CopyFromHelper.java

/*
 * Copyright 2004 Sun Microsystems, Inc.
 *
 * 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 com.rometools.rome.feed.impl;

import java.lang.reflect.Array;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.rometools.rome.feed.CopyFrom;

public class CopyFromHelper {

    private static final Logger LOG = LoggerFactory.getLogger(CopyFromHelper.class);

    private static final Set<Class<?>> BASIC_TYPES = new HashSet<Class<?>>();
    private static final Object[] NO_PARAMS = new Object[0];

    private final Class<? extends CopyFrom> beanInterfaceClass;
    private final Map<String, Class<?>> baseInterfaceMap; // ENTRIES(propertyName,interface.class)
    private final Map<Class<? extends CopyFrom>, Class<?>> baseImplMap; // ENTRIES(interface.class,implementation.class)

    static {
        BASIC_TYPES.add(Boolean.class);
        BASIC_TYPES.add(Byte.class);
        BASIC_TYPES.add(Character.class);
        BASIC_TYPES.add(Double.class);
        BASIC_TYPES.add(Float.class);
        BASIC_TYPES.add(Integer.class);
        BASIC_TYPES.add(Long.class);
        BASIC_TYPES.add(Short.class);
        BASIC_TYPES.add(String.class);
        BASIC_TYPES.add(Date.class);
    }

    public CopyFromHelper(final Class<? extends CopyFrom> beanInterfaceClass, final Map<String, Class<?>> basePropInterfaceMap,
            final Map<Class<? extends CopyFrom>, Class<?>> basePropClassImplMap) {
        this.beanInterfaceClass = beanInterfaceClass;
        baseInterfaceMap = basePropInterfaceMap;
        baseImplMap = basePropClassImplMap;
    }

    public void copy(final Object target, final Object source) {

        try {

            final List<PropertyDescriptor> propertyDescriptors = BeanIntrospector.getPropertyDescriptorsWithGettersAndSetters(beanInterfaceClass);
            for (final PropertyDescriptor propertyDescriptor : propertyDescriptors) {

                final String propertyName = propertyDescriptor.getName();

                if (baseInterfaceMap.containsKey(propertyName)) {

                    final Method getter = propertyDescriptor.getReadMethod();

                    // only copies properties defined as copyFrom-able
                    Object value = getter.invoke(source, NO_PARAMS);
                    if (value != null) {

                        final Method setter = propertyDescriptor.getWriteMethod();

                        final Class<?> baseInterface = baseInterfaceMap.get(propertyName);
                        value = doCopy(value, baseInterface);
                        setter.invoke(target, new Object[] { value });
                    }
                }

            }

        } catch (final Exception e) {
            LOG.error("Error while copying object", e);
            throw new RuntimeException("Could not do a copyFrom " + e, e);
        }

    }

    private CopyFrom createInstance(final Class<? extends CopyFrom> interfaceClass) throws Exception {
        if (baseImplMap.get(interfaceClass) == null) {
            return null;
        } else {
            return (CopyFrom) baseImplMap.get(interfaceClass).newInstance();
        }
    }

    @SuppressWarnings("unchecked")
    private <T> T doCopy(T value, final Class<?> baseInterface) throws Exception {
        if (value != null) {
            final Class<?> vClass = value.getClass();
            if (vClass.isArray()) {
                value = (T) this.<Object> doCopyArray((Object[]) value, baseInterface);
            } else if (value instanceof Collection) {
                value = (T) this.<Object> doCopyCollection((Collection<Object>) value, baseInterface);
            } else if (value instanceof Map) {
                value = (T) this.<Object, Object> doCopyMap((Map<Object, Object>) value, baseInterface);
            } else if (isBasicType(vClass)) {
                // value = value; // nothing to do here
                if (value instanceof Date) { // because Date it is not inmutable
                    value = (T) ((Date) value).clone();
                }
            } else { // it goes CopyFrom
                if (value instanceof CopyFrom) {
                    final CopyFrom source = (CopyFrom) value;
                    CopyFrom target = createInstance(source.getInterface());
                    if (target == null) {
                        target = (CopyFrom) value.getClass().newInstance();
                    }
                    target.copyFrom(source);
                    value = (T) target;
                } else {
                    throw new Exception("unsupported class for 'copyFrom' " + value.getClass());
                }
            }
        }
        return value;
    }

    private <T> T[] doCopyArray(final T[] array, final Class<?> baseInterface) throws Exception {
        final Class<?> elementClass = array.getClass().getComponentType();
        final int length = Array.getLength(array);
        @SuppressWarnings("unchecked")
        final T[] newArray = (T[]) Array.newInstance(elementClass, length);
        for (int i = 0; i < length; i++) {
            final Object element = doCopy(Array.get(array, i), baseInterface);
            Array.set(newArray, i, element);
        }
        return newArray;
    }

    private <T> Collection<T> doCopyCollection(final Collection<T> collection, final Class<?> baseInterface) throws Exception {

        // expecting a set or a list
        final Collection<T> newCollection;
        if (collection instanceof Set) {
            newCollection = new LinkedHashSet<T>();
        } else {
            newCollection = new ArrayList<T>();
        }

        for (final T item : collection) {
            final T copied = doCopy(item, baseInterface);
            newCollection.add(copied);
        }

        return newCollection;

    }

    private <S, T> Map<S, T> doCopyMap(final Map<S, T> map, final Class<?> baseInterface) throws Exception {

        final Map<S, T> newMap = new HashMap<S, T>();

        for (final Entry<S, T> entry : map.entrySet()) {
            // TODO mustn't the key be copied too?
            final T copiedValue = doCopy(entry.getValue(), baseInterface);
            newMap.put(entry.getKey(), copiedValue);
        }

        return newMap;

    }

    private boolean isBasicType(final Class<?> type) {
        return BASIC_TYPES.contains(type);
    }

}