xdocs/index.xml - turbine-fulcrum-factory - Git at Google

 <?xml version="1.0"?>
 <!--
  Licensed to the Apache Software Foundation (ASF) under one
  or more contributor license agreements.  See the NOTICE file
  distributed with this work for additional information
  regarding copyright ownership.  The ASF licenses this file
  to you under the Apache License, Version 2.0 (the
  "License"); you may not use this file except in compliance
  with the License.  You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing,
  software distributed under the License is distributed on an
  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  KIND, either express or implied.  See the License for the
  specific language governing permissions and limitations
  under the License.
 -->

 <document>

   <properties>
     <title>Factory Component</title>
     <author email="epugh@upstate.com">Eric Pugh</author>
     <author email="tv@apache.org">Thomas Vandahl</author>
   </properties>

   <body>

   <section name="Overview">
 <p>
 The Factory Service instantiates objects from the given class name
 using either the given class loader or an applicable one found from the class
 loader repository. If neither one is specified, the default class loader
 will be used.
 </p>

 <p>
 The service provides the following benefits compared to Class.forName():
 </p>
 <ul>
 <li>support for parameters in constructors,</li>
 <li>internal class loader repository, which can be specified in resources,</li>
 <li>optional class specific factories, which can be used for customized instantiation, and</li>
 <li>integration with the Pool Service supporting recycling of instances created by the service.</li>
 </ul>
   </section>

 <section name="Configuration">
     <subsection name="Role Configuration">
       <source><![CDATA[
     <role
         name="org.apache.fulcrum.factory.FactoryService"
         shorthand="factory"
         default-class="org.apache.fulcrum.factory.DefaultFactoryService"/>
       ]]></source>
     </subsection>

     <subsection name="Component Configuration">
       <table>
         <tr>
           <th>Item</th>
           <th>Datatype</th>
           <th>Cardinality</th>
           <th>Description</th>
         </tr>
         <tr>
           <td>classloader</td>
           <td>String</td>
           <td>[0..n]</td>
           <td>
             A class loader. Class loaders will be tried in sequence when
             trying to create an object instance.
           </td>
         </tr>
         <tr>
           <td>object-factory</td>
           <td>Complex</td>
           <td>[0|1]</td>
           <td>
             The parent element for object factories. Sub-elements define
             factories for certain class names. You can define one
             <code>default</code> factory that will be used if no others
             match. See the configuration example below.
           </td>
         </tr>
       </table>
     </subsection>

     <subsection name="Component Configuration Example">
       <source><![CDATA[
     <factory>
         <classloader>java.net.URLClassLoader</classloader>
         <object-factory>
             <javax.xml.parsers.DocumentBuilder>
                 org.foo.xml.DomBuilderFactory
             </javax.xml.parsers.DocumentBuilder>
             <default>
                 org.some.default.Factory
             </default>
         </object-factory>
     </factory>
       ]]></source>
     </subsection>
   </section>

   <section name="Usage">
     <p>
       In Turbine, the Factory Service is currently only used internally by the Pool Service.
       Applications can also use the service instead of Class.forName() and for unifying
       initialization, configuration and access to vendor specific object factories.
       The following is a simplified example of a customized DOM parser factory:
     </p>

     <source><![CDATA[
 package org.foo.xml;

 import javax.xml.parsers.DocumentBuilder;
 import javax.xml.parsers.DocumentBuilderFactory;
 import javax.xml.parsers.ParserConfigurationException;

 import org.apache.fulcrum.factroy.FactoryException;
 import org.apache.fulcrum.factory.Factory;

 /**
  * A factory for instantiating DOM parsers.
  */
 public class DomBuilderFactory implements Factory<DocumentBuilder>
 {
     /**
      * The implementation of the factory.
      */
     private DocumentBuilderFactory factory;

     /**
      * Initializes the factory.
      */
     public void init(String className)
         throws FactoryException
     {
         factory = DocumentBuilderFactory.newInstance();
     }

     /**
      * Gets a DocumentBuilder instance.
      */
     public DocumentBuilder getInstance()
         throws FactoryException
     {
         try
         {
             return factory.newDocumentBuilder();
         }
         catch (ParserConfigurationException x)
         {
             throw new FactoryException(x);
         }
     }

     /**
      * Gets a DocumentBuilder instance.
      * The given loader is ignored.
      */
     public DocumentBuilder getInstance(ClassLoader loader)
         throws FactoryException
     {
         return getInstance();
     }

     /**
      * Gets a DocumentBuilder instance.
      * Constructor parameters are ignored.
      */
     public DocumentBuilder getInstance(Object[] params, String[] signature)
         throws FactoryException
     {
         return getInstance();
     }

     /**
      * Gets a DocumentBuilder instance.
      * The given loader and constructor parameters are ignored.
      */
     public DocumentBuilder getInstance(ClassLoader loader,
         Object[] params,
         String[] signature)
         throws FactoryException
     {
         return getInstance();
     }

     /**
      * Returns false as given class loaders are not supported.
      */
     public boolean isLoaderSupported()
     {
         return false;
     }
 }
 ]]></source>

     <p>
       The customized DOM parser factory must be specified in the component
       configuration like in the configuration example above before it can
       be used.
     </p>

     <p>
     A DOM parser can now be instantiated with the following code fragment:
     </p>

     <source><![CDATA[
 // Access the service singleton.
 FactoryService service = (FactoryService)container.lookup(FactoryService.ROLE);

 // Create a new DOM parser.
 DocumentBuilder parser =
     service.getInstance("javax.xml.parsers.DocumentBuilder");
 ]]></source>

   </section>
 </body>
 </document>
	<?xml version="1.0"?>
	<!--
	Licensed to the Apache Software Foundation (ASF) under one
	or more contributor license agreements. See the NOTICE file
	distributed with this work for additional information
	regarding copyright ownership. The ASF licenses this file
	to you under the Apache License, Version 2.0 (the
	"License"); you may not use this file except in compliance
	with the License. You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing,
	software distributed under the License is distributed on an
	"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
	KIND, either express or implied. See the License for the
	specific language governing permissions and limitations
	under the License.
	-->

	<document>

	<properties>
	<title>Factory Component</title>
	<author email="epugh@upstate.com">Eric Pugh</author>
	<author email="tv@apache.org">Thomas Vandahl</author>
	</properties>

	<body>

	<section name="Overview">
	<p>
	The Factory Service instantiates objects from the given class name
	using either the given class loader or an applicable one found from the class
	loader repository. If neither one is specified, the default class loader
	will be used.
	</p>

	<p>
	The service provides the following benefits compared to Class.forName():
	</p>
	<ul>
	<li>support for parameters in constructors,</li>
	<li>internal class loader repository, which can be specified in resources,</li>
	<li>optional class specific factories, which can be used for customized instantiation, and</li>
	<li>integration with the Pool Service supporting recycling of instances created by the service.</li>
	</ul>
	</section>

	<section name="Configuration">
	<subsection name="Role Configuration">
	<source><![CDATA[
	<role
	name="org.apache.fulcrum.factory.FactoryService"
	shorthand="factory"
	default-class="org.apache.fulcrum.factory.DefaultFactoryService"/>
	]]></source>
	</subsection>

	<subsection name="Component Configuration">
	<table>
	<tr>
	<th>Item</th>
	<th>Datatype</th>
	<th>Cardinality</th>
	<th>Description</th>
	</tr>
	<tr>
	<td>classloader</td>
	<td>String</td>
	<td>[0..n]</td>
	<td>
	A class loader. Class loaders will be tried in sequence when
	trying to create an object instance.
	</td>
	</tr>
	<tr>
	<td>object-factory</td>
	<td>Complex</td>
	<td>[0\|1]</td>
	<td>
	The parent element for object factories. Sub-elements define
	factories for certain class names. You can define one
	<code>default</code> factory that will be used if no others
	match. See the configuration example below.
	</td>
	</tr>
	</table>
	</subsection>

	<subsection name="Component Configuration Example">
	<source><![CDATA[
	<factory>
	<classloader>java.net.URLClassLoader</classloader>
	<object-factory>
	<javax.xml.parsers.DocumentBuilder>
	org.foo.xml.DomBuilderFactory
	</javax.xml.parsers.DocumentBuilder>
	<default>
	org.some.default.Factory
	</default>
	</object-factory>
	</factory>
	]]></source>
	</subsection>
	</section>

	<section name="Usage">
	<p>
	In Turbine, the Factory Service is currently only used internally by the Pool Service.
	Applications can also use the service instead of Class.forName() and for unifying
	initialization, configuration and access to vendor specific object factories.
	The following is a simplified example of a customized DOM parser factory:
	</p>

	<source><![CDATA[
	package org.foo.xml;

	import javax.xml.parsers.DocumentBuilder;
	import javax.xml.parsers.DocumentBuilderFactory;
	import javax.xml.parsers.ParserConfigurationException;

	import org.apache.fulcrum.factroy.FactoryException;
	import org.apache.fulcrum.factory.Factory;

	/**
	* A factory for instantiating DOM parsers.
	*/
	public class DomBuilderFactory implements Factory<DocumentBuilder>
	{
	/**
	* The implementation of the factory.
	*/
	private DocumentBuilderFactory factory;

	/**
	* Initializes the factory.
	*/
	public void init(String className)
	throws FactoryException
	{
	factory = DocumentBuilderFactory.newInstance();
	}

	/**
	* Gets a DocumentBuilder instance.
	*/
	public DocumentBuilder getInstance()
	throws FactoryException
	{
	try
	{
	return factory.newDocumentBuilder();
	}
	catch (ParserConfigurationException x)
	{
	throw new FactoryException(x);
	}
	}

	/**
	* Gets a DocumentBuilder instance.
	* The given loader is ignored.
	*/
	public DocumentBuilder getInstance(ClassLoader loader)
	throws FactoryException
	{
	return getInstance();
	}

	/**
	* Gets a DocumentBuilder instance.
	* Constructor parameters are ignored.
	*/
	public DocumentBuilder getInstance(Object[] params, String[] signature)
	throws FactoryException
	{
	return getInstance();
	}

	/**
	* Gets a DocumentBuilder instance.
	* The given loader and constructor parameters are ignored.
	*/
	public DocumentBuilder getInstance(ClassLoader loader,
	Object[] params,
	String[] signature)
	throws FactoryException
	{
	return getInstance();
	}

	/**
	* Returns false as given class loaders are not supported.
	*/
	public boolean isLoaderSupported()
	{
	return false;
	}
	}
	]]></source>

	<p>
	The customized DOM parser factory must be specified in the component
	configuration like in the configuration example above before it can
	be used.
	</p>

	<p>
	A DOM parser can now be instantiated with the following code fragment:
	</p>

	<source><![CDATA[
	// Access the service singleton.
	FactoryService service = (FactoryService)container.lookup(FactoryService.ROLE);

	// Create a new DOM parser.
	DocumentBuilder parser =
	service.getInstance("javax.xml.parsers.DocumentBuilder");
	]]></source>

	</section>
	</body>
	</document>