WebServices Interview Questions

What is SOAP?

• SOAP stands for Simple Object Access Protocol
• SOAP is a communication protocol
• SOAP is for communication between applications
• SOAP is a format for sending messages
• SOAP communicates via Internet
• SOAP is platform independent
• SOAP is language independent
• SOAP is based on XML
• SOAP is simple and extensible
• SOAP allows you to get around firewalls
• SOAP is a W3C recommendation

Review WSDL

Services are defined using six major elements:

• types, which provides data type definitions used to describe the messages exchanged.
• message, which represents an abstract definition of the data being transmitted. A message consists of logical parts, each of which is associated with a definition within some type system.
• portType, which is a set of abstract operations. Each operation refers to an input message and output messages.
• binding, which specifies concrete protocol and data format specifications for the operations and messages defined by a particular portType.
• port, which specifies an address for a binding, thus defining a single communication endpoint.
• service, which is used to aggregate a set of related ports.

<?xml version="1.0" encoding="utf-8"?>

<wsdl:definitions xmlns:s="http://www.w3.org/2001/XMLSchema" xmlns:soap12="http://schemas.xmlsoap.org/wsdl/soap12/" xmlns:mime="http://schemas.xmlsoap.org/wsdl/mime/" xmlns:tns="https://taxes.test.com/test/webservices/" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:tm="http://microsoft.com/wsdl/mime/textMatching/" xmlns:http="http://schemas.xmlsoap.org/wsdl/http/" xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" targetNamespace="https://taxes.test.com/test/webservices/" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/">

  <wsdl:types>

    <s:schema elementFormDefault="qualified" targetNamespace="https://taxes.test.com/test/webservices/">    

      <s:element name="IdHdr" type="tns:IdHdr" />

      <s:complexType name="IdHdr">

        <s:sequence>

          <s:element minOccurs="0" maxOccurs="1" name="token" type="s:string" />

          <s:element minOccurs="0" maxOccurs="1" name="address" type="s:string" />

        </s:sequence>      

      </s:complexType> 

      <s:element name="GetSQList"> element names became classes

        <s:complexType />

      </s:element>

      <s:element name="GetSQListResponse">

        <s:complexType>

          <s:sequence>

            <s:element minOccurs="0" maxOccurs="1" name="GetSQListResult" type="s:string" />

            <s:element minOccurs="0" maxOccurs="1" name="processMessage" type="s:string" />

          </s:sequence>

        </s:complexType>

      </s:element>

    </s:schema>

  </wsdl:types>

  <wsdl:message name="GetSQListSoapIn">

    <wsdl:part name="parameters" element="tns:GetSQList" />

  </wsdl:message>

  <wsdl:message name="GetSQListSoapOut">

    <wsdl:part name="parameters" element="tns:GetSQListResponse" />

  </wsdl:message>

  <wsdl:message name="GetSQListIdHdr">

    <wsdl:part name="IdHdr" element="tns:IdHdr" />

  </wsdl:message>

  <wsdl:portType name="OTPWebServiceSoap">   This became the interface

    <wsdl:operation name="GetSQList"> This became method in the above interface

      <wsdl:documentation xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/">-- Get List of Security Questions --</wsdl:documentation>

      <wsdl:input message="tns:GetSQListSoapIn" />

      <wsdl:output message="tns:GetSQListSoapOut" />

    </wsdl:operation>

  </wsdl:portType>

  <wsdl:binding name="OTPWebServiceSoap" type="tns:OTPWebServiceSoap">

    <soap:binding transport="http://schemas.xmlsoap.org/soap/http" />

    <wsdl:operation name="GetSQList">

      <soap:operation soapAction="https://taxes.test.com/test/webservices/GetSQList" style="document" />

      <wsdl:input>

        <soap:body use="literal" />

        <soap:header message="tns:GetSQListIdHdr" part="IdHdr" use="literal" />

      </wsdl:input>

      <wsdl:output>

        <soap:body use="literal" />

      </wsdl:output>

    </wsdl:operation>

  </wsdl:binding>

  <wsdl:service name="OTPWebService"> This will be the class with WSDL location and all

    <wsdl:port name="OTPWebServiceSoap" binding="tns:OTPWebServiceSoap">

      <soap:address location="http://localhost/test/webservices/otpwebservice.asmx" />

    </wsdl:port> soap:address location Will became the Endpoint

  </wsdl:service>

 </wsdl:definitions>

Q: What are the different elements of WSDL?

1. Type
2. Message
3. Porttype
4. Binding
5. Service

Type : The data types used by the web service. We have all xsd imports here

Message : The messages used by the web service

<wsdl:message name="HelloWorldRequest">

                        <wsdl:part name="header" element="am:TransactionHeader"></wsdl:part>

                        <wsdl:part name="parameters" element="amt:HelloWorldRequest"></wsdl:part>

            </wsdl:message>

            <wsdl:message name="HelloWorldResponse">

                        <wsdl:part name="parameters" element="amt:HelloWorldResponse"></wsdl:part>

            </wsdl:message>

PortTpe : The operations performed by the web service

<wsdl:portType name="HelloPort">

                        <wsdl:operation name="HelloWorld">

                                    <wsdl:input message="am:HelloWorldRequest" />

                                    <wsdl:output message="am:HelloWorldResponse" />

                        </wsdl:operation>

           

            </wsdl:portType>

Binding: The communication protocols used by the web service and message format.

Service : A collection of related end points

Documentation

WSDL uses the optional wsdl:document element as a container for human readable documentation. The content of the element is arbitrary text and elements ("mixed" in XSD). The documentation element is allowed inside any WSDL language element.

SOAPAction

<wsdl:binding name="OTPWebServiceSoap" type="tns:OTPWebServiceSoap">

<soap:binding transport="http://schemas.xmlsoap.org/soap/http"/>

<wsdl:operation name="GetVersion">

<soap:operation soapAction="https://taxes.test.com/test/webservices/GetVersion" style="document"/>

<wsdl:input>

<soap:body use="literal"/>

<soap:header message="tns:GetVersionIdHdr" part="IdHdr" use="literal"/>

</wsdl:input>

<wsdl:output>

<soap:body use="literal"/>

</wsdl:output>

</wsdl:operation>

The SOAPAction URI is used to uniquely identify the particular operation of a service. As stated in the specification,. it is must for SOAP over HTTP.

SOAPAction is generally a combination of a web-service namespace and operation name like - http://abc.com/ws/ServiceName/1.0/OperationName wherehttp://abc.com/ws/ServiceName/1.0 is a meaningful namespace which represents that service "ServiceName" is a web-service (ws) of enterprise abc and it's version is 1.0

Above one is an example only and it may vary across the organizations and implementations because of the standards but ultimately it is represented in that context only whereas location attribute of soap:address element is always an address where service is available. In case of SOAP over HTTP, location attribute will hold a HTTP/HTTPS URL where this service is exposed and for any user to consume this service, will have to hit that URL.

Q: Difference between RPC and document style in WSDL Binding

The <wsdl:binding> element of the WSDL contains a pair of parameters that influence the form of the resulting SOAP messages: binding style (RPC or document) and use (encoded or literal).

Style. Mostly we will be using document not RPC

            Document: the content of <soap:Body> is specified by XML Schema defined in the <wsdl:type> section. It does not need to follow specific SOAP conventions.

            RPC: The structure of an RPC style <soap:Body> element needs to obay some specifications

Use

            use="literal" means that the type definitions literally follow an XML schema definition.

            use="encoded" refers to the representation of application data in XML, usually according to the SOAP encoding rules.

How to resolve NameConflicts while generating stubs?

Error
Thrown by JAXB : A class/interface with the same name "com.." is already in use. Use a class customization to resolve this conflict. at line 945 column 7 of schema http://.../amtpf.asmx?WSDL

Use the below extra arg in pom.xml to solve this

<extraargs>
<extraarg>-autoNameResolution</extraarg>
</extraargs> 
Or Use a binding xml like below so that you will have control over the class names

<bindingFiles>
<bindingFile>
${basedir}/resources/sample jaxws_binding.xml
</bindingFile>
</bindingFiles>

Sample sample jaxws_binding.xml

<jaxws:bindings wsdlLocation="w2.wsdl" 
          xmlns:jaxws="http://java.sun.com/xml/ns/jaxws" 
          xmlns:xs="http://www.w3.org/2001/XMLSchema" 
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
          xmlns:jaxb="http://java.sun.com/xml/ns/jaxb" 
          xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" 
          xsi:schemaLocation="http://java.sun.com/xml/ns/jaxb  
http://java.sun.com/xml/ns/jaxb/bindingschema_2_0.xsd
                http://java.sun.com/xml/ns/jaxws  
http://java.sun.com/xml/ns/jaxws/wsdl_customizationschema_2_0.xsd"> 
    
    <jaxws:bindings 
node="wsdl:definitions/wsdl:types/xs:schema[@targetNamespace='http://schemas.test.com/DDM/Tax']"> 

<jaxb:bindings 
node="xs:complexType[@name='GL1099R']/xs:sequence/xs:element[@name='RECID']"> 
            <jaxb:property name="DRTType"/> 
         </jaxb:bindings> 
<jaxb:bindings 
node="xs:complexType[@name='FDB_L5_DIVIDEND']/xs:sequence/xs:element[@name='RECID']"> 
            <jaxb:property name="RECID22"/> 
            </jaxb:bindings> 

How to Add soap header?
Add this in pom.xml

<wsdlOptions>
<wsdlOption>
<wsdl>${basedir}/resources/w2.wsdl</wsdl>
<extendedSoapHeaders>true</extendedSoapHeaders>
</wsdlOption>

</wsdlOptions>

How to give custom wsdl URL path


<wsdlOption>
  <wsdl>${basedir}/resources/amtpf.wsdl</wsdl>

 <wsdlLocation>classpath/createAccount.wsdl</wsdlLocation>

</wsdlOption>
And in the Client side Use the below code
URL url = OTPWebService.class.getClassLoader().getResource("createAccount.wsdl");
        if (url == null) {
            System.out.println("Can not initialize the default wsdl "+OTPWebService.class.getClassLoader().getResource("createAccount.wsdl"));
        }
        WSDL_LOCATION = url;

How to make WSDL location null

<extraargs>
       <extraarg>-client</extraarg>
      <extraarg>-wsdlLocation</extraarg>
      <wsdlurl />
</extraargs>

How to set dynamic endpoint in WS Client?
Map<String, Object> requestContext = ((BindingProvider)otpServiceSoap).getRequestContext();
requestContext.put(BindingProvider.ENDPOINT_ADDRESS_PROPERTY, "http://domain/webservices/otpwebservice.asmx");