45+ Best Web Services Interview Questions & Answers in 2021
Here's a list of Web Services interview questions and answers to help you ace your interview round.
Web services use the standardized XML messaging system, readily available over the Web and to private networks. To pursue a career in web application development, you must be familiar with web services. Therefore, to help you prepare for your upcoming job interview, we have compiled a list of top web services interview questions and answers. Let's get started:
Best Web Services Interview Questions and Answers
1. What are Web Services?
Answer: Web Services are standard software systems that provide communication between two devices (clients and servers). Various applications written in different languages can communicate over the network through web services.
2. List the various components of Web services.
Answer: These are the various components of Web services:
- Resource Description Framework (RDF)
- Simple Object Access Protocol (SOAP)
- Universal Description, Discovery, and Integration (UDDI)
- Web Service Description Language (WSDL)
- Extensible Markup Language (XML)
3. How does a web service work?
Answer: A web service allows communication among several applications using open standards such as HTML, XML, WSDL, and SOAP. It is possible to create a Java-based web service on Solaris, accessible from your Visual Basic program on Windows. Alternatively, you can use C# to create web services that run on Windows and which are invoked by your web application based on Java Server Pages (JSP).
4. What are the advantages of web services?
Answer: Web services offer the following advantages:
- Help expose existing functionalities over the network so that other applications can use them.
- Delivers certain required functionality to client applications.
- It's easily deployable, integrable, and reusable.
- Due to loose coupling, it facilitates a simple integration.
- Based on a standardized web service protocol stack for communication.
- Due to the use of SOAP over HTTP protocol, the communication costs are relatively low.
- It supports interoperability, so applications can effortlessly share data and services among themselves.
5. Could you explain the term Interoperability in the context of Web services?
Answer: In general, interoperability refers to the ability of two or more products or systems to work together without any special requirements. In web services, interoperability refers to the communication and sharing of data and services among applications.
6. What are the different types of web services?
Answer: Web services fall into two categories:
- SOAP: Usually consists of a contract or WSDL file.
- RESTful: It does not require a contract or WSDL file.
7. What are the main features of web services?
- It utilizes a standardized XML messaging system.
- It is self-describing using basic XML grammar.
- A simple find mechanism makes it easy to find.
- You can access it over the Internet or via a private network (intranet).
- It is not dependent on any single operating system or programming language.
8. What is UDDI, and what are its features? What language does it use?
Answer: UDDI stands for Universal Description Discovery and Integration. It is an XML-based standard in the service discovery layer of the web service protocol stack. Moreover, it uses Web Service Description Language (WSDL).
As the UDDI functions as a directory, it is used to find and publish web services over the Internet. UDDI has the following main features:
- Open framework
- It acts as a database containing all WSDL files.
- It helps businesses discover and communicate with each other over the Internet.
- UDDI uses COBRA, Java RMI, and SOAP protocols for establishing communication.
9. What tools are used to test web services?
Answer: Testing web services is done with the following tools:
- Poster (Firefox)
- SoapUI (for RESTful and SOAP web services)
- Postman (Chrome Extension)
10. What is SOAP?
Answer: SOAP or Simple Object Access Protocol is an XML-based protocol for using web services. It is independent on both platform and language. Moreover, SOAP allows you to interact with other programming language applications.
11. What are the key features of SOAP?
Answer: SOAP has the following features:
- Communication Protocol
- Simple and Extensible
- It is a format for sending messages.
- SOAP is developed as a W3C standard.
- SOAP allows you to bypass firewalls.
- Using SOAP, you can communicate over the Internet.
- Communication between applications takes place via SOAP.
12. What are the advantages of SOAP web services?
Answer: SOAP web services offer the following advantages:
- Both platform- and language-independent.
- Facilitates communication between various applications
- Sends and receives messages using HTTP protocol and XML.
- In addition to eliminating firewall issues, it is vendor-neutral.
- Provides and uses its security known as WS Security.
- It separates the communication and encoding protocol from the runtime environment.
- The ability to circulate messages in a distributed and decentralized manner.
13. What are the disadvantages of SOAP web services?
Answer: SOAP web services have the following disadvantages:
- Slower performance
- Lack of security features.
- Clients and web services are tightly integrated.
- You have to follow its strict standards.
- It does not support testing in web browsers.
- Other lightweight formats are not supported (except for XML).
14. What do you mean by RESTful Web Services? What are the various advantages of the same?
Answer: REST stands for Representational State Transfer. It is an architectural style for developing Web-based applications in a stateless client-server environment. We call RESTful Web Services the web services that use HTTP methods to implement the REST architecture. As part of the REST architectural style, data and functionality are accessed via URIs. Also, modifiability, performance, and scalability are desirable properties of RESTful Web Services. RESTful Web Services offer the following advantages:
- Fast and lightweight protocol
- Loosely coupled implementation
- Consumes less bandwidth and resources
- It is capable of being easily tested over web browsers.
- You can write it in any programming language.
- It offers support for several data formats, such as JSON, technologies, and plain text.
15. What is the difference between SOAP and REST web services?
Answer: The below table will clear all your doubts related to SOAP and REST web services.
|SOAP is a Protocol.
|REST is an Architectural Style.
|It stands for Simple Object Access Protocol.
|It stands for Representational State Transfer.
|SOAP can not use REST since it is a protocol.
|Due to its concept, REST can use any protocol, including SOAP or HTTP.
|SOAP exposes business logic through services interfaces.
|Business logic is exposed using URIs in REST.
|It allows XML data format only.
|REST supports different data formats such as plain text, HTML, XML, and JSON.
|SOAP defines standards that must be strictly followed.
|REST does not define too many standards like SOAP.
16. What are the various elements of a SOAP message?
Answer: The various elements of a SOAP message are:
- Body - This file contains the call and response messages. It is also defined as a child element of the envelope that contains entire application-derived XML data, which is sent in the SOAP message.
- Envelope - It is the mandatory root element. It translates the XML document and determines when the SOAP message begins and ends.
- Fault Element - It resolves the errors in the messages during processing. The error appears as a child element of the body if there is one.
- Header - It contains optional message header attributes containing application-specific information. This element can appear several times in a single SOAP message to add new features and functions.
17. What do you understand by WSDL?
Answer: WSDL or Web Service Description Language is a simple XML document that resides in the Service Description layer of the web service protocol stack. This describes the technical details or locates the UI for the web service. WSDL includes the following important information:
- Method name
- Port types
- Header information
- Service endpoint
- Method parameters
18. What are the various elements of WSDL documents?
Answer: The various elements of WSDL documents are:
- Binding: In addition to defining ports, it also defines the protocols and the data formats.
- Message: It specifies the data elements for each operation. It could be a complete document or an argument yet to be mapped.
- Operations: Processes a message by defining the operations that need to be performed.
- Port Type: Binding operations are defined by it.
- Types: As an XML schema, it defines the message categories used by the web services.
19. Explain the loosely coupled architecture of web services.
Answer: Consumers of a web service are not directly connected to the web service. It is possible to change the web service interface over time without compromising the client's ability to interact with the service. In a tightly coupled system, the client and server logic are closely intertwined, meaning that if one interface changes, the other must be updated. The use of loosely coupled architectures makes software systems easier to manage and facilitates easier integration between them.
20. Give a real-life example of a web service?
Answer: The IBM web service browser is a real-life example of a web service. The purpose of this browser is to display web services demos. These web services can be used in conjunction with SOAP, UDDI, and WSDL, which provide a plug-and-play integration. Among its applications are weather forecast services, traffic reporting services, stock quotes, and so on.
21. What is a web service protocol stack?
Answer: Web services protocol stack consists of various protocols or procedures used to explore and execute several kinds of web services. There are four layers in it, including the following:
- XML Messaging
- Service Discovery
- Service Transport
- Service Description
22. What do you mean by synchronicity?
Answer: Synchronicity is the process that binds the client to the execution of the service. When synchronous invocations occur, the client waits for the service to complete its operation before continuing. Furthermore, synchronous operations allow a client to invoke a service and then perform different actions.
23. What is a remote procedure call (RPC)?
Answer: Remote procedure calls are calls made to methods hosted by related web services. Compared to the Web, RPC is much older. It provides developers with a mechanism for defining interfaces that can be called over a network. The interface can be as simple as a single function call or as complex as an API.
24. What is the usage of Service Transport Layer in Web service protocol stack?
Answer: Messages are transported between applications using the Service Transport Layer. It consists of Hypertext Transport Protocol (HTTP), Simple Mail Transfer Protocol (SMTP), File Transfer Protocol (FTP), and the latest protocols like Blocks Extensible Exchange Protocol (BEEP).
25. What is the usage of the Service Discovery layer in Web Service Protocol Stack?
Answer: The Service Discovery layer allows for the centralization of services into a universal registry and offers easy publish/find functionality. Currently, service discovery is handled through UDDI (Universal Description, Discovery, and Integration).
26. Which are the browsers that allow access to Web Service?
Answer: Web Services are accessible via various browsers including:
- Mozilla Firefox
- Internet Explorer
- Google Chrome and several others
27. What is meant by SOAP message?
Answer: SOAP messages refer to data sent from the web service to the application. Any programming language-based client application can receive XML data from a server through a web service. Moreover, SOAP messages are delivered via HTTP.
28. Define Distributed Technologies?
**Answer: With distributed technologies, applications can be segmented into different units and transferred to different computer networks and systems. As a result of the increase in distributed applications, distributed technologies have emerged.
29. What are the standards in Web services?
Answer: In Web Services, there are several standards. Among them are:
- HTTP: It facilitates in communication channels.
- SOAP: It is used for structuring data.
- WSDL: It is used to create an interface definition.
- UDDI: It is used for creating business registries.
30. Can we test the ASP .Net service?
Answer: It is possible to test ASP .NET services regularly. You can do this by making a call for the URL of the .asmx file is made in the browser, which shows complete information regarding web services on the page.
31. Is there any Microsoft solution for distributed applications?
Answer: Microsoft offers two distributed application solutions. These are:
- . NET Remoting
- . NET web services
32. What is DISCO in web services?
Answer: DISCO stands for discovery in web services. You can use it to group web services that are interrelated. On the server, DISCO files are created by the company that offers web services in order to make them available and provide access to all the links for the web services.
33. What is the pre-requisite for deploying Web Service?
Answer: Before deploying Web Services, you must meet the following requirements.
- Web Application Directory.
- Bin Directory.
- Web.Config File.
- Disco File.
- Webservice.asmx File.
34. Is it possible to bind SOAP and WSDL?
Answer: It is possible to bind SOAP and WSDL. You can accomplish this using the following two attributes:
- Name – Describes the name of the binding
- Type – Describes the port for the binding
35. What points should you consider while binding in WSDL?
Answer: A port must not do the following when binding in WSDL:
- Add any other binding information besides the address.
- Put more than one address.
36. What is the need for the
<Envelope> element in the SOAP document?
<Envelope> is the root element of every SOAP message. In an XML document, the root element is the first element. The envelope is, in turn, divided into two parts. The first part is the header, and the second is the body. The header contains the routing data, which includes the client's source and destination addresses. The body holds the actual data.
37. Explain BEEP?
Answer: BEEP refers to Blocks Extensible Exchange Protocol. It is an alternative to FTP and HTTP. A crucial component of the BEEP is developing new protocols for applications such as instant messaging, file transfer, and network management. It is an approach layered directly over TCP known as the Internet Engineering Task Force (IETF). The following are some of the built-in features of the BEEP protocol:
- Error Handling
- Initial Handshake Protocol
38. What is XML-RPC?
Answer: XML-RPC is a protocol for performing RPCs using XML messages. Moreover, it can connect different environments and establish connections between computers of different types and environments.
39. Explain the two attributes of the
<Port> element in WSDL.
<Port> element is associated with a specific binding by defining an individual endpoint. A
<Port> element has two attributes:
- Binding: Binding must be performed according to the linking rules defined by WSDL.
- Name: identifies the unique name within the WSDL document.
40. Explain web service architecture?
Answer: Three layers make up the web service framework. They serve the following purposes:
- Service Provider - The service provider's role is to make the web service available to the clients via the web.
- Service Requestor - As with any client application, service requestors are all consumers of web services. Any client application can access the web service through an XML request made via a network connection by sending out an XML request.
- Service Registry - It's a centralized directory system that identifies web services for client applications. Developers can use it to find existing web services and to create new ones as well.
41. What is SOA?
Answer: SOA stands for Service Oriented Architecture. It is an architectural pattern that consists of services. Using the communication protocol, application components provide services to other components in SOA. The following are key principles regarding SOA:
- The service contract must contain the entire description of the services in addition to being standardized.
- Services should be reusable for a variety of application types
- Loose coupling is defined as less dependency between the web services and the client
- The application must adhere to the Service Abstraction rule, according to which the service should not expose how functionality is executed to the client.
- Stateless services must be discoverable and stateless.
42. What are the advantages of having XML-based Web services?
Answer: XML eliminates network, operating system, or platform bindings. Web Services-based applications were therefore designed with high interoperability in mind.
43. How many Communication protocols can be used to implement a SOAP message? Are SOAP messages are tied to any protocol?
Answer: The term "communication protocol" refers to the protocols used to transmit information over the internet. With Transport protocols, applications from different backgrounds can quickly communicate with each other without knowing the inner workings of each system. Using HTTP (Hyper-Text Transfer Protocol) to implement a SOAP message is possible, whereas FTP (File Transfer Protocol) can be used as a reliable transport mechanism. BEEP and SMTP can also be used as transport mechanisms.
SOAP messages are not tied to any specific protocol. Any of the open transport protocols can be used.
44. Explain the difference between Web Service Provider/Publisher and Web Service requestor/Consumer.
Answer: The Web Service Provider provides web services for the various applications, regardless of their background, whereas the Web Service Requestor/Consumer is the one who requests the web services.
45. Explain the role of web service provider/ Publisher.
Answer: A Web Service provider implements web services and makes them available to web service requestors/consumers.
46. How are the terms "Platform-independent" and "Diverse Application" are related to each other in the context of XML-RPC?
Answer: "Platform-independent" and "Diverse application" were related because XML-RPC uses HTTP for transporting SOAP messages over the Internet. HTTP is a universal standard protocol for exchanging information over the Internet. Thus, it leads to cross-platform support/platform independence. Therefore, because it is platform-independent, it leads to diverse applications that can access web services.
47. Explain the role of web service requestor/ consumer.
Answer: As a Web Service Requestor or Consumer, your role is to take advantage of preexisting web services provided by Web Service Publishers. By sending a SOAP message to the Web Service provider, a Web Service Requestor/Consumer requests the information from the Web Service provider. As a result, in-Turn Web Service Publisher sends back the requested information as a SOAP message.
48. What are the requirements to access a Web Service?
Answer: Any application that wishes to access a Web service should support XML requests and responses. Therefore, there is no need to install any app to access web services.
49. Do we need security in web services? Explain?
Answer: Web services do need security, to ensure that private information and transactions are secure. Through SSL or Service Socket Layer, which helps in creating an Entrust Secure Transaction Platform, web services are made secure.
50. How did the concept of security services generated?
Answer: It was introduced before the increasing use of the virtual world, and after a series of frauds, hackings, and viruses affected the process of data exchange and made data vulnerable. To secure the web services from activities that could be harmful to users, the security services are developed and updated at regular intervals. Security services include integration, authentication, encryption, digital signatures, and authorization.