[6785] | 1 | /**************************************************************** |
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| 2 | * Licensed to the Apache Software Foundation (ASF) under one * |
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| 3 | * or more contributor license agreements. See the NOTICE file * |
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| 4 | * distributed with this work for additional information * |
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| 5 | * regarding copyright ownership. The ASF licenses this file * |
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| 6 | * to you under the Apache License, Version 2.0 (the * |
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| 7 | * "License"); you may not use this file except in compliance * |
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| 8 | * with the License. You may obtain a copy of the License at * |
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| 9 | * * |
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| 10 | * http://www.apache.org/licenses/LICENSE-2.0 * |
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| 11 | * * |
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| 12 | * Unless required by applicable law or agreed to in writing, * |
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| 13 | * software distributed under the License is distributed on an * |
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| 14 | * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * |
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| 15 | * KIND, either express or implied. See the License for the * |
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| 16 | * specific language governing permissions and limitations * |
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| 17 | * under the License. * |
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| 18 | ****************************************************************/ |
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| 19 | package org.apache.james.mime4j.dom; |
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| 20 | |
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| 21 | import java.io.BufferedReader; |
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| 22 | import java.io.IOException; |
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| 23 | import java.io.InputStream; |
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| 24 | import java.io.InputStreamReader; |
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| 25 | import java.net.URL; |
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| 26 | import java.util.Enumeration; |
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| 27 | |
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| 28 | /** |
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| 29 | * Utility class to load Service Providers (SPI). |
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| 30 | * This will deprecated as soon as mime4j will be upgraded to Java6 |
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| 31 | * as Java6 has javax.util.ServiceLoader as a core class. |
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| 32 | */ |
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| 33 | class ServiceLoader { |
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| 34 | |
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| 35 | private ServiceLoader() { |
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| 36 | } |
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| 37 | |
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| 38 | /** |
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| 39 | * Loads a Service Provider for the given interface/class (SPI). |
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| 40 | */ |
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| 41 | static <T> T load(Class<T> spiClass) { |
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| 42 | String spiResURI = "META-INF/services/" + spiClass.getName(); |
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| 43 | ClassLoader classLoader = spiClass.getClassLoader(); |
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| 44 | try { |
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| 45 | Enumeration<URL> resources = classLoader.getResources(spiResURI); |
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| 46 | while (resources.hasMoreElements()) { |
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| 47 | URL resource = resources.nextElement(); |
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| 48 | InputStream instream = resource.openStream(); |
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| 49 | try { |
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| 50 | BufferedReader reader = new BufferedReader(new InputStreamReader(instream)); |
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| 51 | String line; |
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| 52 | while ((line = reader.readLine()) != null) { |
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| 53 | line = line.trim(); |
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| 54 | int cmtIdx = line.indexOf('#'); |
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| 55 | if (cmtIdx != -1) { |
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| 56 | line = line.substring(0, cmtIdx); |
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| 57 | line = line.trim(); |
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| 58 | } |
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| 59 | |
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| 60 | if (line.length() == 0) { |
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| 61 | continue; |
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| 62 | } |
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| 63 | |
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| 64 | Class<?> implClass = classLoader.loadClass(line); |
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| 65 | if (spiClass.isAssignableFrom(implClass)) { |
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| 66 | Object impl = implClass.newInstance(); |
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| 67 | return spiClass.cast(impl); |
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| 68 | } |
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| 69 | } |
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| 70 | reader.close(); |
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| 71 | } finally { |
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| 72 | instream.close(); |
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| 73 | } |
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| 74 | } |
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| 75 | return null; |
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| 76 | } catch (IOException ex) { |
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| 77 | throw new ServiceLoaderException(ex); |
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| 78 | } catch (ClassNotFoundException ex) { |
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| 79 | throw new ServiceLoaderException("Unknown SPI class '" |
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| 80 | + spiClass.getName() + "'", ex); |
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| 81 | } catch (IllegalAccessException ex) { |
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| 82 | // Not visible |
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| 83 | return null; |
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| 84 | } catch (InstantiationException ex) { |
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| 85 | throw new ServiceLoaderException("SPI class '" |
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| 86 | + spiClass.getName() + "' cannot be instantiated", ex); |
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| 87 | } |
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| 88 | } |
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| 89 | |
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| 90 | } |
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