home | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Commons Collections example source code file (AbstractInputCheckedMapDecorator.java)

This example Commons Collections source code file (AbstractInputCheckedMapDecorator.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Collections tags/keywords

abstractinputcheckedmapdecorator, abstractinputcheckedmapdecorator, abstractiteratordecorator, abstractmapdecorator, abstractmapentrydecorator, abstractsetdecorator, entryset, entryset, entrysetiterator, iterator, mapentry, mapentry, object, object, reflection, util

The Commons Collections AbstractInputCheckedMapDecorator.java source code

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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.apache.commons.collections.map;

import java.lang.reflect.Array;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import org.apache.commons.collections.iterators.AbstractIteratorDecorator;
import org.apache.commons.collections.keyvalue.AbstractMapEntryDecorator;
import org.apache.commons.collections.set.AbstractSetDecorator;

/**
 * An abstract base class that simplifies the task of creating map decorators.
 * <p>
 * The Map API is very difficult to decorate correctly, and involves implementing
 * lots of different classes. This class exists to provide a simpler API.
 * <p>
 * Special hook methods are provided that are called when objects are added to
 * the map. By overriding these methods, the input can be validated or manipulated.
 * In addition to the main map methods, the entrySet is also affected, which is
 * the hardest part of writing map implementations.
 * <p>
 * This class is package-scoped, and may be withdrawn or replaced in future
 * versions of Commons Collections.
 *
 * @since Commons Collections 3.1
 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
 * 
 * @author Stephen Colebourne
 */
abstract class AbstractInputCheckedMapDecorator
        extends AbstractMapDecorator {

    /**
     * Constructor only used in deserialization, do not use otherwise.
     */
    protected AbstractInputCheckedMapDecorator() {
        super();
    }

    /**
     * Constructor that wraps (not copies).
     * 
     * @param map  the map to decorate, must not be null
     * @throws IllegalArgumentException if map is null
     */
    protected AbstractInputCheckedMapDecorator(Map map) {
        super(map);
    }

    //-----------------------------------------------------------------------
    /**
     * Hook method called when a value is being set using <code>setValue.
     * <p>
     * An implementation may validate the value and throw an exception
     * or it may transform the value into another object.
     * <p>
     * This implementation returns the input value.
     * 
     * @param value  the value to check
     * @throws UnsupportedOperationException if the map may not be changed by setValue
     * @throws IllegalArgumentException if the specified value is invalid
     * @throws ClassCastException if the class of the specified value is invalid
     * @throws NullPointerException if the specified value is null and nulls are invalid
     */
    protected abstract Object checkSetValue(Object value);

    /**
     * Hook method called to determine if <code>checkSetValue has any effect.
     * <p>
     * An implementation should return false if the <code>checkSetValue method
     * has no effect as this optimises the implementation.
     * <p>
     * This implementation returns <code>true.
     * 
     * @return true always
     */
    protected boolean isSetValueChecking() {
        return true;
    }

    //-----------------------------------------------------------------------
    public Set entrySet() {
        if (isSetValueChecking()) {
            return new EntrySet(map.entrySet(), this);
        } else {
            return map.entrySet();
        }
    }

    //-----------------------------------------------------------------------
    /**
     * Implementation of an entry set that checks additions via setValue.
     */
    static class EntrySet extends AbstractSetDecorator {
        
        /** The parent map */
        private final AbstractInputCheckedMapDecorator parent;

        protected EntrySet(Set set, AbstractInputCheckedMapDecorator parent) {
            super(set);
            this.parent = parent;
        }

        public Iterator iterator() {
            return new EntrySetIterator(collection.iterator(), parent);
        }
        
        public Object[] toArray() {
            Object[] array = collection.toArray();
            for (int i = 0; i < array.length; i++) {
                array[i] = new MapEntry((Map.Entry) array[i], parent);
            }
            return array;
        }
        
        public Object[] toArray(Object array[]) {
            Object[] result = array;
            if (array.length > 0) {
                // we must create a new array to handle multi-threaded situations
                // where another thread could access data before we decorate it
                result = (Object[]) Array.newInstance(array.getClass().getComponentType(), 0);
            }
            result = collection.toArray(result);
            for (int i = 0; i < result.length; i++) {
                result[i] = new MapEntry((Map.Entry) result[i], parent);
            }

            // check to see if result should be returned straight
            if (result.length > array.length) {
                return result;
            }

            // copy back into input array to fulfil the method contract
            System.arraycopy(result, 0, array, 0, result.length);
            if (array.length > result.length) {
                array[result.length] = null;
            }
            return array;
        }
    }

    /**
     * Implementation of an entry set iterator that checks additions via setValue.
     */
    static class EntrySetIterator extends AbstractIteratorDecorator {
        
        /** The parent map */
        private final AbstractInputCheckedMapDecorator parent;
        
        protected EntrySetIterator(Iterator iterator, AbstractInputCheckedMapDecorator parent) {
            super(iterator);
            this.parent = parent;
        }
        
        public Object next() {
            Map.Entry entry = (Map.Entry) iterator.next();
            return new MapEntry(entry, parent);
        }
    }

    /**
     * Implementation of a map entry that checks additions via setValue.
     */
    static class MapEntry extends AbstractMapEntryDecorator {

        /** The parent map */
        private final AbstractInputCheckedMapDecorator parent;

        protected MapEntry(Map.Entry entry, AbstractInputCheckedMapDecorator parent) {
            super(entry);
            this.parent = parent;
        }

        public Object setValue(Object value) {
            value = parent.checkSetValue(value);
            return entry.setValue(value);
        }
    }

}

Other Commons Collections examples (source code examples)

Here is a short list of links related to this Commons Collections AbstractInputCheckedMapDecorator.java source code file:

new blog posts

 

Copyright 1998-2016 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.