Add dependencyInjection class for role of DI containers in JavaFx

Author: Dokyeongyun

src/main/java/root/javafx/DI/DependencyInjection.java

@@ -0,0 +1,82 @@
+package root.javafx.DI;
+
+import java.io.IOException;
+import java.lang.reflect.InvocationTargetException;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.ResourceBundle;
+
+import javafx.fxml.FXMLLoader;
+import javafx.fxml.JavaFXBuilderFactory;
+import javafx.scene.Parent;
+import javafx.util.Callback;
+
+public class DependencyInjection {
+
+	/**
+	 * A map of all Controllers that can be injected, and the methods responsible
+	 * for doing so.
+	 */
+	private static final Map<Class<?>, Callback<Class<?>, Object>> injectionMethods = new HashMap<>();
+	private static ResourceBundle bundle = null;
+
+	public static Parent load(String location) throws IOException {
+		FXMLLoader loader = getLoader(location);
+		return loader.load();
+	}
+
+	public static FXMLLoader getLoader(String location) {
+		return new FXMLLoader(DependencyInjection.class.getResource(location), bundle, new JavaFXBuilderFactory(),
+				controllerClass -> constructController(controllerClass));
+	}
+
+	public static void setBundle(ResourceBundle bundle) {
+		DependencyInjection.bundle = bundle;
+	}
+
+	public static void addInjectionMethod(Class<?> controller, Callback<Class<?>, Object> method) {
+		injectionMethods.put(controller, method);
+	}
+
+	public static void removeInjectionMethod(Class<?> controller) {
+		injectionMethods.remove(controller);
+	}
+
+	/**
+	 * Determine whether a stored method is available If one is, return the custom
+	 * controller If one is not, return the default controller
+	 * 
+	 * @param controllerClass the class of controller to be created
+	 * @return the controller created
+	 */
+	private static Object constructController(Class<?> controllerClass) {
+		if (injectionMethods.containsKey(controllerClass)) {
+			return loadControllerWithSavedMethod(controllerClass);
+		} else {
+			return loadControllerWithDefaultConstructor(controllerClass);
+		}
+	}
+
+	/**
+	 * Load a controller using the saved method
+	 * 
+	 * @param controller the class of the controller to be loaded
+	 * @return the loaded controller
+	 */
+	private static Object loadControllerWithSavedMethod(Class<?> controller) {
+		try {
+			return injectionMethods.get(controller).call(controller);
+		} catch (Exception e) {
+			throw new IllegalStateException(e);
+		}
+	}
+
+	private static Object loadControllerWithDefaultConstructor(Class<?> controller) {
+		try {
+			return controller.getConstructor().newInstance();
+		} catch (InstantiationException | IllegalAccessException | InvocationTargetException
+				| NoSuchMethodException e) {
+			throw new IllegalStateException(e);
+		}
+	}
+}