Realized that the jclass and jmethodID variables in the callbacks cannot be static

There's no guarantee that ALL calls to the callbacks will be on the same class as they're just interfaces and user defined

java/jni/com_zerotierone_sdk_Node.cpp

@@ -77,27 +77,21 @@ namespace {
 
         JNIEnv *env = ref->env;
 
-        static jclass configListenerClass = NULL;
-        static jmethodID callbackMethod = NULL;
+        jclass configListenerClass = NULL;
+        jmethodID callbackMethod = NULL;
 
+        configListenerClass = env->GetObjectClass(ref->configListener);
         if(configListenerClass == NULL)
         {
-            configListenerClass = env->GetObjectClass(ref->configListener);
-            if(configListenerClass == NULL)
-            {
-                return -1;
-            }
+            return -1;
         }
 
+        callbackMethod = env->GetMethodID(configListenerClass,
+            "onNetworkConfigurationUpdated",
+            "(JLcom/zerotierone/sdk/VirtualNetworkConfigOperation;Lcom/zerotierone/sdk/VirtualNetworkConfig;)I");
         if(callbackMethod == NULL)
         {
-            callbackMethod = env->GetMethodID(configListenerClass,
-                "onNetworkConfigurationUpdated",
-                "(JLcom/zerotierone/sdk/VirtualNetworkConfigOperation;Lcom/zerotierone/sdk/VirtualNetworkConfig;)I");
-            if(callbackMethod == NULL)
-            {
-                return -2;
-            }
+            return -2;
         }
 
         jobject operationObject = createVirtualNetworkConfigOperation(env, operation);
@@ -129,26 +123,20 @@ namespace {
 
         JNIEnv *env = ref->env;
 
-        static jclass frameListenerClass = NULL;
-        static jmethodID callbackMethod = NULL;
+        jclass frameListenerClass = NULL;
+        jmethodID callbackMethod = NULL;
 
+        frameListenerClass = env->GetObjectClass(ref->frameListener);
         if(frameListenerClass == NULL)
         {
-            frameListenerClass = env->GetObjectClass(ref->frameListener);
-            if(frameListenerClass == NULL)
-            {
-                return;
-            }
+            return;
         }
 
+        callbackMethod = env->GetMethodID(frameListenerClass,
+            "onVirtualNetworkFrame", "(JJJJJ[B)V");
         if(callbackMethod == NULL)
         {
-            callbackMethod = env->GetMethodID(frameListenerClass,
-                "onVirtualNetworkFrame", "(JJJJJ[B)V");
-            if(callbackMethod == NULL)
-            {
-                return;
-            }
+            return;
         }
 
         jbyteArray dataArray = env->NewByteArray(frameLength);
@@ -178,27 +166,21 @@ namespace {
 
         JNIEnv *env = ref->env;
 
-        static jclass dataStoreGetClass = NULL;
-        static jmethodID callbackMethod = NULL;
+        jclass dataStoreGetClass = NULL;
+        jmethodID callbackMethod = NULL;
 
+        dataStoreGetClass = env->GetObjectClass(ref->dataStoreGetListener);
         if(dataStoreGetClass == NULL)
         {
-            dataStoreGetClass = env->GetObjectClass(ref->dataStoreGetListener);
-            if(dataStoreGetClass == NULL)
-            {
-                return -2;
-            }
+            return -2;
         }
 
+        callbackMethod = env->GetMethodID(dataStoreGetClass,
+            "onDataStoreGet",
+            "(Ljava/lang/String;[BJ[J)J");
         if(callbackMethod == NULL)
         {
-            callbackMethod = env->GetMethodID(dataStoreGetClass,
-                "onDataStoreGet",
-                "(Ljava/lang/String;[BJ[J)J");
-            if(callbackMethod == NULL)
-            {
-                return -2;
-            }
+            return -2;
         }
 
         jstring nameStr = env->NewStringUTF(objectName);
@@ -227,38 +209,30 @@ namespace {
 
         JNIEnv *env = ref->env;
 
-        static jclass dataStorePutClass = NULL;
-        static jmethodID callbackMethod = NULL;
-        static jmethodID deleteMethod = NULL;
+        jclass dataStorePutClass = NULL;
+        jmethodID callbackMethod = NULL;
+        jmethodID deleteMethod = NULL;
 
+
+        dataStorePutClass = env->GetObjectClass(ref->dataStorePutListener);
         if(dataStorePutClass == NULL)
         {
-            dataStorePutClass = env->GetObjectClass(ref->dataStorePutListener);
-            if(dataStorePutClass == NULL)
-            {
-                return -1;
-            }
+            return -1;
         }
 
+        callbackMethod = env->GetMethodID(dataStorePutClass,
+            "onDataStorePut",
+            "(Ljava/lang/String;[BZ)I");
         if(callbackMethod == NULL)
         {
-            callbackMethod = env->GetMethodID(dataStorePutClass,
-                "onDataStorePut",
-                "(Ljava/lang/String;[BZ)I");
-            if(callbackMethod == NULL)
-            {
-                return -2;
-            }
+            return -2;
         }
 
+        deleteMethod = env->GetMethodID(dataStorePutClass,
+            "onDelete", "(Ljava/lang/String;)I");
         if(deleteMethod == NULL)
         {
-            deleteMethod = env->GetMethodID(dataStorePutClass,
-                "onDelete", "(Ljava/lang/String;)I");
-            if(deleteMethod == NULL)
-            {
-                return -3;
-            }
+            return -3;
         }
 
         jstring nameStr = env->NewStringUTF(objectName);