Download Jaliya Ekanayake

Expose an Stateless Session Bean
as a Web Service
Jaliya Ekanayake
Agenda
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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
Web Services - Basics
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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
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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.
The Model
Client
SOAP
Handler
SOAP msg
SOAP msg
Network
Client
SOAP
Handler
Service
Server
The Web Services Model
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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
Benefits of Web Services
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Interoperability in a heterogeneous environment
Business services through the Web
Integration with existing systems
Tools Support
Support more client types
Programming productivity
Simple Web Service Example
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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
SOAP
Over HTTP
SOAP
Handler
Service
Servlet Container
JAX-RPC Service Endpoint with SOAP Over HTTP
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Example Using Apache Axis
 The Code Snippet for the Service >>
 The Code Snippet for the client >>
 Demo
What is available in J2EE Technology
Web Browser,
Applets
and optionally
Java Bean
Components
HTTP
JSPs
and Servlets
Session Beans
Entity Beans
Message Driven
Beans
Web Tier
Business Tier
RMI
Application Clients or IIOP
(Java)
Client Tier
J2EE Server
DB
EIS Tier
J2EE Architecture
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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
EJB Web Services (JSR 109)
Web Browser,
Applets
and optionally
Java Bean
Components
HTTP
JSPs
and Servlets
RMI
or IIOP
Application Clients
(Java)
Application Clients
(Java/Non Java)
Client Tier
SOAP
Session Beans
Entity Beans
Message Driven
Beans
DB
SOAP
Handler
Business Tier
Web Tier
J2EE Server
EIS Tier
Web Services in J2EE
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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.
Exposing an Stateless EJB as a Web Service
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Simple Steps
 Define the service interface (Depending on the business functionality that needs to
be exposed) >>
 Generate the WSDL for the above service end point >>
► E.g. Using Java2WSDL from Apache
 java org.apache.axis.wsdl.Java2WSDL -a -o
"CardValidatorService.wsdl" -n "urn:ejb-ws" -l
"REPLACE_WITH_ACTUAL_URL" test.ejb.CardValidatorService
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Create or Generate JAX-RPC Mapping file >>
Add the WSDL JAX-RPC Mapping file to the Manifest
Modify the ejb-jar.xml >>
Add webservices.xml >>
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
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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
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IDEs and other tools
 Eclipse + Lomboz+ Jboss (Open source tool set)
 IBM WebSphere Studio
 Sun Java™ System Application Server Platform Edition 8.1
Best Practices
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Services should be coarse grain
Avoid overusing Web services in your applications
Design your Web service so that it creates minimal network traffic >>
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.
Known Limitations and Issues
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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
Sample Scenario
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/startguide40/ws.html
► Designing Web Services with the J2EE 1.4 Platform: JAX-RPC, SOAP, and XML
Technologies
 http://java.sun.com/blueprints/guidelines/designing_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
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http://www.javaworld.com/javaworld/jw-08-2004/jw-0802-ejbws.html
http://publib.boulder.ibm.com/infocenter/iadthelp/index.jsp?topic=/com.ibm.etools.webs
ervice.doc/concepts/cjsr109.html
http://dev2dev.bea.com/products/wlserver/articles/Gilbode.jsp
http://incubator.apache.org/projects/geronimo/
http://java.sun.com/developer/technicalArticles/J2EE/j2ee_ws/#design
Thank You
CardValidator Web Service (JSE)
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CardValidator Client (JSE)
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Web service endpoint for the stateless EJB
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ejb-jar.xml
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