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From "Sean Qiu" <sean.xx....@gmail.com>
Subject Re: [classlib][lang] Is it possible to new an object without invoking any constructor?
Date Thu, 15 Nov 2007 08:07:39 GMT
Interesting subject.
It seems harmony has so many functionalities to explore.

2007/11/15, Andrew Zhang <zhanghuangzhu@gmail.com>:
>
> On Nov 15, 2007 2:46 PM, Andrew Zhang <zhanghuangzhu@gmail.com> wrote:
>
> >
> >
> > On Nov 15, 2007 2:31 PM, Jimmy,Jing Lv <firepure@gmail.com> wrote:
> >
> > > 2007/11/15, Andrew Zhang <zhanghuangzhu@gmail.com>:
> > > > On Nov 15, 2007 1:22 PM, Jimmy,Jing Lv < firepure@gmail.com> wrote:
> > > >
> > > > > A simple thought is using the JNI call AllocObject(JNIEnv *env,
> > > jclass
> > > > > clazz);
> > > > > however we need to implement a native api then :)
> > > > >
> > > >
> > > > Thanks Jimmy!
> > > >
> > >
> > > :)
> > >
> > > > AllocObject looks like what I want. ObjectInputStream#newInstance is
> > > even
> > > > closer (it has defined a native method). Is it possible to refactor?
> > > > Comments? Thanks!
> > > >
> > >
> > > Hmm, it seems the current native method newInstance is used for
> > > ObjectInputStream itself, so refactor it may not be a good idea (will
> > > surely break Harmony function) .
> >
> >
> > No, I mean add a similar method in the ObjectInputStream, e.g private
> > static native allocObject(Class <?> c);
> >
> > Or put it in some util class in o.a.h package. Any comments or
> objections?
> >
>
> Found it! It's already in misc module.
>
>
> working_classlib\modules\misc\src\main\java\org\apache\harmony\misc\accessors\ObjectAccessor.java
>
> public final native Object allocateObject(Class c);
>
>
> >
> > I suggest define it in some utility
> > > class or your own class :)
> > >
> > > > Java_java_io_ObjectInputStream_newInstance (JNIEnv * env, jclass
> > > clazz,
> > > >                                             jobject
> > > instantiationClass,
> > > >                                             jobject
> constructorClass)
> > > > {
> > > >   jmethodID mid =
> > > >     (*env)->GetMethodID (env, constructorClass, "<init>", "()V");
> > > >
> > > >   if (mid == 0)
> > > >     {
> > > >       /* Cant newInstance,No empty constructor... */
> > > >       return (jobject) 0;
> > > >     }
> > > >   else
> > > >     {
> > > >       /* Instantiate an object of a given class and constuct it
> using
> > > >          the constructor of the other class. */
> > > >       jobject obj;
> > > >       obj = (*env)->AllocObject(env, instantiationClass);  // I want
> > > this
> > > > method :)
> > > >       if (obj != NULL) {
> > > >         (*env)->CallNonvirtualVoidMethod(env, obj, constructorClass,
> > > mid);
> > > >       }
> > > >       return obj;
> > > >     }
> > > >
> > > > }
> > > >
> > > >
> > > > > 2007/11/15, Andrew Zhang < zhanghuangzhu@gmail.com>:
> > > > > > Hi,
> > > > > >
> > > > > > Is it possible to new an object without invoking any
> constructor?
> > > I know
> > > > > the
> > > > > > question is a bit weird. What I want is to create an object
with
> > > all
> > > > > > null/default value for its fields.
> > > > > > Reseting all fields to null by reflection is a possible
> solution,
> > > but is
> > > > > > there any existing special method (no matter it's low level
or
> > > Harmony
> > > > > > specific) which can achieve this goal?
> > > > > > Thanks!
> > > > > >
> > > > > >
> > > > > > --
> > > > > > Best regards,
> > > > > > Andrew Zhang
> > > > > >
> > > > > > http://zhanghuangzhu.blogspot.com/
> > > > > >
> > > > >
> > > > >
> > > > > --
> > > > >
> > > > > Best Regards!
> > > > >
> > > > > Jimmy, Jing Lv
> > > > > China Software Development Lab, IBM
> > > > >
> > > >
> > > >
> > > >
> > > > --
> > > > Best regards,
> > > > Andrew Zhang
> > > >
> > > > http://zhanghuangzhu.blogspot.com/
> > > >
> > >
> > >
> > > --
> > >
> > > Best Regards!
> > >
> > > Jimmy, Jing Lv
> > > China Software Development Lab, IBM
> > >
> >
> >
> >
> > --
> >
> > Best regards,
> > Andrew Zhang
> >
> > http://zhanghuangzhu.blogspot.com/
> >
>
>
>
> --
> Best regards,
> Andrew Zhang
>
> http://zhanghuangzhu.blogspot.com/
>



-- 
Sean Qiu
http://xiaoxia.turendui.com

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