Transcript Slide 1
Expose an Stateless Session Bean as a Web Service
Jaliya Ekanayake
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
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.
The Model
Client SOAP Handler SOAP msg Network SOAP msg SOAP Handler Service Client Server ► 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
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
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
SOAP Over HTTP
Service SOAP Handler Servlet Container JAX-RPC Service Endpoint with SOAP Over HTTP ► 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 Application Clients (Java) RMI or IIOP JSPs and Servlets Web Tier
Client Tier
Session Beans Entity Beans Message Driven Beans Business Tier
J2EE Server
J2EE Architecture DB
EIS Tier
► ► ► ► ► 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 RMI or IIOP Application Clients (Java) Application Clients (Java/Non Java) SOAP JSPs and Servlets SOAP Handler Web Tier
Client Tier
Session Beans Entity Beans Message Driven
J2EE Server
Web Services in J2EE Beans Business Tier DB
EIS Tier
► ► ► 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
► 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
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.
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
► ► ► ► ► ► ► ►
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 >> 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
► ► ► ► ► 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
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
► ► ► ► ► 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