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From "Andrew Zhang" <zhanghuang...@gmail.com>
Subject Re: [classlib][lang] Is it possible to new an object without invoking any constructor?
Date Thu, 15 Nov 2007 06:46:40 GMT
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?

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/

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