Expose an Stateless Session Bean as a Web Service

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Expose an Stateless Session Bean as a Web Service

• Jaliya Ekanayake

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Agenda

• Few Definitions
• The Basics of Web Services
• Benefits of Web Services
• Simple Web Service Example
• What is available in J2EE Technology
• EJB Web Services
• Exposing an EJB as a Web Service
• Tools Support
• Best Practices
• Sample Scenario

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Web Services - Basics

• Definitions
• Web service is a software application identified
  by a URI RFC 2396, whose interfaces and
  bindings are capable of being defined, described,
  and discovered as XML artifacts. A Web service
  supports direct interactions with other software
  agents using XML based messages exchanged via
  Internet-based protocols. W3C
• Web services--software components that are
  programmatically accessible over standard
  Internet protocols Java Blue Prints
• Web Services in 2005
• But ultimately what I really expect in this
  coming years that that Web services will go from
  that thing that you have tried once or twice, to
  an integral part of almost all your development
  projects. -Matt Powell the content strategist at
  the MSDN Web Services Developer Center.

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The Model
Client
Server
SOAP Handler
SOAP Handler
Client
Service
SOAP msg
SOAP msg
Network
The Web Services Model

• SOAP Handler
• Takes the parameters from the native client
  address space and transform (serialize) then to
  SOAP.
• Takes the SOAP from the network and transform
  (de-serialize) it to parameters of the native
  service address space.
• SOAP Handler may accept SOAP messages sent on
  various transport protocols.
• E.g. HTTP, SMTP, TCP etc..
• HTTP is the most popular protocol

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Benefits of Web Services

• Interoperability in a heterogeneous environment
• Business services through the Web
• Integration with existing systems
• Tools Support
• Support more client types
• Programming productivity

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Simple Web Service Example

• Simplest way is to use JSE(JAX-RPC Service
  Endpoint)
• Expose Java classes directly as web services
• Can use SOAP Endpoints based on Servlet
  Containers, e.g. Apache Axis
• E.g. JSE with SOAP over HTTP
• Example Using Apache Axis
• The Code Snippet for the Service gtgt
• The Code Snippet for the client gtgt
• Demo

SOAP Handler
Service
SOAP Over HTTP
Servlet Container
JAX-RPC Service Endpoint with SOAP Over HTTP
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What is available in J2EE Technology

• EJB components, by design, are meant for
  distributed computing
• EJB components are scalable, transactional, and
  secure
• J2EE Containers provide primary services such as
  Naming, Login, Transaction, Deployment and
  Security
• Developer can focus more on Business Logics
• Tons of applications have already bean written
  using EJBs

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EJB Web Services (JSR 109)

• J2EE 1.4 Allows JAX-RPC (JSR 101) Web Services
  using Stateless Session Beans.
• JAX-RPC hides the complexity of SOAP messages
  from the developer.
• J2EE web services can be invoked by any web
  service client, and any J2EE web service client
  can invoke any web service.

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Exposing an Stateless EJB as a Web Service

• Simple Steps
• Define the service interface (Depending on the
  business functionality that needs to be exposed)
  gtgt
• Generate the WSDL for the above service end point
  gtgt
• E.g. Using Java2WSDL from Apache
• java org.apache.axis.wsdl.Java2WSDL -a -o
  "CardValidatorService.wsdl" -n "urnejb-ws" -l
  "REPLACE_WITH_ACTUAL_URL" test.ejb.CardValidatorSe
  rvice
• Create or Generate JAX-RPC Mapping file gtgt
• Add the WSDL JAX-RPC Mapping file to the Manifest
• Modify the ejb-jar.xml gtgt
• Add webservices.xml gtgt
• Package and Deploy
• Demo
• Accessing the web service can be done by J2EE,
  J2SE, J2ME or any other clients that are running
  on different platforms.

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Tools Support

• Servers that support JSR109
• Sun Java System Application Server Platform
  Edition 8.1
• JBOSS-4.0.1RC1
• Oracle Application Server Containers for J2EE
  (OC4J) 10.0.3
• Sun ONE (Open Network Environment) Application
  Server
• IBM Websphere V6
• Weblogic Server 7.0
• Apache Geronimo
• IDEs and other tools
• Eclipse Lomboz Jboss (Open source tool set)
• IBM WebSphere Studio
• Sun Java System Application Server Platform
  Edition 8.1

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Best Practices

• Services should be coarse grain
• Avoid overusing Web services in your applications
• Design your Web service so that it creates
  minimal network traffic gtgt
• Avoid maintaining any kind of state information
  in your EJB components that are exposed as Web
  services.
• Use JAX-RPC data types as the method parameters
  for the Web service to give it interoperability
  with heterogeneous Web services
• Avoid types such as Collection, HashMap, and
  Lists as parameters for your Web service if
  interoperability is important for your
  application
• Avoid exposing an EJB component that involves
  long-running transactions as a Web service.
• Weigh the security requirements against
  performance, because security comes with a higher
  cost. The performance costs of end-to-end
  security are high.

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Known Limitations and Issues

• Some Web Service Standards are still in draft
  level
• May degrade the performance if used incorrectly
• Possible security threats (SOAP over HTTP)
• Interoperability issues (WS-I Basic Profile)
• Matching Requirements

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Sample Scenario
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Summary

• Basics of Web Services
• What is already there in J2EE
• How to expose an EJB as a Web Service
• Best Practices

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References

• JBOSS Documentation
• http//docs.jboss.org/jbossas/getting_started/star
  tguide40/ws.html
• Designing Web Services with the J2EE 1.4
  Platform JAX-RPC, SOAP, and XML Technologies
• http//java.sun.com/blueprints/guidelines/designin
  g_webservices/
• Web Services for J2EE, Version 1.0 (JSR109)
• ftp//www-126.ibm.com/pub/jsr109/spec/1.0/websvcs-
  1_0-fr.pdf
• Tutorial for building J2EE Applications using
  JBOSS and ECLIPSE
• http//www.tusc.com.au/tutorial/html/chap1.html
• http//www.javaworld.com/javaworld/jw-08-2004/jw-0
  802-ejbws.html
• http//publib.boulder.ibm.com/infocenter/iadthelp/
  index.jsp?topic/com.ibm.etools.webservice.doc/con
  cepts/cjsr109.html
• http//dev2dev.bea.com/products/wlserver/articles/
  Gilbode.jsp
• http//incubator.apache.org/projects/geronimo/
• http//java.sun.com/developer/technicalArticles/J2
  EE/j2ee_ws/design

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Thank You
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CardValidator Web Service (JSE)

• ltlt

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CardValidator Client (JSE)

• ltlt

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Web service endpoint for the stateless EJB

• ltlt

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ejb-jar.xml

• ltlt