Web services interview questions

Web services interview questions

1. What are Web Services?

A Web Service is an application component that allows two apps to communicate or exchange information over the Internet. Web services are based on a client-server approach, in which client programmes may easily access web services via the network. Web Services employ the XML communications system and provide end-users with a user-friendly interface.

2. List some of the advantages of Web Services.

Some of the advantages of Web Services are:

Reusability: A single web service can be utilised by several client applications simultaneously.

They're just like web apps in terms of easy deployment and integration.

Interoperability: Web services are network-based, run on the HTTP/SOAP protocol, and transmit data using XML/JSON. Therefore they may be written in any programming language. Web services may be created in Java, and clients can be written in PHP, and vice versa.

Loose Coupling: Because the client code for web services is entirely separate from the server code, we have achieved loose coupling in our programme.

Multiple service versions can be running at the same time.

3. What are the various components of Web Services?

The components of Web Services are:

Extensible Markup Language (XML)

Simple Object Access Protocol (SOAP)

Web Service Description Language (WSDL)

Resource Description Framework (RDF)

 

Universal Description, Discovery, and Integration (UDDI)

4. Explain the features of a Web Service.

The features of a Web Service include:

They use a standardised XML messaging system.

They are available over the Internet or on private networks.

They can be synchronous or asynchronous.

They are not tied to any one operating system or programming language.

 

They are discoverable via a simple find mechanism.

5. Define the various types of Web Services.

The are two types of Web Services:

SOAP (Simple Object Access Protocol): It is also known as a transport-independent messaging protocol, and it is based on the XML protocol. Its main goal is to transfer a message.

RESTful (Representational State Transfer): It was created to address the inadequacies of SOAP and to improve the effectiveness of web services.

6. How does Web Service work?

A web service uses open standards like HTML, XML, WSDL, and SOAP to allow communication between different applications.

You can use C# to create new web services on Windows that can be called from your JavaServer Pages(i.e. JSP)-based web application running on Linux.

7. Explain SOAP.

SOAP is an industry-standard protocol for creating and implementing web services based on XML. It is platform and language-neutral. As a result, the server may be built on Java, while the client could be based on .NET and PHP and vice versa.

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8. What are RESTful Web Services?

REST (Representational State Transfer) is a stateless, client-server architecture approach used to create web-based applications. It's a kind of online service whose primary objective is to improve the efficiency of web services. It is a web service that implements the REST architecture using HTTP methods. Restful services are structurally based, unlike SOAP, which is protocol-based. There is no contract or WSDL file in it.

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9. What are the differences between SOAP and REST?

The main point of differences between them are:

• Java API: The Java API for RESTful Web Services is JAX-RS, while the Java API for SOAP Web Services is JAX-WS.
• Data Format and Preference: REST is recommended here since it supports a variety of data forms, including HTML and JSON. Only the XML data format is supported by SOAP.
• Security: REST does not have its own security techniques or a specified binding contract. On the other hand, SOAP binds client programmes and web services using the WSDL contract and has its own security techniques.
• Requirement: REST utilises URIs to expose business logic and requires less bandwidth and resources. On the other hand, SOAP employs service interfaces to expose business logic and demands greater bandwidth and resources.

 

Coupling: SOAP has a close coupling between web services and clients. It also establishes some guidelines that must be adequately adhered to. REST, on the other hand, does not adhere to many standards while still allowing for flexible coupling.

10. What is the Interoperability of Web Services?

Interoperability is the capacity of distinct applications to communicate with one another, share data, and provide services to one another. There are no limitations on the sort of application that may be used to communicate.

If any code is written, it will be considered generic code that all programmes will understand.

As a result, the cost of building custom code for each application is lower.

11. What are the tools used to test web services?

Client stubs generated from WSDL or tools like Soap UI can be used to test SOAP web services programmatically.

Programs, curl commands, and browser extensions can all be used to evaluate REST web services. Resources supporting the GET method may be tested directly in the browser without additional software.

12. Explain Synchronicity.

Synchronicity refers to the client's connection to the service's execution.

The client blocks and waits for the service to finish its action before continuing in synchronous invocations. Clients can use asynchronous operations to call a service and subsequently perform other tasks.

13. Explain web service architecture.

There are three different layers in web service architecture. They are:

• Service Provider: As the name implies, the service provider has to construct the web service and make it available to client applications for use over the Internet.
• Service Requestor: It is basically any consumer of web service like any client application. Client applications are written in any language. They contact web services for any type of functionality by sending XML requests over the available network connection.
• Service Registry: It is a centralised registry that assists client applications in locating online services. Existing web services can be found here, and developers can also create new ones.

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14. Is it possible to keep a user's session in web services?

Because web services are stateless, it is impossible to keep track of user sessions.

15. What is the difference between SOA and Web Services?

Service Oriented Architecture (SOA) is an architectural pattern in which applications are built in terms of services that may be accessed across a network using a communication protocol. SOA is a design pattern, not a set of instructions for execution.

Web Services are Services in the SOAP architecture, providing a way to implement the SOA design.

16. Define web service protocol stack.

The web service protocol stack is a collection of protocols for exploring and executing online services. Service Transport, Service Description, XML Messaging, and Service Discovery are the four layers that make up the overall stack.

17. Explain each layer of the web service protocol stack.

HTTP, SMTP, FTP, and Blocks Extensible Exchange Protocol all use the Service Transport layer to convey messages between various applications (BEEP). Messages are encoded in XML format by the XML Messaging layer so that they may be understood at both ends, such as XML-RPC and SOAP. The Service Description layer, often known as WSDL, specifies the user interface for a web service. The Service Discovery layer combines services into a common registry and provides basic publishing capabilities, such as UDDI.

18. Define JAX-WS API.

The Java API for XML Web Services (JAX-WS) is a Java API that uses XML to create web services servers and client applications. We don't need to incorporate anything else that works with it because it's part of the standard Java API.

19. Why do we need security in web services?

We need web service security so that private information and transactions can be reliable. SSL, or Service Socket Layer, is used to secure online services, which aids in creating an Entrust Secure Transaction Platform.

20. What is XML-RPC?

RPC stands for Distant Process Call, a technique of calling a procedure or function available on any remote computer. Extensible Markup Language (XML) is a markup language like HTML.

As a result, XML-RPC is a simple protocol for performing RPCs utilising XML communications. This has long been regarded as a valuable tool for linking various surroundings and establishing connections amongst a wide range of systems.

21. What are some features of XML-RPC?

The features of XML-RPC are:

• XML-RPC is considered platform-independent.
• HTTP POST helps send XML encoded requests.
• The HTTP response has the XML response embedded in it.

 

Diverse applications can communicate through it.

22. Explain UDDI and detail its features.

UDDI is an XML-based standard in the service discovery layer of the web service protocol stack. It functions as a directory for posting and locating web services online.

The following are some of UDDI's features:

• It's a platform-independent framework that's available to everyone.
• Its communication protocols include SOAP, COBRA, and Java RMI.
• It aids in the discovery of businesses and facilitates online engagement between them.

 

It functions as a database for all WSDL files.

23. UDDI uses which language?

WSDL (Web Service Description Language) is the language used by UDDI.

24. What is a SOAP message?

The data supplied to the application through web services is referred to as a SOAP message. SOAP is an XML document that is provided over web services to send data to a client application developed in any computer language.

The hypertext transfer protocol is used to convey SOAP messages.

25. How do you access a web service?

The steps involved in accessing a web service are:

• The information is packed into a SOAP message by the client application.
• The POST method is used to send a SOAP message to the server as a body of Hyper-Text Markup Language.
• The web service unpacks the SOAP message and turns it into a command that the application can interpret.
• The information is processed by the application, which then bundles it and sends it back to the client as a SOAP message.

The results are then obtained by unpacking the SOAP message by the Client.

26. What are EIS and EPS? Explain the difference between the two.

Entrust Identification Service is abbreviated as EIS, and Entrust Privacy Service is abbreviated as EPS. The Entrust Identification Services, created by the Entrust Security Platform, allows businesses to manage the trusted identities that perform different Web Services operations.

The Entrust Privacy Service, on the other hand, deals with security and secrecy by encrypting data so that only the parties involved and authorised workers have access to it.

27. Define DISCO in web services.

DISCO stands for Discovery In Web Services. It aids in the grouping of a list of interconnected online services. The firm that supplies web services issues the DISCO file on the server so that all web services' links may be available and used within the local network.

28. What are Distributed Technologies?

Distributed Technologies enable the application to be segmented into multiple components and transferred to other computer systems and networks. Distributed technologies have risen in response to the development in the number of distributed applications.

29. What is the use of javax.xml.ws.Endpoint class?

The Endpoint class contains methods for creating endpoints and publishing existing implementations as web services. This is useful for testing web services before making changes and deploying them on a live server.

30. Explain the use of the sun-jaxws.xml file.

When JAX-WS web services are deployed in a servlet container like Tomcat, this file is used to give endpoint information. The endpoint name, implementation class, and URL pattern are all contained in this file, which is located in the WEB-INF directory. Example,

<?xml version="1.0" encoding="UTF-8"?>
<endpoints xmlns="https://java.sun.com/xml/ns/jax-ws/ri/runtime" version="2.0">
  <endpoint
        name="Web services interview questions"
        implementation="com.journaldev.jaxws.service.websiImpl"
        url-pattern="/websiWS"/>
</endpoints>

31. What is WSDL in Web Services?

Web Service Description Language (WSDL) is an XML-based document that contains technical information about the web service. Method name, port types, service endpoint, binding, method arguments, and other helpful information may be found in the WSDL document.

32. Define BEEP.

Blocks Extensible Exchange Protocol (BEEP) is tasked with developing new protocols for various applications, including instant messaging, network administration, and file sharing. It's known as the new Internet Engineering Task Force (IETF), and it's built directly on top of TCP.

Also see, Bank interview questions

33. What is WS-Security, and why is it important?

WS-Security is a standard for securing web services through various security features such as authentication, integrity, and confidentiality. It is important because it ensures that messages exchanged between web services are protected against threats like tampering and eavesdropping, providing a secure environment for data transactions.

34. How does a Web Service differ from a Web API?

A Web Service and a Web API both enable communication over the internet but differ significantly. Web Services typically use standardized protocols such as SOAP (Simple Object Access Protocol) and WSDL (Web Services Description Language). They rely on XML for data exchange and are known for their strict standards and robust features like built-in security and error handling. In contrast, Web APIs are more flexible and generally use HTTP/HTTPS protocols. 

They often follow REST (Representational State Transfer) principles and use lightweight data formats such as JSON. Web APIs are simpler, focusing on providing resources and are designed to be easily integrated with web and mobile applications. Overall, Web Services are more complex and feature-rich, suited for enterprise environments, while Web APIs are lightweight and user-friendly, ideal for modern web and mobile applications.

35. Explain the purpose of WSDL in Web Services.

WSDL (Web Services Description Language) is an XML-based language that defines the functionalities and interfaces of a web service. It serves several key purposes:

1. Service Description: WSDL details the operations provided by the web service, including methods, input and output parameters, and data types.
2. Interaction Details: It specifies how to access the service, including the endpoint URL and communication protocols.
3. Contract Definition: It acts as a contract between the service provider and the consumer, outlining how to interact with the service.
4. Automation: WSDL enables tools to automatically generate client-side code for interacting with the service, simplifying development.

In essence, WSDL ensures a clear, standardized way to describe web services, facilitating effective client-server communication.

36. What is the role of the XML schema in web services?

The XML schema defines the structure and data types of XML messages exchanged between web services. It ensures that the data conforms to a specified format, promoting consistency and interoperability between different systems and services by validating the XML data against predefined rules.

37. How do you implement error handling in a Web Service?

Error handling in a Web Service can be implemented by defining fault elements in the WSDL file and using specific fault messages. For SOAP-based services, faults are communicated using <soap:Fault> elements, while RESTful services often use standard HTTP status codes to indicate errors, with detailed error messages in the response body.

38. How do you ensure data consistency in a distributed web service environment?

Data consistency in a distributed web service environment can be ensured through mechanisms like distributed transactions, consistency models (e.g., eventual consistency), and synchronization techniques. Tools like distributed databases and coordination services (e.g., Zookeeper) help maintain consistency across multiple nodes.

39. What is a RESTful Resource, and How is it Used?

A RESTful resource is a key concept in RESTful web services. In REST (Representational State Transfer) architecture, resources are entities or objects that can be identified and manipulated via standard HTTP methods. These resources represent data or functionality and are accessed through Uniform Resource Identifiers (URIs).

Key Aspects of RESTful Resources:

HTTP Methods:

• GET: Retrieves the state of a resource. For example, GET /users/123 might fetch the details of a user with ID 123.
• POST: Creates a new resource. For example, POST /users with a request body containing user details creates a new user.
• PUT: Updates an existing resource. For example, PUT /users/123 with updated user information modifies the existing user.
• DELETE: Removes a resource. For example, DELETE /users/123 deletes the user with ID 123.

URIs: Each resource is accessed via a unique URI. For example, https://api.example.com/products/456 might be the URI for accessing a product with ID 456.

Stateless Communication: Each request to a RESTful web service must contain all the information needed for the server to fulfill the request. The server does not store any client context between requests.

Representations: Resources can have different representations, such as JSON or XML. The representation format is usually specified in the request headers or accepted in the response.

Example: In a RESTful online bookstore, a resource could be a book. The URIs for interacting with this resource might include:

• GET /books/789 to retrieve information about the book with ID 789.
• POST /books to add a new book to the inventory.
• PUT /books/789 to update details of the book with ID 789.
• DELETE /books/789 to remove the book with ID 789 from the inventory.

RESTful resources are fundamental to RESTful web services, providing a structured and intuitive way to interact with web-based applications and services.

40. What is a Service-Oriented Architecture (SOA)?

Service-Oriented Architecture (SOA) is an architectural pattern that involves designing software systems as a collection of loosely coupled, reusable services. Each service performs a specific business function and interacts with other services over a network, promoting scalability, flexibility, and easier integration across different systems.

Service-Oriented Architecture (SOA) is a design pattern that structures software systems as a collection of independent services. Each service in an SOA architecture is a self-contained unit that performs a specific business function or process. These services communicate with each other over a network, usually through standard protocols such as HTTP or SOAP.

Key Features of SOA:

Loose Coupling: Services are designed to be independent, which means changes in one service should not directly impact others. This promotes flexibility and makes it easier to maintain and update the system.

Reusability: Services can be reused across different applications and processes, reducing redundancy and development effort. Once a service is created, it can be leveraged by multiple clients or other services.

Interoperability: SOA enables different systems and technologies to work together seamlessly. This is achieved through standardized communication protocols and data formats, such as XML or JSON.

Scalability: Services can be scaled independently based on demand. For instance, if a particular service experiences high traffic, it can be scaled up without affecting other services.

Integration: SOA facilitates integration between disparate systems and applications. This is particularly useful in enterprises with multiple legacy systems that need to work together.

Example: An online retail system might have separate services for user management, inventory control, and payment processing. Each service communicates with the others to complete transactions, but they operate independently, allowing for easier updates and scalability.

Web Services MCQ

41. What does WSDL stand for?

• a. Web Service Description Language
• b. Web Service Design Language
• c. Web Service Deployment Language
• d. Web Service Data Language
  Answer: a. Web Service Description Language

42. Which protocol is commonly used for SOAP web services?

• a. HTTP
• b. FTP
• c. SMTP
• d. POP3
  Answer: a. HTTP

43. What is the main function of UDDI?

• a. Define web service interfaces
• b. Discover and publish web services
• c. Secure web service messages
• d. Transform XML data
  Answer: b. Discover and publish web services

44. What is a typical use of HTTP status codes in RESTful services?

• a. To format XML responses
• b. To indicate the success or failure of HTTP requests
• c. To encrypt data
• d. To manage service security
  Answer: b. To indicate the success or failure of HTTP requests

45. In which format are SOAP messages typically transmitted?

• a. JSON
• b. XML
• c. CSV
• d. HTML
  Answer: b. XML

46. What does the <soap:Fault> element in a SOAP message represent?

• a. Service request
• b. Service response
• c. Error information
• d. Data transformation
  Answer: c. Error information

47. What is the main difference between SOAP and REST?

• a. SOAP uses XML only, REST can use various formats
• b. SOAP is stateless, REST is stateful
• c. SOAP is lightweight, REST is heavy
• d. SOAP uses HTTP only, REST uses multiple protocols
  Answer: a. SOAP uses XML only, REST can use various formats

48. What is a common format used for RESTful web services responses?

• a. XML
• b. CSV
• c. JSON
• d. HTML
  Answer: c. JSON

49. What role does an XML schema play in SOAP-based web services?

• a. Encrypts the XML data
• b. Validates the structure of XML messages
• c. Transforms XML data to JSON
• d. Manages service discovery
  Answer: b. Validates the structure of XML messages

50. How does WS-Security contribute to web service security?

• a. It describes web service operations
• b. It provides encryption and authentication
• c. It formats SOAP messages
• d. It handles data transformation
  Answer: b. It provides encryption and authentication

Frequently Asked Questions

Is there any particular application required to access web services?

You do not need to install any particular software to use the online service. Any program supporting XML-based object request and response can use the web service.

Which protocol is used to call a web service?

Web services employ well-known protocols like HyperText Transfer Protocol (HTTP) and Java Message Service (JMS) to receive requests and provide answers. A web service could support more than one protocol. The WSDL file specifies which protocols a web service supports.

Why are web services required?

You can use web services to expose the functionality of your current programmes over the Internet. Other apps can utilise the functionality of your software once it is available on the network.

Conclusion

In this article, we covered web services interview questions. We learned the most asked web interview questions from beginner to advanced level. 

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