ReflectionUtils.java

/*
 * Copyright 2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.obm.messagepack.util;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.msgpack.MessagePack;

import java.lang.reflect.Method;
import java.util.*;

/**
 * This code crawls the entire object graph, looking for interesting objects that are found on your service interface. It ignores
 * obviously incorrect objects like objects from MesssagePack itself (which shouldnt be registered), and objects from the JDK that
 * already are registered (like 'int') or shouldn't be (like 'void')
 *
 * @author Josh Long
 */
public abstract class ReflectionUtils {

    private static Log log = LogFactory.getLog(ReflectionUtils.class);


    /**
     * Callback for the {@link TypeUtils#getGenericTypesForReturnValue(java.lang.reflect.Method)} method.
     */
    public static interface ClassTraversalCallback {
        void doWithClass(Class<?> o);
    }

    /**
     * Utility object to help traverse objects to "discover" any related types.
     */
    private static class ObjectClassTraverser {

        private Set<String> prefixesToAvoid = new HashSet<String>();

        private ObjectClassTraverser(Set<String> prefixesToAvoid) {
            this.prefixesToAvoid = prefixesToAvoid;
        }

        private Collection<Class> findClassesToVisit(Method method) {
            Set<Class> classes = new HashSet<Class>();
            classes.add(method.getReturnType());
            Collections.addAll(classes, method.getParameterTypes());
            Collections.addAll(classes, TypeUtils.getGenericTypesForReturnValue(method));
            return classes;
        }

        private org.springframework.util.ReflectionUtils.MethodFilter nonObjectMethodsFilter = new org.springframework.util.ReflectionUtils.MethodFilter() {
            private List<Method> methods = Arrays.asList(Object.class.getDeclaredMethods());
            private String packageForJavaLang = String.class.getPackage().getName();

            @Override
            public boolean matches(Method method) {

                if (log.isDebugEnabled()) {
                    log.debug(method.toGenericString());
                    log.debug("is found? : " + methods.contains(method));
                }

                return !method.getDeclaringClass().getPackage().getName().equalsIgnoreCase(packageForJavaLang)
                               && !methods.contains(method);
            }
        };

        private boolean shouldSkip(Class<?> clzz) {
            String className = clzz.getName();
            for (String p : this.prefixesToAvoid) {
                if (className.startsWith(p)) {
                    return true;
                }
            }
            return false;
        }


        protected void doCrawl(Class<?> clzz, final Set<Class> toVisit, final ClassTraversalCallback callback) {
            org.springframework.util.ReflectionUtils.MethodCallback mc = new org.springframework.util.ReflectionUtils.MethodCallback() {
                @Override
                public void doWith(Method method) throws IllegalArgumentException, IllegalAccessException {
                    Collection<Class> classesToVisit = findClassesToVisit(method);
                    for (Class c : classesToVisit) {
                        if (!isUninterestingClass(c) && !shouldSkip(c)) {
                            if (!toVisit.contains(c)) {
                                toVisit.add(c);
                                doCrawl(c, toVisit, callback);
                                callback.doWithClass(c);
                            }
                        }
                    }
                }
            };
            org.springframework.util.ReflectionUtils.doWithMethods(clzz, mc, nonObjectMethodsFilter);
        }
    }

    public static void crawlJavaBeanObjectGraph(Class<?> src, ClassTraversalCallback objectCallback, Set<String> classNamePrefixesToAvoid) {
        final Set<Class> classesToVisit = new HashSet<Class>();
        ObjectClassTraverser classTraverser = new ObjectClassTraverser(classNamePrefixesToAvoid);
        classTraverser.doCrawl(src, classesToVisit, objectCallback);
    }

    public static void crawlJavaBeanObjectGraph(Class<?> src, ClassTraversalCallback objectCallback) {
        crawlJavaBeanObjectGraph(src, objectCallback, new HashSet<String>());
    }


    /**
     * is the class a unique class likely to be worth registering?
     *
     * @param clazz
     * @return
     */
    public static boolean isUninterestingClass(Class<?> clazz) {
        String javaPackage = "java";
        String messagePackPackage = MessagePack.class.getPackage().getName();
        String clazzName = clazz.getName();
        return !(!clazzName.startsWith(javaPackage) && !clazzName.startsWith(messagePackPackage) &&
                         !clazz.isInterface() && !clazz.isPrimitive() && !clazz.isArray() &&
                         !clazzName.startsWith(MessagePack.class.getPackage().getName()));
    }

}