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| <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"> |
| <chapter id="middle-tier" xmlns:xi="http://www.w3.org/2001/XInclude"> |
| <title>The Middle Tier</title> |
| <section id="middle-tier.introduction"> |
| <title>Introduction</title> |
| <para> |
| @greenpages@’ middle-tier provides implementations of the <literal>Directory</literal> and <literal>Listing</literal> |
| interfaces that can be used by the Web bundle. |
| The implementation will use EclipseLink JPA to access a database via a <literal>DataSource</literal> published in the |
| OSGi service registry. |
| </para> |
| |
| <section id="middle-tier.introduction.database"> |
| <title>The database</title> |
| <para> |
| The @greenpages@ application uses a very simple database that contains a single table. |
| The table, named <literal>LISTING</literal>, consists of four columns: |
| <informaltable pgwide="0"> |
| <tgroup cols="4"> |
| <tbody> |
| <row> |
| <entry><literal>LISTING_NUMBER</literal></entry> |
| <entry><literal>FIRST_NAME</literal></entry> |
| <entry><literal>LAST_NAME</literal></entry> |
| <entry><literal>EMAIL_ADDRESS</literal></entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable> |
| Scripts are provided with the sample source code (in <literal>$GREENPAGES_HOME/db</literal>) to start, create, and populate the database. |
| These will be used during the creation of the middle tier. |
| </para> |
| </section> |
| |
| <section id="middle-tier.introduction.jpa"> |
| <title>Using JPA</title> |
| <para> |
| The middle tier will provide JPA-based implementations of the <literal>Directory</literal> and <literal>Listing</literal> interfaces with the four |
| attributes of a <literal>Listing</literal> (first name, last name, email address, and id) being mapped to the corresponding columns in the |
| <literal>LISTING</literal>. |
| JPA will be used to implement the queries that search the database and return <literal>Listings</literal>. |
| </para> |
| </section> |
| |
| <section id="middle-tier.introduction.structure"> |
| <title>Structure</title> |
| <para> |
| The middle tier consists of two bundles, <literal>greenpages.jpa</literal> that publishes a <literal>Directory</literal> |
| implementation for consumption by the Web bundle, and <literal>greenpages.db</literal> to configure and publish the |
| <literal>DataSource</literal> used to access the database. |
| </para> |
| <mediaobject> |
| <imageobject role="fo"> |
| <imagedata fileref="images/middle-tier/structure.png" format="PNG" align="center" width="10cm"/> |
| </imageobject> |
| <imageobject role="html"> |
| <imagedata fileref="images/middle-tier/structure.png" format="PNG" align="center"/> |
| </imageobject> |
| </mediaobject> |
| </section> |
| </section> |
| |
| <xi:include href="create-db-project.xml"/> |
| <xi:include href="building-jpa-module.xml"/> |
| <xi:include href="trying-it-out.xml"/> |
| <xi:include href="applying-best-practices.xml"/> |
| |
| </chapter> |
