jena-extras/jena-querybuilder/src/test/java/org/apache/jena/arq/querybuilder/WhereValidator.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.jena.arq.querybuilder;

import java.util.List;

import org.apache.jena.sparql.syntax.*;
import org.apache.jena.sparql.util.NodeIsomorphismMap;

/**
 * Class to validate that an element exists in another element structure.
 * 
 * The WhereValidator traverses the element tree that it is attempting to match.
 * Once it finds a node that matches the target element an attempt is made to match
 * all elements enclosed by the target.  If a match is found the matcher stops and
 * the <code>matching</code> variable will be <code>true</code>.  if a match is not
 * the matcher continues to scan for the next candidate until a match is found or all
 * candidates are exhausted.
 * 
 * Usage:
 * <code> <pre>
 *  WhereValidator wv = new WhereValidator( target );
 *  query.getQueryPattern().visit( wv );
 *  assertTrue( wv.matching );
 *  </pre></code>
 */
public class WhereValidator implements ElementVisitor {
	
	private Element target;
	public boolean matching = false;
	private NodeIsomorphismMap nim;
	
	/**
	 * Constructor.
	 * @param target The target element to locate.
	 */
	public WhereValidator( Element target )
	{
		this.target = target;
		this.nim = new NodeIsomorphismMap();
	}
	
	private void checkMatching(Element el)
	{
		if (!matching)
		{
			matching = el.equalTo(target, nim);
		}
	}

	@Override
	public void visit(ElementTriplesBlock el) {
		checkMatching( el );
		return;
	}

	@Override
	public void visit(ElementPathBlock el) {
		checkMatching( el );
		return;
	}

	@Override
	public void visit(ElementFilter el) {
		checkMatching( el );
		return;
	}

	@Override
	public void visit(ElementAssign el) {
		checkMatching( el );
		return;
	}

	@Override
	public void visit(ElementBind el) {
		checkMatching( el );
		return;
	}

    @Override
    public void visit(ElementFind el) {
        checkMatching( el );
        return;
    }

    @Override
	public void visit(ElementData el) {
		checkMatching( el );
		return;
	}

	private void checkList( List<Element> lst )
	{
		for (Element e : lst)
		{
			e.visit( this );
			if (matching)
			{
				return;
			}
		}
	}
	@Override
	public void visit(ElementUnion el) {
		checkMatching( el );
		if (!matching)
		{
			checkList( el.getElements() );
		}
		return;
	}

	@Override
	public void visit(ElementOptional el) {
		checkMatching( el );
		if (!matching)
		{
			el.getOptionalElement().visit(this);
		}
	}

	@Override
	public void visit(ElementGroup el) {
		checkMatching( el );
		if (!matching)
		{
			checkList( el.getElements() );
		}
	}

	@Override
	public void visit(ElementDataset el) {
		checkMatching( el );
		if (!matching)
		{
			el.getElement().visit( this );
		}
		
	}

	@Override
	public void visit(ElementNamedGraph el) {
		checkMatching( el );
		if (!matching)
		{
			el.getElement().visit( this );
		}
	}

	@Override
	public void visit(ElementExists el) {
		checkMatching( el );
		if (!matching)
		{
			el.getElement().visit( this );
		}
	}

	@Override
	public void visit(ElementNotExists el) {
		checkMatching( el );
		if (!matching)
		{
			el.getElement().visit( this );
		}
	}

	@Override
	public void visit(ElementMinus el) {
		checkMatching( el );
		if (!matching)
		{
			el.getMinusElement().visit( this );
		}
	}

	@Override
	public void visit(ElementService el) {
		checkMatching( el );
		if (!matching)
		{
			el.getElement().visit( this );
		}
	}

	@Override
	public void visit(ElementSubQuery el) {
		checkMatching( el );
		if (!matching)
		{
			el.getQuery().getQueryPattern().visit(this);
		}
	}
	
}