Web servicesoverview

Web Services OverviewWeb Services Overview
Marlon PierceMarlon Pierce
Community Grids LabCommunity Grids Lab
Indiana UniversityIndiana University

AssignmentsAssignments
 Download and install Tomcat (again).Download and install Tomcat (again).
• http://jakarta.apache.org/tomcat/http://jakarta.apache.org/tomcat/
• You will need two tomcat servers.You will need two tomcat servers.
 Install Apache Axis.Install Apache Axis.
• Use “HappyAxis” to make sure you have done soUse “HappyAxis” to make sure you have done so
correctly.correctly.
• http://ws.apache.org/axis/http://ws.apache.org/axis/
 Design and deploy a sample web service.Design and deploy a sample web service.
 Write a client application to use the web service.Write a client application to use the web service.
 Use Google and Amazon WSDL to design yourUse Google and Amazon WSDL to design your
own client.own client.

This Lecture…This Lecture…
 This lecture is intended toThis lecture is intended to introduceintroduce
the main concepts of Web Services.the main concepts of Web Services.
 We will also look at some thingsWe will also look at some things
((SOAP, WSDLSOAP, WSDL) in detail…) in detail…
 But the primary purpose is toBut the primary purpose is to
introduce topics that will all beintroduce topics that will all be
covered incovered in greater detailgreater detail in futurein future
lectures.lectures.

What Are Web Services?What Are Web Services?
 Web services framework is an XML-based distributedWeb services framework is an XML-based distributed
object/service/component system.object/service/component system.
• SOAP, WSDLSOAP, WSDL, WSIL, UDDI, WSIL, UDDI
• Intended to supportIntended to support machine-to-machinemachine-to-machine interactions over theinteractions over the
network.network.
 Basic ideas is to build anBasic ideas is to build an platform and programmingplatform and programming
language-independentlanguage-independent distributed invocation system out ofdistributed invocation system out of
existingexisting Web standardsWeb standards..
• Most standards defined by W3C, Oasis (IP considerations)Most standards defined by W3C, Oasis (IP considerations)
• Interoperability really works, as long as you can map XMLInteroperability really works, as long as you can map XML
message to a programming language type, structure, class,message to a programming language type, structure, class,
etc.etc.
 Very loosely defined, when compared toVery loosely defined, when compared to CORBACORBA, etc., etc.
 Inherit both good and bad of the webInherit both good and bad of the web
• Scalable, simple, distributedScalable, simple, distributed
• But no centralized management, system is inefficient, must beBut no centralized management, system is inefficient, must be
tolerant of failures.tolerant of failures.

Basic Architectures:Basic Architectures:
Servlets/CGI and Web ServicesServlets/CGI and Web Services
Browser
Web
Server
HTTP GET/POST
DB
JDBC
Web
Server
DB
JDBC
Browser
Web
Server
SOAP
GUI
Client
SOAP
WSDL
WSDL
WSDL
WSDL

Explanation of Previous SlideExplanation of Previous Slide
 The diagram on the left represents a standardThe diagram on the left represents a standard
web application.web application.
• Browsers converse with web servers using HTTPBrowsers converse with web servers using HTTP
GET/POST methods.GET/POST methods.
• Servlets or CGI scripts process the parameters and takeServlets or CGI scripts process the parameters and take
action, like connect to a DB.action, like connect to a DB.
• Examples:Examples: Google, AmazonGoogle, Amazon
 On the right, we have a Web services system.On the right, we have a Web services system.
• Interactions may be either through the browser orInteractions may be either through the browser or
through a desktop client (Java Swing, Python, Windows,through a desktop client (Java Swing, Python, Windows,
etc.)etc.)
• I will explain how to do this in several more lectures.I will explain how to do this in several more lectures.
• Examples:Examples: Google, AmazonGoogle, Amazon

Some TerminologySome Terminology
 The diagram on the left is called aThe diagram on the left is called a client/serverclient/server
system.system.
 The diagram on the right is called aThe diagram on the right is called a multi-tieredmulti-tiered
architecture.architecture.
 SOAPSOAP: Simple Object Access Protocol: Simple Object Access Protocol
• XML Message format between client and service.XML Message format between client and service.
 WSDLWSDL: Web Service Description Language.: Web Service Description Language.
• Describes how the service is to be usedDescribes how the service is to be used
• Compare (for example) to Java Interface.Compare (for example) to Java Interface.
• Guideline for constructing SOAP messages.Guideline for constructing SOAP messages.
• WSDL is an XML language for writingWSDL is an XML language for writing ApplicationApplication
Programmer InterfacesProgrammer Interfaces (APIs).(APIs).

Amazon and Google ExperimentAmazon and Google Experiment
with Web Serviceswith Web Services
 Both Google and Amazon have conductedBoth Google and Amazon have conducted
open experiments with Web services.open experiments with Web services.
 Why? To allow partners to develop customWhy? To allow partners to develop custom
user interfaces and applications that workuser interfaces and applications that work
Google and Amazon data and services.Google and Amazon data and services.
 You can download their APIs and try them.You can download their APIs and try them.
• http://www.google.com/apis/http://www.google.com/apis/
• http://www.amazon.com/webserviceshttp://www.amazon.com/webservices

Why Use Web Services?Why Use Web Services?
 Web services provide a cleanWeb services provide a clean separationseparation
between a capability and its user interface.between a capability and its user interface.
 This allows a company (Google) with aThis allows a company (Google) with a
sophisticated capability and huge amountssophisticated capability and huge amounts
of data to make that capability available toof data to make that capability available to
its partners.its partners.
• ““Don’t worry about howDon’t worry about how PageRankPageRank works orworks or
web robots or data storage. We will do that.web robots or data storage. We will do that.
You just use this WSDL API to build your clientYou just use this WSDL API to build your client
application to use our search engine.”application to use our search engine.”

A Google AsideA Google Aside
 Google’sGoogle’s PageRankPageRank system was developedsystem was developed
by two Stanford grad students.by two Stanford grad students.
 OpenOpen algorithm published in scholarlyalgorithm published in scholarly
journals, conferences.journals, conferences.
• Previous (and lousy) search engines were allPrevious (and lousy) search engines were all
proprietary.proprietary.
 See for exampleSee for example
http://www7.scu.edu.au/programme/fullphttp://www7.scu.edu.au/programme/fullp
apers/1921/com1921.htmapers/1921/com1921.htm

When To Use Web Services?When To Use Web Services?
 Applications do not have severe restrictions onApplications do not have severe restrictions on
reliability and speedreliability and speed..
 Two or more organizations need toTwo or more organizations need to cooperatecooperate
• One needs to write an application that uses another’sOne needs to write an application that uses another’s
service.service.
 Services can beServices can be upgraded independentlyupgraded independently ofof
clients.clients.
• Google can improve PageRank implemenation withoutGoogle can improve PageRank implemenation without
telling me.telling me.
• Just don’t change the WSDL.Just don’t change the WSDL.
 Services can be easily expressed with simpleServices can be easily expressed with simple
request/responserequest/response semantics and simplesemantics and simple statestate..
• HTTP and Cookies, for example.HTTP and Cookies, for example.

Relationship to PreviousRelationship to Previous
WorkWork
Connecting to Bryan’sConnecting to Bryan’s
Lectures on XML, Java, JavaLectures on XML, Java, Java
Servlets and JSP.Servlets and JSP.

XML OverviewXML Overview
 XML is a language for building languages.XML is a language for building languages.
 Basic rules: be well formed and be validBasic rules: be well formed and be valid
 Particular XML “dialects” are defined by anParticular XML “dialects” are defined by an
XML Schema.XML Schema.
• XML itself is defined by its own schema.XML itself is defined by its own schema.
 XML is extensible via namespacesXML is extensible via namespaces
 Many non-Web services dialectsMany non-Web services dialects
• RDF, SVG,GML, XForms, XHTMLRDF, SVG,GML, XForms, XHTML
 Many basic tools available: parsers, XPathMany basic tools available: parsers, XPath
and XQuery for searching/querying, etc.and XQuery for searching/querying, etc.

XML and Web servicesXML and Web services
 XML provides a natural substrate for distributedXML provides a natural substrate for distributed
computing:computing:
• Its just a data description.Its just a data description.
• Platform, programming language independent.Platform, programming language independent.
 So let’s describe the pieces.So let’s describe the pieces.
 Web Services Description Language (WSDL)Web Services Description Language (WSDL)
• Describes how to invoke a service (compare with CORBADescribes how to invoke a service (compare with CORBA
IDL).IDL).
• Can bind to SOAP, other protocols for actual invocation.Can bind to SOAP, other protocols for actual invocation.
 Simple Object Access Protocol (SOAP)Simple Object Access Protocol (SOAP)
• Wire protocol extension for conveying RPC calls.Wire protocol extension for conveying RPC calls.
• Can be carried over HTTP, SMTP.Can be carried over HTTP, SMTP.

Web Service ArchitecturesWeb Service Architectures
 The following examples illustrate how WebThe following examples illustrate how Web
services interact with clients.services interact with clients.
 For us, a client is typically a JSP, servlet,For us, a client is typically a JSP, servlet,
or portlet that a user accesses throughor portlet that a user accesses through
browser.browser.
 You can also build other clientsYou can also build other clients
• Web serviceWeb service interoperabilityinteroperability means that clientsmeans that clients
and services can be in different programmingand services can be in different programming
languages (C/C++, python, java, etc).languages (C/C++, python, java, etc).

Browser Interface
User Interface
Server + Client
Stubs
Server plus
Service
Implementations
Backend
Resources
HTTP(S)
SOAP/HTTP(S)
Local invocation, JDBC
connection or Grid Protocol
UI Server has stubs
for all services (data
base access, job
submission, file
transfer, etc.)
A particular server
has several
service implementations.
Backend is a database,
application code plus
operating system.

User Interface Server
DB Service 1
JDBC
DB
Job Sub/Mon
And File
Services
Operating and
Queuing
Systems
User Interface
DB Service 2
JDBC
DB
Host 1 Host 2 Host 3

Before Going On…Before Going On…
 In the next several slides we’ll go into theIn the next several slides we’ll go into the
details of WSDL and SOAP.details of WSDL and SOAP.
 But in practice,But in practice, you don’t need to workyou don’t need to work
directly with eitherdirectly with either..
• Most tools that I’m familiar with generate theMost tools that I’m familiar with generate the
WSDL for you from your class.WSDL for you from your class.
• SOAP messages are constructed by classes.SOAP messages are constructed by classes.
• GeneratedGenerated client stubsclient stubs will even hide SOAPwill even hide SOAP
classes behind a local “façade” that looks like aclasses behind a local “façade” that looks like a
local class but actually constructs SOAP calls tolocal class but actually constructs SOAP calls to
the remote server.the remote server.

Web ServicesWeb Services
Description LanguageDescription Language
Defines what your serviceDefines what your service
does and how it is invoked.does and how it is invoked.

WSDL OverviewWSDL Overview
 WSDL is an XML-based Interface DefinitionWSDL is an XML-based Interface Definition
Language.Language.
• You can define the APIs for all of your services in WSDL.You can define the APIs for all of your services in WSDL.
 WSDL docs are broken into five major parts:WSDL docs are broken into five major parts:
• Data definitionsData definitions (in XML) for custom types(in XML) for custom types
• Abstract message definitionsAbstract message definitions (request, response)(request, response)
• Organization of messages into “Organization of messages into “portsports” and “” and “operationsoperations””
((classes and methods).classes and methods).
• Protocol bindingsProtocol bindings (to SOAP, for example)(to SOAP, for example)
• Service point locationsService point locations (URLs)(URLs)
 Some interesting featuresSome interesting features
• A single WSDL document can describe several versionsA single WSDL document can describe several versions
of an interface.of an interface.
• A single WSDL doc can describe several related services.A single WSDL doc can describe several related services.

The Java CodeThe Java Code
public String[] execLocalCommand(Stringpublic String[] execLocalCommand(String
command) {command) {
Runtime rt = Runtime.getRuntime();Runtime rt = Runtime.getRuntime();
String stdout="",stderr="";String stdout="",stderr="";
try {try {
Process p = rt.exec(command);Process p = rt.exec(command);
BufferedReader in=BufferedReader in=
new BufferedReader(newnew BufferedReader(new
InputStreamReader(p.getInputStream()));InputStreamReader(p.getInputStream()));
BufferedReader err=BufferedReader err=
new BufferedReader(newnew BufferedReader(new
InputStreamReader(p.getErrorStream()));InputStreamReader(p.getErrorStream()));

Java Code ContinuedJava Code Continued
String line;String line;
while((line=in.readLine())!= null)while((line=in.readLine())!= null)
{stdout+=line+"n";}{stdout+=line+"n";}
in.close();in.close();
while ((line=err.readLine())!=null)while ((line=err.readLine())!=null)
{stderr+=line+"n";}{stderr+=line+"n";}
err.close();err.close();
}//End of try{}}//End of try{}
catch (Exception eio) {…}catch (Exception eio) {…}
String[] retstring=new String[2];String[] retstring=new String[2];
retstring[0]=stdout;retstring[0]=stdout;
retstring[1]=stderr;retstring[1]=stderr;
return retstring;return retstring;
} //End of method} //End of method

WSDL Example: JobWSDL Example: Job
SubmissionSubmission
 Our example is a simple service that canOur example is a simple service that can
executes local (to the server) commands.executes local (to the server) commands.
 Service implementation (in Java) has aService implementation (in Java) has a
single methodsingle method
• ExecLocal takes a single string argument (theExecLocal takes a single string argument (the
command to exec)command to exec)
• Returns a 2D string array (standard out andReturns a 2D string array (standard out and
error).error).
 The WSDL maps to a Java interface in thisThe WSDL maps to a Java interface in this
case.case.

The Full WSDLThe Full WSDL
 The following slide contains the WSDLThe following slide contains the WSDL
definition for the Job Submit service.definition for the Job Submit service.
• I omitted some data definitions to get into oneI omitted some data definitions to get into one
page with a decent font.page with a decent font.
 As you can see, WSDL is veryAs you can see, WSDL is very verboseverbose
• Typically, you don’t write WSDLTypically, you don’t write WSDL
• This file was actually generated from my JavaThis file was actually generated from my Java
class byclass by Apache AxisApache Axis..
 We will go through the parts of the doc inWe will go through the parts of the doc in
some detail.some detail.

<?xml version="1.0" encoding="UTF-8"?>
<wsdl:definitions>
<wsdl:message name="execLocalCommandResponse">
<wsdl:message name="execLocalCommandRequest">
<wsdl:portType name="SJwsImp">
<wsdl:operation name="execLocalCommand" parameterOrder="in0">
<wsdl:input message="impl:execLocalCommandRequest"
name="execLocalCommandRequest"/>
<wsdl:output message="impl:execLocalCommandResponse"
name="execLocalCommandResponse"/>
</wsdl:operation>
</wsdl:portType>
<wsdl:binding name="SubmitjobSoapBinding" type="impl:SJwsImp">
<wsdlsoap:binding style="rpc" transport="http://schemas.xmlsoap.org/soap/http"/>
<wsdl:operation name="execLocalCommand">
<wsdlsoap:operation soapAction=""/>
<wsdl:input name="execLocalCommandRequest">
<wsdl:output name="execLocalCommandResponse">
</wsdl:operation>
</wsdl:binding>
<wsdl:service name="SJwsImpService">
<wsdl:port binding="impl:SubmitjobSoapBinding" name="Submitjob">
</wsdl:service>
</wsdl:definitions>

WSDL Elements IWSDL Elements I
 TypesTypes: describes custom XML data types: describes custom XML data types
(optional) used in messages.(optional) used in messages.
• For OO languages, types are a limited objectFor OO languages, types are a limited object
serialization.serialization.
• We’ll see an example for defining arrays.We’ll see an example for defining arrays.
 MessageMessage: abstractly defines the messages that: abstractly defines the messages that
need to be exchanged.need to be exchanged.
• Conventionally messages are used to group requestsConventionally messages are used to group requests
and responses.and responses.
• Each method/function in the interface contains 0-1Each method/function in the interface contains 0-1
request and 0-1 response messages.request and 0-1 response messages.
• Consists ofConsists of partpart elements. Usually you need one part forelements. Usually you need one part for
each variable sent or received. Parts can either be XMLeach variable sent or received. Parts can either be XML
primitive types or custom complex types.primitive types or custom complex types.

TypesTypes for Job Submissionfor Job Submission
 Recall that the job submissionRecall that the job submission
service sends a string (theservice sends a string (the
command) and returns a 2D array.command) and returns a 2D array.
 StringsStrings are XML Schemaare XML Schema primitiveprimitive
typestypes, so we don’t need a special, so we don’t need a special
definition in our WSDL.definition in our WSDL.
 ArraysArrays areare not primitive typesnot primitive types. They. They
are defined in the SOAP schema, soare defined in the SOAP schema, so
we will import that definition.we will import that definition.
• In other words, SOAP has rules for arrayIn other words, SOAP has rules for array
encoding; vanilla XML does not.encoding; vanilla XML does not.

Example: WSDLExample: WSDL typestypes for Customfor Custom
Data DefinitionData Definition
<wsdl:types>
<schema targetNamespace="http://.../GCWS/services/Submitjob"
xmlns:impl="http://.../GCWS/services/Submitjob"
xmlns="http://www.w3.org/2001/XMLSchema">
<import namespace="http://schemas.xmlsoap.org/soap/encoding/" />
<complexType name="ArrayOf_xsd_string">
<complexContent>
<restriction base="soapenc:Array">
<attribute ref="soapenc:arrayType"
wsdl:arrayType="xsd:string[]" />
</restriction>
</complexContent>
</complexType>
<element name="ArrayOf_xsd_string" nillable="true"
type="impl:ArrayOf_xsd_string" />
</schema>
</wsdl:types>

What Does It Mean?What Does It Mean?
 We start with some usefulWe start with some useful
namespace definitions.namespace definitions.
 We next import the SOAP schemaWe next import the SOAP schema
• It has the array definitions we need.It has the array definitions we need.
 Finally, we define our own local XMLFinally, we define our own local XML
complex type, ArrayOf_xsd_string.complex type, ArrayOf_xsd_string.
• This extends the SOAP array typeThis extends the SOAP array type
• We restrict this to String arrays.We restrict this to String arrays.

MessageMessage Elements for JobElements for Job
Submission ServiceSubmission Service
 Our service implementation has one method ofOur service implementation has one method of
the form (in Java)the form (in Java)
public String[] execLocalCommand(String cmd)public String[] execLocalCommand(String cmd)
 This will require one “request” message and oneThis will require one “request” message and one
“response” message.“response” message.
 Each message has oneEach message has one part:part:
• Request message must send the String cmd.Request message must send the String cmd.
• Response must get back the String[] array (definedResponse must get back the String[] array (defined
previously as a custom type).previously as a custom type).
 If we had to pass two input variables, ourIf we had to pass two input variables, our
“request” message would need two part“request” message would need two part
elements.elements.
 Note the name attributes of messages areNote the name attributes of messages are
important!important!

Message Examples for JobMessage Examples for Job
Submission ServiceSubmission Service
<wsdl:message
name="execLocalCommandResponse">
<wsdl:part
name="execLocalCommandReturn"
type="impl:ArrayOf_xsd_string" />
</wsdl:message>
<wsdl:message
name="execLocalCommandRequest">
<wsdl:part name="in0" type="xsd:string" />
</wsdl:message>

portTypesportTypes
 portTypeportType elements map messages toelements map messages to
operationsoperations..
 You can think of portType==class,You can think of portType==class,
operation==class methods.operation==class methods.
 Operations can contain input, output,Operations can contain input, output,
and/or fault bindings for messages.and/or fault bindings for messages.
 An operation may support of the followingAn operation may support of the following
message styles:message styles:
• One-way: request onlyOne-way: request only
• Two-way: request/responseTwo-way: request/response
• Solicit-response: server “push” and client responseSolicit-response: server “push” and client response
• Notification: one-way server pushNotification: one-way server push

portType for JobSubmitportType for JobSubmit
 We previously defined the messagesWe previously defined the messages
and types needed. Now we bindand types needed. Now we bind
them into the portType structure.them into the portType structure.
 PortType names are importantPortType names are important
• Will be referenced byWill be referenced by bindingbinding element.element.
 Note names of previously definedNote names of previously defined
messages are used as references inmessages are used as references in
the operations.the operations.

<wsdl:portType name="SJwsImp">
<wsdl:operation name="execLocalCommand"
parameterOrder="in0">
<wsdl:input
message="impl:execLocalCommandRequest"
name="execLocalCommandRequest" />
<wsdl:output
message="impl:execLocalCommandResponse"
name="execLocalCommandResponse" />
</wsdl:operation>
</wsdl:portType>
Example WSDL NuggetExample WSDL Nugget

Some Notes on the PortTypeSome Notes on the PortType
DefinitionDefinition
 PortTypes refer to messages by namePortTypes refer to messages by name
• The message attribute in <input> andThe message attribute in <input> and
<output> elements of <operation> refer to<output> elements of <operation> refer to
the name attributes of the previously definedthe name attributes of the previously defined
messages.messages.
• The operation and portType names willThe operation and portType names will
similarly be used for reference in forthcomingsimilarly be used for reference in forthcoming
tags.tags.
 Also note “parameterOrder” does what youAlso note “parameterOrder” does what you
would expect. For the current example,would expect. For the current example,
there is only one input parameter.there is only one input parameter.

PortType BindingsPortType Bindings
 portTypes are abstract interfaceportTypes are abstract interface
definitions.definitions.
• Don’t say anything about how to invoke aDon’t say anything about how to invoke a
remote method.remote method.
 Remote invocations are defined inRemote invocations are defined in bindingbinding
elements.elements.
 Binding elements are really just placeBinding elements are really just place
holders that are extended for specificholders that are extended for specific
protocolsprotocols
• WSDL spec provides SOAP, HTTP GET/POST,WSDL spec provides SOAP, HTTP GET/POST,
and MIME extension schema examples.and MIME extension schema examples.

SOAP Bindings for JobSubmitSOAP Bindings for JobSubmit
ServiceService
 Note that the binding element contains a mixtureNote that the binding element contains a mixture
of tags from different namespaces (wsdl andof tags from different namespaces (wsdl and
wsdlsoap).wsdlsoap).
 WSDL child elements forWSDL child elements for bindingbinding element areelement are
operation, input,operation, input, andand output.output.
 WSDLSOAP elements are from a different XMLWSDLSOAP elements are from a different XML
schema (a new one, neither WSDL nor SOAP).schema (a new one, neither WSDL nor SOAP).
• This is how you extend WSDL bindings: define a newThis is how you extend WSDL bindings: define a new
schema that gives mapping instructions from WSDL toschema that gives mapping instructions from WSDL to
the protocol of choice.the protocol of choice.
 The binding element name is important, will beThe binding element name is important, will be
used as a reference by the final port binding.used as a reference by the final port binding.

<wsdl:binding
name="SubmitjobSoapBinding" type="impl:SJwsImp">
<wsdlsoap:binding style="rpc"
transport="http://schemas.xmlsoap.org/soap/http" />
<wsdl:operation name="execLocalCommand">
<wsdlsoap:operation soapAction="" />
<wsdl:input name="execLocalCommandRequest">
<wsdlsoap:body
encodingStyle=http://schemas.xmlsoap.org/soap/encoding/
namespace="http://.../GCWS/services/Submitjob"
use="encoded" />
</wsdl:input>
<wsdl:output name="execLocalCommandResponse">
<wsdlsoap:body
encodingStyle=http://schemas.xmlsoap.org/soap/encoding/
namespace=http://.../GCWS/services/Submitjob
use="encoded" />
</wsdl:output>
</wsdl:operation>
</wsdl:binding>

A Closer Look at SOAP BindingA Closer Look at SOAP Binding
<wsdlsoap:body<wsdlsoap:body
encodingStyle=encodingStyle=http://schemas.xmlsoap.org/http://schemas.xmlsoap.org/
soap/encoding/soap/encoding/
namespace=namespace=http://.../GCWS/services/Submihttp://.../GCWS/services/Submi
tjobtjob use="use="encodedencoded" />" />
 All this really means is “encode the message byAll this really means is “encode the message by
the rules in encodingStyle and put it in the SOAPthe rules in encodingStyle and put it in the SOAP
body.”body.”
 The bindings are just instructions that must beThe bindings are just instructions that must be
implemented by the SOAP message generator.implemented by the SOAP message generator.

Service and Port DefinitionsService and Port Definitions
 So far, we have defined the classSo far, we have defined the class
method interfaces (portTypes) andmethod interfaces (portTypes) and
the rules for binding to a particularthe rules for binding to a particular
protocol.protocol.
 PortPort elements define how theelements define how the
bindings (and thus the portTypes)bindings (and thus the portTypes)
are associated with a particularare associated with a particular
server.server.
 TheThe serviceservice element collectselement collects ports.ports.

<wsdl:service name="SJwsImpService">
<wsdl:port
binding="impl:SubmitjobSoapBinding"
name="Submitjob">
<wsdlsoap:address
location="http://.../GCWS/services/Submitjob" />
</wsdl:port>
</wsdl:service>
Service and Port Elements for theService and Port Elements for the
Job Submission ServiceJob Submission Service

ExplanationExplanation
 Note the port element’s binding attributeNote the port element’s binding attribute
points to the appropriatepoints to the appropriate bindingbinding elementelement
by name.by name.
 The only purpose of the port element is toThe only purpose of the port element is to
point to a service location (a URL). This ispoint to a service location (a URL). This is
done by extension (SOAP in this case.)done by extension (SOAP in this case.)
 Ports are child elements of thePorts are child elements of the serviceservice
element. A service can contain one orelement. A service can contain one or
more ports.more ports.
• Note the value of multiple ports: a singleNote the value of multiple ports: a single
portType may correspond to several ports,portType may correspond to several ports,
each with a different protocol binding andeach with a different protocol binding and
service point.service point.

WSDL TriviaWSDL Trivia
 The schema rules allow all of the elements weThe schema rules allow all of the elements we
have discussed to appear zero or more times.have discussed to appear zero or more times.
 A single WSDL file may contain many portTypesA single WSDL file may contain many portTypes
(although this is not usual).(although this is not usual).
• You may want to do this to support multiple interfaceYou may want to do this to support multiple interface
definitions of a service for backward compatibility.definitions of a service for backward compatibility.
 Multiple ports may also be used to provideMultiple ports may also be used to provide
different views of a servicedifferent views of a service
• One portType defines the interface.One portType defines the interface.
• Another provides access to metadata about the service.Another provides access to metadata about the service.
• Yet another may define how the service interacts withYet another may define how the service interacts with
other servicesother services via notification/event systemsvia notification/event systems..

Simple Object AccessSimple Object Access
ProtocolProtocol
A message format forA message format for
exchanging structured, typedexchanging structured, typed
informationinformation

SOAP BasicsSOAP Basics
 SOAP is often thought of as a protocol extensionSOAP is often thought of as a protocol extension
for doing RPC over HTTP.for doing RPC over HTTP.
 This is not completely accurate: SOAP is an XMLThis is not completely accurate: SOAP is an XML
message format for exchanging structured, typedmessage format for exchanging structured, typed
data.data.
 It may be used for RPC in client-serverIt may be used for RPC in client-server
applications but is also suitable for messagingapplications but is also suitable for messaging
systems (like JMS) that follow one-to-many (orsystems (like JMS) that follow one-to-many (or
publish-subscribe) models.publish-subscribe) models.
 SOAP is not a transport protocol. You mustSOAP is not a transport protocol. You must
attach your message to a transport mechanismattach your message to a transport mechanism
like HTTP.like HTTP.

SOAP StructureSOAP Structure
 A SOAP message is contained in anA SOAP message is contained in an
envelop.envelop.
 The envelop element in turn containThe envelop element in turn contain
(in order)(in order)
• An optionalAn optional headerheader with one or morewith one or more
child entrieschild entries..
• AA bodybody element that can contain one orelement that can contain one or
more child entries. These child entriesmore child entries. These child entries
may contain arbitrary XML data.may contain arbitrary XML data.

SOAP HeadersSOAP Headers
 Headers are really just extension pointsHeaders are really just extension points
where you can include elements fromwhere you can include elements from
other namespaces.other namespaces.
• i.e., headers can contain arbitrary XML.i.e., headers can contain arbitrary XML.
 Header entries may optionally have aHeader entries may optionally have a
“mustUnderstand” attribute.“mustUnderstand” attribute.
• mustUnderstand=1 means the messagemustUnderstand=1 means the message
recipient must process the header element.recipient must process the header element.
• If mustUnderstand=0 or is missing, the headerIf mustUnderstand=0 or is missing, the header
element is optional.element is optional.

SOAP BodySOAP Body
 Body entries are really just placeholdersBody entries are really just placeholders
for arbitrary XML from some otherfor arbitrary XML from some other
namespace.namespace.
 The body contains the XML message thatThe body contains the XML message that
you are transmitting.you are transmitting.
 The message format is not specified byThe message format is not specified by
SOAP.SOAP.
• The <Body></Body> tag pairs are just a wayThe <Body></Body> tag pairs are just a way
to notify the recipient that the actual XMLto notify the recipient that the actual XML
message is contained therein.message is contained therein.
• The recipient decides what to do with theThe recipient decides what to do with the
message.message.

Example MessagesExample Messages
 Recall the WSDL interface for “SubmitJob”Recall the WSDL interface for “SubmitJob”
• Sends one string commandSends one string command
• Returns array of strings for standard out and error.Returns array of strings for standard out and error.
 The envelop is decorated with a few usefulThe envelop is decorated with a few useful
namespacesnamespaces::
• soapenv defines the versionsoapenv defines the version
• xsd is the Schema definition itselfxsd is the Schema definition itself
• xsi defines some useful constants.xsi defines some useful constants.
 The body is just an arbitrary XMLThe body is just an arbitrary XML
fragment.fragment.
• Assumes the recipient knows what this means.Assumes the recipient knows what this means.
• Recipient must looks up the ExecLocalCommand operation inRecipient must looks up the ExecLocalCommand operation in
the JobSubmit service and passes it one string argument.the JobSubmit service and passes it one string argument.
• The ns1 namespace tells the recipient the WSDL namespaceThe ns1 namespace tells the recipient the WSDL namespace
that defines the service.that defines the service.
• xsi:type lets the recipient know that the arbitrary XML elementxsi:type lets the recipient know that the arbitrary XML element
in0 is in fact a string, as defined by the XML Schema.in0 is in fact a string, as defined by the XML Schema.

<soapenv:Envelope
xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xsd=http://www.w3.org/2001/XMLSchema
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
<ns1:execLocalCommand
soapenv:encodingStyle
="http://schemas.xmlsoap.org/soap/encoding/"
xmlns:ns1
="http://.../GCWS/services/Submitjob/GCWS/services/Submitjob">
<in0 xsi:type="xsd:string">/usr/bin/csh /tmp/job.script</in0>
</ns1:execLocalCommand>
</soapenv:Body>
</soapenv:Envelope>
SOAP RequestSOAP Request

Example ResponseExample Response
 The structure is the same as the request.The structure is the same as the request.
 The interesting thing here is that theThe interesting thing here is that the
request returns a 2-element array of tworequest returns a 2-element array of two
strings.strings.
• Arrays not defined by XML schemaArrays not defined by XML schema
• SOAP encoding does define arrays, so useSOAP encoding does define arrays, so use
xsi:type to point to this definition.xsi:type to point to this definition.
• <item></item> surrounds each array<item></item> surrounds each array
element.element.
 Note that arbitrary XML returns canNote that arbitrary XML returns can
likewise be encoded this way.likewise be encoded this way.
• Use xsi:type to point to a schema.Use xsi:type to point to a schema.

<soapenv:Envelope
xmlns:soapenv=http://schemas.xmlsoap.org/soap/envelope/
xmlns:xsd=http://www.w3.org/2001/XMLSchema
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
<ns1:execLocalCommandResponse
soapenv:encodingStyle=
http://schemas.xmlsoap.org/soap/encoding/
xmlns:ns1="http://../services/Submitjob">
<execLocalCommandReturn xsi:type="soapenc:Array“
soapenc:arrayType="xsd:string[2]"
xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/">
<item></item> <item></item>
</execLocalCommandReturn>
</ns1:execLocalCommandResponse>
</soapenv:Body>
</soapenv:Envelope>
SOAP ResponseSOAP Response

Developing WebDeveloping Web
ServicesServices
Using Apache Axis to developUsing Apache Axis to develop
Java implementations of WebJava implementations of Web
services.services.

Web Service DevelopmentWeb Service Development
ToolsTools
 Web service toolkits exist for variousWeb service toolkits exist for various
programming languages:programming languages:
• C++,Python, Perl, various MicrosoftC++,Python, Perl, various Microsoft
.NET kits..NET kits.
 We’ll concentrate on building JavaWe’ll concentrate on building Java
Web services with Apache Axis.Web services with Apache Axis.
 Language and implementationLanguage and implementation
interoperability is addressed throughinteroperability is addressed through
WS-I.WS-I.
• http://www.ws-i.org/http://www.ws-i.org/

Apache Axis OverviewApache Axis Overview
 Apache Axis is a toolkit for converting JavaApache Axis is a toolkit for converting Java
applications into Web services.applications into Web services.
 Axis service deployment tools allow you toAxis service deployment tools allow you to
publish your service in a particularpublish your service in a particular
application server (Tomcat).application server (Tomcat).
 Axis client tools allow you to convertAxis client tools allow you to convert
WSDL into client stubs.WSDL into client stubs.
 Axis runtime tools accept incoming SOAPAxis runtime tools accept incoming SOAP
requests and redirect them to therequests and redirect them to the
appropriate service.appropriate service.

Developing and Deploying aDeveloping and Deploying a
ServiceService
 Download and install Tomcat and Axis.Download and install Tomcat and Axis.
 Write a Java implementationWrite a Java implementation
• Our SubmitJob is a simple example but services can getOur SubmitJob is a simple example but services can get
quite complicated.quite complicated.
• Compile it into Tomcat’s classpath.Compile it into Tomcat’s classpath.
 Write a deployment descriptor (WSDD) for yourWrite a deployment descriptor (WSDD) for your
service.service.
• Will be used by Axis runtime to direct SOAP calls.Will be used by Axis runtime to direct SOAP calls.
 Use Axis’s AdminClient tool to install your WSDDUse Axis’s AdminClient tool to install your WSDD
file.file.
• The tells the axis servlet to load your class and directThe tells the axis servlet to load your class and direct
SOAP requests to it.SOAP requests to it.
 That’s it.That’s it.
• Axis will automatically generate the WSDL for yourAxis will automatically generate the WSDL for your
service.service.

<deployment name="Submitjob"
xmlns="http://xml.apache.org/axis/wsdd/"
xmlns:java="http://xml.apache.org/axis/wsdd/providers/java">
<service name="Submitjob" provider="java:RPC">
<parameter name="scope" value="request"/>
<parameter name="className"
value="WebFlowSoap.SJwsImp"/>
<parameter name="allowedMethods"
value="execLocalCommand"/>
</service>
</deployment>
Sample WSDDSample WSDD

ExplanationExplanation
 Use Axis’s command-lineUse Axis’s command-line
AdminClient tool to deploy this to theAdminClient tool to deploy this to the
server.server.
 Axis will create a service calledAxis will create a service called
• http://your.server/services/SubmitJobhttp://your.server/services/SubmitJob
 WSDL for service is available fromWSDL for service is available from
• http://your.server/services/SubmitJob?http://your.server/services/SubmitJob?
wsdlwsdl
 A list of all services is available fromA list of all services is available from
• http://your.server/serviceshttp://your.server/services

Check your Tomcat Server
for a list of deployed
services.

WSDL generated by
inspecting the Java
implementation. Can be
download from the
server.
(XML was shown in
earlier slides)

Building a Client with AxisBuilding a Client with Axis
 Obtain the WSDL file.Obtain the WSDL file.
 Generate client stubsGenerate client stubs
• Stubs look like local objects but reallyStubs look like local objects but really
convert method invocations into SOAPconvert method invocations into SOAP
calls.calls.
 Write a client application with theWrite a client application with the
stubsstubs
• Can be a Java GUI, a JSP page, etc.Can be a Java GUI, a JSP page, etc.
 Compile everything and run.Compile everything and run.

Sample Java Client CodeSample Java Client Code
/**Create SubmitJob client object and point to the/**Create SubmitJob client object and point to the
service you want to use */service you want to use */
SubmiJob sjws = newSubmiJob sjws = new
SubmitJobServiceLocator().getSubmitjob(newSubmitJobServiceLocator().getSubmitjob(new
URL(http://your.server/services/SubmitJob));URL(http://your.server/services/SubmitJob));
/** Invoke the method as if local. *//** Invoke the method as if local. */
String[] messages =String[] messages =
sjws.execLocalCommand(command);sjws.execLocalCommand(command);

Two Notes On Client StubsTwo Notes On Client Stubs
 Axis stubs convert method calls intoAxis stubs convert method calls into
SOAP requests but WSDL does notSOAP requests but WSDL does not
require the use of SOAP.require the use of SOAP.
• Web Service Invocation Framework (WSIF)Web Service Invocation Framework (WSIF)
from IBM allows flexibility of protocols. (Alekfrom IBM allows flexibility of protocols. (Alek
Slominski, IU)Slominski, IU)
 Client stubs introduce versioningClient stubs introduce versioning
problemsproblems..
• We are developing dynamic (stubless) clientsWe are developing dynamic (stubless) clients
that construct SOAP messages by inspectingthat construct SOAP messages by inspecting
WSDL at runtime.WSDL at runtime.

Web Service URLsWeb Service URLs
 JavaJava
• http://xml.apache.org/axis/http://xml.apache.org/axis/
 XSOAP: C++ and Java toolkits for WSXSOAP: C++ and Java toolkits for WS
• http://www.extreme.indiana.edu/xgws/xsoap/http://www.extreme.indiana.edu/xgws/xsoap/
 gSOAP: C++ SOAP toolkitgSOAP: C++ SOAP toolkit
• http://www.cs.fsu.edu/~engelen/soap.htmlhttp://www.cs.fsu.edu/~engelen/soap.html
 Python Web Services:Python Web Services:
• http://pywebsvcs.sourceforge.net/http://pywebsvcs.sourceforge.net/
 Perl:Perl:
• http://www.soaplite.com/http://www.soaplite.com/

Web servicesoverview

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