Tecnologie per servizi web: WSDL, WSFL

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Models and Languages for Coordination and
Orchestration IMT- Institutions Markets
Technologies - Alti Studi Lucca
WS Technologies II WSDL
Roberto Bruni Dipartimento di Informatica
Università di Pisa
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Contents

• WSDL
• Some Java tools

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Contents

• WSDL
• Some Java tools

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What is the Story so Far?

• With UDDI (and SOAP) we know how to find and
  discover new services
• as if we looked at the yellow pages
• What can we do with discovered services?
• should we contact the service provider and ask
  for technical support in programming the right
  SOAP calls?
• No, this would be a waste of time for both us and
  the provider!
• Instead, the provider should prepare a
  unambiguous description of the WS to be exposed
• automatically downloadable, understandable, and
  usable for connecting to the specific WS
• WSDL fixes the standard for such description

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Web Services Description Language (WSDL)

• WSDL is an XML-based language for the description
  of Web Services
• (and the methods to access them)
• A WSDL document is just a particular XML document
  
• it resides in a file with suffix .wsdl
• it can be checked for validity against the WSDL
  Schema
• it describes how to "interface with" and use WS
• and also the binding protocol to access WS
• it is a bit complex for human beings
• but it is unambiguous for a machine

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The Seven Elements of WSDL

• Essentially, WSDL documents consist of 7 key
  elements
• message types (data structures)
• messages
• basic units of communication between WS and
  clients
• typed data to be communicated as a single logical
  transmission
• operations
• sequences of messages related to a single action
• interfaces (called port types in WSDL v1)
• logical groups of operations representing
  abstract services
• bindings
• associations between interfaces and concrete
  protocols / data formats
• endpoints (called ports in WSDL v1)
• associations between interface bindings and
  network addresses
• services (collections of endpoints)

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A View at WSDL Hierarchical Structure

• ltdefinitionsgt
• lttypesgt
• ltmessagegt
• ltinterfacegt
• ltoperationgt
• ltinputgt
• ltoutputgt
• ltbindinggt
• ltservicegt
• ltendpointgt

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Types

• A type is the most basic WSDL element
• completely analogous to a Schema document (.xsd)
• XML Schema are in fact used for defining message
  types
• a type can correspond to
• a struct, in C
• a class with variables but without methods, in
  Java
• types are necessary to describe the main elements
  and parameters in a method call

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Examplethe Class Address.java

• public class Address
• public String name
• public String address1
• public String address2
• public String city
• public String state
• public String zip
• public class MyClass
• public void myMethod(Address myAddress)
• //do something

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The Schema address.xsd

• ltxsdschema targetNamespace"/address.xsd"
• xmlnsxsd"http//www.w3.org/2001/XMLS
  chema"
• xmlnsaddr"/address.xsd"gt
• ltxsdelement name"address"
  type"addraddressType" /gt
• ltxsdcomplexType name"addressType"gt
• ltxsdsequencegt
• ltxsdelement name"name"
  type"xsdstring"/gt
• ltxsdelement name"address1"
  type"xsdstring"/gt
• ltxsdelement name"address2"
  type"xsdstring"/gt
• ltxsdelement name"city"
  type"xsdstring"/gt
• ltxsdelement name"state"
  type"xsdstring"/gt
• ltxsdelement name"zip"
  type"xsdstring"/gt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• lt/xsdschemagt

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Example address.xsd with Anonymous Types

• ltxsdschema targetNamespace"/address.xsd"
• xmlnsxsd"http//www.w3.org/2001/XMLS
  chema"gt
• ltxsdelement name"address"gt
• ltxsdcomplexTypegt
• ltxsdsequencegt
• ltxsdelement name"name"
  type"xsdstring"/gt
• ltxsdelement name"address1"
  type"xsdstring"/gt
• ltxsdelement name"address2"
  type"xsdstring"/gt
• ltxsdelement name"city"
  type"xsdstring"/gt
• ltxsdelement name"state"
  type"xsdstring"/gt
• ltxsdelement name"zip"
  type"xsdstring"/gt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• lt/xsdelementgt
• lt/xsdschemagt

Only if addressType is not used elsewhere
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Example valid XML document for address.xsd

• ltaddressgt
• ltnamegtArthur Fonzarellilt/namegt
• ltaddress1gt123 W. Wisconsinlt/address1gt
• ltaddress2gtApt. 4lt/address2gt
• ltcitygtMilwaukeelt/citygt
• ltstategtWIlt/stategt
• ltzipgt53222lt/zipgt
• lt/addressgt

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The Type address in WSDL I

• lt?xml version"1.0"?gt
• ltwsdldefinitions nameAddressType
• targetNamespace/addressType.w
  sdl
• xmlnstns/addressType.wsdl
• xmlnswsdlhttp//schemas.xmlso
  ap.org/wsdl/gt
• ltwsdltypesgt
• ltxsdschema targetNamespace/addressType.w
  sdl
• xmlnsxsdhttp//www.w3.org/200
  1/XMLSchemagt
• ltxsdelement name"Address"gt
• ltxsdcomplexTypegt
• ltxsdallgt
• ltxsdelement name"name"
  type"xsdstring"/gt
• ltxsdelement name"address1"
  type"xsdstring"/gt
• ltxsdelement name"address2"
  type"xsdstring"/gt
• ltxsdelement name"city"
  type"xsdstring"/gt
• ltxsdelement name"state"
  type"xsdstring"/gt

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The Type address in WSDL II

• lt!-- (segue)
  --gt
• ltxsdelement name"zip"
  type"xsdstring"/gt
• lt/xsdallgt
• lt/xsdcomplexTypegt
• lt/xsdelementgt
• lt/xsdschemagt
• lt/wsdltypesgt
• lt/wsdldefinitionsgt

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Messages

• On the contrary of types, messages do not have an
  immediate analogy with Java...
• so we will push it...
• Imagine a setting where any method can have three
  parameters at most
• WSDL relies on such assumption
• (input, output and a third one, fault, for
  exception handling)
• Thus we must group the parameters of methods
• this is what messages are for!
• they have a sub-component part for each parameter
  

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Example a Message

• public void order(Address shipTo, Address
  billTO)
• //do something

lt?xml version"1.0"?gt ltwsdldefinitions gt
ltwsdltypesgt lt!--
Aggiungiamo un messaggio --gt
ltwsdlmessage name"purchase"gt ltwsdlpart
name"billTo" element"tnsaddress"/gt
ltwsdlpart name"shipTo" element"tnsaddress"/gt
lt/wsdlmessagegt lt/wsdldefinitionsgt
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Operations

• wsdloperation is probably the simplest WSDL
  element
• it correspond to an abstract method in Java
• but, as said, it has some limitation
• three parameters at most input, output, fault
• essentially there are four main different kinds
  of operations
• one-way
• (from the client to the service)
• request/response
• (request from the client and response back from
  the service)
• notification
• (from the service to the client)
• solicit/response
• (message from the service and response from the
  client)

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One-way Operations

• In general, operations are described by the
  element wsdloperation that can contain one or
  more messages
• (wsdlinput, wsdloutput, wsdlfault)
• In one-way operations, only the input element is
  allowed
• ex.

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Request/Response Operations

• Both input and output are defined
• optionally, an additional fault element
• ex.

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Notification Operations

• Converse of one-way operations
• only output message is allowed
• example
• for notifying the client about the current status
  of the order

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Solicit/Response Operations

• Useful when a service needs some information from
  the client
• example
• construction of a site with variable bandwidth

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Interfaces (Port Types)

• For the moment we have only surveyed standalone
  operations
• but all the operations make sense only when
  considered within a port type
• What is a port type?
• W3C it defines a group of abstract operations
  and their corresponding abstract messages
• it is equivalent to a Java interface
• (in WSDL v2, port types are called interfaces)
• Syntactically, it is defined by an element
  wsdlinterface (wsdlportType in WSDL v1)
• which contains one or more wsdloperation elements

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Example Interface
lt?xml version"1.0"?gt ltwsdldefinitions gt
ltwsdltypesgt lt/wsdltypesgt ltwsdlmessage
name"purchase"gt lt/wsdlmessagegt
ltwsdlportType name"submitPurchaseType"gt
ltwsdloperation name"submitPurchase"gt
ltwsdlinput message"tnspurchase" /gt
lt/wsdloperationgt lt/wsdlportTypegt lt/wsdldefin
itionsgt
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Binding

• For the moment we have just considered "abstract"
  elements
• upon receiving a ltwsdlinterfacegt we have all the
  information on how to use it
• but we cannot create a direct instance
• To instantiate the interface we must provide the
  information that are necessary to interact with
  it
• in particular
• which transport method will the interface use?
• which communication format are we going to use?
• The binding defines all details that are needed

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SOAP Binding on HTTP I

• lt?xml version"1.0"?gt
• ltwsdldefinitions name"purchaseExample"
• targetNamespace"/purchaseExamp
  le.wsdl"
• xmlnstns"/purchaseExample.wsd
  l"
• xmlnssoap"http//schemas.xmlso
  ap.org/wsdl/soap"
• xmlnswsdl"http//schemas.xmlso
  ap.org/wsdl/"gt
• lt!-- Types --gt
• ltwsdltypesgt lt/wsdltypesgt
• lt!-- MESSAGES --gt
• ltwsdlmessage name"purchaseMessage"gt
  lt/wsdlmessagegt
• lt! PORT TYPES --gt
• ltwsdlportType name"purchaseType"gt
• lt!-- OPERATIONS --gt
• ltwsdloperation name"purchaseOperation"gt
• ltwsdlinput messagetnspurchaseMessage
  /gt
• lt/wsdloperationgt
• lt/wsdlportTypegt

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SOAP Binding on HTTP II

• lt!-- (segue)
  --gt
• lt!-- BINDING --gt
• ltwsdlbinding name"purchaseBinding"
• type"tnspurchaseType"gt
• ltsoapbinding style"document"
• transport"http//schemas.xmls
  oap.org/soap/http" /gt
• ltwsdloperation name"tnspurchaseOperation"
  gt
• ltwsdlinputgt
• ltsoapbody use"literal" /gt
• lt/wsdlinputgt
• lt/wsdloperationgt
• lt/wsdlbindinggt
• lt/wsdldefinitionsgt

HTTP
ex. SOAP, HTTP e SMTP
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Endpoints (Ports)

• Once defined the binding to the transport
  protocol we can link the method call to a
  specific IP address
• the binding defined the communication protocol,
  but not the address of the machine hosting the
  service
• sych information is given by the element
  wsdlendpoint
• (called wsdlport in WSDL v1)
• An endpoint contains
• a name
• a binding
• a network address

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Example Going Further on Previous Example

• lt!-- (segue)
  --gt
• lt!-- BINDING --gt
• ltwsdlbinding namepurchaseBinding
  typetnspurchaseTypegt
• ltsoapbinding styledocument
  transport/http /gt
• ltwsdloperation nametnspurchaseOperation
  gt
• ltwsdlinputgt ltsoapbody useliteral /gt
  lt/wsdlinputgt
• lt/wsdloperationgt
• lt/wsdlbindinggt
• lt!-- PORTS --gt
• ltwsdlport namePurchase_ServicePort
• bindingtnspurchaseBindinggt
• ltsoapaddress
• locationhttp//www.fluidimagination.com
  8080/soap/servlet/rpcrouter /gt
• lt/wsdlportgt
• lt/wsdldefinitionsgt

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Services

• Now we have all ingredients
• the only thing left is to combine them in a
  single offert
• analogous to a whole Java class
• The element wsdlservice is the very first
  element exposed to the interest of users who get
  the .wsdl document
• it groups all endpoints
• it allows the server to check if the services
  really supports all the required operations

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Example for the Last Time

• lt!-- (segue)
  --gt
• lt!-- BINDING --gt
• ltwsdlbinding namepurchaseBinding
  typetnspurchaseTypegt
• lt/wsdlbindinggt
• lt!-- SERVICES --gt
• ltwsdlservice namePurchase_Servicegt
• ltdocumentationgtblah blah blahlt/documentation
  gt
• ltwsdlport bindingtnspurchaseBinding
• namePurchase_ServicePortgt
• ltsoapaddress location /gt
• lt/wsdlportgt
• lt/wsdlservicegt
• lt/wsdldefinitionsgt

full example
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Summary
WSDL v1 Java
types classes without methods
messages parameters, return value, errors
port types and operations interfaces
bindings remote communication protocol
services and ports remote classes
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A WSDL v2 ExampleGreatH Hotel Reservation I

• Hotel GreatH is located in a remote island
• for years it has been relying on fax/phone
  reservations
• now, even though the facilities and prices at
  GreatH are better than what its competitor
  offers, GreatH notices that its competitor is
  getting more customers than GreatH
• after research, GreatH realizes that this is
  because the competitor offers a Web service that
  permits travel agent reservation systems to
  reserve rooms directly over the Internet

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A WSDL v2 ExampleGreatH Hotel Reservation II

• GreatH then wants to build a reservation Web
  service with the following functionalities
• CheckAvailability
• the client must specify a check-in date, a
  check-out date, and room type
• the Web service will provide the room rate if
  such a room is available
• If any input data is invalid, the service should
  return an error
• The service will accept a checkAvailability
  message and return a checkAvailabilityResponse or
  invalidDataFault message
• MakeReservation
• the client must provide a name, address, and
  credit card information
• the service will return a confirmation number if
  the reservation is successful
• the service will return an error message if the
  credit card number or any other data field is
  invalid
• The service will accept a makeReservation message
  and return a makeReservationResponse or
  invalidCreditCardFault message.

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A WSDL v2 ExampleGreatH Hotel Reservation III

• GreatH knows that later the WS will need to
  support transactions and secured transmission
• but initially we consider the implementation of
  only minimal functionality
• to simplify the example, we will consider only
  the CheckAvailability operation
• GreatH.wsdl

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Using WSDL in a UDDI Registry

• WSDL complements the UDDI standard by providing a
  uniform way of describing
• the abstract interface and
• protocol bindings
• of arbitrary network services
• Next, we try to clarify the relationship between
  the two
• describe how WSDL can be used in UDDI business
  service descriptions
• WSDL service descriptions can be structured in
  multiple ways
• if the reusable information is separated from the
  information that is specific to a given service
  instance, the use of WSDL and UDDI together
  becomes particularly simple

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Authoring UDDI Service Descriptions I

• The first step is to create the WSDL service
  interface definition
• Typically, industry groups will define a set of
  service types, and describe them with one or more
  service interface definition WSDL documents
• The service interface definition will include
  service interfaces and protocol bindings, and
  will be made publicly available
• The WSDL service interface definitions are then
  registered as a special kind of UDDI tModels,
  called wsdlSpec tModels
• the overviewDoc field in each new tModel will
  point to the corresponding WSDL document

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Authoring UDDI Service Descriptions II

• Next, programmers will build services that
  conform to the industry standard service
  definitions
• either manually or using appropriate UDDI-aware
  tooling, programmers will retrieve the tModel
  description of the industry standard definition
• following the overviewDoc link they will obtain
  the corresponding WSDL document
• WSDL-aware tooling, in turn, can help generate an
  implementation
• (that supports the standard interfaces and
  bindings)

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Authoring UDDI Service Descriptions III

• Finally, the new service must be deployed and
  registered in the UDDI repository
• either manually or using WSDL/UDDI-aware tooling,
  a UDDI businessService data structure is
• created,
• and then registered
• Typically when using WSDL/UDDI-aware tools, some
  type of deployment descriptor document will be
  generated at that same time

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Import Element

• The ltimport location"..."gt element in WSDL
  allows the separation of elements of service
  description into two parts
• service interface definition (SInt)
• service implementation definition (SImp)
• Typically, information common to a certain
  category of business services, such as
• message formats,
• portTypes (abstract interfaces),
• and protocol bindings,
• are included in the reusable portion (SInt),
• while information pertaining to a particular
  service endpoint (i.e., port definition) is
  included in the other portion (SImp)
• Within the context of UDDI,
• we will be concerned only with the reusable
  portion

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WSDL and UDDIMonolithic Approach

• Relevant UDDI Structures
• businessService
• bindingTemplate
• how and where the service is accessed
• it specifies a network endpoint address (in the
  accessPoint element) and a stack of tModels
  describing the service
• one tModelInstanceInfo inside the
  tModelInstanceDetails element for each relevant
  tModel
• tModel, aka service type definition
• one for each interface/portType
• classified using uddi-orgtypes taxonomy, as
  being of type "wsdlSpec"
• must have an overviewDoc whose overviewURL points
  to the WSDL document defining the
  interface/portType

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Sketch of businessService Structure

• ltbusinessServicegt
• (...)
• ltbindingTemplatesgt
• ltbindingTemplategt
• (...)
• ltaccessPoint urlType"http"gt
• http//www.etc.com/
• lt/accessPointgt
• lttModelnstanceDetailsgt
• lttModelnstanceInfo tModelKey"..."gt
• lt/tModelnstanceInfogt
• (...)
• lt/tModelnstanceDetailsgt
• lt/bindingTemplategt
• (...)
• lt/bindingTemplatesgt
• lt/businessServicegt

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Example tModel

• lttModel authorizedName"..." operator"..."
  tModelKey"..."gt
• ltnamegtStockQuote Servicelt/namegt
• ltdescription xmllang"en"gt
• WSDL description of a standard stock quote
  service interface
• lt/descriptiongt
• ltoverviewDocgt
• ltdescription xmllang"en"gtWSDL source
  document.lt/descriptiongt
• ltoverviewURLgthttp//stockquote-definitions/stq
  .wsdllt/overviewURLgt
• lt/overviewDocgt
• ltcategoryBaggt
• ltkeyedReference tModelKey"uuidC1ACF26D-9672-
  4404-9D70-39B756E62AB4"
• keyName"uddi-orgtypes"
• keyValue"wsdlSpec"/gt
• lt/categoryBaggt
• lt/tModelgt

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Example businessService

• ltbusinessService businessKey"..."
  serviceKey"..."gt
• ltnamegtStockQuoteServicelt/namegt
• ltdescriptiongt (...) lt/descriptiongt
• ltbindingTemplatesgt
• ltbindingTemplategt
• (...)
• ltaccessPoint urlType"http"gt
• http//example.com/stockquote
• lt/accessPointgt
• lttModelnstanceDetailsgt
• lttModelnstanceInfo tModelKey"..."gt
• lt/tModelnstanceInfogt
  
• lttModelnstanceDetailsgt
• lt/bindingTemplategt
• lt/bindingTemplatesgt
• lt/businessServicegt

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WSDL and UDDIModular Approach

• The Monolithic approach can be replaced by an
  expanded modelling that encompasses the
• flexibility
• and reusability
• of WSDL
• fine grain "taxonomy-zation" of WSDL artefacts
• portType/interface
• binding
• service
• port/endpoint

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Modular Mapping Overview
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