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

libadblockplus-android/jni/JniCallbacks.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 "JniCallbacks.h"
 
+// precached in JNI_OnLoad and released in JNI_OnUnload
+JniGlobalReference<jclass>* exceptionHandlerClass;
+
+void JniCallbacks_OnLoad(JavaVM* vm, JNIEnv* env, void* reserved)
+{
+  exceptionHandlerClass = new JniGlobalReference<jclass>(env, env->FindClass(PKG("JniExceptionHandler")));
+}
+
+void JniCallbacks_OnUnload(JavaVM* vm, JNIEnv* env, void* reserved)
+{
+  if (exceptionHandlerClass)
+  {
+    delete exceptionHandlerClass;
+    exceptionHandlerClass = NULL;
+  }
+}
+
 JniCallbackBase::JniCallbackBase(JNIEnv* env, jobject callbackObject)
-  : callbackObject(new JniGlobalReference<jobject>(env, callbackObject)),
-    exceptionLoggerClass(new JniGlobalReference<jclass>(env, env->FindClass(PKG("JniExceptionHandler"))))
+  : callbackObject(new JniGlobalReference<jobject>(env, callbackObject))
 {
   env->GetJavaVM(&javaVM);
 }
 
 JniCallbackBase::~JniCallbackBase()
 {
 
 }
 
 void JniCallbackBase::LogException(JNIEnv* env, jthrowable throwable) const
 {
-  jmethodID logMethod = env->GetStaticMethodID(exceptionLoggerClass->Get(), "logException", "(Ljava/lang/Throwable;)V");
+  jmethodID logMethod = env->GetStaticMethodID(
+    exceptionHandlerClass->Get(), "logException", "(Ljava/lang/Throwable;)V");
   if (logMethod)
   {
-    env->CallStaticVoidMethod(exceptionLoggerClass->Get(), logMethod, throwable);
+    env->CallStaticVoidMethod(exceptionHandlerClass->Get(), logMethod, throwable);
   }
 }
 
 void JniCallbackBase::CheckAndLogJavaException(JNIEnv* env) const
 {
   if (env->ExceptionCheck())
   {
     JniLocalReference<jthrowable> throwable(env, env->ExceptionOccurred());
     env->ExceptionClear();
     LogException(env, *throwable);
   }
 }