| /* |
| |
| 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.batik.util; |
| |
| import java.io.BufferedReader; |
| import java.io.IOException; |
| import java.io.InputStream; |
| import java.io.InputStreamReader; |
| import java.io.Reader; |
| import java.net.URL; |
| import java.util.ArrayList; |
| import java.util.Enumeration; |
| import java.util.HashMap; |
| import java.util.Iterator; |
| import java.util.List; |
| |
| /** |
| * This class handles looking up service providers on the class path. |
| * It implements the system described in: |
| * |
| * <a href="http://java.sun.com/j2se/1.3/docs/guide/jar/jar.html#Service%20Provider">JAR |
| * File Specification Under Service Provider</a>. Note that this |
| * interface is very similar to the one they describe which seems to |
| * be missing in the JDK. |
| * |
| * @author <a href="mailto:Thomas.DeWeeese@Kodak.com">Thomas DeWeese</a> |
| * @version $Id$ |
| */ |
| public class Service { |
| |
| // Remember providers we have looked up before. |
| static HashMap providerMap = new HashMap(); |
| |
| /** |
| * Returns an iterator where each element should implement the |
| * interface (or subclass the baseclass) described by cls. The |
| * Classes are found by searching the classpath for service files |
| * named: 'META-INF/services/<fully qualified classname> that list |
| * fully qualifted classnames of classes that implement the |
| * service files classes interface. These classes must have |
| * default constructors. |
| * |
| * @param cls The class/interface to search for providers of. |
| */ |
| public static synchronized Iterator providers(Class cls) { |
| String serviceFile = "META-INF/services/"+cls.getName(); |
| |
| // System.out.println("File: " + serviceFile); |
| |
| List l = (List)providerMap.get(serviceFile); |
| if (l != null) |
| return l.iterator(); |
| |
| l = new ArrayList(); |
| providerMap.put(serviceFile, l); |
| |
| ClassLoader cl = null; |
| try { |
| cl = cls.getClassLoader(); |
| } catch (SecurityException se) { |
| // Ooops! can't get his class loader. |
| } |
| // Can always request your own class loader. But it might be 'null'. |
| if (cl == null) cl = Service.class.getClassLoader(); |
| |
| // No class loader so we can't find 'serviceFile'. |
| if (cl == null) return l.iterator(); |
| |
| Enumeration e; |
| try { |
| e = cl.getResources(serviceFile); |
| } catch (IOException ioe) { |
| return l.iterator(); |
| } |
| |
| while (e.hasMoreElements()) { |
| InputStream is = null; |
| Reader r = null; |
| BufferedReader br = null; |
| try { |
| URL u = (URL)e.nextElement(); |
| // System.out.println("URL: " + u); |
| |
| is = u.openStream(); |
| r = new InputStreamReader(is, "UTF-8"); |
| br = new BufferedReader(r); |
| |
| String line = br.readLine(); |
| while (line != null) { |
| try { |
| // First strip any comment... |
| int idx = line.indexOf('#'); |
| if (idx != -1) |
| line = line.substring(0, idx); |
| |
| // Trim whitespace. |
| line = line.trim(); |
| |
| // If nothing left then loop around... |
| if (line.length() == 0) { |
| line = br.readLine(); |
| continue; |
| } |
| // System.out.println("Line: " + line); |
| |
| // Try and load the class |
| Object obj = cl.loadClass(line).getDeclaredConstructor().newInstance(); |
| // stick it into our vector... |
| l.add(obj); |
| } catch (Exception ex) { |
| // Just try the next line |
| } |
| line = br.readLine(); |
| } |
| } catch (Exception ex) { |
| // Just try the next file... |
| } catch (LinkageError le) { |
| // Just try the next file... |
| } finally { |
| // close and release all io-resources to avoid leaks |
| if (is != null) { |
| try { |
| is.close(); |
| } catch (IOException ignored) { |
| } |
| is = null; |
| } |
| if (r != null) { |
| try{ |
| r.close(); |
| } catch (IOException ignored) { |
| } |
| r = null; |
| } |
| if (br != null) { |
| try { |
| br.close(); |
| } catch (IOException ignored) { |
| } |
| br = null; |
| } |
| } |
| } |
| return l.iterator(); |
| } |
| } |