JNI - FindClass

[muthu muruges]

Hi,

I am invoking java methods from 'C' using JNI. For me the FindClass method returns '0' (zero) even though the classpath is set properly. I have set the classpath using vmargs.options, in that option string I am passing the classpath as "-Djava.class.path=<myclasspath>". The above error is not consistent, many of the times it is passing. Can you help me please to identify the root cause of this error?

Thanks,
Muruges

[Joel McNary]

I don't think that we can offer much help without more information. Could you please post the code that you are using?

Also, what happens if you put the class in the system's classpath? Is it a problem where the switch that you are specifying is incorrect?

[muthu muruges]

Thanks for the update.

Here is the code

 
int
as_init_jni_jvm(void)
{
jint res;
JNIEnv *env;
JavaVMInitArgs vm_args;
JavaVMOption options[5];
 
char cpathBuff[2048];
char ldpathBuff[1024];
char indInstBuff[1235];
char *cpath = NULL;
char *ldpath = NULL;
 
 
 
/* Disable JIT */
options[0].optionString = "-Djava.compiler=NONE";
 
/* Path for user classes */
cpath = getenv("CLASSPATH");
sprintf(cpathBuff,"%s%s","-Djava.class.path=",cpath);
options[1].optionString = cpathBuff;
 
ldpath = getenv("LD_LIBRARY_PATH");
sprintf(ldpathBuff,"%s%s","-Djava.library.path=",ldpath);
/* Set native library path */
options[2].optionString = ldpathBuff;
/* Print JNI related messages */
options[3].optionString = "-verbose:jni";
/* Set Indigo install location */
sprintf(indInstBuff, "%s%s", "-D<mykey>=", ind_ins_loc);
options[4].optionString = indInstBuff;
 

vm_args.version = JNI_VERSION_1_4;
vm_args.options = options;
vm_args.nOptions = 5;
vm_args.ignoreUnrecognized = JNI_TRUE;
 
res = JNI_CreateJavaVM(&jvm, (void **) &env, &vm_args);
if (res < 0) {
as_error("Can't create Java VM\n");
return -1;
}
as_info("JVM created\n");
return 0;
}
.......
.......
.......
void 
ctrlpath_init(int id)
{
ctrlpath_env_t *cp_env;
 
JNIEnv *env;
JavaVMAttachArgs args;
jint res;
jclass scc_cls, nspe_cls, sys_cls, daof_cls, logger_cls;
jmethodID mid_scc_getInstance;
jmethodID mid_nspe_getInstance;
jmethodID mid_createStorageContainer;
jmethodID mid_releaseStorageContainer;
jmethodID mid_notifyFileAttrChange;
jmethodID mid_system_exit;
jmethodID mid_logger_setLogLevel;
jobject scc, nspe;
jfieldID fid_db_up;
jboolean db_init;
 
as_debug("Control Path starting \n");
        .............
        .............
        .............
/* Attach to the JVM created in asfsd_init_jni_jvm. Each thread cannot
   have individual JVM. 
 */
args.version = JNI_VERSION_1_4;
args.name = "cpworker";
args.group = NULL;
res = (*jvm)->AttachCurrentThread(jvm, (void **) &env, &args);
as_debug("Thread %d attached to JVM\n", id);
 
/* Find the Class StorageContainerController */
scc_cls = (*env)->FindClass(env, CLASS_SCC);
if (scc_cls == 0) {
(*env)->ExceptionDescribe(env);
(*env)->ExceptionClear(env);
as_error("Can't find class StorageContainerController\n");
exit(1);
}
as_debug("Class StorageContainerController found\n");
        ...........
        ...........
        ...........
 

Some times I am getting my error message "Can't find class StorageContainerController".
I don't believe it occurs because of the incorrect classpath. If classpath is the root cause then I would have hit this issue in all of my tries.

The classpath key is correct.
[ February 16, 2005: Message edited by: muthu muruges ]