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WSDL: Web Services DescriptionLanguage

#6#

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Outline What is WSDL?

WSDL Specifcation XML Schema Data Typing

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What is WSDL? WSDL is a specifcation defning how to describe web services in a

common XML grammar.

WSDL describes o!r critica" pieces o data $nterace inormation describing a"" p!b"ic"y avai"ab"e

!nctions

Data type inormation or a"" message re%!ests and message

responses

&inding inormation abo!t the transport protoco" to be !sed

'ddress inormation or "ocating the specifed service

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What is WSDL? WSDL represents a contract between the service re%!estor and the

service provider

&!t in m!ch the same way that a (ava interace represents a

contract between c"ient code and the act!a" (ava ob)ect.

The cr!cia" dierence is that WSDL is p"atorm* and "ang!age*

independent and is !sed primari"y +a"tho!gh not e,c"!sive"y- to

describe S'/ services.

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What is WSDL? 0sing WSDL1 a c"ient can "ocate a web service and invo2e any o its

p!b"ic"y avai"ab"e !nctions.

With WSDL*aware too"s1 yo! can a"so a!tomate this process1 enab"ing

app"ications to easi"y integrate new services with "itt"e or no man!a" code.

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WSDL Specification WSDL is an XML grammar or describing web services. The

specifcation itse" is divided into si, ma)or e"ements

defnitions

types

message

portType

binding

service

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WSDL Specification

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WSDL Specification Defnitions The defnitions e"ement m!st be the root e"ement

o a"" WSDL doc!ments.

$t defnes the namespace o the web service1 dec"ares m!"tip"e

namespaces !sed thro!gho!t the remainder o the doc!ment1

and contains a"" the service e"ements described here.

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WSDL Specification types The types e"ement describes a"" the data types !sed between

the c"ient and server.

WSDL is not tied e,c"!sive"y to a specifc typing system1 b!t it

!ses the W34 XML Schema specifcation as its dea!"t choice.

$ the service !ses on"y XML Schema b!i"t*in simp"e types1 s!ch as

strings and integers1 the types element is not required. ' !"" disc!ssion o the types e"ement and XML Schema is

deerred to the end o the chapter.

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WSDL Specification Message The message e"ement describes a one*way

message1 whether it is a sing"e message re%!est or a sing"e

message response.

$t defnes the name o the message and contains 5ero or

more message part e"ements1 which can reer to messageparameters or message ret!rn va"!es.

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WSDL Specification portType The portType e"ement combines m!"tip"e message

e"ements to orm a comp"ete oneway or ro!nd*trip operation.

or e,amp"e1 a portType can combine one re%!est and one

response message into a sing"e re%!est7response operation1 most co

mmon"y !sed in S'/ services.

8ote that a portType can +and re%!ent"y does- defne m!"tip"e

operations.

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WSDL Specification Binding The binding e"ement describes the concrete

specifcs o how the service wi"" be imp"emented on the wire.

WSDL inc"!des b!i"t*in e,tensions or defning S'/ service

s1 and S'/*specifc inormation thereore goes here.

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WSDL Specification Service The service e"ement defnes the address or

invo2ing the specifed service.

Most common"y1 this inc"!des a 09L or invo2ing the

S'/ service.

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WSDL Specification $n addition to the si, ma)or e"ements1 the WSDL specifcation a"so

defnes the o""owing !ti"ity e"ements

Documentation The doc!mentation e"ement is !sed to provide h!man*

readab"e doc!mentation and can be inc"!ded inside any other WSDL e"e

ment.

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WSDL Specification Import The import e"ement is !sed to import other WSDL

doc!ments or XML Schemas.

This enab"es more mod!"ar WSDL doc!ments.

or e,amp"e1 two WSDL doc!ments can import the same basic

e"ements and yet inc"!de their own service e"ements to ma2e the

same service avai"ab"e at two physica" addresses. 8ote1 however1 that not a"" WSDL too"s s!pport the import

!nctiona"ity as o yet.

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WSDL Example :,amp"e +word-

http://wsdl-example.doc/http://wsdl-example.doc/

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Definition

The defnitions e"ement specifes n!mero!s namespaces

that wi"" be !sed thro!gho!t the remainder o the doc!ment

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Definition

;wsd"defnitions

,m"nshttp

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Definition

The !se o namespaces is important or dierentiating e"ements1 and it

enab"es the doc!ment to reerence m!"tip"e e,terna" specifcations1 inc"!ding

WSDL specifcation S'/ specifcation

the XML Schema specifcation.

The defnitions e"ement a"so specifes a target8amespace attrib!te.

The target8amespace is a convention o XML Schema that enab"es the

WSDL doc!ment to reer to itse".

ina""y1 the defnitions e"ement specifes a dea!"t namespace

,m"nswsd"

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Message

There is message e"ements in WSDL.

)alsSoapIn )alsSoap+ut

)als,rraySoapIn

)als,rraySoap+ut

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Message;wsd"message name

;wsd"part name

;wsd"message name ;wsd"part name

;wsd"message name

;wsd"part name

;wsd"message name

;wsd"part name

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portType

;wsd"portType name

;wsd"operation name

;wsd"inp!t message

;wsd"o!tp!t message

;7wsd"operation>

;wsd"operation name

;wsd"inp!t message

;wsd"o!tp!t message

;7wsd"operation>

;7wsd"portType>

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portType

WSDL s!pports o!r basic patterns o operation

One-way

The service receives a message. The operation thereore has asing"e inp!t e"ement.

Request-response

The service receives a message and sends a response. The operation

thereore has one inp!t e"ement1 o""owed by one o!tp!t e"ement. Solicit-response

Notifcation

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portType

Solicit-response

The service sends a message and receives a response. The

operation thereore has one o!tp!t e"ement1 o""owed by one inp!t

e"ement.

Notifcation

The service sends a message. The operation thereore has a sing"e

o!tp!t e"ement.

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portType

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bining

The binding e"ement provides specifc detai"s on how a portType

operation wi"" act!a""y be transmitted over the wire.

&indings can be made avai"ab"e via m!"tip"e transports1 inc"!ding

@TT/ A:T1 @TT/ /ST1 or S'/.

$n act1 yo! can speciy m!"tip"e bindings or a sing"e portType.

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bining

;wsd"binding name

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service

The service e"ement specifes the "ocation o the service.

&eca!se this is a S'/ service1 we !se the soapaddress e"e

ment1 and speciy the "oca" host address

;soapaddress "ocation

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WSDL !nvocation Tools

yo! co!"d man!a""y create a S'/ c"ient to invo2e the

service. ' better a"ternative is to automatically invo2e the s

ervice via a WSDL invocation too".

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"ML Schema Data Typing

$n order or a S'/ c"ient to comm!nicate eective"y with a S'/

server1 the c"ient and server m!st agree on a data type system.

&y dea!"t1 XML B.C does not provide a data type system. $ncontrast1 every programming "ang!age provides some basic aci"ity

or dec"aring data types1 s!ch as integers1 oats1 do!b"es1 and strings.

WSDL does not aim to create a standard or XML data typing.

$n act1 WSDL is specifca""y designed or ma,im!m e,ibi"ity andis thereore not tied e,c"!sive"y to any one data type system.

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"ML Schema Data Typing

WSDL does dea!"t to the W34 XML Schema specifcation.

The XML Schema specifcation is a"so c!rrent"y the most wide"y !sed

specifcation or data typing.

There is two acts are cr!cia""y important.

irst1 the XML Schema specifcation inc"!des a basic type system

or encoding most data types.

Second1 the XML Schema specifcation provides a aci"ity orcreatingnew data types.

This is important i yo! want to create data types that go beyond

what is a"ready defned within the Schema.

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"ML Schema Data Typing

or e,amp"e1 a service might ret!rn an array o oats or a more comp"e, stoc2

%!ote ob)ect containing the high1 "ow1 and vo"!me fg!res or a specifc stoc2.

Whenever yo!r service goes beyond the simp"e XML Schema data types1 yo!

m!st dec"are these new data types within the WSDL types e"ement.

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#rrays

The WSDL f"e now inc"!des a types e"ement. $nside this e"ement1

we have defned two new comp"e, types.

the XML Schema defnes simp"e types and comp"e, types.

Simp"e types cannot have e"ement chi"dren or attrib!tes1

comp"e, types can have e"ement chi"dren and attrib!tes.

We have dec"ared comp"e, types in o!r WSDL f"e1 beca!se an

array may have m!"tip"e e"ements1 one or each va"!e in the array.

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$omplex Types

!r fna" topic is the !se o comp"e, data types. or e,amp"e1 consider a

home monitoring service that provides a concise !pdate on yo!r home.

The data ret!rned co!"d inc"!de m!"tip"e data e"ements1 s!ch as the c!rrenttemperat!re1

sec!rity stat!s1 and whether the garage door is open or c"osed.

:ncoding this data into WSDL re%!ires additiona"

2now"edge o XML Schemas1 which reinorces the main precept that the

more yo! 2now

abo!t XML Schemas1 the better yo! wi"" !nderstand comp"e, WSDL f"es.

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%uestion & #ns'er