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Declaring component types

XML
<component
    classname="my.Implementation"
    name="my-type">
</component>
Annotations
@Component(name="my-type")
public class Implementation {
  // ...
}

Attribute name

Required

Default value

 

classname

yes

 

indicates the implementation class (automatic when using annotations).

name

no

implementation class name

specifies the component type name.

public
(public_factory for annotations)

no

true

specifies if the component type is accessible from others bundle or is private.

factory-method
(factory_method for annotations)

no

 

specifies a static method to call instead of the 'regular' constructor to create POJO objects.

Creating component instances

XML
<instance component="my-type"/>
<instance component="my.Implementation"/>
<instance component="my-type" name="my-instance"/>
<instance component="my-type" name="my-instance">
    <property name="property1" value="value1"/>
</instance>

Attribute name

Required

Default value

 

component

yes

 

specifies the component type (either by using the name or the class name)

name

no

generated

specifies the instance name.

  • Instances can contains a configuration given under the key-value form. Properties can also by complex type.
  • How-to use iPOJO factories
Annotations
@Component(name="my-type")
@Instantiate
public class Implementation {
  // ...
}

Providing services

XML
<component classname="my.service.implementation" name="my-service-impl">
   <provides/>
</component>
<instance name="my-service-impl"/>
Annotations
@Component
@Provides
public class Implementation implements FooService {
   ...
}
  • Only instances provides really services, so don't forget to declare an instance.
  • Published service interfaces must be implemented by your component implementation

    Attribute name

    Required

    Default value

     

    specifications

    no

    all implemented interfaces

    specifies the published service interfaces

    strategy

    no

    singleton

    specifies the service object creation policy among singleton, service (OSGi Service Factory), method (use the factory method), instance (an object per instance)

  • Providing OSGi services

Publishing service properties

XML
<component classname="my.service.implementation" name="my-service-impl">
  <provides>
	<property name="foo" field="m_foo" />
	<property name="bar" field="m_bar" mandatory="true" />
	<property name="baz" type="java.lang.String" /> <!-- Static property (do not change at runtime) -->
  </provides>
</component>
<instance name="my-service-impl"> <!-- The configuration has to inject value in unvalued mandatory properties -->
  <property name="bar" value="5"/>
  <property name="baz" value="my string"/>
<instance/>
Annotations
@Component
@Provides(specifications= {FooService.class, BarService.class},
properties= {
	@StaticServiceProperty(name="baz", type="java.lang.String")})
public class ProvidesProperties implements FooService, BarService {
    
    @ServiceProperty(name = "foo")
    public int m_foo = 0;
    
    @ServiceProperty(name="bar", mandatory=true)
    public int m_bar;
    
// ...
}

Attribute name

Required

Default value

 

name

no

field name

specifies the published property name

mandatory

no

false

specifies if the property has to receive a value from the instance configuration

value

no

 

specifies the default property value

field

no

(automatic with annotations)

specifies the field attached to the service property

type

Only if there is no field (generated)

Type of the property

Using services with field injection

XML
<component classname="my.consumer.Implementation">
    <requires field="fs" />
    <requires field="bs" />
</component>
Annotations
@Component
public class Dependency {

    @Requires
    public FooService fs;

    @Requires
    public BarService[] bs;
    
    //...
}

Attribute name

Required

Default value

 

id

no

field name

dependency id

field

no

automatically detected with annotations

injected field

optional

no

false

specifies if the dependency if optional

aggregate

no

false
(automatically detected with fields)

specifies if the dependency is aggregate of scalar

specification

yes/no

can be discovered from the code

specifies the required service specification. This attribute is required when the service type cannot be inferred from the code (Collection type for fields, callbacks without service objects)

filter

no

no filter

specifies the dependency LDAP filter

from

no

 

specifies a specific provider by its name

policy

no

dynamic

specifies the binding policy among dynamic, static and dynamic-priority

nullable

no

true

enables/disables nullable object injection for optional dependencies

default-implementation // defaultimplementation for annotations

no

 

specifies the default-implementation for optional dependencies

comparator

no

 

specifies the comparator class used to sort service providers

Using services with method injection

XML
<component classname="my.consumer.Implementation">
    <requires>
	<callback type="bind" method="bind" />
	<callback type="unbind" method="unbind" />
        <callback type="modified" method="modified" /> <!-- for filtered service dependencies, to be notified when a service is modified but still match -->
    </requires>	
</component>
Annotations
@Component
public class Dependency {

    @Unbind
    public synchronized void unbindBaz(BazService bz) {
        //...
    }
    
    @Bind
    public synchronized void bindBaz(BazService bz) {
        // ...
    }

    @Modified
    public synchronized void modifiedBaz() {
        // ...
    }

  //...
}

Attribute name

Required

Default value

 

id

no

field name

dependency id

field

no

automatically detected with annotations

injected field

optional

no

false

specifies if the dependency if optional

aggregate

no

false
(automatically detected with fields)

specifies if the dependnency is aggregate of scalar

specification

yes/no

can be discovered from the code

specifies the required service specification. This attribute is required when the service type cannot be infered from the code (Collection type for fields, callbacks without service objects)

filter

no

no filter

specifies the dependency LDAP filter

from

no

 

specifies a specific provider by its name

policy

no

dynamic

specifies the binding policy among dynamic, static and dynamic-priority

nullable

no

true

enables/disables nullable object injection for optional dependencies

default-implementation // default implementation for annotations

no

 

specifies the default-implementation for optional dependencies

comparator

no

 

specifies the comparator class used to sort service providers

Sub-Element name

Required

Default value

 

callback

no

callback specifies bind and unbind method. Two attributes are required (discovered automatically with annotations). type specified if the callback is a bind or unbind method (among {bind, unbind, modified}. The method attribute specified the method to call. The modified callback is called when the service properties of a bound service are modified and the service still match the filter.

Configuring service dependencies in the instance configuration

Configuring the from attribute

  • Thanks to the requires.from property, it is possible to override the from attribute value.
<component 
   classname="...MyComponent"
   name="FOO">
	<requires field="m_foo" id="id1">
		<callback type="bind" method="bind"/>
		<callback type="unbind" method="unbind"/>
	</requires>
</component>

<instance name="FOO1" component="FOO"/> <!-- Use the default 'from' value -->

<instance name="FOO2" component="FOO">
	<property name="requires.from">
		<property name="id1" value="myprovider"/>
	</property>
</instance>

Configuring the filter attribute

  • Thanks to the requires.filters property, it is possible to override the filter attribute value.
<component 
   classname="org.apache.felix.ipojo.example.FilteredDependency" 
   name="FOO">
	<requires field="m_foo" fiter="(foo.property=FOO)" id="id1">
		<callback type="bind" method="bind"/>
		<callback type="unbind" method="unbind"/>
	</requires>
</component>

<instance name="FOO1" component="FOO"/> <!-- Use the default 'filter' value -->

<instance name="FOO2" component="FOO">
	<property name="requires.filters">
		<property name="id1" value="(foo.property=BAR)"/>
	</property>
</instance>

Reacting to lifecycle state changes

Immediate components

  • A POJO object (implementation object) is created as soons as the instance becomes valid
  • Instances that don't provide services becomes automatically immediate
    XML
    <component classname="my.service.implementation" name="my-service-impl" immediate="true">
       <provides/>
    </component>
    
    Annotations
    @Component(immediate=true)
    @Provides
    public class Implementation implements FooService {
       ...
    }
    

    Attribute name

    Required

    Default value

     

    immediate

    no

    false // true for instances that don't provide a service

    specifies if the instance is immediate or not

  • Lifecycle Callback Handler

Lifecycle callbacks

XML
<component classname="my.implementation" name="my-impl">
    <callback transition="validate" method="start" />
    <callback transition="invalidate" method="stop" />
</component>
Annotations
@Component
public class Implementation {
    
    @Validate
    public void start() {
        
    }
    
    @Invalidate
    public void stop() {
        
    }
}

Declaring properties

XML
<component classname="my.Implementation" name="my-impl">
    <properties propagation="true" managedservice="MyPID">
        <property name="boo" method="setBoo" />
	<property field="m_bar" mandatory="true"/>
	<property field="m_foo" value="4"/>
    </properties>
</component>
<instance component="my-impl">
    <property name="boo" value="..."/>
    <property name="m_bar" value="..."/>
</instance>
<instance component="my-impl">
    <property name="boo" value="..."/>
    <property name="m_bar" value="..."/>
    <property name="managed.service.pid" value="AnotherPID"/>
</instance>
Annotations
@Component(managedservice="MyPID", propagation=true)
public class Implementation {
    
    @Property(name="boo")
    public void setBoo(int boo) {
        //...
    }
        
    @Property(mandatory=true)
    public int m_bar;

    @Property(value="4")
    public int m_foo;
}

Attribute name

Required

Default value

 

propagation

no

false

specifies if the properties propagation (properties are also published as service properties) is enabled or disabled

managedservice

no

instance name

specifies the PID of the published managed service. // This value can be overidden by the managed.service.pid instance property

name

no

field name or computed from the method name

specifies if the the property name

value

no

 

specifies the default property value

field

no

automatically detected with annotations

specifies the field in which the property value will be injected

method

no

automatically detected with annotations

specifies the setter method in which the property value will be injected

mandatory

no

false

specifies if the property has to receive a value from the instance configuration

PostRegistration and PostUnregistration callbacks

  • This feature is part of the provided service handler, and so requires that the component provides a service.
  • The callback receives a ServiceReference as parameter.
    XML
    <component
         classname="...">
        <provides
    	post-unregistration="unregistered" post-registration="registered"/>
    </component>
    
    Annotations
    @PostRegistration
    public void registered(ServiceReference ref) {
    	System.out.println("Registered");
    }
    
    @PostUnregistration
    public void unregistered(ServiceReference ref) {
    	System.out.println("Unregistered");
    }
    
  • Provided Service Handler

Controlling service publication

  • This feature is part of the provided service handler, and so requires that the component provides a service.
  • It allows a component to force the un-publication of a service.
    XML
    <component
         classname="...">
        <provides>
            <controller field="controller" value="false"/>
        </provides>
    </component>
    
    Annotations
    @ServiceController(value="false")
    private boolean controller
    
  • Provided Service Handler

Using 'arch'

  • Deploy the 'arch' command bundle (available for Felix and Equinox)
  • Launch the 'arch' command in the OSGi Framework Shell
    Felix Shell
    arch => displays instances name & state (equivalent to arch \-instances)
    arch -instance $instance_name => displays complete information about the instance $instance_name
    arch -factories => display the list of available factories
    arch -factory $factory_name => display complete information about the factory $factory_name
    arch -handlers => list available handlers
    
    Felix Gogo
    ipojo:instances => displays instances name & state (equivalent to arch \-instances)
    ipojo:instance $instance_name => displays complete information about the instance $instance_name
    ipojo:factories => display the list of available factories
    ipojo:factory $factory_name => display complete information about the factory $factory_name
    ipojo:handlers => list available handlers
    

Temporal Dependencies

  • Temporal dependencies are injected in fields. When accessing to the service, the thread waits for the service availability. If a timeout is reached, a timeout policy is executed.
  • Service objects can be injected as proxies and be given to collaborator objects.
  • Temporal dependencies are implemented as an external handlers. To use them, deploy and start the temporal dependency handler bundle.
XML
<iPOJO xmlns:temporal="org.apache.felix.ipojo.handler.temporal">
<component
    className="my.Implementation">

    <!-- Temporal dependency configuration -->
    <temporal:requires field="mytemporal"/>
    <provides/>
</component>
</iPOJO>
Annotations
import org.apache.felix.ipojo.annotations.Component;
import org.apache.felix.ipojo.handler.temporal.Requires;
import org.apache.felix.ipojo.test.scenarios.annotations.service.FooService;

@Component
public class Implementation {
    
    @Requires // org.apache.felix.ipojo.handler.temporal.Requires
    private FooService mytemporal;
    
}

Attribute name

Required

Default value

 

field

no

automatically detected with annotations

specifies the field in which the service object will be injected

timeout

no

3000 ms

specifies the timeout value (in ms). When the timeout is reached, the on timeout policy is executed

onTimeout

no

Runtime Exception

specifies the on timeout policy. Possible values are: null, nullable, empty, default-implementation (class name)

specification

only when using Collections

 

specifies the required service specification. This attribute is required when the injected field is a Collection

proxy

no

false

enables/disables proxy injection. Service injected as proxies can be given to collaborators

filter

no

no filter

Filter use to discover matching filter.

Sending and receiving events

Receiving events

  • The event admin handler allows receiving events from the Event Admin.
  • The event admin handler is implemented as an external handlers. To use it, deploy and start the event admin handler bundle and an implementation of the event admin service.
  • Event (or data) are receive thanks to a callback method.
XML
<ipojo
    xmlns:ev="org.apache.felix.ipojo.handlers.event.EventAdminHandler">
	<component className="...MyComponent">
		<ev:subscriber
			name="mySubscriber"
			callback="receive"
			topics="foo"/>
	</component>
</ipojo>
Annotations
@Component
public class MyComponent {
    
    @Subscriber(name="s1", data_key="data")
    public void receive1(Object foo) {
        // Nothing
    }
    
    @Subscriber(name="s2", topics="foo,bar", filter="(foo=true)")
    public void receive2(Event foo) {
        // Nothing
    }
    
    
    @Subscriber(name="s3", topics="foo", data_key="data", data_type="java.lang.String")
    public void receive3(String foo) {
        // Nothing
    }

Attribute name

Required

Default value

 

name

yes

 

specifies the name of the event subscriber, acting as a unique identifier. This name is used to configure event subscription in the instance configuration.

callback (or method)

yes
automatically detected with annotations

 

specifies The name of the method called each time an event is received. This method takes only one parameter, of type org.osgi.service.event.Event by default, but this type can be overridden by defining the data-key and/or the data-type attributes.

topics

yes

 

specifies the list (comma-separated-list) of the topics that the handler will listen to. Each event sent on a topic present in this list will be sent to the specified callback method. This parameter can be overridden by instances

data-key
data_key when using annotations

no

 

specifies the data key used when you want to receive data events. This attribute's value is the key corresponding to the received data in the event's dictionary.
If you use this attribute, the parameter passed to the callback method is the the value associated to this key, not the whole event. This attribute is generally used with the data-type attribute to specify the received object type. If an event is received and it does not contain such a key, it is ignored (with a warning message).

data-type
data_type when using annotations

no

java.lang.Object

specifies the type of objects (java.lang.Object by default) that the callback expects. It is used to determine the unique callback method (in case of multiple methods with the same name) and to check type compliance at event reception. Data events that are not corresponding to the specified type will be ignored (with a warning message).

filter

no

no filter

specifies the event LDAP filter used to filter incoming events before sending them to the callback. The syntax of this field is described in the OSGi EventAdmin Specification. If you don't specify a filter, all events sent on the listened topics will be considered.

  • Instance configuration
    • event.topics : overrides topics attribute
    • event.filter : overrides filter attribute
Instance configuration
<instance component="...MyComponent">
		<property name="event.topics">
			<property name="mySubscriber" value="foo"/>
		</property>
		<property name="event.filter">
			<property name="mySubscriber"
				    value="|((arg=Minibar)(arg=Coconuts))"/>
		</property>
	</instance>

Sending events

  • The event admin handler allows sending events to the Event Admin.
  • The event admin handler is implemented as an external handlers. To use it, deploy and start the event admin handler bundle and an implementation of the event admin service.
  • To send events, your code must contains a org.apache.felix.ipojo.handlers.event.publisher.Publisher field.
XML
<ipojo
    xmlns:ev="org.apache.felix.ipojo.handlers.event.EventAdminHandler">
	<component className="...MyComponent">
		<ev:publisher
			name="myPublisher"
			field="m_publisher"
			topics="bar,nuts"/>
	</component>
	<instance component="...MyComponent"/>
</ipojo>
Annotations

@Component
public class MyComponent {
    // We use qualified names to avoid conflict.
    @org.apache.felix.ipojo.handlers.event.Publisher(name="p1", synchronous=true)
    org.apache.felix.ipojo.handlers.event.publisher.Publisher publisher1;
    
    @org.apache.felix.ipojo.handlers.event.Publisher(name="p2", synchronous=false, topics="foo,bar", data_key="data")
    org.apache.felix.ipojo.handlers.event.publisher.Publisher publisher2;
    
    @org.apache.felix.ipojo.handlers.event.Publisher(name="p3", synchronous=true, topics="bar")
    org.apache.felix.ipojo.handlers.event.publisher.Publisher publisher3;

    // ...

    public void doSomething() {
        Dictionary e = new Properties();
        //...
        // Fill out the event

        // Send event
        publisher1.send(e);
    }
}

Attribute name

Required

Default value

 

name

yes

 

specifies the name of the event publisher, acting as a unique identifier. This name is used to configure event publishing in the instance configuration.

field

yes
automatically detected with annotations

 

specifies The name of the field used to send events. The field is initialized at component instantiation time. The type of the field must be : org.apache.felix.ipojo.handlers.event.publisher.Publisher.

topics

yes

 

specifies the list (comma-separated-list) of the topics on which events will be sent. This parameter can be overridden by instances

data-key
data_key when using annotations

no

user.data

specifies the data key used when you want to send data events. This attribute's value is the key, in the event's dictionary, in which sent data are stored. When you use the sendData method of the Publisher, the given object is placed in the event dictionary, associated with the specified data-key.

synchronous

no

false

specifies if event sending is synchronous or not.

  • Instance configuration
    • event.topics : overrides topics attribute
Instance configuration
<instance component="...MyComponent">
		<property name="event.topics">
			<property name="myPublisher" value="foo"/>
		</property>
	</instance>

Extender Pattern

  • Allows implementing an Extender pattern without handling obscure details
  • The extender pattern handler is implemented as an external handlers. To use it, deploy and start the external pattern handler bundle.
XML
<ipojo xmlns:extender="org.apache.felix.ipojo.extender">
	<component
		classname="org.apache.felix.ipojo.extender.Myextender">
		
                <!—Extender Pattern handler configuration -->
		<extender:extender 
                  extension="My-Extension"
                  onArrival="onArrival" 
                  onDeparture="onDeparture" 
                />

		<callback transition="invalidate" method="stopping" />
		<callback transition="validate" method="starting" />
	</component>
</ipojo>

Annotations
@Component
@org.apache.felix.ipojo.extender.Extender(extension="My-Extension", onArrival="onArrival", onDeparture="onDeparture")
public class Myextender {
    
    public void onArrival(Bundle bundle, String extension) {
        // handle matching bundle arrival
    }
    
    public void onDeparture(Bundle bundle) {
        // handler matching bundle departure
    }
}

Attribute name

Required

Default value

 

extension

yes

 

specifies the required extension (i.e. the required Manifest key)

onArrival

yes

 

specifies the method called when a matching bundle arrives. The method receives the Bundle object and the extension value

onDeparture

yes

 

specifies the method called when a matching bundle leaves. The method receives the Bundle object

Whiteboard Pattern

  • Allows implementing a Whiteboard pattern without handling obscure details
  • The whiteboard pattern handler is implemented as an external handlers. To use it, deploy and start the whiteboard pattern handler bundle.
XML
<ipojo xmlns:wbp="org.apache.felix.ipojo.whiteboard">
     <component 
          classname="org.apache.felix.ipojo.test.MyWhiteBoardPattern"
      >
        <wbp:wbp 
   	      filter="(my.property=1)" 
              onArrival="onArrival" 
              onDeparture="onDeparture" 
              onModification="onModification"
         />
       
         <provides/>
      </component>
Annotations
@Component
@org.apache.felix.ipojo.whiteboard.Wbp(filter="(my.property=1)", 
        onArrival="onArrival", 
        onDeparture="onDeparture",
        onModification="onModification")
public class WhiteBoardWIModification {
    
    public void onArrival(ServiceReference ref) {
        // ...
    }
 
    public void onDeparture(ServiceReference ref) {
        // ...
    }
    
    public void onModification(ServiceReference ref) {
        // ...
    }

}

Attribute name

Required

Default value

 

filter

yes

 

specifies LDAP filter used to detect required service providers

onArrival

yes

 

specifies the method called when a matching service provider arrives. The method receives the ServiceReference object

onDeparture

yes

 

specifies the method called when a matching service provider leaves. The method receives the ServiceReference object

omModification

no

 

specifies the method called when a matching service provider is modified and is still matching. The method receives the ServiceReference object

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