[configuration] AbstractConfiguration based SubsetConfiguration

[Emmanuel Bourg]

Jörg's patch made me realize that SubsetConfiguration could be much 
shorter by extending AbstractConfiguration, the key translation just 
happens in the add/getPropertyDirect methods, there is no need to 
overwrite all the getters of the Configuration interface. I'm attaching 
the modified implementation, let me know how it works for you. It 
doesn't contain the interpolation changes, I'm still working on it.

Emmanuel Bourg

/*
 * Copyright 2004 The Apache Software Foundation.
 *
 * 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.apache.commons.configuration;

import org.apache.commons.collections.Transformer;
import org.apache.commons.collections.iterators.TransformIterator;

import java.util.Iterator;

/**
 * A subset of another configuration. The new Configuration object contains
 * every key from the parent Configuration that starts with prefix. The prefix
 * is removed from the keys in the subset.
 *
 * @author Emmanuel Bourg
 * @version $Revision: 1.1 $, $Date: 2004/03/09 10:31:31 $
 */
public class SubsetConfiguration extends AbstractConfiguration {

    protected Configuration parent;
    protected String prefix;
    protected String delimiter;

    /**
     * Create a subset of the specified configuration
     *
     * @param parent The parent configuration
     * @param prefix The prefix used to select the properties.
     */
    public SubsetConfiguration(Configuration parent, String prefix) {
        this.parent = parent;
        this.prefix = prefix;
    }

    /**
     * Create a subset of the specified configuration
     *
     * @param parent    The parent configuration
     * @param prefix    The prefix used to select the properties.
     * @param delimiter The prefix delimiter
     */
    public SubsetConfiguration(Configuration parent, String prefix, String delimiter) {
        this.parent = parent;
        this.prefix = prefix;
        this.delimiter = delimiter;
    }

    /**
     * Return the key in the parent configuration associated to the specified
     * key in this subset.
     *
     * @param key The key in the subset.
     */
    protected String getParentKey(String key) {
        if ("".equals(key) || key == null) {
            return prefix;
        } else {
            return delimiter == null ? prefix + key : prefix + delimiter + key;
        }
    }

    /**
     * Return the key in the subset configuration associated to the specified
     * key in the parent configuration.
     *
     * @param key The key in the parent configuration.
     */
    protected String getChildKey(String key) {
        if (!key.startsWith(prefix)) {
            throw new IllegalArgumentException("The parent key '" + key + "' is not in 
the subset.");
        } else {
            String modifiedKey = null;
            if (key.length() == prefix.length()) {
                modifiedKey = "";
            } else {
                int i = prefix.length() + (delimiter != null ? delimiter.length() : 0);
                modifiedKey = key.substring(i);
            }

            return modifiedKey;
        }
    }

    /**
     * Return the parent configuation for this subset.
     */
    public Configuration getParent() {
        return parent;
    }

    /**
     * Return the prefix used to select the properties in the parent configuration.
     */
    public String getPrefix() {
        return prefix;
    }

    /**
     * Set the prefix used to select the properties in the parent configuration.
     */
    public void setPrefix(String prefix) {
        this.prefix = prefix;
    }

    public Configuration subset(String prefix) {
        return parent.subset(getParentKey(prefix));
    }

    public boolean isEmpty() {
        return !getKeys().hasNext();
    }

    public boolean containsKey(String key) {
        return parent.containsKey(getParentKey(key));
    }

    public void addPropertyDirect(String key, Object value) {
        parent.addProperty(getParentKey(key), value);
    }

    public void clearProperty(String key) {
        parent.clearProperty(getParentKey(key));
    }

    public Object getPropertyDirect(String key) {
        return parent.getProperty(getParentKey(key));
    }

    public Iterator getKeys(String prefix) {
        return new TransformIterator(parent.getKeys(getParentKey(prefix)), new 
Transformer() {
            public Object transform(Object obj) {
                return getChildKey((String) obj);
            }
        });
    }

    public Iterator getKeys() {
        return new TransformIterator(parent.getKeys(prefix), new Transformer() {
            public Object transform(Object obj) {
                return getChildKey((String) obj);
            }
        });
    }

}

---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]