Can't find class because of try catch block ?!

Question

Hello,
I'm using the JNI to use a java library from my c++ code.
JNI can't find the "Comverse10" class below, but when i put the try catch block in createMessage in comment, FindClass succeeds ?!
Unfortunatly i need the code inside the try block ;-)
I tried a few things, but none of them worked:
- let createMessage throw the exception (public void createMessage throws ElementAlreadyExistsException ), so there isn't a try catch block in createMessage => result: the same
- make a "wrapper" class Comverse that has a Comverse10 object as attribute and just calls the corresponding Comverse10.function. Result: Comvers could be found, but not constructed (NewObject failed).
Can someone tell me what is going on ?!
Thank you,
Pieter.
//Comverse10 class
public class Comverse10 {
MultimediaMessage message;
/** Creates a new instance of Comverse10 */
public Comverse10() {
public void createMessage() {
TextMediaElement text1 = new TextMediaElement("Pieter");
text1.setColor(Color.blue);
SimpleSlide slide1 = new SimpleSlide();
//if i put this try catch block in comment, it works ?!
try{
slide1.add(text1);
catch(com.comverse.mms.mmspade.api.ElementAlreadyExistsException e){}
MessageContent content = new MessageContent();
content.addSlide(slide1);
this.message = new MultimediaMessage();
message.setContent(content);
message.setSubject("Mijn subjectje");
for those of you who are intersted: here's my C++ code:
//creation of JVM
HRESULT Java::CreateJavaVMdll()
     HRESULT HRv = S_OK;
char classpath[1024];
     jint res;
     if(blog)     this->oDebugLog->Printf("CreateJavaVMdll()");
     strcpy(classpath,"-Djava.class.path="); /*This tells jvm that it is getting the class path*/
     strcat(classpath,getenv("PATH"));
     strcat(classpath,";D:\\Projects\\RingRing\\MMSComposer;C:\\Progra~1\\j2sdk1~1.1_0\\lib");     //;C:\\Comverse\\MMS_SDK\\SDK\\lib\\mail.jar;C:\\Comverse\\MMS_SDK\\SDK\\lib\\activation.jar;C:\\Comverse\\MMS_SDK\\SDK\\lib\\mmspade.jar
     //------Set Options for virtual machine
     options[0].optionString = "-Djava.compiler=NONE"; //JIT compiler
     options[1].optionString = classpath;                                        //CLASSPATH
     //------Set argument structure components
     vm_args.options = options;
     vm_args.nOptions = 2;
     vm_args.ignoreUnrecognized = JNI_TRUE;
     vm_args.version = JNI_VERSION_1_4;
     /* Win32 version */
     HINSTANCE hVM = LoadLibrary("C:\\Program Files\\j2sdk1.4.1_01\\jre\\bin\\client\\jvm.dll");
     if (hVM == NULL){
          if(blog) oDebugLog->Printf("Can't load jvm.dll");
          return E_FAIL;
     if(blog) oDebugLog->Printf("jvm.dll loaded\n");
     LPFNDLLFUNC1 func = (LPFNDLLFUNC1)GetProcAddress(hVM, "JNI_CreateJavaVM");
     if(!func){
          if(blog)     oDebugLog->Printf("Can't get ProcAddress of JNI_CreateJavaVM");
          FreeLibrary(hVM);     hVM = NULL;
          return E_FAIL;
     if(blog)     oDebugLog->Printf("ProcAddress found");
     res = func(&jvm,(void**)&env,&vm_args);
     if (res < 0) {
if(blog)     oDebugLog->Printf("Can't create JVM with JNI_CreateJavaVM %d\n",res);
return E_FAIL;
     if(blog)     oDebugLog->Printf("JVM created");
     return HRv;
//finding Comverse10 class:
HRESULT CALLAS MMSComposer::InitializeJNI(void)
     HRESULT HRv=E_FAIL;
     DWORD T=0;
     try
          if(blog)     oDebugLog->Printf("\nInitializeJNI()");
          bJVM = FALSE;
          jni = new Java(oDebugLog);
          if(jni->CreateJavaVMdll()!=S_OK){
               if(blog)     oDebugLog->Printf("CreateJavaVMdll() failed");     
               return HRv;
          jclass jcls = jni->env->FindClass("Comverse10");
          if (jcls == 0) {
if(blog)     oDebugLog->Printf("Can't find Comverse10 class");
               jclass jcls2 = jni->env->FindClass("test");
               if (jcls2 == 0) {
                    if(blog)     oDebugLog->Printf("Can't find test class");
                    return HRv;
               if(blog)     oDebugLog->Printf("test class found %08x",jcls2);
return HRv;
          if(blog)     oDebugLog->Printf("Comverse10 class found %08x",jcls);
          jmethodID mid = jni->env->GetMethodID(jcls , "<init>", "()V");
          if (mid == 0) {
               if(blog)     oDebugLog->Printf("Can't find Comverse10() constructor");
return HRv;
          if(blog)     oDebugLog->Printf("Comverse10() constructor found");
          jobject jobj = jni->env->NewObject(jcls,mid);
          if(jobj==0)
               if(blog)     oDebugLog->Printf("Can't construct a Comverse10 object");
return HRv;
          if(blog)     oDebugLog->Printf("Comverse10 object constucted");
          //Create Global reference, so java garbage collector won't delete it
          jni->jobj_comv = jni->env->NewGlobalRef(jobj);
          if(jni->jobj_comv==0)
               if(blog)     oDebugLog->Printf("Can't create global reference to Comverse10 object");
return HRv;
          if(blog)     oDebugLog->Printf("global reference to Comverse10 object %08x created",jni->jobj_comv);
          bJVM=TRUE;
          HRv=S_OK;
     }     catch( IDB * bgError ) { throw bgError->ErrorTrace("InitializeJNI::~InitializeJNI",HRv, 0, T); }
          catch(...) { throw IDB::NewErrorTrace("InitializeJNI::~InitializeJNI",HRv, 0, T ); }
          return HRv;

Answer 1

>
I would guess that the real problem is that that the
exception you are catching is not in the class path
that you are defining.Thanks jschell, that was indeed the case.
I don't have the docs, but I would guess that
FindClass() only returns null if an exception is
thrown. And you are not checking for the exception.
Which would tell you the problem.Ok, i'll remember that. But what with exceptions thrown in my java code, the documents say
// jthrowable ExceptionOccurred(JNIEnv *env);
// Determines if an exception is being thrown. The exception stays being thrown until either the native code calls ExceptionClear(), or the Java code handles the exception
so, what if the java code throws an exception and catches it, will i be able to see that in my c++ code with ExceptionOccurred ?
or
should the java method be declared to throw the exception (and not catch it inside the method)
Again, thank you for your help, it's greatly appreciated !