In this post we cover almost every portion of the concept of Web services that you need to be familiar with to answer any tier questions. You would also find the best Web Services Interview Questions and Answers in classifications so you can only get in a specific provision if necessary.
Varieties of web applications developed on various programming platforms are available today. Making sure full and accurate connections between such diverse applications becomes much more difficult. The solution to the issue is ‘ web services, ‘ that thinks and acts as a way to communicate between all these various web applications with different programming languages developed. Web services use structured XML communication system that is easily accessible through internet or private networks.
Table of Contents
Basics of Web Services
1. What is a Web Service?
Web services are based on customer-server system where customer applications will obtain network services. Web services supply endpoint URLs, and provide network access techniques by user programs written in java, shell script or many other technologies. Web services are stateless, and do not preserve a web applications user session.
2. How does a web service work?
A Web service uses open standards such as HTML, XML, WSDL and SOAP to interact between different applications. You can construct a web service on Java on Ubuntu that can be accessed from your Windows-premised Visual Basic project. In addition, C# can be used to create new Windows enact web services for your Java Server Pages (JSP) web application, which runs under Linux.
3. What are the advantages of web services?
Some of the main benefits of web services are these:
- Interoperability: An application can interact with another application in any language using web services.
- Reusability: The web service may be exposed to other applications.
- Modularity: We can build a service for a certain task, such as tax calculations, using the Web service.
- A Standard protocol for every application program: Web services use standardized protocol to make it understandable for customer applications compiled in various languages. This usual procedure contributes to cross – platform achievement.
- Cheaper cost for communication: Web services do use SOAP over HTTP to allow anyone to use the Internet that already exists for web service.
4. What are the components of web service?
The various web services components are as follows:
- SOAP- Simple Object Access Protocol
- UDDI- Universal Description, Discovery, and Integration
- WSDL- Web Service Description language
- RDF- Resource Description Framework
- XML- Extensible Markup Language
5. Explain the term Interoperability with respect of Web services?
This applies in the same way when we talk about web interoperability. The same applies to web services when we are talking about’ interoperability.’ In this context it decide the interaction between different applications, information sharing and services. The type of request to be communicated is not restricted. When a script is published, it will be viewed as a standard script which all applications understand. Therefore, for each application, the costs of writing particular scripts are lowered.
6. Define web service protocol stack and its layers?
The protocol stack of Web service comprises of four layers. This is as follows:
1) Service transport: It is the first layer that enables transport XML messages between different client programs and uses the protocols listed below:
- HTTP(Hypertext Transport Protocol)
- SMTP(Simple Mail Transport Protocol)
- FTP(File Transfer Protocol)
- BEEP(Block Extensible Exchange Protocol)
2) XML messaging: This is premised on the XML model, which encodes messages in prevalent XML format that others can easily understand. This layer comprises:
- SOAP(Simple Object Access Protocol)
3) Service description: The layer involves descriptions of location, features available and XML messaging data types describing a public interface to a particular web service. Include this layer:
- WSDL(Web Service Description Language)
4) Service discovery: This layer provides a way of publishing and finding web services throughout the web. This layer contains:
- UDDI(Universal Description, Discovery, and Integration)
7. Explain web service architecture?
The Web Service Framework comprises of three different layers of architecture. The following are the roles of the layers:
- Service Provider: As the name implies, the function of the service provider is to develop the internet services and make it available via the internet to customer software for their use.
- Service Requester: As with the client application, service requester is essentially a user of web services. User programs are compiled for all types of functions in any language contact Web service by transferring XML requires via the internet connection available.
- Service Registry: Service Registry is the core repository that supports the location of customer web services. The current web services can be found here, and also the new programmers can also build them.
The service provider makes the current web services accessible for customer applications with the ‘ Publish ‘ interface of the registry service. The service requester is able to attach or override the services with all information given by the service register.
8. Enlist few advantages of web services?
- Each application is currently available on the web and it is the web service, providing the user applications with some necessary functionality.
- In order to support other applications, web services can help to expose existing functions over the network.
- It has characteristics such as ‘ Interoperability ‘ that decide interaction between different applications, data sharing, and services between them.
- For communication, web services are using standard internet service protocol stack consisting of 4 layers, namely Transportation Service, XML Messages, Description and Discovery Service.
- It offers minimal interaction costs due to SOAP’s application over the HTTP protocol (Simple Object Access Protocol).
- It is easy to install, assimilate and reusable.
- It allows easy integration among various features in the loose coupling function.
9. Explain BEEP?
BEEP stands for Blocks Extendable Exchange Protocol. It is known as the new Task Force for Internet Engineering (IETF) directly layered over TCP. It is called the new IETF (Internet Engineering Task Force), which is directly superimposed across TCP. It has some integrated functionalities such as:
- Error handling
- Handshake Protocol
REST and SOAP web services
10. What do you know about RESTful Web Services?
REST stands for Representational State Transfer. For the development of the application obtained through web, REST is described as a stateless client-server architecture. When web services use HTTP methods, they are regarded as RESTful Web Services for implementation of the theory of REST architecture. Data and features in this architectural style are used as resources and can be accessed via URIs. With RESTful web services, web services can perform best by creating properties such as:
11. Explain the advantages of RESTful web services?
The benefits of RESTful web services are mentioned below:
- These can be written in any programming language and it can be carried out on every framework. The language and framework are totally independent.
- REST is compact and is viewed quick due to less bandwidth and resource consumption.
- The system includes several technologies and data formats such as plaintext, XML, JSON, etc.
- This can be examined feasibly over browsers and has loosely coupled implementations.
12. What is the difference between a REST web service and a SOAP web service?
The key variations between REST and SOAP are described below:
- REST promotes various formats such as text, JSON and XML where as SOAP supports only XML.
- REST operates on a transport layer via HTTP(S) only where as SOAP can also be used on separate transport layer protocols.
- REST operates with resources and every single URL is a resource description where as SOAP operates with business operations that use various workflows to create certain business logic.
- SOAP – oriented reads can not be archived because SOAP needs to cache where as REST – oriented reads can be archived.
- SOAP promotes the security of SSL and WS – security where as REST promotes SSL security only.
- SOAP promotes ACID (Atomicity, Consistency, Isolation, Durability) ; REST promotes transactions, but it does not comply with ACID and can not provide two commit phases.
13. Explain different HTTP methods supported by RESTful web services?
Some prevalent HTTP methods and functions that are endorsed by RESTful web services are mentioned below:
- GET: Read-only access to the resource.
- PUT: Creation of new resource.
- DELETE: Removal of a resource.
- POST: Update of an existing resource.
- OPTIONS: Get supported operations on the resource.
- HEAD: Returns HTTP header only, nobody.
14. For designing a secure RESTful web service, what are the best factors that should be followed?
Because HTTP URL paths were used as a component of the RESTful web service, they have to be safeguarded.
- Carry out approval of all SQL injection attack parameters on a server.
- Carry out authentication based on the user session when requests are requested.
- Do not use private information such as a username, password for session tokens, etc. This should be transmitted through the POST method.
- Proper limitations on methods such as GET, POST, PUT, DELETE, etc. are to be applied.
- Wherever necessary, standard HTTP error message must be invoked.
15. What are SOAP Web services?
The XML based protocol, known for the design and the development of web services and the interaction of applications on various platforms with different software languages over the Internet is described as the Simple Object Access Protocol (SOAP). It is independent of both the platform and language.
16. How does SOAP work?
SOAP provides a user interface that is accessible by the client object, and the application that it sends is accessible from a server object. The user interface generates some documents or processes comprising the server object and the server object interface name. The HTTP uses the POST method, which scans the method and sends the result to the client, to the server. Using POST method, HTTP sends the XML to the server, which examines the way and transfers the results to the customer. The server provides more XML to answer the user interface request via HTTP. Any strategy can be used by the client to send XML, such as the SMTP Server or POP3 protocol for delivering messages or answering queries.
17. What are the advantages and disadvantages of SOAP?
The benefits of SOAP web services are mentioned below:
- SOAP provides interaction between different applications and is independent of language and platform.
- It is also extremely easy to transmit and receive messages using the standard HTTP protocol and XML.
- They define and employ their own safety called WS security.
- It disconnects encoding and interaction from the working environment.
- It removes difficulties with the firewall and is impartial with the seller.
- It enables messages to be circulated in distributed and decentralized environments.
The following are SOAP web services disadvantages:
- Not supporting lightweight formats other than XML.
- On browsers, not easily testable.
- There are no safety facilities.
- SOAP is a slow and browser testing process that can not easily be carried out.
- Web services and clients are strongly linked and describe certain requirements which must be accompanied strictly.
18. What are the elements of a SOAP message?
SOAP is similar to other XML documents and has the following items:
- Envelope: It converts the XML document and defines the beginning and termination for SOAP message. This element is determined as the root element.
- Header: This element includes the optional message header features containing particular application information. This element can take place several times to add new features and functions.
- Body: This element is required and includes request and response notifications. It is also described as a child element in the envelope involving all the XML data extracted from the application swapped in the SOAP message.
- Fault element: The fault element handles errors which take place throughout message processing. This element is then available as a child element in the body if the error is present. But only one fault block can exist.
19. What are the important characteristics of SOAP envelope element?
In the previous question, we saw the fundamental work of the SOAP envelope, now let us see some of its features:
- SOAP packaging is a process for packaging.
- The root message of each soap message is compulsory.
- For each envelope element, only one body element is permitted.
- The envelope changes when you change the SOAP version.
- This should occur as the first child when the header element is present.
- For specification, the ENV prefix and envelope element are used.
- In case of optional SOAP encoding, a namespace and an optional encoding style are used.
20. Define SOA?
An architectural model made up of services is described as a service orientated architecture (SOA). In this application components, other components are provided with services using network communication protocol. This interaction includes the exchange of information or cooperation of services. The following are some of the fundamental principles on which SOA is based:
- All descriptions of the services must be simplified in the service contract.
- The loose connection between the web services and the client defines the less dependence.
- Service Abstraction must be followed which says that the service must not indicate how the features of the client application was executed.
- In order to operate with different application types, services should be reusable.
- Stateless services should have a user friendliness characteristic.
- Services solve major issues and enable various users to use the services.
21. What is WSDL?
WSDL is the Web Description Language service. It is an XML document, which is included in the Web Service Protocol Stack Service Description Layer, which outlines the technical information or the user interface for web service. Some of the important information in the WSDL document are as follows:
- Method name
- Port types
- Service end point
- Method parameters
- Header information
- Origin, etc
22. What is difference between Top Down and Bottom Up approach in SOAP Web Services?
The first WSDL document to develop the web service deal with the client is developed in the Top Down approach, and afterwards the code is written and called the first contract. This is difficult to implement, as classes have to be written in order to confirm the WSDL contract. The advantage is that both customer and server code can be penned simultaneously.
The first web service code is written in the Bottom Up method, followed by WSDL generation. It is also called the last approach of the contract. This approach can be implemented easily because WSDL is code – based. This approach client code must wait until WSDL is started from the server side.
23. What are the different elements of WSDL documents?
The various elements and brief descriptions of the WSDL document are included below:
- Types: This sets out the forms of message data used by web services in the form of an XML scheme.
- Message: This describes the data components for the full document or argument to be mapped for each transaction, which can contain messages.
- Port Type: WSDL offers a variety of services. The type port determines the collection of binding transactions.
- Binding: Finds and describes for each port type, the protocol and the data format.
- Operations: This specifies how a message can be processed for the operation.
24. Enlist the operation types response used in WSDL?
Basically, WSDL defines four types of response type operations. These are elaborated below:
- One-way: Get a message, but don’t return the response.
- Request-Response: The request is received and the reply is returned.
- Solicit-Response: Wait for the reply, send a request.
- Notification: Doesn’t expect a response, but sends a message.
Perhaps the most popular type of operation involves request – response.
25. What is UDDI?
UDDI is a universal description, discovery and integration . UDDI is a web service repository where customer applications can search for web services. Web services can enter and making it accessible for customer applications to the UDDI server.
26. What is the difference between SOA and WEB SERVICE?
Service – oriented (SOA) architecture consists of a modular approach in application development which involves the use by conventional interoperability of distributed, loosed – coupled elements (Loose Coupling) with standardized interfaces. Software systems developed according to a service-oriented architecture are usually used as a series of web-based services which communicate with SOAP protocol, however there are other applications (for example, jini-based, CORBA-based, REST-based). Web services using XML, JSON and other web protocols, such as HTTP (S), SMTP, etc, are implementing this concept.
27. How many Communication protocols can be used to implement a SOAP message? Is SOAP messages are tied to any protocol?
Applications from different backgrounds can communicate quickly with each other without knowing the internal functions of the various systems using transport protocols. Applications from diverse backgrounds can interact rapidly with one another without understanding the internal functions of the various systems using transport protocols. A SOAP message can be implemented with HTTP (HyperText Transfer Protocol), while FTP (File Transfer Protocol) is a trustworthy process for transportation. For the transport mechanism, SMTP and BEEP may also be used. The SOAP message is not linked to any protocol. Any open transportation protocol can be used.
28. What is the use of Accept and Content-Type Headers in HTTP Request?
These are key headers for restful web services. Accept headers indicates what kind of response clients are accepting to the web service. Therefore, when a web service is able to send an answer in XML and in JSON format, and the client sends Accept header to “application / xml,” the XML reply is sent. The server sends the JSON response for the Accept “application / json” header. The header Content – Type is being used to inform the server the format of the information sent. The server attempts to analyze the Content – Type header as XML data if it is a “application / xml.” In HTTP Post and Put requests, this header is useful.
29. What are the primary security issues of web service?
Web services demand very high degree of privacy that could only be accomplished through the Entrust Secure Transaction Platform in order to guarantee trustworthy transactions and safe private information. Web service exploitable vulnerabilities are divided into three widely mentioned segments Security challenges:
1) Confidentiality: There are several uses for a single web service and a obvious weak link to their endpoints can be established on the service path. It is therefore necessary to keep the communication confidential. It is therefore necessary to keep the communication confidential.
2) Authentication: Authentication is carried out essentially to check the subscribers ‘ identity and ensure that the subscriber using the web service is entitled or not to use it? Authentication is also performed to follow the practice of the user. For this purpose, there are several options to consider:
- Application level authentication
- HTTP digest and HTTP basic authentication
- Client certificates
3) Network Security: It is a major problem that calls for tools to filter traffic on web services.
30. What do you know about foundation security services?
The following are the foundation security services:
- Digital Signatures
- Encryption processes
31. What is a Resource in Restful web services?
The basic concept of restful architecture is resource. A resource is a type object, connected with many other resources and techniques used. Resources are recognized through their URI, HTTP methods, data type and data format request / response.
32. Explain the actions performed by SOAPUI?
SOAPUI is a functional test solution, open source, free and cross – platform. Some actions taken by SOAPUI are mentioned below:
- They can help to develop functional testing suites, safety and loading.
- Testing driven data and testing based on scenarios are also done.
- It can represent web services and has integrated reporting capabilities.
33. What are different ways to test web services?
SOAP web services could be programmatically examined via the creation of WSDL client stubs or software like soap user interface. With programs, curl instructions and browser extensions, REST web services can be easily tested. GET method resources can be evaluated without any programs using the browser itself.
34. What is Entrust Identification Service?
The Entrust Secure Transaction Platform categorizes Entrust Identification Service, which offers necessary safety functionality for secure transaction. This helps companies to regulate completely the identities trusted for transactions with web services.
35. What is Entrust Entitlements Service?
Entrust Entitlement service would be those whose challenge is to validate the services that manage to obtain the web services. It essentially guarantees protection in business activities as well as certain verification services.
Advanced Web Services Questions
36. How is authentication handled in web services?
In web services, authentication is normally handled using JWT tokens generated using the backend servers that serve the APIs. These tokens are refreshed at regular intervals to authorise the user
37. What are the benefits of web services over normal Servlet request?
Web services allows to get data faster and support variety of response types. Web services also allow to validate and format the data with strict envelope standards
38. What are the major applications of web services?
Web services are primarily used in projects where the frontend is expected to be isolated from the backend. Additionally, web services can also be used to expose backend business logic to other third-party users. Other uses involve:
- Storage of data using web service
- Authentication using web service
- Getting seed data using web service
39. Why are web services getting more popular?
Web services are independent endpoints providing and consuming data irrespective of the operating system and programming language of the source interface. This allows the frontend to be easily modified and upgraded without worrying about affecting the backend.
40. What are some popular Java frameworks for building web services?
The most popular ways of building web services in Java are:
- Spring REST Controller
Those were the most important questions regarding We Services. These questions have been answered with the aim to make your interview easier. However, there is always more to explore.
You are welcome to contribute with your comments and we will include them in the article!