Java tutorial
/* * 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; import java.util.Collection; import java.util.Map; import org.apache.commons.configuration2.interpol.ConfigurationInterpolator; import org.apache.commons.configuration2.interpol.Lookup; import org.apache.commons.configuration2.sync.SynchronizerSupport; /** * <p>The main Configuration interface.</p> * <p>This interface allows accessing and manipulating a configuration object. * The major part of the methods defined in this interface deals with accessing * properties of various data types. There is a generic {@code getProperty()} * method, which returns the value of the queried property in its raw data * type. Other getter methods try to convert this raw data type into a specific * data type. If this fails, a {@code ConversionException} will be thrown.</p> * <p>For most of the property getter methods an overloaded version exists that * allows to specify a default value, which will be returned if the queried * property cannot be found in the configuration. The behavior of the methods * that do not take a default value in case of a missing property is not defined * by this interface and depends on a concrete implementation. E.g. the * {@link AbstractConfiguration} class, which is the base class * of most configuration implementations provided by this package, per default * returns <b>null</b> if a property is not found, but provides the * {@link AbstractConfiguration#setThrowExceptionOnMissing(boolean) * setThrowExceptionOnMissing()} * method, with which it can be configured to throw a {@code NoSuchElementException} * exception in that case. (Note that getter methods for primitive types in * {@code AbstractConfiguration} always throw an exception for missing * properties because there is no way of overloading the return value.)</p> * <p>With the {@code addProperty()} and {@code setProperty()} methods * new properties can be added to a configuration or the values of properties * can be changed. With {@code clearProperty()} a property can be removed. * Other methods allow to iterate over the contained properties or to create * a subset configuration.</p> * * @author Commons Configuration team * @version $Id$ */ public interface Configuration extends ImmutableConfiguration, SynchronizerSupport { /** * Return a decorator Configuration containing every key from the current * Configuration that starts with the specified prefix. The prefix is * removed from the keys in the subset. For example, if the configuration * contains the following properties: * * <pre> * prefix.number = 1 * prefix.string = Apache * prefixed.foo = bar * prefix = Jakarta</pre> * * the Configuration returned by {@code subset("prefix")} will contain * the properties: * * <pre> * number = 1 * string = Apache * = Jakarta</pre> * * (The key for the value "Jakarta" is an empty string) * <p> * Since the subset is a decorator and not a modified copy of the initial * Configuration, any change made to the subset is available to the * Configuration, and reciprocally. * * @param prefix The prefix used to select the properties. * @return a subset configuration * * @see SubsetConfiguration */ Configuration subset(String prefix); /** * Add a property to the configuration. If it already exists then the value * stated here will be added to the configuration entry. For example, if * the property: * * <pre>resource.loader = file</pre> * * is already present in the configuration and you call * * <pre>addProperty("resource.loader", "classpath")</pre> * * Then you will end up with a List like the following: * * <pre>["file", "classpath"]</pre> * * @param key The key to add the property to. * @param value The value to add. */ void addProperty(String key, Object value); /** * Set a property, this will replace any previously set values. Set values * is implicitly a call to clearProperty(key), addProperty(key, value). * * @param key The key of the property to change * @param value The new value */ void setProperty(String key, Object value); /** * Remove a property from the configuration. * * @param key the key to remove along with corresponding value. */ void clearProperty(String key); /** * Remove all properties from the configuration. */ void clear(); /** * Returns the {@code ConfigurationInterpolator} object used by this * {@code Configuration}. This object is responsible for variable * substitution. * * @return the {@code ConfigurationInterpolator} (can be <b>null</b>) */ ConfigurationInterpolator getInterpolator(); /** * Sets the {@code ConfigurationInterpolator} object to be used by this * {@code Configuration}. This object is invoked for each access of a string * property in order to substitute variables which may be contained. The * argument can be <b>null</b> to disable interpolation at all. * * @param ci the new {@code ConfigurationInterpolator} */ void setInterpolator(ConfigurationInterpolator ci); /** * Creates and installs a new {@code ConfigurationInterpolator} for this * {@code Configuration} based on the passed in arguments. This method * creates a default {@code ConfigurationInterpolator} instance and * initializes it with the passed in {@code Lookup} objects. It also adds a * special default {@code Lookup} object that tries to resolve variables by * matching them with properties contained in this {@code Configuration}. * This is also the main difference to the * {@link #setInterpolator(ConfigurationInterpolator)} method * which sets the passed in object as is without adding this special lookup. * * @param prefixLookups the map with {@code Lookup} objects associated with * specific prefixes (can be <b>null</b>) * @param defLookups a collection with default {@code Lookup} objects (can * be <b>null</b>) * @see ConfigurationInterpolator */ void installInterpolator(Map<String, ? extends Lookup> prefixLookups, Collection<? extends Lookup> defLookups); }