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jBasics is a collection of useful utility classes for Java. This includes helper for XML, mathematic functions, restful web services helper, pattern oriented programming interfaces and more. Currently Java7 and up is supported. Version 1.0 will required at leaset Java8.
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/*
 * Copyright (c) 2009-2015
 * 	IT-Consulting Stephan Schloepke (http://www.schloepke.de/)
 * 	klemm software consulting Mirko Klemm (http://www.klemm-scs.com/)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package org.jbasics.jee;

import org.jbasics.exception.DelegatedException;
import org.jbasics.pattern.factory.Factory;
import org.jbasics.pattern.factory.ParameterFactory;

import javax.naming.InitialContext;
import javax.naming.NamingException;
import java.util.Properties;

/**
 * Factory to create {@link InitialContext} instances. In most cases when the initial context is to be created without
 * any special environment it is best to use the sharable {@link #INSTANCE} rather than creating your own factory. 
 * The factory implements both the {@link Factory} interface as well as the {@link ParameterFactory} interface. The
 * first always creates an {@link InitialContext} with the default environment given at construction time. The later
 * always creates an {@link InitialContext} with the given environment. If the default environment is used as a parent
 * depends on the settings used at construction time. 
  It is wise to not use the default properties as parent
 * unless it is required. Using this settings means that any time the {@link #create(Properties)} method is called a new
 * properties instance is created and all given properties are copied (shallow copy). However in most cases the amount
 * of properties to copy is quite low that the memory and performance impact is unnoticed. 
 *
 * @author Stephan Schloepke
 * @since 1.0
 */
public class InitialContextFactory implements Factory, ParameterFactory {
	/**
	 * A sharable and thread safe instance with an empty default environment.
	 */
	public static final InitialContextFactory INSTANCE = new InitialContextFactory(null, false);

	private final Properties defaultEnvironment;
	private final boolean useEnvironmentAsParent;

	/**
	 * Creates an {@link InitialContextFactory} with the given environment as default environment. If no default
	 * environment is required null can be supplied. In such a case it is wise to use the shared {@link #INSTANCE}
	 * instead.
	 *
	 * @param environment            The default environment to use if no environment is given or {@link #newInstance()}
	 *                               is called.
	 * @param useEnvironmentAsParent True if the default environment should be used as parent properties even when
	 *                               specific properties are given in {@link #create(Properties)}.
	 */
	public InitialContextFactory(final Properties environment, final boolean useEnvironmentAsParent) {
		if (environment == null || environment.isEmpty()) {
			this.defaultEnvironment = null;
			this.useEnvironmentAsParent = false;
		} else {
			this.defaultEnvironment = (Properties) environment.clone();
			this.useEnvironmentAsParent = useEnvironmentAsParent;
		}
	}

	/**
	 * Creates a new {@link InitialContext} using the environment given as default at construction time.
	 *
	 * @throws DelegatedException If a {@link NamingException} occurs it is packed into a {@link DelegatedException} and
	 *                            thrown.
	 */
	public InitialContext newInstance() {
		return create(null);
	}

	/**
	 * Creates a new {@link InitialContext} with the given environment. If at construction time the default environment
	 * is tagged to be used as parent both are in charge to form the full environment.
	 *
	 * @throws DelegatedException If a {@link NamingException} occurs it is packed into a {@link DelegatedException} and
	 *                            thrown.
	 */
	public InitialContext create(final Properties environment) {
		try {
			if (environment == null) {
				if (this.defaultEnvironment != null) {
					return new InitialContext(this.defaultEnvironment);
				} else {
					return new InitialContext();
				}
			} else if (this.useEnvironmentAsParent) {
				Properties newEnvironment = new Properties(this.defaultEnvironment);
				for (String name : environment.stringPropertyNames()) {
					newEnvironment.setProperty(name, environment.getProperty(name));
				}
				return new InitialContext(newEnvironment);
			} else {
				return new InitialContext(environment);
			}
		} catch (NamingException e) {
			throw DelegatedException.delegate(e);
		}
	}

	/**
	 * Returns true if the default environment is used as parent even when a specific is given when calling {@link
	 * #create(Properties)}.
	 *
	 * @return True if the default environment is used as parent in {@link #create(Properties)}.
	 */
	public boolean isUseEnvironmentAsParent() {
		return this.useEnvironmentAsParent;
	}

	/**
	 * Returns the default environment as a new {@link Properties} instance (shallow copy of the
	 * original). The returned {@link Properties} can be used in any way without modifying the internal default {@link
	 * Properties}.
	 *
	 * @return A shallow copy of the defaults {@link Properties}.
	 */
	public Properties getDefaultEnvironment() {
		return (Properties) this.defaultEnvironment.clone();
	}
}