jni jnienv NewGlobalRef example c c++ java

NewGlobalRef

jobject NewGlobalRef(JNIEnv *env, jobject obj);

Creates a new global reference to the object referred to by the obj argument. The obj argument may be a global or local reference. Global references must be explicitly disposed of by calling DeleteGlobalRef().

LINKAGE:

Index 21 in the JNIEnv interface function table.

PARAMETERS of NewGlobalRef

env: the JNI interface pointer.

obj: a global or local reference.

RETURNS:

Returns a global reference, or NULL if the system runs out of memory.

Example - NewGlobalRef

/* This code is OK */
 jstring
 MyNewString(JNIEnv *env, jchar *chars, jint len)
 {
     static jclass stringClass = NULL;
     ...
     if (stringClass == NULL) {
         jclass localRefCls =
             (*env)->FindClass(env, "java/lang/String");
         if (localRefCls == NULL) {
             return NULL; /* exception thrown */
         }
         /* Create a global reference */
         stringClass = (*env)->NewGlobalRef(env, localRefCls);
 
         /* The local reference is no longer useful */
         (*env)->DeleteLocalRef(env, localRefCls);
 
         /* Is the global reference created successfully? */
         if (stringClass == NULL) {
             return NULL; /* out of memory exception thrown */
         }
     }
     ...
 }