getting-started/src/middle-tier/trying-it-out.xml

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<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
		"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<section id="middle-tier.trying-it-out">
	<title>Trying out the JPA middle tier</title>
	<para>
		Open a Web browser and navigate to <ulink url="http://localhost:8080/greenpages">http://localhost:8080/greenpages</ulink>.
		Click the <emphasis>Submit</emphasis> button. Unfortunately the search will not return any results 
		as the Web bundle is still using the stub <literal>Directory</literal> implementation provided by the
		<literal>greenpages.app</literal> module, rather than the JPA-based implementation that is provided
		by <literal>greenpages.jpa</literal>. 
		This can be confirmed by using the Equinox console or the web-based admin console to examine the services being used
		by <literal>greenpages.web</literal>.
	</para>
	
	<para>
		The service which is being used by the Web bundle can be changed at runtime without having to restart the
		application or the @webserv@. This can be achieved by changing <literal>greenpages.app</literal> so that it no longer
		publishes its <literal>Directory</literal> implementation. As a result of this <literal>Directory</literal>
		service no longer being available, the Web bundle will automatically switch to using the JPA-based
		implementation.
	</para>
	
	<para>
		Open the <literal>osgi-context.xml</literal> file in the <literal>META-INF/spring</literal> folder of the
		<literal>greenpages.app</literal> project and comment out the publication of the directory service:
<programlisting><![CDATA[<!-- <osgi:service interface="greenpages.Directory" ref="directory"/> -->]]>
</programlisting>
	</para>
	
	<para>
		Now save the updated file which will cause the application to be updated and refreshed on the server. 
		Switch back to the Web browser and click
		<emphasis>Submit</emphasis> again.
	</para>
	
	<para>
		This time eight results should be returned. Clicking on any of the 
		<emphasis>View</emphasis> links will display the listing&rsquo;s details. 
		The application is now working.
        All that remains is to apply some best practices to the middle tier.
	</para>
</section>