spring-plugin/src/doc/hera-reference.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book [
<!ENTITY core SYSTEM "../../hera-core/src/doc/core.xml">
<!ENTITY metadata SYSTEM "../../hera-metadata/src/doc/metadata.xml">
]>
<!-- PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" 
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" -->
<book>
  <bookinfo>
    <title>Hera</title>

    <subtitle>The smallest plugin system ever</subtitle>

    <authorgroup>
      <author>
        <firstname>Oliver</firstname>

        <surname>Gierke</surname>

        <affiliation>
          <jobtitle>Software Architect</jobtitle>

          <orgname>Synyx GmbH &amp; Co. KG</orgname>
        </affiliation>

        <email>gierke@synyx.de</email>

        <address>Karlstraße 68, 76137 Karsruhe, Germany</address>
      </author>
    </authorgroup>

    <releaseinfo>V0.4</releaseinfo>

    <pubdate>23.03.2009</pubdate>

    <copyright>
      <year>2009</year>

      <holder>Synyx GmbH &amp; Co. KG</holder>
    </copyright>

    <revhistory>
      <revision>
        <date>04.11.2008</date>

        <author>
          <firstname>Oliver</firstname>

          <surname>Gierke</surname>
        </author>

        <revremark>Initial draft</revremark>
      </revision>

      <revision>
        <date>05.11.2008</date>

        <author>
          <firstname>Oliver</firstname>

          <surname>Gierke</surname>
        </author>

        <revremark>Added metadata module documentation</revremark>
      </revision>

      <revision>
        <date>24.01.2009</date>

        <author>
          <firstname>Oliver</firstname>

          <surname>Gierke</surname>
        </author>

        <revremark>Added remark to inner bean usage</revremark>
      </revision>

      <revision>
        <date>23.03.2009</date>

        <author>
          <firstname>Oliver</firstname>

          <surname>Gierke</surname>
        </author>

        <revremark>Added section on plugin ordering</revremark>
      </revision>
    </revhistory>
  </bookinfo>

  <preface>
    <title>Preface</title>

    <section>
      <title>Introduction</title>

      <para>Building extensible architectures nowadays is a core principle to
      create maintainable applications. This is why fully fledged plugin
      environments like <glossterm><abbrev>OSGi</abbrev></glossterm> are so
      poular these days. Unfortunately the introduction of
      <glossterm><abbrev>OSGi</abbrev></glossterm> introduces a lot of
      complexity to projects.</para>

      <para>Hera provides a more pragmatic approach to plugin development by
      providing the core flexibility of having plugin implementations
      extending a core system's functionality but of course not delivering
      core <abbrev>OSGi</abbrev> features like dynamic class loading or
      runtime installation and deployment of plugins. Although Hera thus is
      not nearly as powerful as <abbrev>OSGi</abbrev>, it servers little man's
      requirements to build a modular extensible application.</para>
    </section>

    <section id="preface.context">
      <title>Context</title>

      <para><itemizedlist spacing="compact">
          <listitem>
            <para>You want to build an extensible architecture minimizing
            overhead as much as possible</para>
          </listitem>

          <listitem>
            <para>You cannot use OSGi as fully fledged plugin architecture for
            whatever reasons</para>
          </listitem>

          <listitem>
            <para>You want to express extensibility by providing dedicated
            plugin interfaces</para>
          </listitem>

          <listitem>
            <para>You want to extend the core system by simply providing an
            implementation of the plugin interface bundled in a JAR file and
            available in the classpath.</para>
          </listitem>

          <listitem>
            <para>(You use Spring in your application)</para>
          </listitem>
        </itemizedlist></para>

      <para>The last point actually is not essential although Hera gains a lot
      of momentum in collaborative use with Spring.</para>
    </section>

    <section>
      <title>Technologies</title>

      <simplesect>
        <title>Spring</title>

        <para>Spring is the defacto standard application framework for Java
        applications. Its consistent programming model, easy configuration and
        wide support for all kinds of third party libraries makes it the first
        class citizen of application frameworks. Hera tightly integrates into
        Spring's component model and extends the core container with some
        custom functionality.</para>
      </simplesect>
    </section>
  </preface>

  &core;

  &metadata;

  <glossary>
    <glossdiv>
      <title>O</title>

      <glossentry>
        <glossterm>OSGi</glossterm>

        <glossdef>
          <para>Open Services Gateway Initiative - a fully fledged plugin
          runtime environment on top of the Java VM - <ulink
          url="http://en.wikipedia.org/wiki/OSGi">http://en.wikipedia.org/wiki/OSGi</ulink>.</para>
        </glossdef>
      </glossentry>
    </glossdiv>

    <glossdiv>
      <title>X</title>

      <glossentry>
        <glossterm>XML</glossterm>

        <glossdef>
          <para>eXtensible Markup Language</para>
        </glossdef>
      </glossentry>

      <glossentry>
        <glossterm>XSD</glossterm>

        <glossdef>
          <para>Xml Schema Definition</para>
        </glossdef>
      </glossentry>
    </glossdiv>
  </glossary>
</book>