Extract CSS and JS references.

bootstrap-extensions/src/main/java/de/agilecoders/wicket/extensions/markup/html/bootstrap/form/ColorPickerTextField.java

@@ -14,8 +14,6 @@
 import org.apache.wicket.markup.head.JavaScriptHeaderItem;
 import org.apache.wicket.markup.html.form.TextField;
 import org.apache.wicket.model.IModel;
-import org.apache.wicket.request.resource.CssResourceReference;
-import org.apache.wicket.request.resource.JavaScriptResourceReference;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -28,10 +26,6 @@
 public class ColorPickerTextField extends TextField<String> {
 
 	private static final long serialVersionUID = 1L;
-	private static JavaScriptResourceReference colorpickerJs = new JavaScriptResourceReference(
-			ColorPickerTextField.class, "js/colorpicker.js");
-	private static CssResourceReference colorpickerCss = new CssResourceReference(
-			ColorPickerTextField.class, "css/colorpicker.css");
 	/**
 	 * bootstrap-colorpicker won't enhance if the textfield was not enabled,
 	 * so we must wait until the first time the textfield is enabled.
@@ -62,8 +56,8 @@ protected void onInitialize() {
 	@Override
 	public void renderHead(IHeaderResponse response) {
 		super.renderHead(response);
-		response.render(CssHeaderItem.forReference(colorpickerCss));
-		response.render(JavaScriptHeaderItem.forReference(colorpickerJs));
+		response.render(CssHeaderItem.forReference(ColorPickerTextFieldCssReference.instance()));
+		response.render(JavaScriptHeaderItem.forReference(ColorPickerTextFieldJavaScriptReference.instance()));
 		if (isEnabledInHierarchy()) {
 			response.render(JavaScriptHeaderItem.forScript("$(document).ready(function() {" +
 					"$('#" + getMarkupId() + "').colorpicker();" +

bootstrap-extensions/src/main/java/de/agilecoders/wicket/extensions/markup/html/bootstrap/form/ColorPickerTextFieldCssReference.java

@@ -0,0 +1,31 @@
+package de.agilecoders.wicket.extensions.markup.html.bootstrap.form;
+
+import org.apache.wicket.request.resource.CssResourceReference;
+
+/**
+ * Bootstrap {@link ColorPickerTextField} CSS reference.
+ *
+ * @author ceefour
+ */
+public class ColorPickerTextFieldCssReference extends CssResourceReference {
+    private static final long serialVersionUID = 1L;
+
+    /**
+     * Singleton instance of this reference
+     */
+    private static final ColorPickerTextFieldCssReference INSTANCE = new ColorPickerTextFieldCssReference();
+
+    /**
+     * @return the single instance of the resource reference
+     */
+    public static ColorPickerTextFieldCssReference instance() {
+        return INSTANCE;
+    }
+
+    /**
+     * Private constructor.
+     */
+    private ColorPickerTextFieldCssReference() {
+        super(ColorPickerTextFieldCssReference.class, "css/colorpicker.css");
+    }
+}

bootstrap-extensions/src/main/java/de/agilecoders/wicket/extensions/markup/html/bootstrap/form/ColorPickerTextFieldJavaScriptReference.java

@@ -0,0 +1,31 @@
+package de.agilecoders.wicket.extensions.markup.html.bootstrap.form;
+
+import org.apache.wicket.request.resource.JavaScriptResourceReference;
+
+/**
+ * Bootstrap {@link ColorPickerTextField} JavaScript reference.
+ *
+ * @author ceefour
+ */
+public class ColorPickerTextFieldJavaScriptReference extends JavaScriptResourceReference {
+    private static final long serialVersionUID = 1L;
+
+    /**
+     * Singleton instance of this reference
+     */
+    private static final ColorPickerTextFieldJavaScriptReference INSTANCE = new ColorPickerTextFieldJavaScriptReference();
+
+    /**
+     * @return the single instance of the resource reference
+     */
+    public static ColorPickerTextFieldJavaScriptReference instance() {
+        return INSTANCE;
+    }
+
+    /**
+     * Private constructor.
+     */
+    private ColorPickerTextFieldJavaScriptReference() {
+        super(ColorPickerTextFieldJavaScriptReference.class, "js/colorpicker.js");
+    }
+}