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Posted to commits@felix.apache.org by bu...@apache.org on 2018/10/09 23:09:56 UTC
svn commit: r1036215 - in /websites/staging/felix/trunk/content: ./
documentation/subprojects/apache-felix-dependency-manager/reference/service-scopes.html
Author: buildbot
Date: Tue Oct 9 23:09:56 2018
New Revision: 1036215
Log:
Staging update by buildbot for felix
Added:
websites/staging/felix/trunk/content/documentation/subprojects/apache-felix-dependency-manager/reference/service-scopes.html
Modified:
websites/staging/felix/trunk/content/ (props changed)
Propchange: websites/staging/felix/trunk/content/
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Added: websites/staging/felix/trunk/content/documentation/subprojects/apache-felix-dependency-manager/reference/service-scopes.html
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--- websites/staging/felix/trunk/content/documentation/subprojects/apache-felix-dependency-manager/reference/service-scopes.html (added)
+++ websites/staging/felix/trunk/content/documentation/subprojects/apache-felix-dependency-manager/reference/service-scopes.html Tue Oct 9 23:09:56 2018
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+<p>Title: Dependency Manager - Service Scopes</p>
+<p>By default service providers are registered once in the osgi registry, and all service consumers share the same service provider instance.
+Now, you can control the scope of the provided services: From the provider side, a "scope" parameter
+is available for all types of DM components and allows to define the scope of the registered service.</p>
+<p>The <code>scope</code> attribute has three enum values: SINGLETON, BUNDLE, PROTOTYPE</p>
+<ul>
+<li>SINGLETON: it's as before: your registered service is a singleton, meaning that the service must be
+instantiated and registered once, and all using services will share the same service instance of your component.</li>
+<li>BUNDLE: the service will be registered as a ServiceFactory, meaning an instance of the component must be
+created for each bundle using the service.</li>
+<li>PROTOTYPE: the service will be registered as a PrototypeServiceFactory, meaning the service is registered as
+a prototype scope service and an instance of the component must be created for each distinct service requester.</li>
+</ul>
+<p>Scoped Services are supported by all kind of DM service components:</p>
+<ul>
+<li>Component</li>
+<li>Aspects</li>
+<li>Adapters</li>
+<li>Bundle Adapters</li>
+<li>Resource Adapters</li>
+</ul>
+<p>When a consumer requests a service (using ServiceDependency), then DM will automatically
+dereference the service like this:</p>
+<ul>
+<li>if the service has a SERVICE_SCOPE service property matching SCOPE_PROTOTYPE, the DM will
+internally derefence the service using the ServiceObject API: so, the consumer will get its own copy
+of the requested service instance.</li>
+<li>else, DM will internally dereference the service, as before.
+When defining scoped component implementation, you can optionally define two special class fields
+in order to get injected with the client Bundle requesting the service, and the ServiceRegisgtration
+Object. Just use @Inject annotations in order to get injected with the client
+Bundle or the ServiceRegistration. You can also define a constructor which takes as argument the
+client bundle as well as the service registration.</li>
+</ul>
+<h1 id="examples">Examples<a class="headerlink" href="#examples" title="Permanent link">¶</a></h1>
+<p>So, here is a MyService component with PROTOTYPE scope, and each requester will get its own copy
+of MyService instance (the MyServiceImpl.start() method will be called for each MyServiceImpl
+instance):</p>
+<div class="codehilite"><pre><span class="kd">public</span> <span class="kd">class</span> <span class="nc">Activator</span> <span class="kd">extends</span> <span class="n">DependencyActivatorBase</span> <span class="o">{</span>
+ <span class="nd">@Override</span>
+ <span class="kd">public</span> <span class="kt">void</span> <span class="nf">init</span><span class="o">(</span><span class="n">BundleContext</span> <span class="n">context</span><span class="o">,</span> <span class="n">DependencyManager</span> <span class="n">dm</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">Exception</span> <span class="o">{</span>
+ <span class="n">dm</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="n">createComponent</span><span class="o">()</span>
+ <span class="o">.</span><span class="na">setScope</span><span class="o">(</span><span class="n">ServiceScope</span><span class="o">.</span><span class="na">PROTOTYPE</span><span class="o">)</span>
+ <span class="o">.</span><span class="na">setInterface</span><span class="o">(</span><span class="n">MyService</span><span class="o">.</span><span class="na">class</span><span class="o">.</span><span class="na">getName</span><span class="o">(),</span> <span class="kc">null</span><span class="o">)</span>
+ <span class="o">.</span><span class="na">setImplementation</span><span class="o">(</span><span class="n">MyServiceImpl</span><span class="o">.</span><span class="na">class</span><span class="o">));</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+
+<span class="kd">public</span> <span class="kd">class</span> <span class="nc">MyServiceImpl</span> <span class="kd">implements</span> <span class="n">MyService</span> <span class="o">{</span>
+ <span class="kt">void</span> <span class="nf">start</span><span class="o">()</span> <span class="o">{</span>
+ <span class="c1">// called on each MyService instance</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<p>The MyServiceImpl, like with annotations, can define a constructor in order to be injected with
+the client bundle invoking the service and also the service Registration:</p>
+<div class="codehilite"><pre><span class="kd">public</span> <span class="kd">class</span> <span class="nc">MyServiceImpl</span> <span class="kd">implements</span> <span class="n">MyService</span> <span class="o">{</span>
+ <span class="kd">public</span> <span class="nf">MyServiceImpl</span><span class="o">(</span><span class="n">Bundle</span> <span class="n">clientBundle</span><span class="o">,</span> <span class="n">ServiceRegistration</span> <span class="n">reg</span><span class="o">)</span> <span class="o">{</span> <span class="o">...</span> <span class="o">}</span>
+ <span class="kt">void</span> <span class="nf">start</span><span class="o">()</span> <span class="o">{</span>
+ <span class="c1">// called on each MyService instance</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<p>(if you want to auto configure the client Bundle, and the ServiceRegistration, then simply define class fields, they will be auto injected, unless you disable auto configuraiton for Bundle/ServiceRegistration using Component.setAutoConfig(Class, boolean) methods.</p>
+<p>Here is a Client component which simply depends on the MyService service using a basic DM
+activator (nothing special to do):</p>
+<div class="codehilite"><pre><span class="kd">public</span> <span class="kd">class</span> <span class="nc">Activator</span> <span class="kd">extends</span> <span class="n">DependencyActivatorBase</span> <span class="o">{</span>
+ <span class="nd">@Override</span>
+ <span class="kd">public</span> <span class="kt">void</span> <span class="nf">init</span><span class="o">(</span><span class="n">BundleContext</span> <span class="n">context</span><span class="o">,</span> <span class="n">DependencyManager</span> <span class="n">dm</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">Exception</span> <span class="o">{</span>
+ <span class="n">dm</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="n">createComponent</span><span class="o">()</span>
+ <span class="o">.</span><span class="na">setImplementation</span><span class="o">(</span><span class="n">Client</span><span class="o">.</span><span class="na">class</span><span class="o">)</span>
+ <span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="n">createServiceDependency</span><span class="o">()</span>
+ <span class="o">.</span><span class="na">setService</span><span class="o">(</span><span class="n">MyService</span><span class="o">.</span><span class="na">class</span><span class="o">,</span> <span class="kc">null</span><span class="o">).</span><span class="na">setRequired</span><span class="o">(</span><span class="kc">true</span><span class="o">).</span><span class="na">setCallbacks</span><span class="o">(</span><span class="s">"bind"</span><span class="o">,</span> <span class="s">"unbind"</span><span class="o">));</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+
+<span class="kd">public</span> <span class="kd">class</span> <span class="nc">Client</span> <span class="o">{</span>
+ <span class="kt">void</span> <span class="nf">bind</span><span class="o">(</span><span class="n">MyService</span> <span class="n">service</span><span class="o">)</span> <span class="o">{</span>
+ <span class="c1">// our client is injected with a specific instance of the MyService component </span>
+ <span class="c1">// that is created for our Client.</span>
+ <span class="c1">// If another component defines a service dependency on MyService, then the other </span>
+ <span class="c1">// component will get its own private copy of MyService component instance</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<h1 id="example-using-serviceobjects-api">Example using ServiceObjects API<a class="headerlink" href="#example-using-serviceobjects-api" title="Permanent link">¶</a></h1>
+<p>If now you want to control the creation of the MyService using raw OSGI ServiceObjects API,
+you can also do it like this:</p>
+<div class="codehilite"><pre><span class="kd">public</span> <span class="kd">class</span> <span class="nc">Client</span> <span class="o">{</span>
+ <span class="kt">void</span> <span class="nf">bind</span><span class="o">(</span><span class="n">ServiceObjects</span><span class="o"><</span><span class="n">MyService</span><span class="o">></span> <span class="n">so</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">MyService</span> <span class="n">s1</span> <span class="o">=</span> <span class="n">so</span><span class="o">.</span><span class="na">getService</span><span class="o">();</span>
+ <span class="n">MyService</span> <span class="n">s2</span> <span class="o">=</span> <span class="n">so</span><span class="o">.</span><span class="na">getService</span><span class="o">();</span>
+ <span class="o">...</span>
+ <span class="n">so</span><span class="o">.</span><span class="na">ungetService</span><span class="o">(</span><span class="n">s1</span><span class="o">);</span> <span class="c1">// will deactivate the MyService s1 instance</span>
+ <span class="n">so</span><span class="o">.</span><span class="na">ungetService</span><span class="o">(</span><span class="n">s2</span><span class="o">);</span> <span class="c1">// will deactivate the MyService s2 instance</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<h1 id="scoped-services-and-initdestroy-callbacks">Scoped services and init/destroy callbacks<a class="headerlink" href="#scoped-services-and-initdestroy-callbacks" title="Permanent link">¶</a></h1>
+<p>When you need to specify dynamic dependencies from your component.init() method,
+the following mechanism will be used:</p>
+<p>first, if your component defines an init callback, then one single component prototype instance singleton is created, as if the component is declared with SCOPE=SINGLETON.
+so, the prototype instance will be invoked in the init callback, but won't be started or stopped
+and when all dependencies are satisfied (including the dynamic dependencies),
+then the ServiceFactory (or PrototypeServiceFactory) is registered.
+And when one client will request a component instance, then a clone will be created and returned.</p>
+<p>Example of a scoped component which defines an init method:</p>
+<div class="codehilite"><pre><span class="kn">import</span> <span class="nn">org.apache.felix.dm.annotation.api.Component</span><span class="o">;</span>
+<span class="kn">import</span> <span class="nn">org.apache.felix.dm.annotation.api.ServiceScope</span><span class="o">;</span>
+
+<span class="nd">@Component</span><span class="o">(</span><span class="n">scope</span><span class="o">=</span><span class="n">ServiceScope</span><span class="o">.</span><span class="na">PROTOTYPE</span><span class="o">)</span>
+<span class="kd">public</span> <span class="kd">static</span> <span class="kd">class</span> <span class="nc">MyServiceImpl</span> <span class="kd">implements</span> <span class="n">MyService</span> <span class="o">{</span>
+
+ <span class="nd">@Init</span>
+ <span class="kt">void</span> <span class="nf">init</span><span class="o">(</span><span class="n">Component</span> <span class="n">comp</span><span class="o">)</span> <span class="o">{</span>
+ <span class="c1">// add dependencies dynamically</span>
+ <span class="o">}</span>
+
+ <span class="nd">@Start</span>
+ <span class="kt">void</span> <span class="nf">start</span><span class="o">()</span> <span class="o">{</span>
+ <span class="c1">// only called on clones, not on the prototype instance</span>
+ <span class="o">}</span>
+
+ <span class="nd">@Stop</span>
+ <span class="kt">void</span> <span class="nf">stop</span><span class="o">()</span> <span class="o">{</span>
+ <span class="c1">// called on each clone, not on the prototype instance singleton</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<h1 id="limitation-when-using-dm-servicedependency-from-api-and-serviceobjects">Limitation when using DM ServiceDependency from API and ServiceObjects<a class="headerlink" href="#limitation-when-using-dm-servicedependency-from-api-and-serviceobjects" title="Permanent link">¶</a></h1>
+<p>When using DependencyManager ServiceDependency from the native API (not using annotations),
+you have to know that the ServiceDependency always internally dereferences and creates the
+scoped service, even if you specify a ServiceObjecs
+parameter in your bind method. If now you really want to disable the auto-deref ServiceDependency
+(because you want to directly use the ServiceObjects API), you must then use the
+"setDereference(false") method on your ServiceDependency: in this way, you tell DM to never
+dereference internally the scoped service. Here is an example:</p>
+<div class="codehilite"><pre><span class="kd">public</span> <span class="kd">class</span> <span class="nc">Activator</span> <span class="kd">extends</span> <span class="n">DependencyActivatorBase</span> <span class="o">{</span>
+ <span class="nd">@Override</span>
+ <span class="kd">public</span> <span class="kt">void</span> <span class="nf">init</span><span class="o">(</span><span class="n">BundleContext</span> <span class="n">context</span><span class="o">,</span> <span class="n">DependencyManager</span> <span class="n">dm</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">Exception</span> <span class="o">{</span>
+ <span class="n">dm</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="n">createComponent</span><span class="o">()</span>
+ <span class="o">.</span><span class="na">setImplementation</span><span class="o">(</span><span class="n">Client</span><span class="o">.</span><span class="na">class</span><span class="o">)</span>
+ <span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="n">createServiceDependency</span><span class="o">()</span>
+ <span class="o">.</span><span class="na">setService</span><span class="o">(</span><span class="n">MyService</span><span class="o">.</span><span class="na">class</span><span class="o">,</span> <span class="kc">null</span><span class="o">).</span><span class="na">setRequired</span><span class="o">(</span><span class="kc">true</span><span class="o">).</span><span class="na">setCallbacks</span><span class="o">(</span><span class="s">"bind"</span><span class="o">,</span> <span class="s">"unbind"</span><span class="o">)</span>
+ <span class="o">.</span><span class="na">setDereference</span><span class="o">(</span><span class="kc">false</span><span class="o">));</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+
+<span class="kd">public</span> <span class="kd">class</span> <span class="nc">Client</span> <span class="o">{</span>
+ <span class="kt">void</span> <span class="nf">bind</span><span class="o">(</span><span class="n">ServiceObjects</span><span class="o"><</span><span class="n">MyService</span><span class="o">></span> <span class="n">so</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">MyService</span> <span class="n">s1</span> <span class="o">=</span> <span class="n">so</span><span class="o">.</span><span class="na">getService</span><span class="o">();</span>
+ <span class="n">MyService</span> <span class="n">s2</span> <span class="o">=</span> <span class="n">so</span><span class="o">.</span><span class="na">getService</span><span class="o">();</span>
+ <span class="o">...</span>
+ <span class="n">so</span><span class="o">.</span><span class="na">ungetService</span><span class="o">(</span><span class="n">s1</span><span class="o">);</span> <span class="c1">// will deactivate the MyService s1 instance</span>
+ <span class="n">so</span><span class="o">.</span><span class="na">ungetService</span><span class="o">(</span><span class="n">s2</span><span class="o">);</span> <span class="c1">// will deactivate the MyService s2 instance</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<p>In the above example, the Activator defines the ServiceDependency using the
+ServiceDependency.setDereference(false) method because it's the Client.bind method which will
+create the MyService instances manually.</p>
+<p>In the future, I will try to auto detect the signatures of the Client.bind method in order to
+never auto-dereference the injected service in case the bind method takes as argument a
+ServiceObjects (or a ServiceReference) method.</p>
+ <div class="timestamp" style="margin-top: 30px; font-size: 80%; text-align: right;">
+ Rev. 1843364 by pderop on Tue, 9 Oct 2018 23:09:14 +0000
+ </div>
+ <div class="trademarkFooter">
+ Apache Felix, Felix, Apache, the Apache feather logo, and the Apache Felix project
+ logo are trademarks of The Apache Software Foundation. All other marks mentioned
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