v0.2.52..v0.2.53 changeset JavaEnvironment.h

diff --git a/hoot-josm/src/main/cpp/hoot/core/jni/JavaEnvironment.h b/hoot-josm/src/main/cpp/hoot/core/jni/JavaEnvironment.h
new file mode 100644
index 0000000..01f1f59
--- /dev/null
+++ b/hoot-josm/src/main/cpp/hoot/core/jni/JavaEnvironment.h
@@ -0,0 +1,84 @@
+/*
+ * This file is part of Hootenanny.
+ *
+ * Hootenanny is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * --------------------------------------------------------------------
+ *
+ * The following copyright notices are generated automatically. If you
+ * have a new notice to add, please use the format:
+ * " * @copyright Copyright ..."
+ * This will properly maintain the copyright information. DigitalGlobe
+ * copyrights will be updated automatically.
+ *
+ * @copyright Copyright (C) 2019, 2020 DigitalGlobe (http://www.digitalglobe.com/)
+ */
+#ifndef JAVA_ENVIRONMENT_H
+#define JAVA_ENVIRONMENT_H
+
+// JNI
+#include <jni.h>
+
+// Qt
+#include <QString>
+
+namespace hoot
+{
+
+class JavaEnvironment;
+
+typedef std::shared_ptr<JavaEnvironment> JavaEnvironmentPtr;
+
+/**
+ * Creates a Java Virtual Machine for use by Hootenanny C++ code that calls Java code in the
+ * hoot-josm library via JNI (Singleton)
+ *
+ *  Helpful JNI reference:
+ *
+ * https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/invocation.html
+ */
+class JavaEnvironment
+{
+
+public:
+
+  static std::string className() { return "hoot::JavaEnvironment"; }
+
+  ~JavaEnvironment();
+
+  /**
+   * Creates a single instance of a JNI environment if none yet exists and returns it.
+   *
+   * @return a pointer to a JNI environment
+   */
+  static JNIEnv* getEnvironment() { return getInstance()->_env; }
+
+  static const JavaEnvironmentPtr& getInstance();
+
+private:
+
+  JavaEnvironment();
+
+  static JavaEnvironmentPtr _theInstance;
+  // A Java VM; is destroyed by this class in the destructor
+  JavaVM* _vm;
+  // A JNI environment
+  JNIEnv* _env;
+
+  void _initVm();
+};
+
+}
+
+#endif // JAVA_ENVIRONMENT_H