Re: About FileXXXputStream 's implementation

From:
"=?gb2312?B?yMrV387etdA=?=" <huang.lightning@gmail.com>
Newsgroups:
comp.lang.java.programmer
Date:
17 Nov 2006 05:41:51 -0800
Message-ID:
<1163770911.567981.61450@h48g2000cwc.googlegroups.com>
To Gordon,Thomas:
      Thanks for your help and suggestion.

On 11=D4 17=C8=D5, =CF =CE=E79=CA=B123=B7=D6, Thomas Fritsch
<i.dont.like.s...@invalid.com> wrote:

=C8=CA=D5=DF=CE=DE=B5=D0 schrieb:> On 11=D4 17=C8=D5, =CF =CE=E78=CA=

=B119=B7=D6, Thomas Fritsch

<i.dont.like.s...@invalid.com> wrote:

=C8=CA=D5=DF=CE=DE=B5=D0 schrieb:
what's the native initIDs method of it used for?The initID method typic=

ally gets some JNI method IDs of the

FileXXXStream class and stores them somewhere in the C code. Later,
other native methods of the class can use these cached method IDs to
call the non-native methods of the class.


By using the first two, I'm sorry,
"env" and "jobject"

en,but initIDs is a static native method, lack the "jobject"...You don'=

t need it for getting method or field IDs.

however,
this method is only called once in the static area,what did it store
in C code?It might do for example look below:


#include "FileInputStream.h"

static jmethodID readMethodID;
static jmethodID closeMethodID;

void Java_FileInputStream_initIDs(JNIEnv *env, jclass c)
{
  readMethodID = env->GetMethodID(env, c, "read", "()I");
  closeMethodID = env->GetMethodID(env, c, "close", "()V");

}void Java_FileInputStream_exampleMethod(JNIEnv *env, jobject obj)
{
  env->CallVoidMethod(env, obj, closeMethodID);

}By the way: If you want a deeper understanding of JNI, I suggest you
work through Sun's JNI tutorial and/or a text-book.
 
--
Thomas

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