Issue 1848 - Clean up local reference handling

jni/JniFilterChangeCallback.cpp

Index: jni/JniFilterChangeCallback.cpp
diff --git a/jni/JniFilterChangeCallback.cpp b/jni/JniFilterChangeCallback.cpp
index a1b19011470495265b67a71fd75ff8ccf4d5e38f..3fe26c87cf03d00350912d51e85d316a021dca01 100644
--- a/jni/JniFilterChangeCallback.cpp
+++ b/jni/JniFilterChangeCallback.cpp
@@ -40,14 +40,15 @@ void JniFilterChangeCallback::Callback(const std::string& arg, const AdblockPlus
 {
   JNIEnvAcquire env(GetJavaVM());
 
-  jclass clazz = env->GetObjectClass(GetCallbackObject());
-  jmethodID method = env->GetMethodID(clazz, "filterChangeCallback", "(Ljava/lang/String;" TYP("JsValue") ")V");
+  jmethodID method = env->GetMethodID(
+      *JniLocalReference<jclass>(*env, env->GetObjectClass(GetCallbackObject())),
+      "filterChangeCallback", "(Ljava/lang/String;" TYP("JsValue") ")V");
 
   if (method)
   {
-    jstring jArg = env->NewStringUTF(arg.c_str());
-    jobject jJsValue = NewJniJsValue(*env, jsValue, jsValueClass->Get());
-    env->CallVoidMethod(GetCallbackObject(), method, jArg, jJsValue);
+    JniLocalReference<jstring> jArg(*env, env->NewStringUTF(arg.c_str()));
+    JniLocalReference<jobject> jJsValue(*env, NewJniJsValue(*env, jsValue, jsValueClass->Get()));
+    env->CallVoidMethod(GetCallbackObject(), method, *jArg, *jJsValue);
   }
 
   CheckAndLogJavaException(*env);