If I understand your question correctly, activators must have a default
constructor. You cannot have an activator that takes arguments, because
the framework has no way of supplying them.
-> richard
On 8/6/09 23:42, MichaelMichael wrote:
> Hi， Richard
> Thanks a lot for you help .Exactly what I want to know .One more short
> question please , thanks .I examine the code of Felix and find the place :
> Felix.createBundleActivator [1]
> What is the case when it comes to classes that newInstance() are not
> applicable , for example there is no constructor without a parameter .Is
> there a workaround other than newInstance() ?Thanks !![1] if (className !=
> null) { className = className.trim(); Class
> clazz; try { clazz =
> impl.getCurrentModule().getClassByDelegation(className); }
> catch (ClassNotFoundException ex) { throw new
> BundleException("Not found: " + className, ex); }
> activator = (BundleActivator) clazz.newInstance(); }
>
>
>> Date: Thu, 6 Aug 2009 10:44:58 -0400
>> From: he...@ungoverned.org
>> To: users@felix.apache.org
>> Subject: Re: A questions about the classloading mechanism in Felix
>>
>> On 8/6/09 10:24, MichaelMichael wrote:
>>
>>> Hi Richard
>>> Thanks for the reply.
>>> Right , the moduleClassloaderBut how does the jvm know which classloader to
>>> pick ??There are a number of bundles and so a number of modules Is there
>>> some tricks inside ?
>>>
>>>
>> It uses the class loader of the class needing to load the class.
>> Essentially, what happens is this:
>>
>> 1. The OSGi framework creates a class loader for each bundle.
>> 2. The OSGi framework loads the bundle's activator class using its
>> class loader.
>> 3. Any classes needed by the activator (and thus all of the bundle)
>> are requested from its class loader.
>>
>> So, the JVM always starts with the class loader of the class which is
>> executing. We don't need to worry about this, it is automatic. Now, not
>> all classes will come from the bundle, some will come from other
>> bundles. In standard Java classes are only loaded from parent class
>> loaders, but in OSGi parent class loaders are not used much.
>>
>> Instead, the bundle's class loader is "wired" to other bundle class
>> loaders (based on imports). So, when a request comes in for a class
>> (such as "new Foo()"), the instigating bundle's class loader is asked,
>> at which point it will go out and ask other bundles if it is importing
>> from them. This part happens in OSGi and it is framework implementation
>> specific.
>>
>> -> richard
>>
>>
>>>
>>>
>>>> Date: Thu, 6 Aug 2009 10:03:43 -0400
>>>> From: he...@ungoverned.org
>>>> To: users@felix.apache.org
>>>> Subject: Re: A questions about the classloading mechanism in Felix
>>>>
>>>> When a bundle loads a class it does NOT go through
>>>> Bundle.loadClass()...this is only if outside code wants to load a class
>>>> from a bundle. When a bundle loads a class, it is loaded from its own
>>>> class loader (called ModuleClassLoader in trunk). The call to this class
>>>> loader's loadClass() method is done automatically by the JVM as needed.
>>>>
>>>> -> richard
>>>>
>>>> On 8/5/09 22:27, MichaelMichael wrote:
>>>>
>>>>
>>>>> Hi all
>>>>> I studying classloading's in felix.I have made many search but there is
>>>>> still one thing I don't understand .
>>>>> The question :(correct if I am wrong )As we know a "new" will invoke a
>>>>> java.lang.classloader.load class normally.In felix , after the
>>>>> frameword(Felix) started , a "new ClassType()"(take the ClassType be a
>>>>> class could be found by the bundle ) will invoke the loadclass of
>>>>> Bundle.loadclass .I am always wandering how could this happens .I
>>>>> followed the source code , and also also tried the
>>>>> thread.setcontextclassloader,all failed .Recently I found that this
>>>>> should replace the systemclassloader ,is this correct ?But how to replace
>>>>> it after the launching of Felix ?
>>>>> Could anyone please explain this to me ?
>>>>> Thanks a billion !!!
>>>>>
>>>>> RegardsMichael
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>>>>>
>>>>>
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