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: [email protected]
>> To: [email protected]
>> 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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