| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| package org.apache.felix.example.servicebased.host; |
| |
| import java.awt.Color; |
| import java.awt.Graphics2D; |
| import java.awt.Point; |
| import javax.swing.ImageIcon; |
| import org.apache.felix.example.servicebased.host.service.SimpleShape; |
| import org.osgi.framework.BundleContext; |
| import org.osgi.framework.ServiceReference; |
| |
| /** |
| * This class is used as a proxy to defer object creation from shape |
| * provider bundles and also as a placeholder shape when previously |
| * used shapes are no longer available. These two purposes are |
| * actually orthogonal, but were combined into a single class to |
| * reduce the number of classes in the application. The proxy-related |
| * functionality is introduced as a way to lazily create shape |
| * objects in an effort to improve performance; this level of |
| * indirection could be removed if eager creation of objects is not |
| * a concern. Since this application uses the service-based extension |
| * appraoch, lazy shape creation will only come into effect if |
| * service providers register service factories instead of directly |
| * registering <tt>SimpleShape</tt> or if they use a technology like |
| * Declarative Services or iPOJO to register services. Since the |
| * example providers register services instances directly there is |
| * no laziness in the example, but the proxy approach is still used |
| * to demonstrate how to make laziness possible and to keep it |
| * similar to the extender-based approach. |
| **/ |
| class DefaultShape implements SimpleShape |
| { |
| private SimpleShape m_shape; |
| private ImageIcon m_icon; |
| private BundleContext m_context; |
| private ServiceReference m_ref; |
| |
| /** |
| * This constructs a placeholder shape that draws a default |
| * icon. It is used when a previously drawn shape is no longer |
| * available. |
| **/ |
| public DefaultShape() |
| { |
| // Do nothing. |
| } |
| |
| /** |
| * This constructs a proxy shape that lazily gets the shape service. |
| * @param context The bundle context to use for retrieving the shape service. |
| * @param ref The service reference of the service. |
| **/ |
| public DefaultShape(BundleContext context, ServiceReference ref) |
| { |
| m_context = context; |
| m_ref = ref; |
| } |
| |
| /** |
| * This method tells the proxy to dispose of its service object; this |
| * is called when the underlying service goes away. |
| **/ |
| public void dispose() |
| { |
| if (m_shape != null) |
| { |
| m_context.ungetService(m_ref); |
| m_context = null; |
| m_ref = null; |
| m_shape = null; |
| } |
| } |
| |
| /** |
| * Implements the <tt>SimpleShape</tt> interface method. When acting as |
| * a proxy, this method gets the shape service and then uses it to draw |
| * the shape. When acting as a placeholder shape, this method draws the |
| * default icon. |
| * @param g2 The graphics object used for painting. |
| * @param p The position to paint the triangle. |
| **/ |
| public void draw(Graphics2D g2, Point p) |
| { |
| // If this is a proxy shape, instantiate the shape class |
| // and use it to draw the shape. |
| if (m_context != null) |
| { |
| try |
| { |
| if (m_shape == null) |
| { |
| // Get the shape service. |
| m_shape = (SimpleShape) m_context.getService(m_ref); |
| } |
| // Draw the shape. |
| m_shape.draw(g2, p); |
| // If everything was successful, then simply return. |
| return; |
| } |
| catch (Exception ex) |
| { |
| // This generally should not happen, but if it does then |
| // we can just fall through and paint the default icon. |
| } |
| } |
| |
| // If the proxied shape could not be drawn for any reason or if |
| // this shape is simply a placeholder, then draw the default icon. |
| if (m_icon == null) |
| { |
| try |
| { |
| m_icon = new ImageIcon(this.getClass().getResource("underc.png")); |
| } |
| catch (Exception ex) |
| { |
| ex.printStackTrace(); |
| g2.setColor(Color.red); |
| g2.fillRect(0, 0, 60, 60); |
| return; |
| } |
| } |
| g2.drawImage(m_icon.getImage(), 0, 0, null); |
| } |
| } |