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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.

How-to use iPOJO factories

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

Providing OSGi services

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

Service Requirement Handler

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.

Service Requirement Handler

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() {
        
    }
}

Lifecycle Callback Handler

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

Configuration Handler

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.

Temporal Service Dependency

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>

Event Admin Handlers

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);
    }
}

Event Admin Handlers

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
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

Extender Pattern Handler

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
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

White Board Pattern Handler

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Child pages

iPOJO-Reference-Card

Declaring component types

Creating component instances

Providing services

Publishing service properties

Using services with field injection

Using services with method injection

Configuring service dependencies in the instance configuration

Configuring the from attribute

Configuring the filter attribute

Reacting to lifecycle state changes

Immediate components

Lifecycle callbacks

Declaring properties

PostRegistration and PostUnregistration callbacks

Controlling service publication

Using 'arch'

Temporal Dependencies

Sending and receiving events

Receiving events

Sending events

Extender Pattern

Whiteboard Pattern

Configuring the `from` attribute

Configuring the `filter` attribute