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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;
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;
/**
* The main Configuration interface.
* 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.
* 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 null 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.)
* 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.
*
*/
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:
*
*
* prefix.number = 1
* prefix.string = Apache
* prefixed.foo = bar
* prefix = Jakarta
*
* the Configuration returned by {@code subset("prefix")} will contain
* the properties:
*
*
* number = 1
* string = Apache
* = Jakarta
*
* (The key for the value "Jakarta" is an empty string)
*
* 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:
*
*
resource.loader = file
*
* is already present in the configuration and you call
*
* addProperty("resource.loader", "classpath")
*
* Then you will end up with a List like the following:
*
* ["file", "classpath"]
*
* @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 null)
*/
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 null 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 null)
* @param defLookups a collection with default {@code Lookup} objects (can
* be null)
* @see ConfigurationInterpolator
*/
void installInterpolator(Map prefixLookups,
Collection defLookups);
}