001 /*
002 GRANITE DATA SERVICES
003 Copyright (C) 2013 GRANITE DATA SERVICES S.A.S.
004
005 This file is part of Granite Data Services.
006
007 Granite Data Services is free software; you can redistribute it and/or modify
008 it under the terms of the GNU Library General Public License as published by
009 the Free Software Foundation; either version 2 of the License, or (at your
010 option) any later version.
011
012 Granite Data Services is distributed in the hope that it will be useful, but
013 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
014 FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License
015 for more details.
016
017 You should have received a copy of the GNU Library General Public License
018 along with this library; if not, see <http://www.gnu.org/licenses/>.
019 */
020
021 package org.granite.scan;
022
023 import java.io.BufferedReader;
024 import java.io.InputStream;
025 import java.io.InputStreamReader;
026 import java.net.URL;
027 import java.util.ArrayList;
028 import java.util.Enumeration;
029 import java.util.Iterator;
030 import java.util.List;
031 import java.util.logging.Level;
032 import java.util.logging.Logger;
033
034 /**
035 * @author Franck WOLFF
036 */
037 public class ServiceLoader<S> implements Iterable<S> {
038
039 // Can't use granite logger here, because service loader can be used to load a specific
040 // logger implementation (stack overflow...)
041 private static final Logger jdkLog = Logger.getLogger(ServiceLoader.class.getName());
042
043 private final Class<S> service;
044 private final ClassLoader loader;
045
046 private List<String> serviceClassNames;
047
048 private Class<?>[] constructorParameterTypes = new Class<?>[0];
049 private Object[] constructorParameters = new Object[0];
050
051 private ServiceLoader(Class<S> service, ClassLoader loader, List<String> servicesNames) {
052 this.service = service;
053 this.loader = loader;
054 this.serviceClassNames = servicesNames;
055 }
056
057 public void setConstructorParameters(Class<?>[] constructorParameterTypes, Object[] constructorParameters) {
058
059 if (constructorParameterTypes == null)
060 constructorParameterTypes = new Class<?>[0];
061 if (constructorParameters == null)
062 constructorParameters = new Object[0];
063
064 if (constructorParameterTypes.length != constructorParameters.length)
065 throw new IllegalArgumentException("constructor types and argurments must have the same size");
066
067 this.constructorParameterTypes = constructorParameterTypes;
068 this.constructorParameters = constructorParameters;
069 }
070
071 public ServicesIterator<S> iterator() {
072 return new ServicesIterator<S>(loader, serviceClassNames.iterator(), constructorParameterTypes, constructorParameters);
073 }
074
075 public void reload() {
076 ServiceLoader<S> serviceLoaderTmp = load(service, loader);
077 this.serviceClassNames = serviceLoaderTmp.serviceClassNames;
078 }
079
080 public static <S> ServiceLoader<S> load(Class<S> service) {
081 return load(service, Thread.currentThread().getContextClassLoader());
082 }
083
084 public static <S> ServiceLoader<S> load(final Class<S> service, final ClassLoader loader) {
085 List<String> serviceClassNames = new ArrayList<String>();
086
087 try {
088 // Standard Java platforms.
089 Enumeration<URL> en = loader.getResources("META-INF/services/" + service.getName());
090 while (en.hasMoreElements())
091 parse(en.nextElement(), serviceClassNames);
092
093 // Android support (META-INF/** files are not included in APK files).
094 en = loader.getResources("meta_inf/services/" + service.getName());
095 while (en.hasMoreElements())
096 parse(en.nextElement(), serviceClassNames);
097
098 return new ServiceLoader<S>(service, loader, serviceClassNames);
099 }
100 catch (Exception e) {
101 jdkLog.log(Level.SEVERE, "Could not load services of type " + service, e);
102 throw new RuntimeException(e);
103 }
104 }
105
106 private static void parse(URL serviceFile, List<String> serviceClassNames) {
107 try {
108 InputStream is = serviceFile.openStream();
109 try {
110 BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));
111
112 String serviceClassName = null;
113 while ((serviceClassName = reader.readLine()) != null) {
114 int comment = serviceClassName.indexOf('#');
115 if (comment >= 0)
116 serviceClassName = serviceClassName.substring(0, comment);
117 serviceClassName = serviceClassName.trim();
118 if (serviceClassName.length() > 0) {
119 jdkLog.log(Level.FINE, "Adding service " + serviceClassName + " from " + serviceFile);
120 serviceClassNames.add(serviceClassName);
121 }
122 }
123 }
124 finally {
125 is.close();
126 }
127 }
128 catch (Exception e) {
129 jdkLog.log(Level.SEVERE, "Could not parse service file " + serviceFile, e);
130 }
131 }
132
133 public static class ServicesIterator<S> implements Iterator<S> {
134
135 private final ClassLoader loader;
136 private final Iterator<String> serviceClassNames;
137 private final Class<?>[] constructorParameterTypes;
138 private final Object[] constructorParameters;
139
140 private ServicesIterator(ClassLoader loader, Iterator<String> servicesNames, Class<?>[] constructorParameterTypes, Object[] constructorParameters) {
141 this.loader = loader;
142 this.serviceClassNames = servicesNames;
143 this.constructorParameterTypes = constructorParameterTypes;
144 this.constructorParameters = constructorParameters;
145 }
146
147 public boolean hasNext() {
148 return serviceClassNames.hasNext();
149 }
150
151 public S next() {
152 String serviceClassName = serviceClassNames.next();
153 jdkLog.log(Level.FINE, "Loading service " + serviceClassName);
154 try {
155 @SuppressWarnings("unchecked")
156 Class<? extends S> serviceClass = (Class<? extends S>)loader.loadClass(serviceClassName);
157 return serviceClass.getConstructor(constructorParameterTypes).newInstance(constructorParameters);
158 }
159 catch (Throwable t) {
160 jdkLog.log(Level.SEVERE, "Could not load service " + serviceClassName, t);
161 throw new RuntimeException(t);
162 }
163 }
164
165 public void remove() {
166 throw new UnsupportedOperationException();
167 }
168 }
169 }