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Tools to assist in the reading of configuration/preferences files in various formats
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/*
 * 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.configuration2.interpol;

import org.apache.commons.text.lookup.StringLookupFactory;

/**
 * 
 * An enumeration class defining constants for the {@code Lookup} objects available for each {@code Configuration}
 * object per default.
 * 
 * 
 * When a new configuration object derived from {@code AbstractConfiguration} is created it installs a
 * {@link ConfigurationInterpolator} with a default set of {@link Lookup} objects. These lookups are defined by this
 * enumeration class.
 * 
 * 
 * All the default {@code Lookup} classes are state-less, thus their instances can be shared between multiple
 * configuration objects. Therefore, it makes sense to keep shared instances in this enumeration class.
 * 
 *
 * Provides access to lookups defined in Apache Commons Text:
 * 
 * "base64Decoder" for the {@code Base64DecoderStringLookup} since Apache Commons Text 1.6.
 * "base64Encoder" for the {@code Base64EncoderStringLookup} since Apache Commons Text 1.6.
 * "const" for the {@code ConstantStringLookup} since Apache Commons Text 1.5.
 * "date" for the {@code DateStringLookup}.
 * "env" for the {@code EnvironmentVariableStringLookup}.
 * "file" for the {@code FileStringLookup} since Apache Commons Text 1.5.
 * "java" for the {@code JavaPlatformStringLookup}.
 * "localhost" for the {@code LocalHostStringLookup}, see {@code #localHostStringLookup()} for key names; since
 * Apache Commons Text 1.3.
 * "properties" for the {@code PropertiesStringLookup} since Apache Commons Text 1.5.
 * "resourceBundle" for the {@code ResourceBundleStringLookup} since Apache Commons Text 1.5.
 * "script" for the {@code ScriptStringLookup} since Apache Commons Text 1.5.
 * "sys" for the {@code SystemPropertyStringLookup}.
 * "url" for the {@code UrlStringLookup} since Apache Commons Text 1.5.
 * "urlDecoder" for the {@code UrlDecoderStringLookup} since Apache Commons Text 1.6.
 * "urlEncoder" for the {@code UrlEncoderStringLookup} since Apache Commons Text 1.6.
 * "xml" for the {@code XmlStringLookup} since Apache Commons Text 1.5.
 * 
 *
 * @since 2.0
 */
public enum DefaultLookups
{

    /**
     * The lookup for Base64 decoding.
     *
     * @since 2.4
     */
    BASE64_DECODER(StringLookupFactory.KEY_BASE64_DECODER,
            new StringLookupAdapter(StringLookupFactory.INSTANCE.base64DecoderStringLookup())),

    /**
     * The lookup for Base64 decoding.
     *
     * @since 2.4
     */
    BASE64_ENCODER(StringLookupFactory.KEY_BASE64_ENCODER,
            new StringLookupAdapter(StringLookupFactory.INSTANCE.base64EncoderStringLookup())),

    /**
     * The lookup for constants.
     *
     * @since 2.4
     */
    CONST(StringLookupFactory.KEY_CONST, new StringLookupAdapter(StringLookupFactory.INSTANCE.constantStringLookup())),

    /**
     * The lookup for dates.
     *
     * @since 2.4
     */
    DATE(StringLookupFactory.KEY_DATE, new StringLookupAdapter(StringLookupFactory.INSTANCE.dateStringLookup())),

    /**
     * The lookup for DNS.
     *
     * @since 2.6
     */
    DNS(StringLookupFactory.KEY_DNS, new StringLookupAdapter(StringLookupFactory.INSTANCE.dnsStringLookup())),

    /**
     * The lookup for environment properties.
     */
    ENVIRONMENT(StringLookupFactory.KEY_ENV,
            new StringLookupAdapter(StringLookupFactory.INSTANCE.environmentVariableStringLookup())),

    /**
     * The lookup for files.
     *
     * @since 2.4
     */
    FILE(StringLookupFactory.KEY_FILE, new StringLookupAdapter(StringLookupFactory.INSTANCE.fileStringLookup())),

    /**
     * The lookup for Java platform information.
     *
     * @since 2.4
     */
    JAVA(StringLookupFactory.KEY_JAVA,
            new StringLookupAdapter(StringLookupFactory.INSTANCE.javaPlatformStringLookup())),

    /**
     * The lookup for localhost information.
     *
     * @since 2.4
     */
    LOCAL_HOST(StringLookupFactory.KEY_LOCALHOST,
            new StringLookupAdapter(StringLookupFactory.INSTANCE.localHostStringLookup())),

    /**
     * The lookup for properties.
     *
     * @since 2.4
     */
    PROPERTIES(StringLookupFactory.KEY_PROPERTIES,
            new StringLookupAdapter(StringLookupFactory.INSTANCE.propertiesStringLookup())),

    /**
     * The lookup for resource bundles.
     *
     * @since 2.4
     */
    RESOURCE_BUNDLE(StringLookupFactory.KEY_RESOURCE_BUNDLE,
            new StringLookupAdapter(StringLookupFactory.INSTANCE.resourceBundleStringLookup())),

    /**
     * The lookup for scripts.
     *
     * @since 2.4
     */
    SCRIPT(StringLookupFactory.KEY_SCRIPT, new StringLookupAdapter(StringLookupFactory.INSTANCE.scriptStringLookup())),

    /**
     * The lookup for system properties.
     */
    SYSTEM_PROPERTIES(StringLookupFactory.KEY_SYS,
            new StringLookupAdapter(StringLookupFactory.INSTANCE.systemPropertyStringLookup())),

    /**
     * The lookup for URLs.
     *
     * @since 2.4
     */
    URL(StringLookupFactory.KEY_URL, new StringLookupAdapter(StringLookupFactory.INSTANCE.urlStringLookup())),

    /**
     * The lookup for URL decoding.
     *
     * @since 2.4
     */
    URL_DECODER(StringLookupFactory.KEY_URL_DECODER,
            new StringLookupAdapter(StringLookupFactory.INSTANCE.urlDecoderStringLookup())),

    /**
     * The lookup for URL decoding.
     *
     * @since 2.4
     */
    URL_ENCODER(StringLookupFactory.KEY_URL_ENCODER,
            new StringLookupAdapter(StringLookupFactory.INSTANCE.urlEncoderStringLookup())),

    /**
     * The lookup for URL decoding.
     *
     * @since 2.4
     */
    XML(StringLookupFactory.KEY_XML, new StringLookupAdapter(StringLookupFactory.INSTANCE.xmlStringLookup()));

    /** The associated lookup instance. */
    private final Lookup lookup;

    /** The prefix under which the associated lookup object is registered. */
    private final String prefix;

    /**
     * Creates a new instance of {@code DefaultLookups} and sets the prefix and the associated lookup instance.
     *
     * @param prefix
     *            the prefix
     * @param lookup
     *            the {@code Lookup} instance
     */
    private DefaultLookups(final String prefix, final Lookup lookup)
    {
        this.prefix = prefix;
        this.lookup = lookup;
    }

    /**
     * Returns the standard {@code Lookup} instance of this kind.
     *
     * @return the associated {@code Lookup} object
     */
    public Lookup getLookup()
    {
        return lookup;
    }

    /**
     * Returns the standard prefix for the lookup object of this kind.
     *
     * @return the prefix
     */
    public String getPrefix()
    {
        return prefix;
    }
}