001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.camel.impl.converter;
018
019
020 import java.io.BufferedReader;
021 import java.io.IOException;
022 import java.io.InputStreamReader;
023
024 import java.lang.reflect.Method;
025
026 import java.net.URL;
027 import java.util.Enumeration;
028 import java.util.HashSet;
029 import java.util.Set;
030 import java.util.StringTokenizer;
031 import static java.lang.reflect.Modifier.isAbstract;
032 import static java.lang.reflect.Modifier.isPublic;
033 import static java.lang.reflect.Modifier.isStatic;
034
035 import org.apache.camel.Converter;
036 import org.apache.camel.TypeConverter;
037 import org.apache.camel.util.ObjectHelper;
038 import org.apache.camel.util.ResolverUtil;
039 import org.apache.commons.logging.Log;
040 import org.apache.commons.logging.LogFactory;
041
042
043 /**
044 * A class which will auto-discover converter objects and methods to pre-load
045 * the registry of converters on startup
046 *
047 * @version $Revision: 37863 $
048 */
049 public class AnnotationTypeConverterLoader implements TypeConverterLoader {
050 public static final String META_INF_SERVICES = "META-INF/services/org/apache/camel/TypeConverter";
051 private static final transient Log LOG = LogFactory.getLog(AnnotationTypeConverterLoader.class);
052 private ResolverUtil resolver = new ResolverUtil();
053 private Set<Class> visitedClasses = new HashSet<Class>();
054
055 public void load(TypeConverterRegistry registry) throws Exception {
056 String[] packageNames = findPackageNames();
057 resolver.findAnnotated(Converter.class, packageNames);
058 Set<Class> classes = resolver.getClasses();
059 for (Class type : classes) {
060 if (LOG.isDebugEnabled()) {
061 LOG.debug("Loading converter class: " + ObjectHelper.name(type));
062 }
063 loadConverterMethods(registry, type);
064 }
065 }
066
067 /**
068 * Finds the names of the packages to search for on the classpath looking
069 * for text files on the classpath at the {@link #META_INF_SERVICES} location.
070 *
071 * @return a collection of packages to search for
072 * @throws IOException is thrown for IO related errors
073 */
074 protected String[] findPackageNames() throws IOException {
075 Set<String> packages = new HashSet<String>();
076 findPackages(packages, Thread.currentThread().getContextClassLoader());
077 findPackages(packages, getClass().getClassLoader());
078 return packages.toArray(new String[packages.size()]);
079 }
080
081 protected void findPackages(Set<String> packages, ClassLoader classLoader) throws IOException {
082 Enumeration<URL> resources = classLoader.getResources(META_INF_SERVICES);
083 while (resources.hasMoreElements()) {
084 URL url = resources.nextElement();
085 if (url != null) {
086 BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream()));
087 try {
088 while (true) {
089 String line = reader.readLine();
090 if (line == null) {
091 break;
092 }
093 line = line.trim();
094 if (line.startsWith("#") || line.length() == 0) {
095 continue;
096 }
097 tokenize(packages, line);
098 }
099 } finally {
100 try {
101 reader.close();
102 } catch (IOException e) {
103 LOG.warn("Caught exception closing stream: " + e, e);
104 }
105 }
106 }
107 }
108 }
109
110 /**
111 * Tokenizes the line from the META-IN/services file using commas and
112 * ignoring whitespace between packages
113 */
114 protected void tokenize(Set<String> packages, String line) {
115 StringTokenizer iter = new StringTokenizer(line, ",");
116 while (iter.hasMoreTokens()) {
117 String name = iter.nextToken().trim();
118 if (name.length() > 0) {
119 packages.add(name);
120 }
121 }
122 }
123
124 /**
125 * Loads all of the converter methods for the given type
126 */
127 protected void loadConverterMethods(TypeConverterRegistry registry, Class type) {
128 if (visitedClasses.contains(type)) {
129 return;
130 }
131 visitedClasses.add(type);
132 try {
133 Method[] methods = type.getDeclaredMethods();
134 CachingInjector injector = null;
135
136 for (Method method : methods) {
137 Converter annotation = method.getAnnotation(Converter.class);
138 if (annotation != null) {
139 Class<?>[] parameterTypes = method.getParameterTypes();
140 if (parameterTypes == null || parameterTypes.length != 1) {
141 LOG.warn("Ignoring bad converter on type: " + type.getName() + " method: " + method
142 + " as a converter method should have one parameter");
143 } else {
144 int modifiers = method.getModifiers();
145 if (isAbstract(modifiers) || !isPublic(modifiers)) {
146 LOG.warn("Ignoring bad converter on type: " + type.getName() + " method: " + method
147 + " as a converter method is not a public and concrete method");
148 } else {
149 Class toType = method.getReturnType();
150 if (toType.equals(Void.class)) {
151 LOG.warn("Ignoring bad converter on type: " + type.getName() + " method: "
152 + method + " as a converter method returns a void method");
153 } else {
154 Class fromType = parameterTypes[0];
155 if (isStatic(modifiers)) {
156 registerTypeConverter(registry, method, toType, fromType,
157 new StaticMethodTypeConverter(method));
158 } else {
159 if (injector == null) {
160 injector = new CachingInjector(registry, type);
161 }
162 registerTypeConverter(registry, method, toType, fromType,
163 new InstanceMethodTypeConverter(injector, method));
164 }
165 }
166 }
167 }
168 }
169 }
170 Class superclass = type.getSuperclass();
171 if (superclass != null && !superclass.equals(Object.class)) {
172 loadConverterMethods(registry, superclass);
173 }
174 } catch (NoClassDefFoundError e) {
175 LOG.debug("Ignoring converter type: " + type.getName() + " as a dependent class could not be found: " + e, e);
176 }
177 }
178
179 protected void registerTypeConverter(TypeConverterRegistry registry, Method method,
180 Class toType, Class fromType, TypeConverter typeConverter) {
181
182 registry.addTypeConverter(toType, fromType, typeConverter);
183 }
184 }