Web ServicesWeb Services

A good choice for sharing A good choice for sharing [ocean science] data.[ocean science] data.

Distributed ComputingDistributed Computing

Connecting systemsConnecting systems

TransparencyTransparency

ScalabilityScalability

Fault ToleranceFault Tolerance

Data Sharing ObstaclesData Sharing Obstacles

PlatformsPlatforms

LanguagesLanguages

TransportsTransports

Data Sharing MethodsData Sharing Methods

CORBA, RMI, DCOMCORBA, RMI, DCOM

ProblemsProblems Goals lacked heterogeneous environment Goals lacked heterogeneous environment Difficult-to-implementDifficult-to-implement Proprietary protocolsProprietary protocols Not modular – crammed specificationsNot modular – crammed specifications

The Web ServiceThe Web Service

Defined: Process between systemsDefined: Process between systemsLeverage Internet standardsLeverage Internet standards Passes XML messages over HTTPPasses XML messages over HTTP

PromotesPromotes Interoperability Interoperability

Perl to C++ to AppleScript…Perl to C++ to AppleScript… Loose couplingLoose coupling

Implementation-independent & VersioningImplementation-independent & Versioning

SOAPSOAP

The Emerging Web Service The Emerging Web Service Interface to existing programsInterface to existing programs Modular DesignModular Design

Extensible – add-on distinct specs Extensible – add-on distinct specs SecuritySecurity ReliabilityReliability

Customizable – combine features as neededCustomizable – combine features as needed No forced modelNo forced model 80+ implementations (platforms,languages)80+ implementations (platforms,languages)

SOAP: RequirementsSOAP: Requirements

ApplicationApplication

Application ServerApplication Server

SOAP ImplementationSOAP Implementation

XML parser (sometimes)XML parser (sometimes)

SOAP: How It WorksSOAP: How It Works

Calls functions of existing programsCalls functions of existing programs Application server knows:Application server knows:

Available functionsAvailable functionsHow to decode requestsHow to decode requestsHow to encode responsesHow to encode responses

XML Request – invokes a function callXML Request – invokes a function callWith function parameters (if necessary)With function parameters (if necessary)

XML ResponseXML ResponsePackages returned data of the functionPackages returned data of the function

SOAP: Getting StartedSOAP: Getting Started

Receiving SOAP requestsReceiving SOAP requests Define a SOAP “Service”Define a SOAP “Service”

Tell Server “Providing” programTell Server “Providing” program

How to translate data (mapping)How to translate data (mapping)

Sending SOAP requestsSending SOAP requests Write SOAP callWrite SOAP call

Knowing what you are receivingKnowing what you are receiving

What parameters to pass along (if necessary)What parameters to pass along (if necessary)

SOAP ExampleSOAP Example

Online Address BookOnline Address Book

Functions:Functions: getAddressForName( name )getAddressForName( name ) addEntry( <some data> )addEntry( <some data> ) getAllListings()getAllListings()

SOAP Response: Notify ServerSOAP Response: Notify Server

<isd:<isd:serviceservice … …

id="urn:AddressFetcher">id="urn:AddressFetcher">

<isd:<isd:providerprovider type="java" ...type="java" ...

methods="getAddressFromName addEntry getAllListings" …methods="getAddressFromName addEntry getAllListings" …

class="samples.addressbook.AddressBook" …class="samples.addressbook.AddressBook" …

……

<isd:mappings><isd:mappings>

… …

</isd:service></isd:service>

SOAP Request: Making the CallSOAP Request: Making the CallURL url = new URL("http://ragnarok.whoi.edu:7001/soap/servlet/rpcrouter");URL url = new URL("http://ragnarok.whoi.edu:7001/soap/servlet/rpcrouter");……

Call call = new Call(); …Call call = new Call(); …

call.setTargetObjectURI("call.setTargetObjectURI("urn:AddressFetcherurn:AddressFetcher");");

call.setMethodName("call.setMethodName("getAddressFromNamegetAddressFromName");");……

Vector params = new Vector();Vector params = new Vector();

params.addElement( … "John B. Good“ …);params.addElement( … "John B. Good“ …);

call.setParams(params);call.setParams(params);

Response response = call.invoke(url);Response response = call.invoke(url);

Parameter ret = response .getReturnValue();Parameter ret = response .getReturnValue();……

<do something><do something>

SOAP: In ActionSOAP: In Action

getAddressFromName(“John B. Good”)getAddressFromName(“John B. Good”)Try itTry it

addEntry(“John Doe ...”)addEntry(“John Doe ...”)Try itTry it

getAddressFromName(“John Doe”)getAddressFromName(“John Doe”)Try itTry it

getAllListings()getAllListings()Try itTry it

SOAP: DrawbacksSOAP: Drawbacks

PerformancePerformance XML lacks efficiency of parsingXML lacks efficiency of parsing

XML Infoset (W3C recommendation)XML Infoset (W3C recommendation) HTTP limitationsHTTP limitations

Popular Web ServicesPopular Web Services

ProductProduct Support OSSupport OS LanguageLanguage

Apache SOAP Apache SOAP UNIX, Windows UNIX, Windows JavaJava

GLUE GLUE UNIX, WindowsUNIX, Windows JavaJava

WASPWASP UNIX, WindowsUNIX, Windows C++C++

SOAP::LiteSOAP::Lite UNIX, WindowsUNIX, Windows PerlPerl

SOAPx4 SOAPx4 UNIXUNIX PHPPHP