Web Services Interview Questions and Answers
Web services interview questions can test the depth of knowledge of a candidate in terms of web services. The use of standard formats and languages for communication and information sharing across various systems is made possible by a collection of protocols and standards called web services.
For developers, developing web services is a crucial skill. It is a growing field, with an average annual salary of $115,975 a year for an API developer (APIs are a type of web service). Learning about web services includes learning various technologies, such as XML and architectures like SOAP (Simple Object Access Protocol), WSDL (Web Services Description Language), RESTful (Representational state transfer) web services, and more.
Different interviewers can pose different types of questions, and it is crucial to be well-prepared to crack one’s dream job. As such, a good set of practice interview questions, such as the web services interview questions listed in this article, may help one to test their knowledge and expertise in the domain.
Table of Contents
- Introduction
- Web Services Interview Questions (Basic)
- Web Services Interview Questions (Advanced)
- Final Thoughts
- Frequently Asked Questions (FAQs)
- Recommended Articles
Key Highlights
- Web services interview questions require in-depth knowledge of SOAP and RESTful web services, their differences, and how they work.
- It is essential to know the architecture and components of web services, such as XML, WSDL, and UDDI.
- Get familiarized with various implementation languages and frameworks like Java, .NET, and Node.js.
- Prepare to answer technical questions on web service security, scalability, performance, testing, debugging, and troubleshooting.
Part 1 – Web Services Interview Questions (Basic)
1. Define web services. Explain its components.
Answer:
A web service is an application that is accessible over the internet, which enables communication or exchange of information between two applications. They usually work on a client-server model where clients can easily access them.
Web services comprise several components that work together to enable communication between different systems over the internet. The main components of web services are:
- XML: This stands for eXtensible Markup Language and is a standard format for exchanging data between different systems.
- WSDL: This stands for Web Services Description Language and is an XML-based format used to describe the functionality of a web service.
- SOAP: This stands for Simple Object Access Protocol and is a messaging protocol used to exchange information between systems over the internet.
- UDDI: This stands for Universal Description, Discovery, and Integration. It is a directory service that helps locate web services online.
2. What is UDDI? What are the features of UDDI?
Answer:
UDDI is a part of the XML-based standard in the service discovery layer of a protocol stack. It uses WSDL (Web Service Description Language) for its work. It finds web services and publishes them on the web. Its main features are:
- It acts like a database containing all WSDL files together.
- The various protocols used for communication are SOAP, COBRA, and Java RMI.
- It is an open framework and platform-independent.
- It enables businesses to identify each other and communicate over the internet.
3. Explain the approaches for developing SOAP web-based service?
Answer:
There are two approaches to developing a SOAP-based web service.
- Contract first approach: When a user uses this approach, first, they need to define XML and WSDL. Then Java classes derive in the contract.
- Contract last approach: When going with this approach, a user must first define Java classes. Then the contract generates, which has a WSDL file from the Java class.
4. What practices ensure a secured RESTful web service?
Answer:
Several best practices can help ensure that a RESTful web service is secure. Some critical methods include the following-
- Use HTTPS: Always use HTTPS to encrypt data in transit and protect against eavesdropping and tampering.
- Authenticate and authorize requests: Implement strong authentication and authorization mechanisms to ensure only authorized users can access the web service.
- Use input validation: Validate and sanitize all user input to prevent injection attacks and other security vulnerabilities.
- Implement rate limiting: Limit the number of requests made to the web service to prevent denial-of-service attacks.
- Use proper error handling: Implement error handling to prevent sensitive information from exposure in error messages.
- Implement encryption and hashing: Implement encryption and hashing for sensitive data to ensure its protection in transit and at rest.
- Use OAuth2 for authentication: Use OAuth2 for authentication, which provides a secure, industry-standard approach for authenticating users and applications.
5. Explain SOA Architecture.
Answer:
Service-Oriented Architecture (SOA) is a design approach focusing on building software systems composed of loosely-coupled, reusable, and interoperable services. The fundamental principles of SOA include the following:
- Service Reusability: One can use services in different contexts and by other applications.
- Service Interoperability: Services can communicate with each other regardless of the programming languages or platforms they use.
- Modularity: Services can develop, deploy, and update independently.
- Service Autonomy: One can operate services independently of other services and have control over their functionality.
- Service Composability: One can combine services to create larger, more complex applications.
Part 2 – Web Services Interview Questions (Advanced)
6. List the operation types and its response used in WSDL.
Answer:
WSDL has four types of operations and responses. They are:
- One-way: Receives a message but does not return any response.
- Request-Response: Receives a request and returns a response.
- Solicit-response: Sends the request and waits for the response.
- Notification: Sends the messages but does not send any response.
7. How to marshal and unmarshal XML documents in Java? Explain with an example.
Answer:
Marshaling is a process of converting the XML document into Java readable format. Un-marshaling is the reverse of this process. In Java, JAXB (Java Architecture for XML Binding) API allows the marshaling and unmarshaling of XML documents. JAXB is a Java-based framework that allows mapping Java objects to and from XML documents.
JAXBContext jc= JAXBContext.newInstance ("com.acme.foo");
// unmarshal from foo.xml
Unmarshaller u = jc.createUnmarshaller ();
FooObject fooObj=
(FooObject)u.unmarshal (new File ("foo.xml") );
// marshal to System.out
Marshaller m = jc.createMarshaller ();
m.marshal (fooObj, System.out);8. Explain the elements of a SOAP message.
Answer:
A SOAP message has the following elements-
- Envelope: This is the mandatory root element. It helps determine the start and end of the SOAP message and translate the XML document.
- Header: This element constitutes header attributes of a message, which contains information about an application. This element occurs multiple times and adds new features and functionalities.
- Body: It is the child element of an envelope containing the derived data from XML. It exchanges as a part of the SOAP message. It is compulsory to have this block, and it includes all call and response messages.
- Fault element: If errors occur during the processing of messages, then the fault element handles them. If there is an error, this element will appear as a part of the body.
9. Enlist the packages available in XML digital signature API.
Answer:
Digital signature APIs elevate electronic signatures to a higher standard. The XML Digital Signature API is a Java-based API that supports XML digital signatures. The API is part of the Java XML Digital Signature Implementation, included in the Java SE platform.
Packages available in the XML Digital Signature API:
- xml.crypto: Contains the core classes and interfaces for XML digital signatures.
- xml.crypto.dom: This package contains DOM-specific implementations of the classes and interfaces in the javax.xml.crypto package.
- xml.crypto.dsig: Has classes and interfaces for creating and validating XML digital signatures.
- xml.crypto.dsig.dom: This package contains DOM-specific implementations of the classes and interfaces in the javax.xml.crypto.dsig package.
- xml.crypto.dsig.keyinfo: This package contains classes and interfaces for representing critical information in XML digital signatures.
- xml.crypto.dsig.spec: Contains classes and interfaces for representing parameters and algorithms used in XML digital signatures.
10. Explain Entrust’s identification, entitlement, and privacy services.
Answer:
Entrust is a company that provides identity and access management solutions to help organizations protect their sensitive data and applications.
Identification Services:
- Entrust Identification services provide a way to authenticate users and devices accessing an organization’s resources.
- It verifies the identity of users, devices, and applications, ensuring only authorized entities access their resources.
- It includes multi-factor authentication, digital certificates, and PKI-based authentication.
Entitlement Services:
- Entrust Entitlement services provide a way to manage and control user access to resources based on their roles, permissions, and other attributes.
- This service enables organizations to grant access to resources only to authorized users, reducing the risk of unauthorized access to sensitive data and applications.
- This service includes role-based access control, policy-based access control, and fine-grained access control.
Privacy Services:
- Entrust Privacy services provide a way to secure sensitive data and communication channels.
- It enables organizations to protect their data and communications from unauthorized access, interception, and manipulation.
- Its main features are encryption, digital signatures, secure messaging, and secure file sharing.
Final Thoughts
By enabling interoperable communication between various systems and applications through a network, web services have emerged as a crucial technology for contemporary software development. Due to this, there is now more demand for qualified individuals who can design, build, and maintain web services. Basic principles, protocols, security, and design patterns are just a few subjects covered in web services interview questions. Thorough knowledge of these subjects and actual work experience with web services are necessary for interview preparation for web services.
Frequently Asked Questions (FAQs)
1. What are the four basic standards for web services?
Answer: The four standards for web services are:
- SOAP (Simple Object Access Protocol)
- XML (eXtensible Markup Language)
- WSDL (Web Services Description Language)
- UDDI (Universal Description, Discovery, and Integration)
2. What are the basics of web services?
Answer: The basics of web services involve open standards and protocols to facilitate communication between different applications or systems over a network. This allows for interoperability between other platforms and programming languages. A uniform resource identifier (URI) accesses web services.
3. What are web service types?
Answer: There are three main types of web services:
- SOAP-based web services
- RESTful web services
- XML-RPC web services
4. What is a web service? Explain.
Answer: A web service is a software system that supports interoperable machine-to-machine interaction over a network. It enables different systems and applications to communicate with each other using standard web protocols such as HTTP, XML, and SOAP. Web services serve various purposes, such as exchanging data between systems, automating business processes, and integrating disparate systems.
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