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JSefa (Java Simple exchange format api) is a simple library for stream-based serialization of java objects to XML, CSV, FLR or any other format and back again using an iterator-style interface independent of the serialization format. The mapping between java object types and types of the serialization format (e. g. xml complex element types) can be defined either by annotating the java classes or programmatically using a simple API. The current implementation supports XML, CSV and FLR - for XML it is based on JSR 173.

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/*
 * Copyright 2007 the original author or authors.
 *
 * 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 net.sf.jsefa.common.config;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import net.sf.jsefa.common.util.OnDemandObjectProvider;

/**
 * The single initial configuration for JSefa. See sub interfaces of {@link InitialConfigurationParameters} for the
 * available parameters.
 * 
 * @see Configuration
 * @author Norman Lahme-Huetig
 * 
 */
public final class InitialConfiguration {

    private static final ConcurrentMap MAP = new ConcurrentHashMap();

    /**
     * Returns the value of the given parameter. If none is configured for the parameter, the
     * defaultValue retrieved from the OnDemandObjectProvider is registered and
     * returned.
     * 
     * @param parameter the parameter
     * @param  the expected type of the parameter value
     * @param defaultValueProvider the provider of the default value to use if none is configured for the parameter
     *                in question.
     * @return the value of the parameter
     */
    @SuppressWarnings("unchecked")
    public static  T get(String parameter, OnDemandObjectProvider defaultValueProvider) {
        T previousValue = (T) MAP.get(parameter);
        if (previousValue != null) {
            return previousValue;
        } else {
            T defaultValue = (T) defaultValueProvider.get();
            previousValue = (T) MAP.putIfAbsent(parameter, defaultValue);
            if (previousValue != null) {
                return previousValue;
            } else {
                return (T) defaultValue;
            }
        }
    }

    /**
     * Returns the value of the given parameter. If none is configured for the parameter, the
     * defaultValue is registered and returned.
     * 
     * @param parameter the parameter
     * @param  the expected type of the parameter value
     * @param defaultValue the default value to use if none is configured for the parameter in question.
     * @return the value of the parameter
     */
    @SuppressWarnings("unchecked")
    public static  T get(String parameter, Object defaultValue) {
        T previousValue = (T) MAP.putIfAbsent(parameter, defaultValue);
        if (previousValue != null) {
            return previousValue;
        } else {
            return (T) defaultValue;
        }
    }

    /**
     * Sets the parameter value of the given parameter to the given value if the parameter is not already bound to
     * another value. Otherwise an {@link InitialConfigurationException} will be thrown.
     * 
     * @param parameter the parameter
     * @param value the value
     * @throws InitialConfigurationException if the parameter is already bound to another value.
     */
    public static void set(String parameter, Object value) {
        Object other = MAP.putIfAbsent(parameter, value);
        if (other != null && !other.equals(value)) {
            throw new InitialConfigurationException("The configuration parameter " + parameter
                    + " is already bound to " + value);
        }
    }

    private InitialConfiguration() {

    }
}