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WSDL
WSDL and UML
EGEE is a project funded by the European Union under contract IST-2003-508833
UML to WSDL process
user
Client application
Servelet
Use case
interface
Class diagram
WSDL
(interface
Definition)
implementation
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Starting with UML
Create a description of requirements
in a use case diagram
Create a description of interactions in
a sequence diagram
Create a description of the application
(methods and attributes/variables) in
a class diagram
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Barnes & Noble price client use
case diagram
This is an extremely simple use
case
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bnclient class diagram
This is the simplest web service client
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Mapping UML - WSDL
Attributes/variables become types
Methods become operations
Classes become portType
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bnquote WSDL
<?xml version="1.0"?>
<definitions name="BNQuoteService" targetNamespace="BNQuoteService.wsdl"
xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns="http://schemas.xmlsoap.org/wsdl/" xmlns:tns="BNQuoteService.wsdl" >
<message name="getPriceRequest">
<part name="isbn" type="xsd:string"/>
</message>
<message name="getPriceResponse">
<part name="return" type="xsd:float"/>
</message>
<portType name="BNQuotePortType">
<operation name="getPrice">
<input message="tns:getPriceRequest" name="getPrice"/>
<output message="tns:getPriceResponse" name="getPriceResponse"/>
</operation>
</portType>
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WSDL continued
<binding name="BNQuoteBinding" type="tns:BNQuotePortType">
<soap:binding style="rpc" transport="http://schemas.xmlsoap.org/soap/http"/>
<operation name="getPrice">
<soap:operation soapAction=""/>
<input name="getPrice">
<soap:body use="encoded" namespace="urn:xmethods-BNPriceCheck"
encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"/>
</input>
<output name="getPriceResponse">
<soap:body use="encoded" namespace="urn:xmethods-BNPriceCheck"
encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"/>
</output>
</operation>
</binding>
<service name="BNQuoteService">
<documentation>Returns price of a book at BN.com given an ISBN number</documentation>
<port name="BNQuotePort" binding="tns:BNQuoteBinding">
<soap:address location="http://services.xmethods.net:80/soap/servlet/rpcrouter"/>
</port>
</service>
</definitions>
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Mapping WSDL to client
<message name="getPriceResponse">
<part name="return" type="xsd:float"/>
</message>
<message name="getPriceRequest">
<part name="isbn” type="xsd:string"/>
</message>
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<portType name="BNQuotePortType">
<operation name="getPrice">
<input message="tns:getPriceRequest"
name="getPrice"/>
<output message="tns:getPriceResponse"
name="getPriceResponse"/>
</operation>
</portType>
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Barnes & Noble price example
sequence diagram
This simple example is a prototype for all
web services
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Web services and state
Web services are generally described as
stateless.
In practice this means that you cannot
guarantee between interactions that you are
interacting with the same instance of the
servlet.
While web services are, in themselves,
inherently stateless they can be made to
behave in a state-full manner
By using a database back end
Using cookies
………etc
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Web services and state 2
One of the reasons that you may be
interacting with different instances of a
servlet lies in the use of web services
factories.
In order to deal with many connections it is
often useful to have a web services factory
create instances for each connection rather
than have a single listening service.
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Design considerations with
Web Services
Granularity
Traffic
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Granularity
At what level in the design do we
introduce services?
Too low and users are swamped in
irrelevant detail
Too high and they can’t access the details
they need
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Example
Inappropriate
Appropriate
Travel agent
Aircraft
Airport flight slots
Maintenance cycle
Aircraft
Airport flight slots
Maintenance cycle
A consideration for both services and operations
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Traffic
Business
Yellow pages service
User
Address
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Traffic 2: Messaging systems
Depends on the available (dedicated)
bandwidth
Don’t want services where very frequent
calls are required (poss > 1 per sec)
Don’t want services to carry very large
amounts of data regularly
Process locally
Pass encapsulated groups of data
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Serialisation
Classes passed over web services are
translated to XML in transport
This means that the object at the
server is not necessarily identical to
the object at the client.
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Summary
Attributes/variables become types
Methods become operations
Classes become portType
Appropriate granularity
Awareness of network traffic
Web services objects are serialised as XML
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