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From Rick McGuire <rick...@gmail.com>
Subject Re: Questions on yoko Util class in yoko-rmi-spec should use the interface class as the key?
Date Tue, 11 Jan 2011 14:39:18 GMT
On 1/11/2011 9:20 AM, Ivan wrote:
>
> Hmm, I have to say that I know little about corba, just from the codes 
> of UtilLoader.loadClass, the first part of that method is trying to 
> load an implementation of the SPI, but the left part is just to load 
> the SPI itself, is it the expected behavior ?
Util.loadClass() is used for a lot more purposes than loading an SPI. 
The problem is occurring because the code is overloading the concepts on 
to the single loadClass() method.  What is needed to fix this problem is 
a solution specific to the task of loading an SPI.

Rick


> If we need to look up a specific provider for an interface, maybe it 
> is better to use the similar method suggested by you. which passing 
> both the SPI and defaultImpl class, then we might first try to look up 
> the impl by ProviderLocator, if failed, try to load the default impl 
> by context classloader or stack classloader...
> Thanks.
>
> 2011/1/11 Rick McGuire <rickmcg@gmail.com <mailto:rickmcg@gmail.com>>
>
>     On 1/11/2011 8:45 AM, Ivan wrote:
>
>         That makes sense, also it is better to remove the codes
>         ProviderLocator.loadClass from the UtilLoader.loadClass
>         method, or that makes the function of loadClass method ambigurous.
>
>
>     For other reasons, I believe it is still necessary to have
>     ProviderLocator.loadClass() part of the loadClass() searches.
>      This is a different, internal situation where we're looking for a
>     specific provider for an interface.
>
>     Rick
>
>
>         2011/1/11 Rick McGuire <rickmcg@gmail.com
>         <mailto:rickmcg@gmail.com> <mailto:rickmcg@gmail.com
>         <mailto:rickmcg@gmail.com>>>
>
>
>            On 1/11/2011 7:35 AM, Ivan wrote:
>
>                I agree with Forrest that those code logic might need to be
>                updated. From the codes fragment below of UtilLoader
>                In the loadClass method, it will first try the
>                ProviderLocator.loadClass, but what
>             ProviderLocation.loadClass
>                expect is an interface class name, like
>             javax.rmi.CORBA.Util.
>                So those codes in the static block of Util, it should
>             first try
>                to load it from ProviderLocator with service provider
>             interface.
>                Comments ?
>
>
>            I think the static code in the Util class should be
>         something like:
>
>
>            // Initialize delegate StringdelegateName=
>          
>          (String)AccessController.doPrivileged(newGetSystemPropertyAction("javax.rmi.CORBA.UtilClass",
>
>
>            defaultDelegate)); try{ // this is a little bit recursive, but
>            this will use the full default search order for locating //
>         this.
>                         delegate  =
>         (UtilDelegate)UtilLoader.loadServiceClass(delegateName,
>         Delegate.class).newInstance();
>            } catch(Throwablee) { org.omg.CORBA.INITIALIZEex=
>            neworg.omg.CORBA.INITIALIZE("Can not create Util delegate:
>
>            "+delegateName); ex.initCause(e); throwex; }
>
>            Where UtilLoader.loadServiceClass() is a method that functions
>            like UtilLoader.loadClass(), but takes both an interface class
>            name that is used to qualify the lookup.
>
>            Rick
>
>                -->
>                static public Class loadClass(String name, String codebase,
>                ClassLoader loader)
>                            throws ClassNotFoundException {
>                        Class result = null;
>
>                        try {
>                            return ProviderLocator.loadClass(name,
>             null, loader);
>                        } catch (ClassNotFoundException e) {
>                            //skip
>                        }
>
>                        ClassLoader stackLoader = null;
>                        ClassLoader thisLoader =
>             UtilLoader.class.getClassLoader();
>                        Class[] stack = _secman.getClassContext();
>                        for (int i = 1; i < stack.length; i++) {
>                            ClassLoader testLoader =
>             stack[i].getClassLoader();
>                            if (testLoader != null && testLoader !=
>             thisLoader)
>                            {
>                                stackLoader = thisLoader;
>                                break;
>                            }
>                        }
>                        ......
>             <---
>
>
>
>
>
>                2011/1/11 Rick McGuire <rickmcg@gmail.com
>             <mailto:rickmcg@gmail.com> <mailto:rickmcg@gmail.com
>             <mailto:rickmcg@gmail.com>>>
>
>
>                    On 1/11/2011 4:46 AM, Forrest Xia wrote:
>
>                        Hi,
>
>                        When I debug a corba related application, I
>             managed to
>                        trace into a piece of yoko code like this:
>
>                        public class Util {
>                           private static UtilDelegate delegate = null;
>                           private static final String defaultDelegate =
>                        "org.apache.yoko.rmi.impl.UtilImpl";
>
>                           // To hide the default constructor we should
>             implement
>                        empty private constructor
>                           private Util() {}
>
>                           static {
>                               // Initialize delegate
>                               String delegateName =
>                        (String)AccessController.doPrivileged(new
>                      
>              GetSystemPropertyAction("javax.rmi.CORBA.UtilClass",
>                        defaultDelegate));
>                               try {
>
>                                   // this is a little bit recursive,
>             but this
>                        will use the full default search order for locating
>                                   // this.
>                        delegate =
>             (UtilDelegate)Util.loadClass(delegateName,
>                        null, null).newInstance();
>                               } catch (Throwable e) {
>                                   org.omg.CORBA.INITIALIZE ex = new
>                        org.omg.CORBA.INITIALIZE("Can not create Util
>             delegate:
>                        "+delegateName);
>                                   ex.initCause(e);
>                                   throw ex;
>                               }
>                           }
>                        ...
>
>                        According to another code in
>                        ProviderRegistryImpl$SPIRegistry(the id's value
>             is the
>                        delegateName variable as highlighted above),
>             while the
>                        registry hashmap's key is
>             "javax.rmi.CORBA.UtilClass",
>                        that will lead CNF exception.
>                        private synchronized BundleProviderLoader
>                        getLoader(String id) {
>                                   // synchronize on the registry instance
>                                   if (registry != null) {
>                                       log.fine("registry: " + registry);
>                                       // return the first match, if any
>                                       List<BundleProviderLoader> list =
>                        registry.get(id);
>                                       if (list != null &&
>             !list.isEmpty()) {
>                                           return list.get(0);
>                                       }
>                                   }
>                                   // no match here
>                                   return null;
>                               }
>
>                        So my question is should we change the Util
>             code to pass
>                        the interface class name to load class? Please
>             advise.
>
>                    I'm not sure I understand the question.  The target
>             class in
>                    question here is a concrete delegate instance, so I
>             don't
>                    understand why you think an interface is needed
>             here.  The
>                    loading in question here is just for the delegate
>             class that
>                    is used for the rmi util class.
>
>                    In any event, you cannot change any of the method
>             signatures
>                    for the javax.rmi.CORBA.Util class.  That is a
>             standard API
>                    class and you can't add that.
>
>                    I think I understand what you wish to do here, and I'd
>                    recommend adding a loadServiceClass() method to the
>                    UtilLoader class and change the initializer in Util
>             to use
>                    that directly rather than recursively calling
>             Util.loadClass().
>
>                    Rick
>
>
>                        Forrest
>
>
>
>
>
>
>
>                --     Ivan
>
>
>
>
>
>         -- 
>         Ivan
>
>
>
>
>
> -- 
> Ivan


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