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SOAP Web Services Interview Questions- Part 2
Even in the world of REST and microservices, SOAP web services continue to be important for many enterprise systems. SOAP offers strong security, strict data contracts, and support for distributed transactions, making it ideal for applications that require robust communication. If you’re applying for roles involving integration, middleware, or enterprise application development, expect interview questions on SOAP.
On this page, we’ve listed important SOAP Web Services interview questions and answers to help you prepare. We cover key topics like the structure of a SOAP message, WSDL, UDDI, and differences between SOAP and REST. The questions are explained in simple language to help you quickly understand the concepts. Whether you’re a fresher or an experienced professional, this guide can help you revise important topics and boost your confidence. Use these questions to practice and improve your knowledge before stepping into your next technical interview.
Answer:
The < Envelope > element is used as a root element of each SOAP message. The Root element, also known as the first element in an XML Document. The Envelope is separated into two parts; one is a header part & the second is a body part. The header contains routing data that stores a client’s source & destination address & the body has the actual data.
Answer:
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SOAP Webservice Other Remote Webservice - SOAP is user-friendly & non-symmetrical
- It provides platform independence with language independence.
- SOAP deploys HTTP protocol and saves data in an XML format.
- SOAP objects are hard to maintain & stateless.
- Other webservices like CORBA or DCOM are popular but more complex.
- CORBA or DCOM does not provide platform & language independence.
- Other remote services like DCOM & COBRA have their binary formats used to transport data in a complex manner.
- Other remote webservices are not hard to maintain.
Answer:
Both are SOAP & JSON are popular in the market; let us discuss some of their major differences:
- SOAP is a set of rules or protocol, while JSON is an object.
- SOAP can utilize JSON for communication, but JSON cannot use SOAP.
- SOAP uses an XML format, but JSON uses the key-value pair.
- It is possible to declare error messages with SOAP, but the same isn’t possible with JSON.
Answer:
Below are the main differences between RESTful webservices & SOAP webservices:
- REST supports distinctive formats such as JSON, XML, text; whereas SOAP only supports XML;
- REST only works over the HTTP on a transport layer; SOAP can use different protocols on a transport layer;
- REST works with resources, each unique URL represents some resource; SOAP works with operations, which implements some business logic via different interfaces;
- SOAP-based reads cannot be cached, as SOAP needs to provide caching; REST-based reads can be cached;
- SOAP supports both SSL security & Web Service-security; REST only supportsSSL security;
- SOAP supports Atomicity, Consistency, Isolation, Durability (ACID); REST supports transactions, but they are not ACID compliant & cannot provide a two-phase commit.
Answer:
Some components that SOAP uses are as follows:
- (Web Services Description Language) or WSDL
- (Simple access object protocol) or SOAP
- (Universal Description, Discovery, and Integration) or UDDI.
Answer:
MTOM stands for Message Transmission Optimization Mechanism. It is a mechanism for transmitting large binary attachments with SOAP messages as raw bytes, thus enabling smaller messages.
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XOP stands for XML-binary Optimized Packaging. It is a mechanism recommended by W3C, defined for serialization of XML Information Sets including binary data & deserialization back into the XML Information Set.
Answer:
JAXB stands for Java Architecture for XML Binding. It is a Java technology that allows for the mapping of XML data to and from Java objects. JAXB provides a convenient way to work with XML data by automatically generating Java classes that correspond to XML schema definitions (XSD). These generated Java classes can then be used to marshal (convert Java objects to XML) and unmarshal (convert XML to Java objects) XML data.
Answer:
SOAP encodingStyle attribute defines the serialization rules used in a SOAP message. This attribute can appear on any element & scoped to that element’s contents & all child elements. It is no default encoding defined for a SOAP message.
Answer:
Web services exchange information between applications over some standard web protocols such as SOAP & HTTP using the XML format. COBRA exchanges information between apps using protocols like IIOP. COBRA or Common Object Request Broker Architecture enables us to communicate between two software written in a different programming language, running on different computers. DCOM avails a Remote procedure calling protocol to exchange information between applications. DCOM and COBRA use a non-standard protocol to send or receive messages, while Web services use a standard protocol like HTTP & SOAP.
Answer:
The wsgen tool helps parse an existing web service implementation class & generates the necessary files like JAX-WS portable artifacts for web service deployment.
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UDDI (Universal Description, Discovery, and Integration) is a directory service where businesses can register and search for web services.
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A binding is a specification that defines how the service should be accessed, including the protocol to use (e.g., HTTP, SMTP) and the message format (e.g., SOAP).
Answer:
Yes, SOAP can be used over various transport protocols such as SMTP and JMS (Java Message Service). However, HTTP is the most common protocol used for SOAP web services.
Answer:
Versioning in SOAP can be handled using techniques like namespace versioning or parameter-based versioning. It’s important to design web services in a way that allows for backward compatibility while introducing new features.
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A SOAP fault is an error message that provides information about a failure that occurred during the processing of a request. It includes details such as the fault code, fault string, and fault actor. SOAP fault handling involves sending back error responses to the client.
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WS-Security is a set of standards that provide security mechanisms for SOAP messages. It ensures confidentiality, integrity, and authentication of messages exchanged between web services.
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SOAP headers contain optional information related to the message. They can carry metadata or authentication information. The body of the message contains the actual payload or data that is being transmitted.
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Key Differences:
- Scope: Web services are a type of software that provides specific functionalities over the internet, often involving data exchange. APIs are a broader concept that defines how different software components can interact, which can include web services but also encompasses other types of interactions.
- Communication: Web services are a specific way of implementing APIs. They often use web-based protocols like HTTP for communication, but APIs can be implemented using different communication methods, such as libraries or frameworks within the same programming language.
- Granularity: Web services tend to expose larger functionalities, like entire services or sets of operations, whereas APIs can be more fine-grained, providing access to specific methods or even individual data elements.
- Data Exchange: Web services often use XML or JSON for data exchange, while APIs can use a variety of data formats.
- Implementation: Web services have specific implementations like SOAP-based or RESTful web services. APIs can be implemented using various technologies, not limited to web services
Answer:
The SOAP HTTP binding specifically refers to using the HTTP protocol as the underlying transport mechanism for sending and receiving SOAP messages. This is one of the most common bindings for SOAP due to the widespread adoption of HTTP as the foundation for web communication.