Web Services

1
Web Services SOAP
2
Web Services Defined
Web services are a new breed of Web application.
They are self-contained, self-describing, modular
applications that can be published, located, and
invoked across the Web. Web services perform
functions, which can be anything from simple
requests to complicated business
processes. ...Once a Web service is deployed,
other applications (and other Web services) can
discover and invoke the deployed service.
-IBMs tutorial on Web Services
3
The Six Key Components

• IBMs definition identifies six key components of
  a web service
• self-contained
• self-describing
• modular applications
• published
• located
• invoked across the web

4
Architectural Perspective

• A web service is essentially a standards-based
  façade, or wrapper for accessing non-standardized
  middleware components

Web Server
XML Request
Web Service
Business Service
Listener
middleware
XML Response
5
Web Services Compared

• Why not use existing distributed, middleware
  solutions like RMI, CORBA, or DCOM?
• DCOM is proprietary, thus negating the goal of
  standards-based interoperability
• RMI is Java-based, and thus does not easily play
  well with other languages
• CORBA comes closer. It is standards-based,
  vendor-neutral, and language-agnostic. It is
  limited however by its inability to utilize the
  power and flexibility of the Internet
• Web Services are standards-based, vendor-neutral,
  language-agnostic, and they have been designed to
  leverage the service-centric, asynchronous nature
  of the Internet

6
Architectural Details
Web Server
SOAP or XML-RPC
HTTP
CORBA, RMI, RMI/IIOP, JMS,
Web Service
Listener
middleware
SOAP or XML-RPC
Jini, DCOM, vendor-specific API, etc.
HTTP

• SOAP and XML-RPC have become accepted standards
  for XML-based messaging. -- wire format
• HTTP is the defacto protocol for the Internet.
  protocol
• The Web Service will parse the request and either
  fulfill the request directly, or invoke one or
  more business services via some middleware API.

7
Implementing Web Services

• Web Services enable new kinds of applications,
  but they do not constitute these applications,
  nor do they build these applications
• It is still necessary to use a programming
  language to design the client and server pieces
  of the communication
• Java, C/C, ASP, Perl, Ruby, etc.
• Web services merely serve as the glue between the
  client and server applications

Server App
Web Service
Client App
8
Invoking a Web Service

• Invocation process
• Client queries a UDDI registry node
• Server returns a list of records matching request
• Client identifies a specific service of interest
• Server binds client to the service so client can
  invoke service methods

Web server
Client application
UDDI registry node
9
Java and Web Services

• Web Services are built on industry specifications
  with the following goals
• language and vendor independent
• facilitate collaboration between applications as
  well as information exchange
• The Java platform is also built on industry
  specifications and has similar goals
• platform independency (Write Once Run
  Anywhere)
• vendor neutrality
• extensibility, integration, and simplified
  connectivity
• As a vendor-neutral, platform-independent
  language, Java is perfect for implementing web
  service applications

10
Suns JAX Pack

• JAXP Java API for XML Processing
• a standard API for parsing XML documents that is
  parser-neutral (similar to JDBC)
• JAXB Java API for XML Binding
• maps XML elements to Java classes
• JAXM Java API for XML Messaging
• provides an API to allow Java components to send
  SOAP messages via HTTP
• JAXR Java API for XML Registries
• provides a standard way to access business
  registries and share information
• JAX-RPC Java API for XML-based RPC
• sends SOAP method calls to remote parties over
  the Internet and receives the results

11
The JAX Pack

• JAXP Processing
• plug in any compliant parser
• supports both SAX and DOM processing
• supports XSL and XSLT
• it is the foundation of any XML processing
  application
• JAXB Binding
• provides a means of mapping XML documents to Java
  objects
• the JAXB complier generates Java classes based
  upon a schema (or DTD)
• these classes contain all the code necessary to
  parse and manipulate XML documents that conform
  to the schema

12
The JAX Pack

• JAXM Messaging
• a standard, XML-centric, means of sending
  messages over the Internet from the Java platform
  
• based on SOAP 1.1 and SOAP with attachments specs
• requires a messaging provider implement the API
• JAXR Registries
• provides a uniform way of accessing business
  registries over the Internet from the Java
  platform
• the API abstracts Java developers from the
  low-level details of UDDI or ebXMLs registry
  service
• JAX-RPC XML-based RPC
• allows Java developers to write pure Java code
  devoid of XML and still access XML-based web
  services

13
SOAP

• Simple Object Access Protocol
• protocol is the key word
• Based on XML-RPC (JAX-RPC)
• XML format for encoding data
• Request/Response architecture
• Transport is normally HTTP
• can be anything (SMTP, SNMP, etc)

14
SOAP In One Slide
SOAP1.1 Message Structure

• XML based protocol for exchange of information
• Encoding rules for datatype instances
• Convention for representing RPC invocations
• Designed for loosely-coupled distributed
  computing
• No remote references
• Used with XML Schema
• Transport independent
• SOAP with Attachments allow arbitrary data to be
  packaged.

SOAP Envelope
Header Entries
Header Element
Body Element
Fault Element
15
A Simple SOAP Request
POST /calendar-request HTTP/1.1 Host
uche.ogbuji.net Content-Type text/plain
charset"utf-8" Content-Length 507
ltSOAP-ENVEnvelope xmlnsSOAP-ENV"http//
schemas.xmlsoap.org/soap/envelope/"
SOAP-ENVencodingStyle"http//schemas.xmlsoap.org
/soap/encoding/" gt ltSOAP-ENVBodygt
ltcAddListing xmlnsc"http//uche.ogbuji.net/soa
p-example/calendar"gt ltcwhengt
ltcDategt
ltdaygt21lt/daygt
ltmonthgt6lt/monthgt
ltyeargt2001lt/yeargt lt/cDategt
lt/cwhengt ltcwhatgtA
total eclipse will be visible across Central
Africa.lt/cwhatgt lt/cAddListinggt
lt/SOAP-ENVBodygt lt/SOAP-ENVEnvelopegt
16
The SOAP Response
HTTP/1.1 200 OK Server PythonSimpleHTTP/2.0
Date Tue, 28 Nov 2000 042303 GMT
Content-type text/xml charset"utf-8"
Content-length 296 ltSOAP-ENVEnvelope
xmlnsSOAP-ENV"http//schemas.xmlsoap.org/soap/
envelope/" SOAP-ENVencodingStyle"http//schema
s.xmlsoap.org/soap/encoding/" gt
ltSOAP-ENVBodygt ltcAddListingResponse
xmlnsc"http//uche.ogbuji.net/soap-example/ca
lendar"/gt lt/SOAP-ENVBodygt
lt/SOAP-ENVEnvelopegt
17
SOAP Envelope

• Simple wrapper for message payload
• May specify encoding for message
• Specification defines one encoding,
• http//schemas.xmlsoap.org/soap/encoding
• Also known as RPC encoding, this handles basic
  primitive types and arrays, composites of these
  types
• Other encodings may be used, including
  user-defined encodings

18
SOAP Header

• Can optionally add information to message
• Authentication information
• Session management
• Transaction management, etc.
• Very flexible, but standards needed
• Only a pair of attributes defined, not widely
  used
• .NET extends with its own set

19
SOAP Body

• Message payload container
• Three commonly-used formats
• RPC encoded -- encoding defined by SOAP
  specification
• Document literal -- XML message with format
  determined by schema (WXS)
• Wrapped -- document literal variation, with call
  parameters as children of root element
• Service defines the format to use (WSDL)

20
SOAP Attachments

• SOAP Body content issues
• Character set restricted in XML (only whitespace
  allowed below 0x20)
• XML must be well formed - single root element,
  all tags closed, etc.
• Binary data must be encoded with heavy overhead
• Attachments use MIME multipart message format
• Any type of data to accompany SOAP
• Avoids XML encoding issues

21
WSDL

• Web Services Description Language (WSDL)
• 1.1 draft specification released March 15, 2001
  by Ariba, IBM, and Microsoft
• an XML-formatted language that defines the ways
  you can contact a web service and describes the
  message formats you should use
• WSDL is essentially the IDL of web services
• makes a neutral declaration of the existence of
  one or more services
• describes the way a client can interact with
  those services

22
WSDL in One Slide
WSDL1.1 Document Structure

• A WSDL document describes
• What the service can do
• Where it resides
• How to invoke it
• WSDL are like IDL but lot more flexible and
  extensible
• Defines binding for SOAP1.1, HTTP GET/POST and
  MIME
• WSDL descriptions can be made available from an
  UDDI registry

WSDL Document
Types
Messages
Port Types
Bindings
Services
23
WSDL Example
lt?xml version"1.0" encoding"UTF-8"?gt ltdefinition
s name"FlightService" targetNamespace...gt
ltmessage name"getFlightArrival"gt ltpart
name"String_1" type"xsdstring"/gt
ltpart name"int_2" type"xsdint"/gt
lt/messagegt ltmessage name"getFlightArrivalRespo
nse"gt ltpart name"result"
type"xsddateTime"/gt lt/messagegt ltportType
name"FlightRemote"gt ltoperation
name"getFlightArrival"gt ltinput
message"tnsgetFlightArrival"/gt ltoutput
message"tnsgetFlightArrivalResponse"/gt
lt/operationgt lt/portTypegt
24
WSDL Sample (cont.)
ltbinding name"FlightRemoteBinding"
type"tnsFlightRemote"gt ltoperation
name"getFlightArrival"gt ltinputgtltsoapbody
encodingStyle"http//schemas.xmlsoap.org/soap/enc
oding/" use"encoded" namespace"http//allf
lighttracking.com/wsdl"/gt lt/inputgt ltoutputgtltsoap
body encodingStyle"http//sch
emas.xmlsoap.org/soap/encoding/"
use"encoded" namespace"http//allflighttrackin
g.com/wsdl"/gt lt/outputgt ltsoapbinding
transport"http//schemas.xmlsoap.org/soap/http"
style"rpc"/gt lt/bindinggt ltservice
name"Flight"gt ltport name"FlightRemotePo
rt" binding"tnsFlightRemoteBinding"gt
ltsoapaddress location"http//localhost8080/axi
s/..."/gt lt/portgt lt/servicegt lt/definiti
onsgt
25
SOAP/WSDL Applications

• Automatic proxy generation
• Web page equivalent services
• Information retrieval (quotes, weather, prices,
  etc.)
• Calculations (interest payments, currency and
  unit conversions, etc.)
• Simple actions (messaging, registration, etc.)
• Developing applications
• Connecting distributed program components (cross
  platform and cross programming language)
• Intrasystem software component communications

26
Web Services Applications

• Wrapper for other components
• Web-enable legacy applications
• Standard wrapper for any enterprise application
• Intranet architectural standard to reduce costs
  and improve development time and reliability
• Integrate middleware components, back-end
  resources, and legacy applications via a common,
  vendor-neutral, language-agnostic API
• B2B facilitator
• Faster time to market for integrating new
  partners into a supply chain or partner intranet
• Extranet portal enabler

27
Software Architecture Today

• Tightly-coupled
• Significant system changes (data model, web
  server, database, etc.) are difficult
• Changes to software architecture require
  unrelated components to be modified
• Long Development Cycles
• Slower time to market due to poor component reuse
• Additional time spent dealing with proprietary
  APIs
• Expensive
• High maintenance and integration costs due to a
  lack of standards and poor design

28
Web Services in a Nutshell

• Loosely Coupled
• Agreement on two things
• wire format (HTML, XML, WML, etc.)standardized
• protocol (HTTP, SMTP, TCP/IP, etc.)
• Implementation details are hidden
• Coarse-Grained
• Cross-network communication must maximize
  efficiency by reducing network round-trips
• Service exposes a façade that may hide many
  smaller services used to fulfill the clients
  request
• Asynchronous (yet conversational)
• Service-oriented requests cannot always be
  immediately performed (e.g. processing, approval,
  shipping, etc.)
• Ability to keep track of a conversation

29
Problem Solvency
30
Web Services Industry

• Microsoft .NET
• The .NET experience, aimed at the consumer
  market
• Imagine you wanted to turn up the heat in your
  house while you were away from home. You could
  use a .NET experience that controls your
  household utilities through a smart device. The
  device you use could be your desktop
  computersmart phoneor a kiosk.
• IBM Dynamic E-Business
• It is the dynamic adaptation of e-business
  processes and associated systems to support
  changing business strategies and tactics.
• For the first time, large companies can be as
  flexible and agile as start-ups in finding better
  ways to be more competitive.

31
Web Services Industry

• Sun ONE
• Smart Web Services contextual
• Integrateable platform as opposed to .NET being
  integrated and proprietary
• MindElectric Glue
• A free SOAP framework designed to speed time to
  market for developing web service components
• Instantly publish any Java object as a web
  service
• Apache Group Axis, SOAP
• Open source SOAP implementations
• Cooperation with Microsoft to ensure
  interoperability with Microsoft SOAP

32
Industry Projections

• IBM
• Web Services will be bigger than Java or XML
  Rod Smith, VP of Emerging Technology, IBM
• Forrester Research
• By 2003, the market for software components used
  to build services will represent a 14.5 billion
  industry.
• Gartner Group
• Within the next 4 years, 60 of all new business
  applications will utilize a service-oriented
  architecture
• By 2004, 40 of financial services transactions
  and 35 of online government services will be web
  service-based

33
Web Services and JBoss

• JBoss comes with axis web service
• jboss-net.sar ---- put in your deploy directory
• Web services may be deployed 2 ways
• Create a .jws file
• Any java class - combined with a web services
  deployment descriptor

34
.jws files

• Automatic Web Services
• Any java class - javaclassname
• File name must be javaclassname.jws
• Access the jws file
• http//localhost8080/TestApps/HelloWorldJWS.jws?w
  sdl
• Wsdl and deployment descriptor is generated
  automatically
• Must make mapping changes in web.xml

35
web.xml
ltservletgt ltservlet-namegtAxisServletlt/servlet-
namegt ltdisplay-namegtApache-Axis
Servletlt/display-namegt ltservlet-classgt
org.apache.axis.transport.http.AxisServlet
lt/servlet-classgt lt/servletgt lt!-- The axis
mappings --gt ltservlet-mappinggt
ltservlet-namegtAxisServletlt/servlet-namegt
lturl-patterngt/servlet/AxisServletlt/url-patterngt
lt/servlet-mappinggt ltservlet-mappinggt
ltservlet-namegtAxisServletlt/servlet-namegt
lturl-patterngt.jwslt/url-patterngt
lt/servlet-mappinggt ltservlet-mappinggt
ltservlet-namegtAxisServletlt/servlet-namegt
lturl-patterngt/services/lt/url-patterngt
lt/servlet-mappinggt
36
The Java client
import localhost.TestApps.AddFunctionJWS_jws. pu
blic class AddFunctionClient public static
void main(String args) try
AddFunctionJWSService afs new
AddFunctionJWSServiceLocator()
AddFunctionJWS af afs.getAddFunctionJWS()
System.out.print("addInt(" args0 ","
args1 ") ") System.out.println(
af.addInt(Integer.valueOf(args0).intV
alue(),
Integer.valueOf(args1).intValue())
) catch (Exception e)
System.err.println("Execution failed.
Exception " e)
37
Getting it all going

• WSDL2Java
• java org.apache.axis.wsdl.WSDL2Java
  http//localhost8080/TestApps/AddFunctionJWS.jws?
  wsdl
• Compile it
• Classpath must include
• . -- current directory
• All the axis jars found in jboss-net.sar
• Run it
• java AddFunctionClient 4 5

38
Exposing Other Classes

• Any java class can be exposed with SOAP
• Must be in classpath
• Must identify in web services deployment
  descriptor (web-services.xml)
• Goes in a .wsr file in the META-INF directory
• Most often, this is only thing in .wsr file
• Very useful for exposing EJBs

39
web-services.xml
lt?xml version"1.0" encoding"UTF-8"?gt ltdeploymen
t xmlns"http//xml.apache.org/axis/wsdd/
" xmlnsxsi"http//www.w3.org/2000/10/XML
Schema-instance" xmlnsjava"http//xml.ap
ache.org/axis/wsdd/providers/java"gt
ltservice name"HelloWorldService"
provider"javaRPC"gt ltparameter
name"className" value"myservice.HelloWorldServic
e"/gt ltparameter
name"allowedMethods" value""/gt
lt/servicegt ltservice name"ExampleEntityBe
an" provider"Handler"gt
ltparameter name"handlerClass" value"org.jboss.ne
t.axis.server.EJBProvider"/gt
ltparameter name"beanJndiName" value"MyExampleEnt
ityBean"/gt ltparameter
name"homeInterfaceName" value"ExampleEntityBeanH
ome"/gt ltparameter
name"allowedMethods" value""/gt
ltrequestFlow name"ExampleEntityBeanRequest"gt
lthandler name
"TransactionRequestHandler" type"javaorg.jboss.
net.axis.server.TransactionRequestHandler"/gt
lt/requestFlowgt
ltresponseFlow name"ExampleEntityBeanResponse"gt
lthandler name"Serialisation
ResponseHandler" type"javaorg.jboss.net.axis.ser
ver.SerialisationResponseHandler"/gt
lthandler name"TransactionResponseHandle
r" type"javaorg.jboss.net.axis.server.Transactio
nResponseHandler"/gt
lt/responseFlowgt lt/servicegt lt/deploymentgt

40
Calling a bean method via SOAP
public String MakeExampleEntityBeanServiceCall()
try
String endpoint "http//localhost8080/jbo
ss-net/services/ExampleEntityBean"
String methodName "EntityHello"
String arg "Quinn"
Service service new
Service() Call call
(Call) service.createCall()

call.setTargetEndpointAddress( new
java.net.URL(endpoint) )
call.setOperationName(methodName)
// Call to
addParameter/setReturnType as described in
user-guide.html
call.addParameter("name", org.apache.axis.Constant
s.XSD_STRING, ParameterMode.IN)
call.setReturnType(org.apache.axis.Constant
s.XSD_STRING)
String ret (String) call.invoke(
new Object arg )
return ret
catch (Exception e)
return("ExampleEntityBeanService
error " e.toString())