Top 20 WSDL Interview Questions and Answers (2024 Guide)

26 April, 2025 admin 0 Comments 1 category

Web Services Description Language (WSDL) is a critical component in SOAP-based web services, acting as a contract between service providers and consumers. Whether you’re a Java developer, integration specialist, or API tester, understanding WSDL interview questions is crucial for roles involving web services.

In this guide, we’ll cover the top 20 WSDL interview questions with detailed answers to help you crack your next technical interview.

What is WSDL and Why is it Used?

Answer:
WSDL (Web Services Description Language) is an XML-based language that describes:

Available web service operations
Input/output message formats
Communication protocols (SOAP/HTTP)
Service endpoints (URLs)

Key Features of WSDL:

Defines service contracts for SOAP-based web services.
Supports machine-readable documentation.
Enables client-code generation (using tools like wsimport).

20 Most Common WSDL Interview Questions and Answers

1. What is the Purpose of WSDL?

Answer:
WSDL serves as a service contract that describes:

Operations (methods like getUser, createOrder)
Message formats (request/response structure)
Protocol bindings (SOAP over HTTP)
Service location (endpoint URL)

2. What are the Key Elements of a WSDL File?

Answer:
A WSDL contains these main elements:

<types> – XML schema definitions (XSD).
<message> – Input/output parameters.
<portType> – Abstract operations (like an interface).
<binding> – Protocol details (SOAP/HTTP).
<service> – Endpoint URL.

3. What is the Difference Between WSDL 1.1 and WSDL 2.0?

Answer:

Feature	WSDL 1.1	WSDL 2.0
HTTP Support	Limited	Native REST support
Message Exchange Patterns	Basic	Advanced (MEPs)
Namespace Handling	Complex	Simplified

4. How to Generate Java Classes from WSDL?

Answer:
Use wsimport (from JDK):

wsimport -keep http://example.com/service?wsdl

This creates client-side stubs for SOAP calls.

5. What is the Role of XSD in WSDL?

Answer:
XSD (XML Schema Definition) defines:

Data types (string, int, custom types).
Request/response structures (e.g., UserRequest).
Example:

<types>  
  <xsd:schema>  
    <xsd:element name="GetUserRequest" type="tns:User"/>  
  </xsd:schema>  
</types>

6. What is SOAP Binding in WSDL?

Answer:
SOAP binding defines:

Transport (HTTP/SMTP).
Message style (RPC or Document).
Example:

<binding name="UserServiceSOAP" type="tns:UserServicePortType">  
  <soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/>  
</binding>

7. How to Test a WSDL Web Service?

Answer:
Use tools like:

SoapUI (GUI testing).
Postman (for SOAP requests).
curl (command line):shCopyDownloadcurl -X POST -H “Content-Type: text/xml” -d @request.xml http://example.com/service

8. What is the Difference Between RPC and Document Style WSDL?

Answer:

RPC Style	Document Style
Encodes parameters as SOAP body elements	Uses XML schema directly
Tightly coupled to SOAP	More flexible for XML processing

9. What is a WSDL Port?

Answer:
A <port> defines:

Service endpoint URL.
Binding protocol (e.g., SOAP).
Example:

<service name="UserService">  
  <port name="UserPort" binding="tns:UserBinding">  
    <soap:address location="http://example.com/user"/>  
  </port>  
</service>

10. How to Handle WSDL Versioning?

Answer:
Best practices:

Use version in namespace (http://example.com/v2).
Avoid breaking changes (add new operations instead of modifying old ones).

11. What is the Difference Between WSDL and REST?

Answer:

WSDL	REST (OpenAPI/Swagger)
Used for SOAP	Used for RESTful APIs
XML-based	JSON/XML support
Strict contract	Flexible endpoints

12. What is UDDI in Relation to WSDL?

Answer:
UDDI (Universal Description, Discovery, and Integration) is a registry where WSDL files are published for discovery.

13. How to Secure a WSDL Service?

Answer:

WS-Security (encryption, digital signatures).
HTTPS for transport security.
SOAP headers for authentication.

14. What is a WSDL Import?

Answer:
<wsdl:import> includes external WSDL/XSD files:

<import namespace="http://example.com/types" location="types.xsd"/>

15. Can WSDL Be Used with JSON?

Answer:
No, WSDL is XML-only. For JSON, use OpenAPI (Swagger).

16. What is a One-Way Operation in WSDL?

Answer:
A one-way operation has only an input (no response):

<operation name="notify">  
  <input message="tns:NotificationMessage"/>  
</operation>

17. How to Debug WSDL Errors?

Answer:

Validate WSDL with xmllint.
Check SOAP fault messages.
Use tcpdump for network-level debugging.

18. What is the Role of SOAPAction in WSDL?

Answer:
SOAPAction is an HTTP header identifying the operation:

POST /service HTTP/1.1  
SOAPAction: "http://example.com/getUser"

19. How to Document a WSDL File?

Answer:
Use <documentation> tags:

<portType name="UserService">  
  <documentation>Service for user management</documentation>  
</portType>

20. What is WS-Policy in WSDL?

Answer:
WS-Policy defines security, QoS policies in WSDL:

<wsp:Policy>  
  <sp:TransportBinding>  
    <sp:TransportToken>  
      <sp:HttpsToken/>  
    </sp:TransportToken>  
  </sp:TransportBinding>  
</wsp:Policy>

Conclusion

Mastering WSDL interview questions is essential for roles in SOAP-based web services. This guide covered WSDL structure, SOAP bindings, XSD integration, and security.

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