diff --git a/widget/android/EventDispatcher.cpp b/widget/android/EventDispatcher.cpp
index 8810f0b5d737..5e8cee1def91 100644
--- a/widget/android/EventDispatcher.cpp
+++ b/widget/android/EventDispatcher.cpp
@@ -467,49 +467,21 @@ nsresult UnboxArrayObject(JSContext* aCx, const jni::Object::LocalRef& aData,
   return NS_OK;
 }
 
-template <class T>
-jfieldID GetValueFieldID(const char* aType) {
-  MOZ_ASSERT(NS_IsMainThread());
-  JNIEnv* const env = jni::GetGeckoThreadEnv();
-  const jfieldID id = env->GetFieldID(
-      typename T::Context(env, nullptr).ClassRef(), "value", aType);
-  env->ExceptionClear();
-  return id;
-}
-
 nsresult UnboxValue(JSContext* aCx, const jni::Object::LocalRef& aData,
                     JS::MutableHandleValue aOut) {
-  static jfieldID booleanValueField = GetValueFieldID<java::sdk::Boolean>("Z");
-  static jfieldID intValueField = GetValueFieldID<java::sdk::Integer>("I");
-  static jfieldID doubleValueField = GetValueFieldID<java::sdk::Double>("D");
+  using jni::Java2Native;
 
   if (!aData) {
     aOut.setNull();
   } else if (aData.IsInstanceOf<jni::Boolean>()) {
-    if (booleanValueField) {
-      aOut.setBoolean(aData.Env()->GetBooleanField(
-                          aData.Get(), booleanValueField) != JNI_FALSE);
-      MOZ_CATCH_JNI_EXCEPTION(aData.Env());
-    } else {
-      aOut.setBoolean(java::sdk::Boolean::Ref::From(aData)->BooleanValue());
-    }
+    aOut.setBoolean(Java2Native<bool>(aData, aData.Env()));
   } else if (aData.IsInstanceOf<jni::Integer>()) {
-    if (intValueField) {
-      aOut.setInt32(aData.Env()->GetIntField(aData.Get(), intValueField));
-      MOZ_CATCH_JNI_EXCEPTION(aData.Env());
-    } else {
-      aOut.setInt32(java::sdk::Number::Ref::From(aData)->IntValue());
-    }
+    aOut.setInt32(Java2Native<int>(aData, aData.Env()));
   } else if (aData.IsInstanceOf<jni::Byte>() ||
              aData.IsInstanceOf<jni::Short>()) {
     aOut.setInt32(java::sdk::Number::Ref::From(aData)->IntValue());
   } else if (aData.IsInstanceOf<jni::Double>()) {
-    if (doubleValueField) {
-      aOut.setNumber(
-          aData.Env()->GetDoubleField(aData.Get(), doubleValueField));
-    } else {
-      aOut.setNumber(java::sdk::Number::Ref::From(aData)->DoubleValue());
-    }
+    aOut.setNumber(Java2Native<double>(aData, aData.Env()));
   } else if (aData.IsInstanceOf<jni::Float>() ||
              aData.IsInstanceOf<jni::Long>()) {
     aOut.setNumber(java::sdk::Number::Ref::From(aData)->DoubleValue());
diff --git a/widget/android/jni/Conversions.cpp b/widget/android/jni/Conversions.cpp
new file mode 100644
index 000000000000..fed46f961ddf
--- /dev/null
+++ b/widget/android/jni/Conversions.cpp
@@ -0,0 +1,91 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "Conversions.h"
+#include "JavaBuiltins.h"
+
+namespace mozilla {
+namespace jni {
+
+template <class T>
+jfieldID GetValueFieldID(JNIEnv* aEnv, const char* aType) {
+  const jfieldID id = aEnv->GetFieldID(
+      typename T::Context(aEnv, nullptr).ClassRef(), "value", aType);
+  aEnv->ExceptionClear();
+  return id;
+}
+
+// Cached locations of the primitive types within their standard boxed objects
+// to skip doing that lookup on every get.
+static jfieldID gBooleanValueField;
+static jfieldID gIntValueField;
+static jfieldID gDoubleValueField;
+
+void InitConversionStatics() {
+  MOZ_ASSERT(NS_IsMainThread());
+  JNIEnv* const env = jni::GetGeckoThreadEnv();
+  gBooleanValueField = GetValueFieldID<java::sdk::Boolean>(env, "Z");
+  gIntValueField = GetValueFieldID<java::sdk::Integer>(env, "I");
+  gDoubleValueField = GetValueFieldID<java::sdk::Double>(env, "D");
+}
+
+template <>
+bool Java2Native(mozilla::jni::Object::Param aData, JNIEnv* aEnv) {
+  MOZ_ASSERT(aData.IsInstanceOf<jni::Boolean>());
+
+  bool result = false;
+  if (gBooleanValueField) {
+    if (!aEnv) {
+      aEnv = jni::GetEnvForThread();
+    }
+    result =
+        aEnv->GetBooleanField(aData.Get(), gBooleanValueField) != JNI_FALSE;
+    MOZ_CATCH_JNI_EXCEPTION(aEnv);
+  } else {
+    result = java::sdk::Boolean::Ref::From(aData)->BooleanValue();
+  }
+
+  return result;
+}
+
+template <>
+int Java2Native(mozilla::jni::Object::Param aData, JNIEnv* aEnv) {
+  MOZ_ASSERT(aData.IsInstanceOf<jni::Integer>());
+
+  int result = 0;
+  if (gIntValueField) {
+    if (!aEnv) {
+      aEnv = jni::GetEnvForThread();
+    }
+    result = aEnv->GetIntField(aData.Get(), gIntValueField);
+    MOZ_CATCH_JNI_EXCEPTION(aEnv);
+  } else {
+    result = java::sdk::Number::Ref::From(aData)->IntValue();
+  }
+
+  return result;
+}
+
+template <>
+double Java2Native(mozilla::jni::Object::Param aData, JNIEnv* aEnv) {
+  MOZ_ASSERT(aData.IsInstanceOf<jni::Double>());
+
+  double result = 0;
+  if (gDoubleValueField) {
+    if (!aEnv) {
+      aEnv = jni::GetEnvForThread();
+    }
+    result = aEnv->GetDoubleField(aData.Get(), gDoubleValueField);
+    MOZ_CATCH_JNI_EXCEPTION(aEnv);
+  } else {
+    result = java::sdk::Number::Ref::From(aData)->DoubleValue();
+  }
+
+  return result;
+}
+
+}  // namespace jni
+}  // namespace mozilla
diff --git a/widget/android/jni/Conversions.h b/widget/android/jni/Conversions.h
new file mode 100644
index 000000000000..1d9e20acc72f
--- /dev/null
+++ b/widget/android/jni/Conversions.h
@@ -0,0 +1,23 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_jni_Conversions_h__
+#define mozilla_jni_Conversions_h__
+
+#include "mozilla/jni/Refs.h"
+
+namespace mozilla {
+namespace jni {
+
+template <typename ArgType>
+ArgType Java2Native(mozilla::jni::Object::Param, JNIEnv* aEnv = nullptr);
+
+void InitConversionStatics();
+
+}  // namespace jni
+}  // namespace mozilla
+
+#endif  // mozilla_jni_Conversions_h__
diff --git a/widget/android/jni/moz.build b/widget/android/jni/moz.build
index b48ca4199e95..4fe6a70f28bc 100644
--- a/widget/android/jni/moz.build
+++ b/widget/android/jni/moz.build
@@ -9,6 +9,7 @@ with Files("**"):
 
 EXPORTS.mozilla.jni += [
     'Accessors.h',
+    'Conversions.h',
     'GeckoBundleUtils.h',
     'Natives.h',
     'Refs.h',
@@ -17,6 +18,7 @@ EXPORTS.mozilla.jni += [
 ]
 
 UNIFIED_SOURCES += [
+    'Conversions.cpp',
     'Utils.cpp',
 ]
 
diff --git a/widget/android/nsWindow.cpp b/widget/android/nsWindow.cpp
index 0e3c65b26f8d..61c1532ced55 100644
--- a/widget/android/nsWindow.cpp
+++ b/widget/android/nsWindow.cpp
@@ -1368,6 +1368,7 @@ void nsWindow::GeckoViewSupport::AttachAccessibility(
 }
 
 void nsWindow::InitNatives() {
+  jni::InitConversionStatics();
   nsWindow::GeckoViewSupport::Base::Init();
   nsWindow::LayerViewSupport::Init();
   nsWindow::NPZCSupport::Init();