Does jni work?

Thu Jan 25 06:03:00 GMT 2001

Hi!
I tried to get a jni test working. I started by the example on the web and
adjusted to compile with gcj (newest snapshot 2001年01月22日 on linux)
These are the files:
===> Makefile <===
all: sample
%: %.java
	gcj -o $@ --main=$(basename $<) $<
libsample.so: sampNat.c sample.h
	gcc -shared -fPIC -o $@ $<
sample.class: sample.java
	gcj -C $< 
sample.h: sample.class
	gcjh -jni sample
sample: libsample.so sample.java
	 gcj -fjni -o $@ --main=sample -L. -lsample sample.java
clean:
	rm -f libsample.so *.class sample.h sampNat.o
===> sampNat.c <===
#include <jni.h>
#include "sample.h"
#include <stdio.h>
void Java_sample_myNative(JNIEnv* env, jobject this, jstring s)
{
 jclass cls;
 jfieldID fid;
 jobject obj;
 jmethodID mid;
 printf("From C\n");
 cls = (*env)->FindClass(env, "java/lang/System");
 if (cls == 0) {
 printf("java/lang/System lookup failed\n");
 return;
 }
 fid = (*env)->GetStaticFieldID(env, cls, "out", "Ljava/io/PrintStream;");
 if (fid == 0) {
 printf("java/lang/System::out lookup failed\n");
 return;
 }
 obj = (*env)->GetStaticObjectField(env, cls, fid);
 if (obj == 0) {
 printf("GetStaticObjectField call failed\n");
 return;
 }
 cls = (*env)->GetObjectClass(env, obj);
 if (cls == 0) {
 printf("GetObjectClass(out) failed\n");
 return;
 }
 mid = (*env)->GetMethodID(env, cls, "println", "(Ljava/lang/String;)V");
 if (mid == 0) {
 printf("println method lookup failed\n");
 return;
 }
 (*env)->CallVoidMethod(env, obj, mid, s);
}
===> sample.java<===
public class sample {
 public native void myNative(String s);
 public void myJava(String s) {
 s = s + ", Java";
 System.out.println(s);
 }
 public static void main(String args[]) {
 sample x = new sample();
 x.myJava("Hello");
 x.myNative("Hello, Java (from C)");
 x.myJava("Goodbye");
 }
 
 static {
 System.loadLibrary("sampNat");
 }
}
the program links successfully, but bombs at execution time with
Exception in thread "main" java.lang.UnsatisfiedLinkError: sampNat: file not found
 at 0x401984e9: java::lang::Throwable::Throwable(java::lang::String*) (/sw/snapshots/lib/libgcj.so.1)
 at 0x4018caf0: java::lang::Error::Error(java::lang::String*) (/sw/snapshots/lib/libgcj.so.1)
 at 0x4018ec40: java::lang::LinkageError::LinkageError(java::lang::String*) (/sw/snapshots/lib/libgcj.so.1)
 at 0x40198980: java::lang::UnsatisfiedLinkError::UnsatisfiedLinkError(java::lang::String*) (/sw/snapshots/lib/libgcj.so.1)
 at 0x4017cd1d: java::lang::Runtime::_load(java::lang::String*, bool) (/sw/snapshots/lib/libgcj.so.1)
 at 0x40190c66: java::lang::Runtime::loadLibrary(java::lang::String*) (/sw/snapshots/lib/libgcj.so.1)
 at 0x4019514e: java::lang::System::loadLibrary(java::lang::String*) (/sw/snapshots/lib/libgcj.so.1)
 at 0x0804bdc4: _ZN6sample_003cclinit_003eEvU (/home/kahlert/LOCAL/Hello/sample.java:17)
 at 0x40178b73: java::lang::Class::initializeClass() (/sw/snapshots/lib/libgcj.so.1)
 at 0x40175cd9: gnu::gcj::runtime::FirstThread::run() (/sw/snapshots/lib/libgcj.so.1)
 at 0x4018081b: java::lang::Thread::run_(java::lang::Object*) (/sw/snapshots/lib/libgcj.so.1)
 at 0x4028e405: _Jv_ThreadSetPriority(_Jv_Thread_t*, int) (/sw/snapshots/lib/libgcj.so.1)
 at 0x4042d6cc: GC_start_routine (/sw/snapshots/lib/libgcjgc.so.1)
 at 0x40445e93: pthread_detach (/lib/libpthread.so.0)
 at 0x4050565a: __clone (/lib/libc.so.6)
Did i make any mistake, or is this known not to work?
Thanks,
Martin.
-- 
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