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    
023    import java.lang.reflect.Method;
024    
025    import java.net.URL;
026    import java.util.Enumeration;
027    import java.util.HashSet;
028    import java.util.Set;
029    import java.util.StringTokenizer;
030    import static java.lang.reflect.Modifier.isAbstract;
031    import static java.lang.reflect.Modifier.isPublic;
032    import static java.lang.reflect.Modifier.isStatic;
033    
034    import org.apache.camel.Converter;
035    import org.apache.camel.Exchange;
036    import org.apache.camel.TypeConverter;
037    import org.apache.camel.util.ObjectHelper;
038    import org.apache.camel.util.ResolverUtil;
039    import org.apache.camel.util.WebSphereResolverUtil;
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: 47146 $
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 AnnotationTypeConverterLoader() {
056            // use WebSphere specific resolver if running on WebSphere
057            if (WebSphereResolverUtil.isWebSphereClassLoader(this.getClass().getClassLoader())) {
058                LOG.info("Using WebSphere specific ResolverUtil");
059                resolver = new WebSphereResolverUtil(META_INF_SERVICES);
060            }
061        }
062    
063        public void load(TypeConverterRegistry registry) throws Exception {
064            String[] packageNames = findPackageNames();
065            resolver.findAnnotated(Converter.class, packageNames);
066            Set<Class> classes = resolver.getClasses();
067            for (Class type : classes) {
068                if (LOG.isDebugEnabled()) {
069                    LOG.debug("Loading converter class: " + ObjectHelper.name(type));
070                }
071                loadConverterMethods(registry, type);
072            }
073        }
074    
075        /**
076         * Finds the names of the packages to search for on the classpath looking
077         * for text files on the classpath at the {@link #META_INF_SERVICES} location.
078         *
079         * @return a collection of packages to search for
080         * @throws IOException is thrown for IO related errors
081         */
082        protected String[] findPackageNames() throws IOException {
083            Set<String> packages = new HashSet<String>();
084            findPackages(packages, Thread.currentThread().getContextClassLoader());
085            findPackages(packages, getClass().getClassLoader());
086            return packages.toArray(new String[packages.size()]);
087        }
088    
089        protected void findPackages(Set<String> packages, ClassLoader classLoader) throws IOException {
090            Enumeration<URL> resources = classLoader.getResources(META_INF_SERVICES);
091            while (resources.hasMoreElements()) {
092                URL url = resources.nextElement();
093                if (url != null) {
094                    BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream()));
095                    try {
096                        while (true) {
097                            String line = reader.readLine();
098                            if (line == null) {
099                                break;
100                            }
101                            line = line.trim();
102                            if (line.startsWith("#") || line.length() == 0) {
103                                continue;
104                            }
105                            tokenize(packages, line);
106                        }
107                    } finally {
108                        ObjectHelper.close(reader, null, LOG);
109                    }
110                }
111            }
112        }
113    
114        /**
115         * Tokenizes the line from the META-IN/services file using commas and
116         * ignoring whitespace between packages
117         */
118        protected void tokenize(Set<String> packages, String line) {
119            StringTokenizer iter = new StringTokenizer(line, ",");
120            while (iter.hasMoreTokens()) {
121                String name = iter.nextToken().trim();
122                if (name.length() > 0) {
123                    packages.add(name);
124                }
125            }
126        }
127    
128        /**
129         * Loads all of the converter methods for the given type
130         */
131        protected void loadConverterMethods(TypeConverterRegistry registry, Class type) {
132            if (visitedClasses.contains(type)) {
133                return;
134            }
135            visitedClasses.add(type);
136            try {
137                Method[] methods = type.getDeclaredMethods();
138                CachingInjector injector = null;
139    
140                for (Method method : methods) {
141                    Converter annotation = method.getAnnotation(Converter.class);
142                    if (annotation != null) {
143                        if (isValidConverterMethod(method)) {
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 = method.getParameterTypes()[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                        } else {
168                            LOG.warn("Ignoring bad converter on type: " + type.getName() + " method: " + method
169                                    + " as a converter method should have one parameter");
170                        }
171                    }
172                }
173    
174                Class superclass = type.getSuperclass();
175                if (superclass != null && !superclass.equals(Object.class)) {
176                    loadConverterMethods(registry, superclass);
177                }
178            } catch (NoClassDefFoundError e) {
179                LOG.debug("Ignoring converter type: " + type.getName() + " as a dependent class could not be found: " + e, e);
180            }
181        }
182    
183        protected void registerTypeConverter(TypeConverterRegistry registry,
184                                             Method method, Class toType, Class fromType, TypeConverter typeConverter) {
185    
186            registry.addTypeConverter(toType, fromType, typeConverter);
187        }
188    
189        protected boolean isValidConverterMethod(Method method) {
190            Class<?>[] parameterTypes = method.getParameterTypes();
191            return (parameterTypes != null) && (parameterTypes.length == 1
192                || (parameterTypes.length == 2 && Exchange.class.isAssignableFrom(parameterTypes[1])));
193        }
194    }