Apache Tuscany : Tuscany SCA Web Application Integration Story

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Tuscany SCA

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SCA Overview
+SCA Java
+SCA Native
+SCA PHP

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Tuscany SDO

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SDO Overview
+SDO Java
+SDO C++
+SDO PHP

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Tuscany DAS

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DAS Overview
+DAS Java
+DAS C++

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Web Application Integration story goals

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Simplify the web application as a client application story
Use a simple approach, familiar to all web application developers

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Integrating using ServletContextLister

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This approach register a context listener on the application web.xml that will bootstrap the runtime when the web-app is started, and closes the runtime when the web-app is shutdown.

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Necessary updates in web.xml

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+<listener>
+ <listener-class>org.apache.tuscany.sca.webapp.TuscanyContextListener</listener-class>
+</listener>
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Then, once this integration part is defined, developers only need to get a reference to the SCADomain in their JSP and then get a reference to a service and start consuming it
+Below, you can find the JSP code snippet to get a SCARuntime reference :

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+SCADomain domain = (SCADomain) application.getAttribute("org.apache.tuscany.sca.SCADomain");
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In order to use this approach, you will need to specify a sca-contribution.xml inside the META-INF directory of your web-app, this file will be used to identify the root of the contribution as well as the list of deployable composites.

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Here is a sample sca-contribution.xml used in the calculator-web application:

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+

+<?xml version="1.0" encoding="UTF-8"?>
+<contribution xmlns="http://www.osoa.org/xmlns/sca/1.0">
+   <deployable composite="Calculator"/>
+</contribution>
+

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Tuscany also supports the scenario where you would drop the SCA composite files inside the META-INF\sca-deployables directory, and this would also be used to identify the root of the contribution and the list of deployable composites.

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pros: Consistent programming model between JSP and Servlets
+cons: require web.xml integration and sca-contribution.xml, although the trend is to make web apps simpler and web.xml is optional in newer specs of J2EE

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Integrating using pure JSP code

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Integration using useBean tag: This approach would be very simple, and would basically ask the developer to add a useBean to instantiate the domain, and a setProperty to set the deployableComposite/

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+<jsp:useBean id="SCADomain" class="org.apache.tuscany.host.embedded.SCADomainBean" scope="application">
+ <jsp:setProperty property="deployableComposite" value="Calculator.composite" />
+</jsp:useBean>
+...
+<%
+ SCADomain domain = (SCADomain) application.getAttribute("SCADomain");
+ CalculatorService calculatorService = domain.getService(CalculatorService.class, "CalculatorServiceComponent");
+%>
+

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Optional attributes can be defined by using the <jsp:setProperty> calls, if no attributes are specified, the sca-contribution.xml will be used to hint the root of the contribution as well as to find the deployable composites.

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In this scenario, the SCADomain is stopped when the application goes out of scope and the garbage collection process the termination of the SCADomain.

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pros: simple, does not involve changes on web.xml
+cons: leaves toping the sca domain/runtime to when garbage collection process the application scope bean, also introduce different programming model between JSP and Servlets.

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References

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http://java.sun.com/j2ee/1.4/docs/tutorial/doc/
+http://java.sun.com/products/jsp/docs.html#syntax
+http://java.sun.com/products/jsp/tags/11/syntaxref11.fm14.html
+http://java.sun.com/products/javabeans/docs/spec.html

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