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    import java.io.BufferedReader;
020    import java.io.IOException;
021    import java.io.InputStreamReader;
022    import java.lang.reflect.Method;
023    
024    import java.net.URL;
025    import java.util.Enumeration;
026    import java.util.HashSet;
027    import java.util.Set;
028    import java.util.StringTokenizer;
029    import static java.lang.reflect.Modifier.isAbstract;
030    import static java.lang.reflect.Modifier.isPublic;
031    import static java.lang.reflect.Modifier.isStatic;
032    
033    import org.apache.camel.Converter;
034    import org.apache.camel.Exchange;
035    import org.apache.camel.FallbackConverter;
036    import org.apache.camel.TypeConverter;
037    import org.apache.camel.spi.PackageScanClassResolver;
038    import org.apache.camel.spi.TypeConverterRegistry;
039    import org.apache.camel.util.ObjectHelper;
040    import org.apache.commons.logging.Log;
041    import org.apache.commons.logging.LogFactory;
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: 749648 $
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        protected PackageScanClassResolver resolver;
053        private Set<Class> visitedClasses = new HashSet<Class>();
054    
055        public AnnotationTypeConverterLoader(PackageScanClassResolver resolver) {
056            this.resolver = resolver;
057        }
058    
059        @SuppressWarnings("unchecked")
060        public void load(TypeConverterRegistry registry) throws Exception {
061            String[] packageNames = findPackageNames();
062            Set<Class> classes = resolver.findAnnotated(Converter.class, packageNames);
063            for (Class type : classes) {
064                if (LOG.isDebugEnabled()) {
065                    LOG.debug("Loading converter class: " + ObjectHelper.name(type));
066                }
067                loadConverterMethods(registry, type);
068            }
069        }
070    
071        /**
072         * Finds the names of the packages to search for on the classpath looking
073         * for text files on the classpath at the {@link #META_INF_SERVICES} location.
074         *
075         * @return a collection of packages to search for
076         * @throws IOException is thrown for IO related errors
077         */
078        protected String[] findPackageNames() throws IOException {
079            Set<String> packages = new HashSet<String>();
080            ClassLoader ccl = Thread.currentThread().getContextClassLoader();
081            if (ccl != null) {
082                findPackages(packages, ccl);
083            }
084            findPackages(packages, getClass().getClassLoader());
085            return packages.toArray(new String[packages.size()]);
086        }
087    
088        protected void findPackages(Set<String> packages, ClassLoader classLoader) throws IOException {
089            Enumeration<URL> resources = classLoader.getResources(META_INF_SERVICES);
090            while (resources.hasMoreElements()) {
091                URL url = resources.nextElement();
092                if (url != null) {
093                    BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream()));
094                    try {
095                        while (true) {
096                            String line = reader.readLine();
097                            if (line == null) {
098                                break;
099                            }
100                            line = line.trim();
101                            if (line.startsWith("#") || line.length() == 0) {
102                                continue;
103                            }
104                            tokenize(packages, line);
105                        }
106                    } finally {
107                        ObjectHelper.close(reader, null, LOG);
108                    }
109                }
110            }
111        }
112    
113        /**
114         * Tokenizes the line from the META-IN/services file using commas and
115         * ignoring whitespace between packages
116         */
117        private void tokenize(Set<String> packages, String line) {
118            StringTokenizer iter = new StringTokenizer(line, ",");
119            while (iter.hasMoreTokens()) {
120                String name = iter.nextToken().trim();
121                if (name.length() > 0) {
122                    packages.add(name);
123                }
124            }
125        }
126    
127        /**
128         * Loads all of the converter methods for the given type
129         */
130        protected void loadConverterMethods(TypeConverterRegistry registry, Class type) {
131            if (visitedClasses.contains(type)) {
132                return;
133            }
134            visitedClasses.add(type);
135            try {
136                Method[] methods = type.getDeclaredMethods();
137                CachingInjector injector = null;
138    
139                for (Method method : methods) {
140                    // this may be prone to ClassLoader or packaging problems when the same class is defined
141                    // in two different jars (as is the case sometimes with specs).
142                    if (ObjectHelper.hasAnnotation(method, Converter.class, true)) {
143                        injector = handleHasConverterAnnotation(registry, type, injector, method);
144                    } else if (ObjectHelper.hasAnnotation(method, FallbackConverter.class, true)) {
145                        injector = handleHasFallbackConverterAnnotation(registry, type, injector, method);
146                    }
147                }
148    
149                Class superclass = type.getSuperclass();
150                if (superclass != null && !superclass.equals(Object.class)) {
151                    loadConverterMethods(registry, superclass);
152                }
153            } catch (NoClassDefFoundError e) {
154                LOG.warn("Ignoring converter type: " + type.getCanonicalName() + " as a dependent class could not be found: " + e, e);
155            }
156        }
157    
158        @SuppressWarnings("unchecked")
159        private CachingInjector handleHasConverterAnnotation(TypeConverterRegistry registry, Class type, CachingInjector injector, Method method) {
160            if (isValidConverterMethod(method)) {
161                int modifiers = method.getModifiers();
162                if (isAbstract(modifiers) || !isPublic(modifiers)) {
163                    LOG.warn("Ignoring bad converter on type: " + type.getCanonicalName() + " method: " + method
164                            + " as a converter method is not a public and concrete method");
165                } else {
166                    Class<?> toType = method.getReturnType();
167                    if (toType.equals(Void.class)) {
168                        LOG.warn("Ignoring bad converter on type: " + type.getCanonicalName() + " method: "
169                                + method + " as a converter method returns a void method");
170                    } else {
171                        Class<?> fromType = method.getParameterTypes()[0];
172                        if (isStatic(modifiers)) {
173                            registerTypeConverter(registry, method, toType, fromType,
174                                    new StaticMethodTypeConverter(method));
175                        } else {
176                            if (injector == null) {
177                                injector = new CachingInjector(registry, type);
178                            }
179                            registerTypeConverter(registry, method, toType, fromType,
180                                    new InstanceMethodTypeConverter(injector, method));
181                        }
182                    }
183                }
184            } else {
185                LOG.warn("Ignoring bad converter on type: " + type.getCanonicalName() + " method: " + method
186                        + " as a converter method should have one parameter");
187            }
188            return injector;
189        }
190    
191        @SuppressWarnings("unchecked")
192        private CachingInjector handleHasFallbackConverterAnnotation(TypeConverterRegistry registry, Class type, CachingInjector injector, Method method) {
193            if (isValidFallbackConverterMethod(method)) {
194                int modifiers = method.getModifiers();
195                if (isAbstract(modifiers) || !isPublic(modifiers)) {
196                    LOG.warn("Ignoring bad fallback converter on type: " + type.getCanonicalName() + " method: " + method
197                            + " as a fallback converter method is not a public and concrete method");
198                } else {
199                    Class<?> toType = method.getReturnType();
200                    if (toType.equals(Void.class)) {
201                        LOG.warn("Ignoring bad fallback converter on type: " + type.getCanonicalName() + " method: "
202                                + method + " as a fallback converter method returns a void method");
203                    } else {
204                        if (isStatic(modifiers)) {
205                            registerFallbackTypeConverter(registry, new StaticMethodFallbackTypeConverter(method, registry));
206                        } else {
207                            if (injector == null) {
208                                injector = new CachingInjector(registry, type);
209                            }
210                            registerFallbackTypeConverter(registry, new InstanceMethodFallbackTypeConverter(injector, method, registry));
211                        }
212                    }
213                }
214            } else {
215                LOG.warn("Ignoring bad fallback converter on type: " + type.getCanonicalName() + " method: " + method
216                        + " as a fallback converter method should have one parameter");
217            }
218            return injector;
219        }
220    
221        protected void registerTypeConverter(TypeConverterRegistry registry,
222                                             Method method, Class toType, Class fromType, TypeConverter typeConverter) {
223            registry.addTypeConverter(toType, fromType, typeConverter);
224        }
225    
226        protected boolean isValidConverterMethod(Method method) {
227            Class<?>[] parameterTypes = method.getParameterTypes();
228            return (parameterTypes != null) && (parameterTypes.length == 1
229                    || (parameterTypes.length == 2 && Exchange.class.isAssignableFrom(parameterTypes[1])));
230        }
231    
232        protected void registerFallbackTypeConverter(TypeConverterRegistry registry, TypeConverter typeConverter) {
233            registry.addFallbackTypeConverter(typeConverter);
234        }
235    
236        protected boolean isValidFallbackConverterMethod(Method method) {
237            Class<?>[] parameterTypes = method.getParameterTypes();
238            return (parameterTypes != null) && (parameterTypes.length == 3
239                    || (parameterTypes.length == 4 && Exchange.class.isAssignableFrom(parameterTypes[1]))
240                    && (TypeConverterRegistry.class.isAssignableFrom(parameterTypes[parameterTypes.length - 1])));
241        }
242    }