Item.java

/*
 * Copyright (c) OSGi Alliance (2009). All Rights Reserved.
 *
 * 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 org.osgi.jmx;

import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.Set;

import javax.management.openmbean.ArrayType;
import javax.management.openmbean.CompositeType;
import javax.management.openmbean.OpenDataException;
import javax.management.openmbean.OpenType;
import javax.management.openmbean.TabularType;

/**
 * The item class enables the definition of open types in the appropriate
 * interfaces.
 *
 * This class contains a number of methods that make it possible to create open
 * types for {@link CompositeType}, {@link TabularType}, and {@link ArrayType}.
 * The normal creation throws a checked exception, making it impossible to use
 * them in a static initializer. They constructors are also not very suitable
 * for static construction.
 *
 *
 * An Item instance describes an item in a Composite Type. It groups the triplet
 * of name, description, and Open Type. These Item instances allows the
 * definitions of an item to stay together.
 *
 * @version $Rev$
 * @Immutable
 */
public class Item {

	/**
	 * The name of this item.
	 */
	private final String name;

	/**
	 * The description of this item.
	 */
	private final String description;

	/**
	 * The type of this item.
	 */
	private final OpenType type;

	/**
	 * Create a triple of name, description, and type. This triplet is used in
	 * the creation of a Composite Type.
	 *
	 * @param name
	 *            The name of the item.
	 * @param description
	 *            The description of the item.
	 * @param type
	 *            The Open Type of this item.
	 * @param restrictions
	 *            Ignored, contains list of restrictions
	 */
	public Item(String name, String description, OpenType type,
			String... restrictions) {
		this.name = name;
		this.description = description;
		this.type = type;
	}

	/**
	 *
	 */

	/**
	 * Create a Tabular Type.
	 *
	 * @param name
	 *            The name of the Tabular Type.
	 * @param description
	 *            The description of the Tabular Type.
	 * @param rowType
	 *            The Open Type for a row
	 * @param index
	 *            The names of the items that form the index .
	 * @return A new Tabular Type composed from the parameters.
	 * @throws RuntimeException
	 *             when the Tabular Type throws an OpenDataException
	 */
	static public TabularType tabularType(String name, String description,
			CompositeType rowType, String... index) {
		try {
			return new TabularType(name, description, rowType, index);
		} catch (OpenDataException e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * Create a Composite Type
	 *
	 * @param name
	 *            The name of the Tabular Type.
	 * @param description
	 *            The description of the Tabular Type.
	 * @param items
	 *            The items that describe the composite type.
	 * @return a new Composite Type
	 * @throws RuntimeException
	 *             when the Tabular Type throws an OpenDataException
	 */
	static public CompositeType compositeType(String name, String description,
			Item... items) {
		return extend(null, name, description, items);
	}

	/**
	 * Return a new Array Type.
	 *
	 * @param dim
	 *            The dimension
	 * @param elementType
	 *            The element type
	 * @return A new Array Type
	 */
	public static <T> ArrayType<T> arrayType(int dim, OpenType<T> elementType) {
	    try {
	        return new ArrayType<T>(dim, elementType);
	    } catch (OpenDataException e) {
	        throw new RuntimeException(e);
	    }
	 }

	/**
	 * Extend a Composite Type by adding new items. Items can override items in
	 * the parent type.
	 *
	 * @param parent
	 *            The parent type, can be <code>null</code>
	 * @param name
	 *            The name of the type
	 * @param description
	 *            The description of the type
	 * @param items
	 *            The items that should be added/override to the parent type
	 * @return A new Composite Type that extends the parent type
	 * @throws RuntimeException
	 *             when an OpenDataException is thrown
	 */
	public static CompositeType extend(CompositeType parent, String name,
			String description, Item... items) {
		Set<Item> all = new LinkedHashSet<Item>();

		if (parent != null) {
			for (Object nm : parent.keySet()) {
				String key = (String) nm;
				all.add(new Item(key, parent.getDescription(key),
						parent.getType(key)));
			}
		}

		Collections.addAll(all, items);

		int size = all.size();
		String names[] = new String[size];
		String descriptions[] = new String[size];
		OpenType types[] = new OpenType[size];

		int m = 0;
		for (Item item : all) {
			names[m] = item.name;
			descriptions[m] = item.description;
			types[m] = item.type;
			m++;
		}

		try {
			return new CompositeType(name, description, names, descriptions,
					types);
		} catch (OpenDataException e) {
			throw new RuntimeException(e);
		}
	}

}