taverna-reference-api/src/main/java/org/apache/taverna/reference/ValueToReferenceConverterSPI.java

/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.apache.taverna.reference;

/**
 * SPI for components that can convert an arbitrary object to an
 * ExternalReferenceSPI representing the value of that object. Used by
 * implementations of {@link ReferenceService#register(Object, int, boolean)} to
 * map arbitrary objects to ExternalReferenceSPI instances if encountered during
 * the registration process. This SPI is only used if the boolean
 * useConverterSPI parameter is set to true on that method.
 * 
 * @author Tom Oinn
 */
public interface ValueToReferenceConverterSPI {
	/**
	 * Can this SPI implementation convert the specified object to an
	 * ExternalReferenceSPI? This test should be as lightweight as possible, and
	 * will usually be based on the Class of the object supplied.
	 * 
	 * @param context
	 *            a ReferenceContext to use if required by the plugin, the
	 *            ability to convert should be interpreted in the scope of this
	 *            context. In general the context probably not used by most
	 *            implementations but it's here if required.
	 * 
	 * @return whether this converter is applicable to the specified object
	 */
	boolean canConvert(Object o, ReferenceContext context);

	/**
	 * Construct and return a new ExternalReferenceSPI implementation which is
	 * in some way equivalent to the supplied object. This is not intended to be
	 * a two-way process necessarily, although the conversion should attempt to
	 * be conservative (so not actually changing the data!).
	 * 
	 * @param context
	 *            a ReferenceContext to use, if required, during construction of
	 *            the new external reference
	 * @return A new instance of ExternalReferenceSPI which references, as far
	 *         as possible, the value represented by the specified object
	 * @throws ValueToReferenceConversionException
	 *             if any problem occurs during the conversion
	 */
	ExternalReferenceSPI convert(Object o, ReferenceContext context)
			throws ValueToReferenceConversionException;
}