xdocs/howto/annotations.xml - turbine-core - Git at Google

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 <document>

  <properties>
   <title>Annotations Howto</title>
  </properties>

 <body>

 <section name="Annotations">

 <p>
 Turbine provides a number of annotations to inject dependencies into your actions,
 screens and layouts. All <code>Assemblers</code> that is, all modules of type
 <code>Action</code>, <code>Screen</code>, <code>Layout</code>, <code>Page</code>,
 <code>Navigation</code> and <code>ScheduledJob</code> as well as all
 <code>Valves</code> in the pipeline support the injection of services,
 configurations and loaders. This relieves you from the burden of looking
 them up at runtime and thus simplifies and accelerates the code.
 </p>

 <subsection name="@TurbineService">
 The annotation can only be used with a field.
 A declared field in a class annotated with <code>@TurbineService</code>
 gets injected an instance of this service at the time the instance
 of the class is created. The field should have the type of the service
 interface like in the following two examples:
 <source><![CDATA[
 // Explicit service name
 @TurbineService( "RunDataService" )
 private RunDataService runDataService;

 // Implicit SERVICE_NAME or ROLE
 @TurbineService
 private FactoryService factory;
 ]]></source>
 This is the equivalent of
 <source><![CDATA[
 runDataService = (RunDataService) TurbineServices
     .getInstance().getService("RunDataService");

 factory = (FactoryService) TurbineServices
     .getInstance().getService(FactoryService.ROLE);
 ]]></source>
 As you an see, the annotation supports an optional parameter, the
 name of the service in the Turbine service repository. If this
 parameter is not present, the annotation processor will look
 for the field <code>SERVICE_NAME</code> and then <code>ROLE</code>
 in the type class of the field to retrieve the service name. If none
 of them can be found, the fully qualified class name of the
 service interface is used to look up the service.
 <br />
 If the service instance cannot be found, the annotation processor
 will throw an exception.
 </subsection>

 <subsection name="@TurbineConfiguration">
 The annotation can only be used with a field.
 If a declared field of the type <code>Configuration</code> is annotated
 with <code>@TurbineConfiguration</code>, Turbine will inject an instance
 of the Turbine configuration object at the time the instance of the class
 is created.
 <source><![CDATA[
 // Injected configuration instance
 @TurbineConfiguration
 private Configuration config;

 // Injected configuration subset instance
 @TurbineConfiguration( "action" )
 private Configuration actionConfig;
 ]]></source>
 This is the equivalent of
 <source><![CDATA[
 config = Turbine.getConfiguration();

 actionConfig = Turbine.getConfiguration().subset("action");
 ]]></source>
 The annotation supports an optional parameter, the
 prefix of the configuration subset to retrieve.
 <br />
 If other fields having simple types are annotated with
 <code>@TurbineConfiguration</code>, Turbine will inject the corresponding
 configuration value. In this case, the annotation parameter defines the
 configuration key and is required. Strings, Lists and most simple types
 are supported. The value will only be set if the key is found in the
 configuration, so that the field can be initialized with a default value.
 <source><![CDATA[
 // Injected configuration value
 @TurbineConfiguration( "module.cache" )
 private boolean moduleCache = true;

 @TurbineConfiguration( "template.homepage" )
 private String templateHomepage;
 ]]></source>
 This is the equivalent of
 <source><![CDATA[
 moduleCache = Turbine.getConfiguration().getBoolean("module.cache", true);
 templateHomepage = Turbine.getConfiguration().getString("template.homepage");
 ]]></source>
 </subsection>

 <subsection name="@TurbineLoader">
 The annotation can only be used with a field.
 A declared field in a class annotated with <code>@TurbineLoader</code>
 gets injected an instance of the specified <code>Loader</code> at
 the time the instance of the class is created. The field should have
 the type of the loader.
 <source><![CDATA[
 // Injected loader instance
 @TurbineLoader( Action.class )
 private ActionLoader actionLoader;
 ]]></source>
 This is the equivalent of
 <source><![CDATA[
 actionLoader = TurbineAssemblerBroker.getLoader(Action.class);
 ]]></source>
 The annotation parameter is required and defines the type of module
 that is to be loaded.
 </subsection>

 <subsection name="@TurbineActionEvent">
 The annotation can only be used with a method.
 A method in a class annotated with <code>@TurbineActionEvent</code>
 is associated to a named action event. The annotation parameter
 is required and defines the name of the event. See the
 <a href="action-event-howto.html">Action Events Howto</a>
 for usage and examples.
 </subsection>

 <subsection name="Performance Considerations">
 It is important to note that the processing of the annotations at
 the time the module class is instantiated takes some time. It is
 therefore strongly recommended to re-use the module instances in
 a production environment by setting the configuration parameter
 <code>module.cache</code> to <code>true</code> in
 <code>TurbineResources.properties</code>.
 </subsection>

 </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>Annotations Howto</title>
	</properties>

	<body>

	<section name="Annotations">

	<p>
	Turbine provides a number of annotations to inject dependencies into your actions,
	screens and layouts. All <code>Assemblers</code> that is, all modules of type
	<code>Action</code>, <code>Screen</code>, <code>Layout</code>, <code>Page</code>,
	<code>Navigation</code> and <code>ScheduledJob</code> as well as all
	<code>Valves</code> in the pipeline support the injection of services,
	configurations and loaders. This relieves you from the burden of looking
	them up at runtime and thus simplifies and accelerates the code.
	</p>

	<subsection name="@TurbineService">
	The annotation can only be used with a field.
	A declared field in a class annotated with <code>@TurbineService</code>
	gets injected an instance of this service at the time the instance
	of the class is created. The field should have the type of the service
	interface like in the following two examples:
	<source><![CDATA[
	// Explicit service name
	@TurbineService( "RunDataService" )
	private RunDataService runDataService;

	// Implicit SERVICE_NAME or ROLE
	@TurbineService
	private FactoryService factory;
	]]></source>
	This is the equivalent of
	<source><![CDATA[
	runDataService = (RunDataService) TurbineServices
	.getInstance().getService("RunDataService");

	factory = (FactoryService) TurbineServices
	.getInstance().getService(FactoryService.ROLE);
	]]></source>
	As you an see, the annotation supports an optional parameter, the
	name of the service in the Turbine service repository. If this
	parameter is not present, the annotation processor will look
	for the field <code>SERVICE_NAME</code> and then <code>ROLE</code>
	in the type class of the field to retrieve the service name. If none
	of them can be found, the fully qualified class name of the
	service interface is used to look up the service.
	<br />
	If the service instance cannot be found, the annotation processor
	will throw an exception.
	</subsection>

	<subsection name="@TurbineConfiguration">
	The annotation can only be used with a field.
	If a declared field of the type <code>Configuration</code> is annotated
	with <code>@TurbineConfiguration</code>, Turbine will inject an instance
	of the Turbine configuration object at the time the instance of the class
	is created.
	<source><![CDATA[
	// Injected configuration instance
	@TurbineConfiguration
	private Configuration config;

	// Injected configuration subset instance
	@TurbineConfiguration( "action" )
	private Configuration actionConfig;
	]]></source>
	This is the equivalent of
	<source><![CDATA[
	config = Turbine.getConfiguration();

	actionConfig = Turbine.getConfiguration().subset("action");
	]]></source>
	The annotation supports an optional parameter, the
	prefix of the configuration subset to retrieve.
	<br />
	If other fields having simple types are annotated with
	<code>@TurbineConfiguration</code>, Turbine will inject the corresponding
	configuration value. In this case, the annotation parameter defines the
	configuration key and is required. Strings, Lists and most simple types
	are supported. The value will only be set if the key is found in the
	configuration, so that the field can be initialized with a default value.
	<source><![CDATA[
	// Injected configuration value
	@TurbineConfiguration( "module.cache" )
	private boolean moduleCache = true;

	@TurbineConfiguration( "template.homepage" )
	private String templateHomepage;
	]]></source>
	This is the equivalent of
	<source><![CDATA[
	moduleCache = Turbine.getConfiguration().getBoolean("module.cache", true);
	templateHomepage = Turbine.getConfiguration().getString("template.homepage");
	]]></source>
	</subsection>

	<subsection name="@TurbineLoader">
	The annotation can only be used with a field.
	A declared field in a class annotated with <code>@TurbineLoader</code>
	gets injected an instance of the specified <code>Loader</code> at
	the time the instance of the class is created. The field should have
	the type of the loader.
	<source><![CDATA[
	// Injected loader instance
	@TurbineLoader( Action.class )
	private ActionLoader actionLoader;
	]]></source>
	This is the equivalent of
	<source><![CDATA[
	actionLoader = TurbineAssemblerBroker.getLoader(Action.class);
	]]></source>
	The annotation parameter is required and defines the type of module
	that is to be loaded.
	</subsection>

	<subsection name="@TurbineActionEvent">
	The annotation can only be used with a method.
	A method in a class annotated with <code>@TurbineActionEvent</code>
	is associated to a named action event. The annotation parameter
	is required and defines the name of the event. See the
	<a href="action-event-howto.html">Action Events Howto</a>
	for usage and examples.
	</subsection>

	<subsection name="Performance Considerations">
	It is important to note that the processing of the annotations at
	the time the module class is instantiated takes some time. It is
	therefore strongly recommended to re-use the module instances in
	a production environment by setting the configuration parameter
	<code>module.cache</code> to <code>true</code> in
	<code>TurbineResources.properties</code>.
	</subsection>

	</section>

	</body>
	</document>