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<div class="content">
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Declaring component types
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<component
classname="my.Implementation"
name="my-type"
>
</component>
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@Component(name="my-type")
public class Implementation {
// ...
}
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How to declare instances
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Attribute name | Required | Default value | |
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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. |
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...
<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>
...
- Instances can contains a configuration given under the
key-value
form. Properties can also by complex type (refer to How-to use iPOJO factories)
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Creating component instances
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<component<instance classnamecomponent="my.service.implementation" name-type"/>
<instance component="my-service-impl".Implementation"/>
<instance <providescomponent="my-type" name="my-instance"/>
</component>
<instance component="my-type" name="my-service-implinstance"/>
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java | java |
title | Annotations |
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@Component
@Provides
public class Implementation implements FooService {
...
}
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...
<property name="property1" value="value1"/>
</instance>
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Attribute name | Required | Default value | |
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component | yes | | specifies the component type (either by using the name or the class name) | name | no | generated | specifies the instance name. |
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- Instances can contains a configuration given under the
key-value
form. Properties can also by complex type. - How-to use iPOJO factories
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@Component(name="my-type")
@Instantiate
public class Implementation {
// ...
}
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Providing services
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<component classname="my.service.implementation" name="my-service-impl">
<provides/> |
...
Publishing service properties
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xml | xml |
title | XML |
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<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/>
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java | java | title | Annotations |
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@Component
@Provides(specifications= {FooService.class, BarService.class})
public class ProvidesProperties implements FooService, BarService {
@ServiceProperty(name = "foo")
public int m_foo = 0;
@ServiceProperty(name="bar", mandatory=true)
public int m_bar;
// ...
}
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Consuming services
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@Component
@Provides
public class Implementation implements FooService {
...
}
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- Only instances provides really services, so don't forget to declare an instance.
- Published service interfaces must be implemented by your component implementation
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Attribute name | Required | Default value | |
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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) |
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- Providing OSGi services
Publishing service properties
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<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/> |
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xml | xml |
title | XML |
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<component classname="my.consumer.Implementation">
<requires field="fs" />
<requires>
<callback type="bind" method="bind" />
<callback type="unbind" method="unbind" />
</requires>
</component>
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@Component
public class Dependency {
@Requires
public FooService fs;@Provides(specifications= {FooService.class, BarService.class},
properties= {
@StaticServiceProperty(name="baz", type="java.lang.String")})
public class ProvidesProperties implements FooService, BarService {
@Unbind@ServiceProperty(name = "foo")
public void unbind(BazService bz) {int m_foo = 0;
//...
}@ServiceProperty(name="bar", mandatory=true)
public @Bind
int m_bar;
public void bind(BazService bz) {
// ...
}
//...
}
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Reacting to lifecycle state changes
Immediate components
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Attribute name | Required | Default value | |
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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 |
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Using services with field injection
...
<component classname="my.service.implementation" name="my-service-impl" immediate="true">
<provides/>
</component>
...
@Component(immediate=true)
@Provides
public class Implementation implements FooService {
...
}
...
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<component classname="my.implementation" name="my-impl"consumer.Implementation">
<callback<requires transitionfield="validate" method="startfs" />
<callback<requires transitionfield="invalidatebs" method="stop" />
</component>
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Code Block |
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@Component
public class ImplementationDependency {
@Validate@Requires
public void start() {
FooService fs;
}@Requires
public @InvalidateBarService[] bs;
public void stop() {
}
}
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Declaring properties
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Attribute name | Required | Default value | |
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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 |
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Using services with method injection
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<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>
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Code Block |
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@Component
public class Dependency {
@Unbind
public synchronized void unbindBaz(BazService bz) {
//...
}
@Bind
public synchronized void bindBaz(BazService bz) {
// ...
}
@Modified
public synchronized void modifiedBaz() {
// ...
}
//...
}
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Attribute name | Required | Default value | |
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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 | |
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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. |
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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.
Code Block |
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| xml |
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| xml |
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1 | From attribute configuration |
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<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>
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Configuring the filter
attribute
- Thanks to the
requires.filters
property, it is possible to override the filter
attribute value.
Code Block |
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| xml |
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| xml |
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1 | Filter attribute configuration |
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<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>
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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
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<component classname="my.service.implementation" name="my-service-impl" immediate="true">
<provides/>
</component>
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@Component(immediate=true)
@Provides
public class Implementation implements FooService {
...
}
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Attribute name | Required | Default value | |
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immediate | no | false // true for instances that don't provide a service | specifies if the instance is immediate or not |
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- Lifecycle Callback Handler
Lifecycle callbacks
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<component classname="my.implementation" name="my-impl">
<callback transition="validate" method="start" />
<callback transition="invalidate" method="stop" />
</component>
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@Component
public class Implementation {
@Validate
public void start() {
}
@Invalidate
public void stop() {
}
}
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Declaring properties
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<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>
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@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;
}
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Attribute name | Required | Default value | |
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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 |
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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. Code Block |
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<component
classname="...">
<provides
post-unregistration="unregistered" post-registration="registered"/>
</component>
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Code Block |
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@PostRegistration
public void registered(ServiceReference ref) {
System.out.println("Registered");
}
@PostUnregistration
public void unregistered(ServiceReference ref) {
System.out.println("Unregistered");
}
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- 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.
Code Block |
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<component
classname="...">
<provides>
<controller field="controller" value="false"/>
</provides>
</component>
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@ServiceController(value="false")
private boolean controller
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- Provided Service Handler
Using 'arch'
- Deploy the 'arch' command bundle (available for Felix and Equinox)
- Launch the 'arch' command in the OSGi Framework Shell
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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
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Code Block |
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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
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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.
Code Block |
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<iPOJO xmlns:temporal="org.apache.felix.ipojo.handler.temporal">
<component
className="my.Implementation">
<!-- Temporal dependency configuration -->
<temporal:requires field="mytemporal"/>
<provides/>
</component>
</iPOJO>
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Code Block |
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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;
}
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Attribute name | Required | Default value | |
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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. |
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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.
Code Block |
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<ipojo
xmlns:ev="org.apache.felix.ipojo.handlers.event.EventAdminHandler">
<component className="...MyComponent">
<ev:subscriber
name="mySubscriber"
callback="receive"
topics="foo"/>
</component>
</ipojo>
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Code Block |
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@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
}
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Attribute name | Required | Default value | |
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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. |
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- Instance configuration
- event.topics : overrides
topics
attribute - event.filter : overrides
filter
attribute
Code Block |
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| xml |
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| xml |
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title | Instance configuration |
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<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>
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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.
Code Block |
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<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>
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Code Block |
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@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);
}
}
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Attribute name | Required | Default value | |
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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. |
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- Instance configuration
- event.topics : overrides
topics
attribute
Code Block |
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| xml |
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| xml |
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title | Instance configuration |
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<instance component="...MyComponent">
<property name="event.topics">
<property name="myPublisher" value="foo"/>
</property>
</instance>
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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.
Code Block |
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<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>
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Code Block |
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@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
}
}
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Attribute name | Required | Default value | |
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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 |
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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.
Code Block |
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<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>
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Code Block |
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@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 |
Code Block |
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xml | xml | title | XML |
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<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>
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Code Block |
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java | java |
title | Annotations |
---|
@Component(managedservice="MyPID", propagation=true)
public class Implementation {
@Property(name="boo")
public void setBoo(int boo) {
// ...
}
public void onModification(ServiceReference @Property(mandatory=true)
ref) {
public int m_bar;
@Property(value="4")
public int m_foo;
}
| Center |
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Using 'arch'
Center |
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Attribute name | Required | Default value | |
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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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- White Board Pattern Handler
Include Page |
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| apache-felix-ipojo-footer |
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| apache-felix-ipojo-footer |
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- Deploy the 'arch' command bundle (available for Felix and Equinox)
- Launch the 'arch' command in the OSGi Framework Shell
Code Block |
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