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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 07:37:02 GMT
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/

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