SCA Java implementation.web (TUSCANY) edited by ant
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http://cwiki.apache.org/confluence/display/TUSCANY/SCA+Java+implementation.web
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http://cwiki.apache.org/confluence/pages/diffpagesbyversion.action?pageId=92446&originalVersion=4&revisedVersion=5
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h3. <implementation.web>
(!) This module is under development. What is described here reflects
unreleased trunk code and is subject to change. Your input and comments are
welcome
The Tuscany Java SCA runtime supports components implemented as JEE web modules
by using the <implementation.web> SCDL extension. Implementation.web is one of
the SCA extensions being formalized in the OASIS Open Composite Services
Architecture with a published [specification
|http://www.oasis-open.org/committees/download.php/28798/SCA_JAVAEE_Integration_V100.pdf]
document.
The web component implementation SCDL has the following format:
{code}
<implementation.web web-uri="<module name>" />
{code}
Implementation.web can be used by components such as Servlets, JSPs, and Web
2.0 style html pages. How it works depends on the way the Tuscany runtime is
being used.
h4. Using implementation.web with Servlets, Filters, and Event listeners
JEE Servlets, Filters, and Event listeners may acquire references to the
services wired to a component which use implementation.web as shown in the
following code snippets.
{code}
<component name="WebClient">
<implementation.web web-uri=""/>
<reference name="service" target="HelloworldService"/>
</component>
{code}
Then when using a JEE container with SCA integration (currently only a
prototype for Tomcat, see below) Servlets, Filters, and Event listeners can use
annotations to acquire references to the services wired to the component as
shown in the following Servlet code snippet (note the Servlet field name
'service' matches the reference name in the SCDL):
{code}
public class HelloworldServlet extends HttpServlet {
@Reference
protected HelloworldService service;
. . .
}
{code}
When the container does not have SCA integration then injection via annotations
does not work, so to work around this the services need to be manually got from
the ComponentContext which may be obtained from the application context. This
is shown in the following code snippet:
{code}
public class HelloworldServlet extends HttpServlet {
public void init(ServletConfig config) {
ComponentContext context =
(ComponentContext)config.getServletContext().getAttribute("org.osoa.sca.ComponentContext");
HelloworldService service = context .getService(HelloworldService.class,
"service");
. . .
}
. . .
}
{code}
See the
[helloworld-servlet|https://svn.apache.org/repos/asf/tuscany/java/sca/samples/helloworld-servlet/]
sample for the complete code of the above Servlet example.
h4. Using implementation.web with JSPs
A JSP tag library is available to expose SCA components in JSP pages. To use
SCA references within a JSP use a taglib to include the SCA tags and define the
reference field with the reference tag.
{code}
<component name="WebClient">
<implementation.web web-uri=""/>
<reference name="service" target="HelloworldService"/>
</component>
{code}
In the .jsp file:
{code}
<%@ taglib uri="http://www.osoa.org/sca/sca_jsp.tld"; prefix="sca" %>
<sca:reference name="service" type="sample.HelloworldService" />
<html>
<body >
<%= service.sayHello("world") %>
</body>
</html>
{code}
See the
[helloworld-jsp|https://svn.apache.org/repos/asf/tuscany/java/sca/samples/helloworld-jsp/]
sample for the complete code of the above JSP example.
h4. Using implementation.web with Web 2.0 style browser clients
Web 2.0 style pages can invoke SCA services by making RPC calls from the remote
browser client to the service-side SCA service. To do this the HTML page
includes Javascript code to import the SCA ComponentContext and then gets
service proxys from that ComponentContext. The org.osoa.sca.componentContext.js
script is generated by Tuscany when a component uses implementation.web.
In the SCDL the reference needs to specify one of the Tuscany Web2.0 bindings
such as binding.jsonrpc or binding.dwr.
(TODO: could this be avoided - something like make binding.jsonrpc the default
sca binding for web2.0 clients?)
{code}
<component name="WebClient">
<implementation.web web-uri=""/>
<reference name="service" target="HelloworldService">
<tuscany:binding.jsonrpc />
</reference>
</component>
{code}
In the html page:
{code}
<html>
<head>
<script type="text/javascript"
src="org.osoa.sca.componentContext.js"></script>
<script language="JavaScript">
function callSayHello() {
componentContext.getService("service").sayHello(
document.getElementById('name').value,
function(reply) {
document.getElementById('result').innerHTML=reply;
});
}
</script>
</head>
<body >
. . .
<input type="text" id="name" width="10">
<button name="submit" onclick="callSayHello()">Say hello</button>
<div id='result'></div>
. . .
</body>
</html>
{code}
See the
[helloworld-web|https://svn.apache.org/repos/asf/tuscany/java/sca/samples/helloworld-web/]
sample for the complete code of the above example.
(!) The following on Web 2.0 callbacks is not yet fully implemented, describing
here to encourage feedback
Tuscany Web 2.0 clients using implementation.web support SCA asynchronous
callbacks using what is known as [Comet or Reverse
Ajax|http://en.wikipedia.org/wiki/Comet_(programming)]. The only Tuscany
binding that currently supports this in binding.dwr.
The following shows the previous sample changed to use callbacks to receive the
replies. A callback binding is added to the reference in the SCDL and the
callback function is defined as a seperate Javascript function defined by the
client and attached to the service proxy object.
{code}
<component name="WebClient">
<implementation.web web-uri=""/>
<reference name="service" target="HelloworldService">
<tuscany:binding.dwr />
<callback>
<tuscany:binding.dwr />
</callback>
</reference>
</component>
{code}
In the html page:
{code}
<html>
<head>
<script type="text/javascript"
src="org.osoa.sca.componentContext.js"></script>
<script language="JavaScript">
componentContext.getService("service").sayHelloCallback =
function(reply) {
document.getElementById('result').innerHTML=reply;
};
function callSayHello() {
componentContext.getService("service").sayHello(document.getElementById('name').value);
}
</script>
</head>
<body >
. . .
<input type="text" id="name" width="10">
<button name="submit" onclick="callSayHello()">Say hello</button>
<div id='result'></div>
. . .
</body>
</html>
{code}
See the
[helloworld-web-callback|https://svn.apache.org/repos/asf/tuscany/java/sca/samples/helloworld-web-callback/]
sample for the complete code of the above example.
h4. Using implementation.web with the Tuscany runtime embedded within a webapp
This is the style all the current Tuscany webapp samples use. When using
implementation.web with the Tuscany runtime embedded within a webapp the
implementation.web web-uri attribute is ignored.
h4. Using implementation.web with the Tuscany runtime integrated into a JEE
server such as Tomcat or Geronimo
The only code that is currently working is some prototype code in the Tuscany
runtime-tomcat module that supports injecting references into Servlets, Filters
and Event listeners using the @Reference annotation.
h4. Using implementation.web with the Tuscany standalone runtime
Nothing implemented yet
h4. Using implementation.web with the Tuscany distributed domain runtime
Nothing implemented yet
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