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To illustrate the composition we will design a Hello World application named HelloComposition. This application offers a service writing a Hello message for each imported Person. Each person is published as a service and is used by the composition to write the message. <IMAGE1>Image Added

Application Design

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• an Hello Service : returning a Hello message
• a Directory service : aggregating Person services to create a Directory
• a Say Hello Service : requiring an Hello Service and a Directory Service to write Hello Service to person contained in the Directory.
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  An "instantiable" service is a service that we can instantiate through a Factory. The following code snippets show the different service specification:

  Code Block
  public interface Hello {

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• public void hello(String name); }

  Code Block
  public interface Directory {

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• public Person getPerson(String name);

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• public List<Person> getPersons();

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• public void addPerson(String name, String adress);

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• public void removePerson(String name); }

  Code Block
  public interface Person {

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• public String getName();

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• public String getAddress(); }

  Code Block
  public interface SayService {

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• public void say(); }

  So to design our application we will use these services to obtain the following applications.

Application Description

To describe our application, we will use the iPOJO ADL:

<composite name="HelloComposition" factory="Hello" architecture="true">
                               <import specification="org.apache.felix.ipojo.composition.ex1.person.Person"  aggregate aggregate="true"/>
                               <export specification="org.apache.felix.ipojo.composition.ex1.say.SayService"/>                      <service specification="org.apache.felix.ipojo.composition.ex1.hello.Hello"/>
                               <service specification="org.apache.felix.ipojo.composition.ex1.say.SayService"/>
                <service specification="org.apache.felix.ipojo.composition.ex1.directory.Directory"/>
</composite>

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<composite name="composite.bar ">
   <service specification="org.apache.felix.ipojo.test.scenarios.service.Hello">                                                  >
          <property name="language" value="en"/>
     </service>
</composite>

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<composite name="composite.bar " architecture="true"><service specification="org.apache.felix.ipojo.test.scenarios.service.Hello">                                                  >
              <property name="language" value="en"/>
</service></composite>

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More documentation on this feature comes soon.