Issue 4442 - Cache class and ctors references in JNI_Load/UnLoad

libadblockplus-android/jni/JniJsValue.cpp

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include <AdblockPlus.h>
 #include "Utils.h"
 #include "JniJsValue.h"
 
 // precached in JNI_OnLoad and released in JNI_OnUnload
-jclass globalJsValueClass;
-jmethodID jsValueClassCtor;
+JniGlobalReference<jclass>* jsValueClass;
+jmethodID jsValueCtor;
 
 void JniJsValue_OnLoad(JavaVM* vm, JNIEnv* env, void* reserved)
 {
-  // precache for performance and avoid attaching threads
-  jclass localJsValueClass = env->FindClass(PKG("JsValue"));
-  globalJsValueClass = (jclass)env->NewGlobalRef(localJsValueClass);
-  jsValueClassCtor = env->GetMethodID(globalJsValueClass, "<init>", "(J)V");
-  env->DeleteLocalRef(localJsValueClass);
+  jsValueClass = new JniGlobalReference<jclass>(env, env->FindClass(PKG("JsValue")));
+  jsValueCtor = env->GetMethodID(jsValueClass->Get(), "<init>", "(J)V");
 }
 
 void JniJsValue_OnUnload(JavaVM* vm, JNIEnv* env, void* reserved)
 {
-  if (globalJsValueClass)
+  if (jsValueClass)
   {
-    env->DeleteGlobalRef(globalJsValueClass);
+    delete jsValueClass;
+    jsValueClass = NULL;
   }
 }
 
+jclass GetJsValueClass()
+{
+  return (jsValueClass != NULL ? jsValueClass->Get() : NULL);
+}
+
 static jboolean JNICALL JniIsUndefined(JNIEnv* env, jclass clazz, jlong ptr)
 {
   try
   {
     return JniGetJsValue(ptr)->IsUndefined() ? JNI_TRUE : JNI_FALSE;
   }
   CATCH_THROW_AND_RETURN(env, JNI_FALSE)
 }
 
 static jboolean JNICALL JniIsNull(JNIEnv* env, jclass clazz, jlong ptr)
@@ skipping 104 matching lines @@
     return NewJniJsValue(env, JniGetJsValue(ptr)->GetProperty(JniJavaToStdString(env, name)));
   }
   CATCH_THROW_AND_RETURN(env, 0)
 }
 
 static void JNICALL JniDtor(JNIEnv* env, jclass clazz, jlong ptr)
 {
   delete JniLongToTypePtr<AdblockPlus::JsValuePtr>(ptr);
 }
 
-jobject NewJniJsValue(JNIEnv* env, const AdblockPlus::JsValuePtr& jsValue, jclass jsValueClass)
+jobject NewJniJsValue(JNIEnv* env, const AdblockPlus::JsValuePtr& jsValue, jclass jsValueClassArg)
 {
   if (!jsValue.get())
   {
     return 0;
   }
 
   jlong ptr = JniPtrToLong(new AdblockPlus::JsValuePtr(jsValue));
-  return env->NewObject(globalJsValueClass, jsValueClassCtor, ptr);
+  return env->NewObject(jsValueClass->Get(), jsValueCtor, ptr);
 }
 
 AdblockPlus::JsValue* JniGetJsValue(jlong ptr)
 {
   return JniLongToTypePtr<AdblockPlus::JsValuePtr>(ptr)->get();
 }
 
 AdblockPlus::JsValuePtr& JniGetJsValuePtr(jlong ptr)
 {
   return *JniLongToTypePtr<AdblockPlus::JsValuePtr>(ptr);
@@ skipping 38 matching lines @@
   { (char*)"asBoolean", (char*)"(J)Z", (void*)JniAsBoolean },
   { (char*)"asList", (char*)"(J)Ljava/util/List;", (void*)JniAsList },
   { (char*)"getProperty", (char*)"(JLjava/lang/String;)" TYP("JsValue"), (void*)JniGetProperty },
   { (char*)"dtor", (char*)"(J)V", (void*)JniDtor }
 };
 
 extern "C" JNIEXPORT void JNICALL Java_org_adblockplus_libadblockplus_JsValue_registerNatives(JNIEnv *env, jclass clazz)
 {
   env->RegisterNatives(clazz, methods, sizeof(methods) / sizeof(methods[0]));
 }