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Guise™ Internet application framework.
There is a newer version: 0.5.3
/*
 * Copyright © 2005-2008 GlobalMentor, Inc. 
 *
 * 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 io.guise.framework.platform;

import java.util.*;

/**
 * Access to the platform user local environment. Properties stored in the environment should be persisted across sessions, using an appropriate platform
 * storage mechanism such as cookies.
 * @author Garret Wilson
 */
public interface Environment {

	/**
	 * Determines if an environment property exists.
	 * @param name The name of the property to check.
	 * @return true if the environment has the given property.
	 */
	public boolean hasProperty(final String name);

	/**
	 * Retrieves an environment property by its name. A {@link ClassCastException} will eventually be thrown if the given value is not the generic type requested.
	 * @param  The type of property value expected.
	 * @param name The name of the property to retrieve.
	 * @return The property value, or null if there is no such property.
	 */
	public  T getProperty(final String name);

	/**
	 * Retrieves an environment property by its name, returning a default value if no value is available. A {@link ClassCastException} will eventually be thrown
	 * if the given value is not the generic type requested.
	 * @param  The type of property value expected.
	 * @param name The name of the property to retrieve.
	 * @param defaultValue The value to return if no such property is available, or null if there is no default value.
	 * @return The property value, or the provided default value if there is no such property.
	 */
	public  T getProperty(final String name, final T defaultValue);

	/**
	 * Retrieves a required environment property by its name, throwing an exception if the value is missing. A {@link ClassCastException} will eventually be
	 * thrown if the given value is not the generic type requested.
	 * @param  The type of property value expected.
	 * @param name The name of the property to retrieve.
	 * @return The property value.
	 * @throws IllegalStateException if no such property exists.
	 */
	public  T getRequiredProperty(final String name);

	/**
	 * Sets an environment property.
	 * @param name The name of the property.
	 * @param value The value to associate with the name.
	 * @throws IllegalArgumentException if the given property cannot be set to the given value or cannot be changed.
	 */
	public void setProperty(final String name, final Object value);

	/**
	 * Sets multiple environment properties.
	 * @param map The map of property names and values to set.
	 * @throws IllegalArgumentException if the given property cannot be set to the given value or cannot be changed.
	 */
	public void setProperties(final Map map);

	/**
	 * Removes the property specified by the given name.
	 * @param name The name of the property to remove.
	 * @throws IllegalArgumentException if the given property cannot be removed.
	 */
	public void removeProperty(final String name);

	/**
	 * Returns the available environment properties as a read-only map of property names and values.
	 * @return The available environment properties.
	 */
	public Map getProperties();
}