WSDL : Web Service Definition Language

Dr. Yuhong YanNRC-IIT-Fredericton

Internet logic

WSDL: describe a web services

• Initialized by IBM, Microsoft, Ariba and 6~ other companies

• 2004.8: w3c releases WSDL 2.0

Interoperability Using WSDL

Get WSDL docInvoke Service

J2EE ContainerService Objects

WSDL description

Client

Service

Service

SOAP

HTTP

WSDL: Describe a web service

• Interface information describing all publicly available functions

• Data type information for all message requests and message responses

• Binding information about the transport protocol to be used

• Address information for locating the specified services

WSDL:

• A contract between requestor and provider• Platform and language-independent• Describe SOAP services• Automatic tool to generate client and sever code

What do we learn?

• WSDL specification• Generate WSDL for a service (from java objects

to WSDL)• Generate java classes from WSDL• Other ways for distributed system: rmi, and

CORBA

An example of WSDL: HelloWorld

<wsdl:definitions targetNamespace="http://localhost:8080/axis/services/urn:HelloWorld" xmlns:apachesoap="http://xml.apache.org/xml-soap" xmlns:impl="http://localhost:8080/axis/services/urn:HelloWorld" xmlns:intf="http://localhost:8080/axis/services/urn:HelloWorld" xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" xmlns:tns1="http://www.w3.org/1999/XMLSchema" xmlns:tns2="http://www.w3.org/2003/05/soap-encoding" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" xmlns:wsdlsoap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:xsd="http://www.w3.org/2001/XMLSchema">

Root element, defines namespaces

WSDL-SOAP binding

xmlschema

WSDL schema

Convention, refer to itself (?)WSDL uses it to generate package name

<Service>

<wsdl:service name="HelloWorldServiceService"> <wsdl:port

binding="impl:urn:HelloWorldSoapBinding" name="urn:HelloWorld">

<wsdlsoap:address location="http://localhost:8080/axis/services/urn:HelloWorld" />

  </wsdl:port></wsdl:service>

Where is the service located?

The service location: the endpoint of the SOAP message

<Binding>

<wsdl:binding name="urn:HelloWorldSoapBinding" type="impl:HelloWorldService">

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

- <wsdl:operation name="sayHello">  <wsdlsoap:operation soapAction="" /> - <wsdl:input name="sayHelloRequest">  <wsdlsoap:body

encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" namespace="http://HelloWorld.samples" use="encoded" />

  </wsdl:input>- <wsdl:output name="sayHelloResponse">  <wsdlsoap:body

encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" namespace="http://localhost:8080/axis/services/urn:HelloWorld" use="encoded" />

  </wsdl:output>  </wsdl:operation>-  </wsdl:binding>

Bind messages to operationsUse SOAP HTTP protocol

<portType>

<wsdl:portType name="HelloWorldService">- <wsdl:operation name="sayHello"

parameterOrder="in0 in1">  <wsdl:input message="impl:sayHelloRequest"

name="sayHelloRequest" />   <wsdl:output

message="impl:sayHelloResponse" name="sayHelloResponse" />

  </wsdl:operation></wsdl:portType>

Bind messages to operations

Operation: sayHello

Input Message: sayHelloRequest

Output Message: sayHelloResponse

<message>

<wsdl:message name="sayHelloRequest">  <wsdl:part name="in0" type="tns2:string" />   <wsdl:part name="in1" type="tns2:string" />   </wsdl:message><wsdl:message name="sayHelloResponse">  <wsdl:part name="sayHelloReturn"

type="tns2:string" />   </wsdl:message>

Define message: sayHelloRequestContent of message

Define massage: sayHelloResponse

Parameter 1, type stringParameter 2, type string

Parameter 1, type string

Structure of WSDL

P121 fig 6-1

<definitions>:Root WSDL Element

<types>:What data types will be transmitted?

<message>:What message will be transmitted?

<portType>:What operations (functions) will be supported?

<binding>:How will the messages be transmitted on the wire?What SOAP-specific details are there?

<service>:Where is the service located?

Definition: <wsdl:definitions>

• Root element• Name of the web service• Declare multiple namespaces

Complex data types: <types>

• Not used if limit to XML schema• Define complex types (correspondent to a class

in java)

Message definitions: <message>

• A request message or a response message• Name of the message• Element <part> defines the data types used in the

message• Types of the parameters for the request message• Types of the return values for the response

message

Operation definitions: <portType>

• Operations: the remote methods• Input/output messages for operations

<wsdl:portType name="HelloWorldService">- <wsdl:operation name="sayHello" parameterOrder="in0

in1">  <wsdl:input message="impl:sayHelloRequest"

name="sayHelloRequest" />   <wsdl:output message="impl:sayHelloResponse"

name="sayHelloResponse" />   </wsdl:operation></wsdl:portType>

Operation patterns supported by WSDL 1.1

P126. fig 6-3

Client

One-way

Request-response

Client

Client

Client

Solicit-response

Notification

Service<input>

Service

Service

Service

<input>

<output>

<output>

<input>

<output>

1

1

2

2

Basic patterns of operation

• One-way: – The service receives a message. – The operation therefore has a single input

element• Request-response:

– The service receives a message and sends a response

– One input element, one output element

Basic patterns of operation (2)

• Solicit-response– The service sends a message and receives a

response– The operation has one output message,

followed by one input message• Notification

– The service sends a message. – The operation has one output message

Transmission protocols: <binding>

• Binding transmission protocols to operations• Axis: http

Service location: <service>

• SOAP endpoint of the web service

Second example: WSDL of StockQuote

• Deploy the sample StockQuoteService• The WSDL is at

http://localhost:8080/axis/services/urn:xmltoday-delayed-quotes?wsdl

Messages

<wsdl:message name="getQuoteRequest">  <wsdl:part name="symbol" type="tns2:string" /> </wsdl:message><wsdl:message name="getQuoteResponse">  <wsdl:part name="getQuoteReturn"

type="xsd:float" />   </wsdl:message>

Operations

<wsdl:portType name="StockQuoteService">- <wsdl:operation name="getQuote"

parameterOrder="symbol">  <wsdl:input message="impl:getQuoteRequest"

name="getQuoteRequest" />   <wsdl:output message="impl:getQuoteResponse"

name="getQuoteResponse" />   </wsdl:operation></wsdl:portType>

Binding

<wsdl:binding name="GetQuoteSoapBinding" type="impl:StockQuoteService">

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

<wsdl:operation name="getQuote">  <wsdlsoap:operation soapAction="" /> - <wsdl:input name="getQuoteRequest">  <wsdlsoap:body

encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" namespace="http://stock.samples" use="encoded" />

  </wsdl:input>- <wsdl:output name="getQuoteResponse">  <wsdlsoap:body

encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" namespace="http://localhost:8080/axis/services/urn:xmltoday-delayed-quotes" use="encoded" />

  </wsdl:output>  </wsdl:operation>  </wsdl:binding>

Service location

<wsdl:service name="StockQuoteServiceService">- <wsdl:port binding="impl:GetQuoteSoapBinding"

name="GetQuote">  <wsdlsoap:address

location="http://localhost:8080/axis/services/urn:xmltoday-delayed-quotes" />

  </wsdl:port>  </wsdl:service>

WSDL Summary

<definitions>:The StockQuoteService

<message>:1) getQuoteRequest: parameter:symbol; type: string2) getQuoteResponse: return float

<portType>:getQuote operation that consists of a request/response service

<binding>:Direction to use the SOAP HTTP transport protocol.

<service>:Service available at: localhost:8080/axis/services/urn:xmltoday-delayed-quotes

Using WSDL with Axis

• Obtaining WSDL for deployed services• WSDL2Java: Building stubs, skeletons, and data• Java2WSDL: Building WSDL from Java

Obtain WSDL for deployed services

• Axis generates WSDL for any deployed services• In the service list, check the WSDL files