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.annotation.Annotation;
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.Exchange;
037    import org.apache.camel.TypeConverter;
038    import org.apache.camel.util.ObjectHelper;
039    import org.apache.camel.util.ResolverUtil;
040    import org.apache.camel.util.WebSphereResolverUtil;
041    import org.apache.commons.logging.Log;
042    import org.apache.commons.logging.LogFactory;
043    
044    /**
045     * A class which will auto-discover converter objects and methods to pre-load
046     * the registry of converters on startup
047     *
048     * @version $Revision: 56884 $
049     */
050    public class AnnotationTypeConverterLoader implements TypeConverterLoader {
051        public static final String META_INF_SERVICES = "META-INF/services/org/apache/camel/TypeConverter";
052        private static final transient Log LOG = LogFactory.getLog(AnnotationTypeConverterLoader.class);
053        private ResolverUtil resolver = new ResolverUtil();
054        private Set<Class> visitedClasses = new HashSet<Class>();
055    
056        public AnnotationTypeConverterLoader() {
057            // use WebSphere specific resolver if running on WebSphere
058            if (WebSphereResolverUtil.isWebSphereClassLoader(this.getClass().getClassLoader())) {
059                LOG.info("Using WebSphere specific ResolverUtil");
060                resolver = new WebSphereResolverUtil(META_INF_SERVICES);
061            }
062        }
063    
064        public void load(TypeConverterRegistry registry) throws Exception {
065            String[] packageNames = findPackageNames();
066            resolver.findAnnotated(Converter.class, packageNames);
067            Set<Class> classes = resolver.getClasses();
068            for (Class type : classes) {
069                if (LOG.isDebugEnabled()) {
070                    LOG.debug("Loading converter class: " + ObjectHelper.name(type));
071                }
072                loadConverterMethods(registry, type);
073            }
074        }
075    
076        /**
077         * Finds the names of the packages to search for on the classpath looking
078         * for text files on the classpath at the {@link #META_INF_SERVICES} location.
079         *
080         * @return a collection of packages to search for
081         * @throws IOException is thrown for IO related errors
082         */
083        protected String[] findPackageNames() throws IOException {
084            Set<String> packages = new HashSet<String>();
085            findPackages(packages, Thread.currentThread().getContextClassLoader());
086            findPackages(packages, getClass().getClassLoader());
087            return packages.toArray(new String[packages.size()]);
088        }
089    
090        protected void findPackages(Set<String> packages, ClassLoader classLoader) throws IOException {
091            Enumeration<URL> resources = classLoader.getResources(META_INF_SERVICES);
092            while (resources.hasMoreElements()) {
093                URL url = resources.nextElement();
094                if (url != null) {
095                    BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream()));
096                    try {
097                        while (true) {
098                            String line = reader.readLine();
099                            if (line == null) {
100                                break;
101                            }
102                            line = line.trim();
103                            if (line.startsWith("#") || line.length() == 0) {
104                                continue;
105                            }
106                            tokenize(packages, line);
107                        }
108                    } finally {
109                        ObjectHelper.close(reader, null, LOG);
110                    }
111                }
112            }
113        }
114    
115        /**
116         * Tokenizes the line from the META-IN/services file using commas and
117         * ignoring whitespace between packages
118         */
119        protected void tokenize(Set<String> packages, String line) {
120            StringTokenizer iter = new StringTokenizer(line, ",");
121            while (iter.hasMoreTokens()) {
122                String name = iter.nextToken().trim();
123                if (name.length() > 0) {
124                    packages.add(name);
125                }
126            }
127        }
128    
129        /**
130         * Loads all of the converter methods for the given type
131         */
132        protected void loadConverterMethods(TypeConverterRegistry registry, Class type) {
133            if (visitedClasses.contains(type)) {
134                return;
135            }
136            visitedClasses.add(type);
137            try {
138                Method[] methods = type.getDeclaredMethods();
139                CachingInjector injector = null;
140    
141                for (Method method : methods) {
142                    // this may be prone to ClassLoader or packaging problems when the same class is defined
143                    // in two different jars (as is the case sometimes with specs).
144                    if (ObjectHelper.hasAnnotation(method, Converter.class, true)) {
145                        if (isValidConverterMethod(method)) {
146                            int modifiers = method.getModifiers();
147                            if (isAbstract(modifiers) || !isPublic(modifiers)) {
148                                LOG.warn("Ignoring bad converter on type: " + type.getName() + " method: " + method
149                                        + " as a converter method is not a public and concrete method");
150                            } else {
151                                Class<?> toType = method.getReturnType();
152                                if (toType.equals(Void.class)) {
153                                    LOG.warn("Ignoring bad converter on type: " + type.getName() + " method: "
154                                            + method + " as a converter method returns a void method");
155                                } else {
156                                    Class<?> fromType = method.getParameterTypes()[0];
157                                    if (isStatic(modifiers)) {
158                                        registerTypeConverter(registry, method, toType, fromType,
159                                                new StaticMethodTypeConverter(method));
160                                    } else {
161                                        if (injector == null) {
162                                            injector = new CachingInjector(registry, type);
163                                        }
164                                        registerTypeConverter(registry, method, toType, fromType,
165                                                new InstanceMethodTypeConverter(injector, method));
166                                    }
167                                }
168                            }
169                        } else {
170                            LOG.warn("Ignoring bad converter on type: " + type.getName() + " method: " + method
171                                    + " as a converter method should have one parameter");
172                        }
173                    }
174                }
175    
176                Class superclass = type.getSuperclass();
177                if (superclass != null && !superclass.equals(Object.class)) {
178                    loadConverterMethods(registry, superclass);
179                }
180            } catch (NoClassDefFoundError e) {
181                LOG.warn("Ignoring converter type: " + type.getName() + " as a dependent class could not be found: " + e, e);
182            }
183        }
184    
185        protected void registerTypeConverter(TypeConverterRegistry registry,
186                                             Method method, Class toType, Class fromType, TypeConverter typeConverter) {
187    
188            registry.addTypeConverter(toType, fromType, typeConverter);
189        }
190    
191        protected boolean isValidConverterMethod(Method method) {
192            Class<?>[] parameterTypes = method.getParameterTypes();
193            return (parameterTypes != null) && (parameterTypes.length == 1
194                || (parameterTypes.length == 2 && Exchange.class.isAssignableFrom(parameterTypes[1])));
195        }
196    }