ElementType.java

/*
 * Copyright (c) 2012 Data Harmonisation Panel
 * 
 * All rights reserved. This program and the accompanying materials are made
 * available under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 3 of the License,
 * or (at your option) any later version.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution. If not, see <http://www.gnu.org/licenses/>.
 * 
 * Contributors:
 *     HUMBOLDT EU Integrated Project #030962
 *     Data Harmonisation Panel <http://www.dhpanel.eu>
 */

package eu.esdihumboldt.hale.common.schema.model.constraint.type;

import java.util.HashMap;
import java.util.Map;

import net.jcip.annotations.Immutable;
import eu.esdihumboldt.hale.common.schema.model.Constraint;
import eu.esdihumboldt.hale.common.schema.model.TypeConstraint;
import eu.esdihumboldt.hale.common.schema.model.TypeDefinition;

/**
 * Specifies a Java binding and optionally a {@link TypeDefinition} for a
 * elements of a collection. This is only relevant for a type if its
 * {@link Binding} is a collection or array, default element binding is
 * {@link Object}.
 * 
 * @author Simon Templer
 */
@Immutable
@Constraint(mutable = false)
public class ElementType implements TypeConstraint {

	/**
	 * ElementType singletons, element binding class mapped to the corresponding
	 * ElementType constraint.
	 */
	private static final Map<Class<?>, ElementType> singletons = new HashMap<Class<?>, ElementType>();

	/**
	 * Get the element type constraint with the given Java binding
	 * 
	 * @param binding the type's Java binding
	 * @return the element type constraint (which is a singleton)
	 */
	public static ElementType get(Class<?> binding) {
		ElementType et = singletons.get(binding);
		if (et == null) {
			et = new ElementType(binding);
			singletons.put(binding, et);
		}
		return et;
	}

	/**
	 * Create an element type constraint with the given element type.
	 * 
	 * @param elementType the element type definition
	 * @return the element type constraint
	 */
	public static ElementType createFromType(TypeDefinition elementType) {
		return new ElementType(elementType);
	}

	/**
	 * The element type definition
	 */
	private final TypeDefinition definition;

	/**
	 * The element type binding. May be <code>null</code>.
	 */
	private final Class<?> binding;

	/**
	 * Creates a default element binding constraint with {@link Object} binding
	 * and no type definition.
	 * 
	 * @see Constraint
	 */
	public ElementType() {
		this(Object.class);
	}

	/**
	 * Creates a constraint with the given type definition
	 * 
	 * @param elementType the element type
	 */
	private ElementType(TypeDefinition elementType) {
		super();

		this.definition = elementType;
		this.binding = null;
	}

	/**
	 * Creates an element type with the given binding.
	 * 
	 * @param binding the element type binding
	 */
	private ElementType(Class<?> binding) {
		super();

		this.binding = binding;
		this.definition = null;
	}

	/**
	 * Get the Java binding for collection elements of the type
	 * 
	 * @return the element binding
	 */
	public Class<?> getBinding() {
		if (definition == null) {
			return binding;
		}
		return definition.getConstraint(Binding.class).getBinding();
	}

	/**
	 * Get the type definition for collection elements of the type
	 * 
	 * @return the type definition, may be <code>null</code>
	 */
	public TypeDefinition getDefinition() {
		return definition;
	}

	/**
	 * @see TypeConstraint#isInheritable()
	 */
	@Override
	public boolean isInheritable() {
		// inherit unless overridden
		return true;
	}

}