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h1. How to use iPOJO annotations

_You can use annotations to define your component types. This page presents supported iPOJO annotations._

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h2. Getting iPOJO Annotations:

iPOJO Annotations are defines inside the org.apache.felix.ipojo.annotations project. You can download the Jar file of this project from the [download|Download] page. Sources are available on the [Felix trunk

|http://felix.apache.org/site/sourcecode.html].
Once added to your class path / build path / dependencies, you can use the annotations as normal annotations. These annotations are automatically processed by the iPOJO manipulator.

h3. In Eclipse

Add the org.apache.felix.ipojo.annotations jar file in your build path. Do not forget to use a Java compiler accepting annotations (1.5 or higher).

h3. In Maven

Add the following dependency:

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<dependency>
      <groupId>org.apache.felix</groupId>
      <artifactId>org.apache.felix.ipojo.annotations</artifactId>
      <version>1.2.0</version>
</dependency>
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Moreover, you need to set that the source code and the target code are Java 1.5 code. To achieve this, just add the following plugin in your plugins section:

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<plugin>
        <groupId>org.apache.maven.plugins</groupId>
	<artifactId>maven-compiler-plugin</artifactId>
	<configuration>
	  <source>1.5</source>
	  <target>1.5</target>
	</configuration>
</plugin>

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h3. In Ant

Just add the org.apache.felix.ipojo.annotations jar file  in your class path.

h2. An example of usage

To illustrate annotations usage, let taking the tutorial example. In this tutorial, there are two components:

* The first one provides the hello service

* The second one uses the provided hello service

You can download the archive containing the examples

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h2. Defined Annotations

This section lists defined annotations and how to use them.

h3. @Component

*Goal:* Defines a component type
*Target:* The component implementation class
*Attributes:*
* name : defines the component type name (optional, default = the class name)
* immediate: defines the component type as immediate (optional, default = "false")
* architecture: enable the architecture exposition (optional, default = "false")
* propagation: enable configuration property propagation (on provided services) (optional, default = "false")
* managedservice : set the Managed Service PID. (optional, default = no PID (i.e. the managed service will not be exposed)). 
* factory_method : set the factory-method. The specified method must be a static method and  return a pojo object.(optional,  default = iPOJO uses the 'regular' constructor). 
* public_factory : set if the component type is public. (optional, default = true). 

h3. @Provides

*Goal:* Defines that the component type provide services
*Target:* The component implementation class
*Attributes:*
* specifications: defines the provided interface (optional, default = all implemented interfaces)
* strategy : the service object creation strategy. Possible values : SINGLETON, SERVICE, METHOD, INSTANCE or the strategy class name. With SINGLETON there is only one POJO per component instance, SERVICE means OSGi Service factory,  METHOD delegates the creation to the factory-method of the component, INSTANCE creates one service object per requiring instance. For other strategies, specify the qualified name of the CreationStrategy class. (optional, default =  SINGLETON) 

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		<img src="http://people.apache.org/~clement/ipojo/site/information.gif"> <b>OSGi Service Factory</b>
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The <tt>SERVICE</tt> strategy means OSGi service factory. So, one service object per asking bundle will be created.
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		<img src="http://people.apache.org/~clement/ipojo/site/information.gif"> <b>Changes between the 1.0.0 and the 1.2.0</b>
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The <tt>factory</tt> attribute became <tt>strategy</tt>. A third policy is now available (<tt>instance</tt>) allowing to create one service object per asking instance. Moreover, it is also possible to indicates the <tt>CreationStrategy</tt> class name. 
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h3. @Requires

*Goal:* Defines a service dependency

*Target:* Field

*Attributes:

*
* Filter: defines the LDAP filter (optional)

* Optional: defines if the dependency is optional (optional, default = "false")

* Id: defines the dependency Id (useful to identify bind & unbind methods) (optional, default = field name) (if a dependency with the same id is already created (by a @bind or @unbind annotation), it merges the dependencies).

* Nullable: enable or disable the Null Object injection when the dependency is optional and no providers are available (optional, default = "true")

* Default-Implementation: set the Default-Implmentation (optional, by default iPOJO uses a Null object)

* Policy: defines the binding policy (accepted value : dynamic, static, dynamic-priority) (optional, default = "dynamic")

* Comparator: defines the comparator to use to sort service references (optional, default = OSGi Service Reference Comparator)

* From : defines the specific provider to use

* Specification : the required service specification. This attribute is required for Collection field. (optional, default = annotated field type).

 

h3. @ServiceProperty

*Goal:* Defines a service property

*Target:* Field

*Attributes:

*
* name: property name (optional, default=field name

* value: property value (optional, default=no value)

* mandatory : is the property mandatory? (optional, default=false)

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		<img src="http://people.apache.org/~clement/ipojo/site/information.gif"> <b>Mandatory property</b>
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A mandatory property must receive a value either from the component type description (<tt>value</tt> attribute, or the instance configuration.
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h3. @Property

*Goal:* Defines a property
*Target:* Field or Method
*Attributes:*
* name: property name (optional, default=field name computed by removing "set" from the method name (for instance setFoo(String ff) will get the Foo name))
* value: property value (optional, default=no value)
* mandatory : is the property mandatory? (optional, default=false)

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		<img src="http://people.apache.org/~clement/ipojo/site/information.gif"> <b>Field and Method</b>
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If another property with the same name is defined the method or the field is added to the existing property.
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h3. @Updated *\[ News in the 1.3.0-SNAPSHOT version \]*

*Goal:* Defines method called when a reconfiguration is completed.

*Target:* a method (receiving a dictionary in argument)

h3. @Bind

*Goal:* Defines a bind method

*Target:* Method

*Attributes:

*
* Id: Dependency Id, if the id is already defines in a "@requires " or "@unbind" annotation, it adds this method as a bind method of the already created dependency. (optional, default= no id, compute an id if the method name begin by "bind" (for instance "bindFoo" will have the "Foo" id))

* Specification : required dependency (optional)

* Aggregate : is the dependency an aggregate dependency (optional, default= "false")

* Optional: is the dependency an optional dependency (optional, default= "false")

* Filter: dependency LDAP filter (optional)

* Policy: defines the binding policy (accepted value : dynamic, static, dynamic-priority) (optional, default = "dynamic"

)
* Comparator: defines the comparator to use to sort service references (optional, default = OSGi Service Reference Comparator)

* From : defines the specific provider to use

h3. @Unbind

*Goal:* Defines an unbind method

*Target:* Method

*Attributes:

*
* Id: Dependency Id, if the id is already defines in a "@requires" or "@bind" annotation, it adds this method as an unbind method of the already created dependency. (optional, default= no id, compute an id if the method name begin by "unbind" (for instance "unbindFoo" will have the "Foo" id))

* Specification : required dependency (optional)

* Aggregate : is the dependency an aggregate dependency (optional, default= "false")

* Optional: is the dependency an optional dependency (optional, default= "false")

* Filter: dependency LDAP filter (optional)

* Policy: defines the binding policy (accepted value : dynamic, static, dynamic-priority) (optional, default = "dynamic")

* Comparator: defines the comparator to use to sort service references (optional, default = OSGi Service Reference Comparator)

* From : defines the specific provider

 to use

h3. @Validate

*Goal:* defines a validate lifecycle callback
*Target:* method

h3. @Invalidate

*Goal:* defines a validate lifecycle callback
*Target:* method

h3. Temporal Dependencies (external handler)

The temporal dependency handler is an external handler. However, it can be used with an annotation defined in the iPOJO annotations jar file. 
The annotation is org.apache.felix.ipojo.handler.temporal.Requires and targets a field.

 
*Attributes:

*
 * filter : specify the dependency filter

 * timeout : specify the dependency timeout (optional)

 * onTimeout : specify the onTimeout action (null, nullable, empty-array, default-implementation (specify the class name in this case) (optional).

 * specification : the required service specification. This attribute is required for Collection field. (optional, default = annotated field type).

 
 *  Proxy :  Inject a proxy instead of the real object. This allows passing this reference to collaborators. (Default = false) 



h3. Exposing instances as a JMX MBean (external handler)

The JMX Handler allows exposing an instance as a JMX MBean. To configure the JMX handler directly from your code, three annotations are provided. They are in the {{org.apache.felix.ipojo.handlers.jmx}} package

The {{@org.apache.felix.ipojo.handlers.jmx.Config}} ({{@Config}} if the package it correctly imported) annotation is a type annotation (so placed on the {{class}} element. This annotation indicates that the instance will be exposed as an MBean. This annotation supports:

* usesMOSGi: set to {{true}} to use MOSGi. Otherwise, the MBean will be exposed in the MBean Platform Server (default: {{false}}).

* objectname: set the MBean objectname. The objectname must follow JMX specification. (default: {{package-name:factory-name:instance-name}})

* domain: set the MBean domain. (default: {{package-name}})

* name: set the MBean name. (default: {{instance-name}}).

The {{@org.apache.felix.ipojo.handlers.jmx.Property}} ({{@Property}}) annotation is a field annotation indicating that the field is exposed in the MBean. The supported attributes are:

* name: set the property name

* rights: set the access permission. Possible values are {{r}} (read only) and {{w}} (read and write). By default, properties are in read-only mode.

* notification: enables notification on this property. By default notifications are disabled.

The {{@org.apache.felix.ipojo.handlers.jmx.Method}} ({{@Method}}) annotation is a method annotation indicating that the method is exposed in the MBean. Only one attribute can be customized:

* description: set the method description.


h2.

 Advanced topics and FAQ

h3. Metadata file and annotation merge

It is possible to defines component type both in the metadata file (in XML) and by using annotation. However, if a component type defined by using annotations has the same name than a type define in the XML file, the XML descriptor override the annotation defined type. However, a warning message is launched during the manipulation.

h3. Instance creation

Annotation can only be used to define component type. To define instances, you need to use the XML descriptor. Instance can refer to annotated types by referring to their names.

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h3. Using Custom Annotations

External handlers can provides their own annotations. Using these annotations just requires to add them to your build path. To external handlers annotations, please refer to the external handler documentation.
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