org.springmodules.cache.util.Reflections.java Source code

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Here is the source code for org.springmodules.cache.util.Reflections.java

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/*
 * Created on Nov 25, 2005
 *
 * 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.
 *
 * Copyright @2005 the original author or authors.
 */
package org.springmodules.cache.util;

import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.lang.reflect.Method;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;

import org.springframework.util.ReflectionUtils;

import org.springmodules.util.Objects;

/**
 * <p>
 * Reflection-related utility methods.
 * </p>
 *
 * @author Omar Irbouh
 * @author Alex Ruiz
 */
public abstract class Reflections {

    private static final int INITIAL_HASH = 7;

    private static final int MULTIPLIER = 31;

    /**
     * <p>
     * This method uses reflection to build a valid hash code.
     * </p>
     *
     * <p>
     * It uses <code>AccessibleObject.setAccessible</code> to gain access to
     * private fields. This means that it will throw a security exception if run
     * under a security manager, if the permissions are not set up correctly. It
     * is also not as efficient as testing explicitly.
     * </p>
     *
     * <p>
     * Transient members will not be used, as they are likely derived fields,
     * and not part of the value of the <code>Object</code>.
     * </p>
     *
     * <p>
     * Static fields will not be tested. Superclass fields will be included.
     * </p>
     *
     * @param obj
     *          the object to create a <code>hashCode</code> for
     * @return the generated hash code, or zero if the given object is
     *         <code>null</code>
     */
    public static int reflectionHashCode(Object obj) {
        if (obj == null)
            return 0;

        Class targetClass = obj.getClass();
        if (Objects.isArrayOfPrimitives(obj) || Objects.isPrimitiveOrWrapper(targetClass)) {
            return Objects.nullSafeHashCode(obj);
        }

        if (targetClass.isArray()) {
            return reflectionHashCode((Object[]) obj);
        }

        if (obj instanceof Collection) {
            return reflectionHashCode((Collection) obj);
        }

        if (obj instanceof Map) {
            return reflectionHashCode((Map) obj);
        }

        // determine whether the object's class declares hashCode() or has a
        // superClass other than java.lang.Object that declares hashCode()
        Class clazz = (obj instanceof Class) ? (Class) obj : obj.getClass();
        Method hashCodeMethod = ReflectionUtils.findMethod(clazz, "hashCode", new Class[0]);

        if (hashCodeMethod != null) {
            return obj.hashCode();
        }

        // could not find a hashCode other than the one declared by java.lang.Object
        int hash = INITIAL_HASH;

        try {
            while (targetClass != null) {
                Field[] fields = targetClass.getDeclaredFields();
                AccessibleObject.setAccessible(fields, true);

                for (int i = 0; i < fields.length; i++) {
                    Field field = fields[i];
                    int modifiers = field.getModifiers();

                    if (!Modifier.isStatic(modifiers) && !Modifier.isTransient(modifiers)) {
                        hash = MULTIPLIER * hash + reflectionHashCode(field.get(obj));
                    }
                }
                targetClass = targetClass.getSuperclass();
            }
        } catch (IllegalAccessException exception) {
            // ///CLOVER:OFF
            ReflectionUtils.handleReflectionException(exception);
            // ///CLOVER:ON
        }

        return hash;
    }

    private static int reflectionHashCode(Collection collection) {
        int hash = INITIAL_HASH;

        for (Iterator i = collection.iterator(); i.hasNext();) {
            hash = MULTIPLIER * hash + reflectionHashCode(i.next());
        }

        return hash;
    }

    private static int reflectionHashCode(Map map) {
        int hash = INITIAL_HASH;

        for (Iterator i = map.entrySet().iterator(); i.hasNext();) {
            Map.Entry entry = (Map.Entry) i.next();
            hash = MULTIPLIER * hash + reflectionHashCode(entry);
        }

        return hash;
    }

    private static int reflectionHashCode(Map.Entry entry) {
        int hash = INITIAL_HASH;
        hash = MULTIPLIER * hash + reflectionHashCode(entry.getKey());
        hash = MULTIPLIER * hash + reflectionHashCode(entry.getValue());
        return hash;
    }

    private static int reflectionHashCode(Object[] array) {
        int hash = INITIAL_HASH;
        int arraySize = array.length;
        for (int i = 0; i < arraySize; i++) {
            hash = MULTIPLIER * hash + reflectionHashCode(array[i]);
        }

        return hash;
    }
}