepare. The questions cover SOAP basics, architecture, WSDL, protocols, security and more Let’s get started!

What is SOAP?

SOAP is an XML-based messaging protocol for exchanging information among computers. It provides a standard way to communicate between applications running on different operating systems, programming languages and platforms. The SOAP specification defines an XML format for messages, rules for processing them, and bindings to underlying protocols like HTTP, SMTP etc.

Key things to know about SOAP:

  • SOAP stands for Simple Object Access Protocol
  • It relies on XML to format messages and usually uses HTTP for transmission
  • Provides a way for systems to communicate over the internet in a platform and language independent manner
  • Commonly used for building web services and APIs

What are the components of a SOAP message?

A SOAP message contains the following components

  • Envelope – Root element that defines the start and end of the message
  • Header – Optional element that contains metadata like authentication information
  • Body – Mandatory element that contains the actual SOAP message intended for the recipient
  • Fault – Optional element that provides information about any errors that occurred

The body is the core of the message that contains the actual payload. The header and fault elements provide additional functionality and error handling. All this is enclosed in the envelope.

Explain SOAP message structure with an example

Here is an example SOAP request message structure:


<soap:Envelope   xmlns:soap="">  <soap:Header>    <!-- optional header elements -->  </soap:Header>    <soap:Body>    <GetStockPrice>      <StockSymbol>GOOG</StockSymbol>     </GetStockPrice>  </soap:Body></soap:Envelope>

This message has the root Envelope element with the namespace defined. The optional Header is empty in this case. The Body contains the GetStockPrice request with the StockSymbol element.

The response message would also follow a similar structure with the Body containing the stock price instead of the request.

What are the key differences between SOAP and REST?

Uses XML for messaging Uses lighter JSON for messaging
More rigid structure and formal spec Architectural style with flexible implementation
Supports more data types and protocols Limited to HTTP only
Provides WS-* standards for security, transactions etc Depends on HTTPS, OAuth for security
Better support for legacy systems and enterprise apps Better suited for internet-scale applications

What is WSDL and what role does it play in SOAP web services?

WSDL stands for Web Services Description Language. It is an XML-based interface definition language that is used to describe the functionality offered by a SOAP web service.

WSDL provides the following information about a service:

  • What operations are exposed by the service
  • Input and output parameters for each operation
  • Message formats and data types
  • Protocol and transport bindings like HTTP, SMTP
  • Network endpoint where service is located

This allows clients to understand how to use the SOAP service without knowing the implementation. WSDL is key to implementing SOAP-based web services.

Explain RPC style vs document style in SOAP web services

There are two common styles for defining SOAP web services:

RPC (Remote Procedure Call) – Models the service interface as a set of operations similar to calling functions remotely. Each operation has defined input and output parameters.

Document – The message contains one or more documents with the root element defining the document type. Does not expose operations explicitly.

For example, a service to get stock price in RPC style would be:

GetStockPrice(StockSymbol) Returns: StockPrice 

While in Document style:


<GetStockPrice>  <StockSymbol>GOOG</StockSymbol></GetStockPrice>Returns: <StockPrice>  <!-- price details here --> </StockPrice>

RPC style is more common while Document style provides more flexibility.

How does SOAP provide security?

SOAP provides the following security capabilities:

  • Encryption – Sensitive data can be encrypted to prevent eavesdropping
  • Digital signatures – Messages can be digitally signed for tamper detection and non-repudiation
  • Authentication – Users can be authenticated using security tokens
  • Authorization – Service access can be restricted based on permissions

These are implemented using the WS-Security standard which builds on top of SOAP protocol. SSL/TLS at the transport layer can also be used for secure transmission of SOAP messages.

What protocols can be used for SOAP message transmission?

SOAP supports different protocol bindings for message transmission:

  • HTTP – SOAP messages can be easily exchanged using HTTP POST requests and responses. This is the most commonly used protocol for SOAP.
  • SMTP – SOAP messages can be sent via email as attachments over SMTP
  • TCP – Direct TCP connections can be used for point-to-point SOAP messaging
  • JMS – SOAP messages can be sent over Java Messaging Service queues/topics
  • MIME – Used mainly for Soap with Attachments (SwA) when sending binary content

SOAP itself is transport protocol independent. HTTP is the most common binding due to easy firewall traversal.

How does error handling work in SOAP?

SOAP uses a fault element to handle errors. It contains:

  • faultcode – Error code indicating the type of fault
  • faultstring – Human readable explanation of the fault
  • faultactor – Who caused the fault
  • detail – Application specific error details

For example:


<soap:Fault>  <faultcode>soap:Server</faultcode>  <faultstring>Operation Failed</faultstring>  <detail>   ...  </detail></soap:Fault>

When a SOAP fault is generated, no response is returned to the client. The fault message indicates that an error occurred.

This provides a standardized mechanism for SOAP services to communicate errors to clients.

What are the main disadvantages or limitations of SOAP?

Some key limitations of SOAP are:

  • Verbose – SOAP uses XML for all messages which can be slow and bandwidth intensive
  • Complexity – Significant learning curve to build and work with SOAP based web services
  • Difficulty with firewalls – SOAP predominantly uses HTTP POST which may be blocked
  • No support for REST – SOAP is RPC-based and doesn’t work well for REST architectural style
  • Limited browser support – SOAP is not well supported in browsers compared to REST/JSON

How can SOAP and REST work together in an application?

SOAP and REST can complement each other in an application. Some ways they can work together:

  • Use SOAP services for backend APIs and REST for frontend application logic
  • Expose SOAP services internally within an organization and REST externally to public
  • Use REST to provide a simplified interface to complex SOAP services
  • Have REST interface invoke SOAP services on the backend as needed
  • Implement REST for internet scale requirements and SOAP for legacy enterprise integration

The best approach depends on the specific application architecture and use cases. The core strength of each can be leveraged in a complementary manner.

Explain how SOAP Encoding works with some examples

SOAP encoding defines a set of rules for serializing and deserializing data types commonly used in programming languages like strings, arrays, objects etc. This allows transfer of rich data structures via SOAP messages.

For example, to encode an array of integers:


<myArray xsi:type="xsd:int"            xmlns:xsd=""           xmlns:xsi="">  <item>10</item>  <item>20</item></myArray>

The xsi:type indicates array of integers defined in XML Schema. Rules allow both sparse and multi-dimensional arrays. SOAP encoding enables rich data structures beyond just XML.

How can you improve SOAP performance and scalability?

Some ways to improve SOAP performance and scalability:

  • Use compression to reduce

What are some important characteristics of a SOAP envelope element?

  • SOAP message has a root Envelope element
  • Envelope is an obligatory part of the SOAP message.
  • There shouldn’t be more than one header element in an envelope.
  • Envelop version will change if the SOAP version changes.
  • The prefix ENV and the envelope element show that the message is in a SOAP envelope.
  • A namespace and the optional encoding style element are also used to set the optional SOAP encoding.

What are the elements of a SOAP message structure?

It is a common XML document that contains the elements as a SOAP message

Envelope: This is a required root element that turns the XML file into text and sets the start and end points of the message. Header: It is an optional item which contains information about the message being sent. Body: It contains the XML data comprising the message being sent. Fault: It provides the information on errors that occurred while during message processing.

Simple Object Access Protocol Pros and Cons (Explained by Example)


What is the Simple Object Access Protocol SOAP in detail?

6 The Simple Object Access Protocol (SOAP) The SOAP facilitates connectivity in heterogeneous systems and is used to exchange structured information in Web services. It uses several standard Internet protocols to achieve platform and operating system-independent message transmission and message content representation.

What is the SOAP method of interviewing?

What is the SOAP residency interview? The Supplemental Offer and Acceptance Program (SOAP) of the National Resident Matching Program (NRMP) is held immediately after Match Day, and is designed to pair partially matched or unmatched applicants with unfilled training program positions in the US.

What protocol does SOAP use?

SOAP uses the XML Information Set as a message format and relies on application layer protocols, like HTTP, for message transmission and negotiation.

What is a Soap interview question?

Free PDF Download: SOAP Interview Questions 1) What is SOAP? SOAP means Simple Object Access Protocol is a type of communication protocol, a way to structure data prior to transmitting it and is based on XML standard. It is developed to enable communication between applications of different platforms and programming language via internet.

What is SOAP (simple object access protocol)?

Raise your voice! SOAP (Simple Object Access Protocol) is a technological specification designed to support Web services interface with other systems; without it, the Web services are unable to cross operating systems and platforms, and often lack interoperability.

What is SOAP protocol?

It defines the protocol used in communication between client and server. It is based on HTML, uses XML as a format and communicates using SOAP protocol. Even is SOAP has fallen out of favor for new, public-facing API’s, though it is still commonly used for B2B applications because you can define a “data contract” with it.

How does a SOAP request work?

SOAP, a protocol for exchanging structured information in web services using XML, operates over HTTP. To implement a SOAP request, you create an XML document containing the necessary data and send it to the server via HTTP POST. For instance:

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