WildcardProjectionProcessor.java

/*
 * Copyright Aduna (http://www.aduna-software.com/) (c) 1997-2006.
 *
 * Licensed under the Aduna BSD-style license.
 */
package org.openrdf.query.parser.sparql;

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

import org.openrdf.query.MalformedQueryException;
import org.openrdf.query.parser.sparql.ast.ASTDescribe;
import org.openrdf.query.parser.sparql.ast.ASTDescribeQuery;
import org.openrdf.query.parser.sparql.ast.ASTQuery;
import org.openrdf.query.parser.sparql.ast.ASTQueryContainer;
import org.openrdf.query.parser.sparql.ast.ASTSelect;
import org.openrdf.query.parser.sparql.ast.ASTSelectQuery;
import org.openrdf.query.parser.sparql.ast.ASTVar;
import org.openrdf.query.parser.sparql.ast.Node;
import org.openrdf.query.parser.sparql.ast.SyntaxTreeBuilderTreeConstants;
import org.openrdf.query.parser.sparql.ast.VisitorException;

/**
 * Processes 'wildcard' projections, making them explicit by adding the
 * appropriate variable nodes to them.
 * 
 * @author arjohn
 */
class WildcardProjectionProcessor extends ASTVisitorBase {

	public static void process(ASTQueryContainer qc)
		throws MalformedQueryException
	{
		ASTQuery queryNode = qc.getQuery();

		if (queryNode instanceof ASTSelectQuery) {
			ASTSelect selectNode = ((ASTSelectQuery)queryNode).getSelect();

			if (selectNode.isWildcard()) {
				addQueryVars(qc, selectNode);
				selectNode.setWildcard(false);
			}
		}
		else if (queryNode instanceof ASTDescribeQuery) {
			ASTDescribe describeNode = ((ASTDescribeQuery)queryNode).getDescribe();

			if (describeNode.isWildcard()) {
				addQueryVars(qc, describeNode);
				describeNode.setWildcard(false);
			}
		}
	}

	private static void addQueryVars(ASTQueryContainer qc, Node wildcardNode)
		throws MalformedQueryException
	{
		QueryVariableCollector visitor = new QueryVariableCollector();
		try {
			// Collect variable names from query
			qc.jjtAccept(visitor, null);

			// Adds ASTVar nodes to the wildcard node
			for (String varName : visitor.getVariableNames()) {
				ASTVar varNode = new ASTVar(SyntaxTreeBuilderTreeConstants.JJTVAR);
				varNode.setName(varName);
				wildcardNode.jjtAppendChild(varNode);
				varNode.jjtSetParent(wildcardNode);
			}
		}
		catch (VisitorException e) {
			throw new MalformedQueryException(e);
		}
	}

	/*------------------------------------*
	 * Inner class QueryVariableCollector *
	 *------------------------------------*/

	private static class QueryVariableCollector extends ASTVisitorBase {

		private Set<String> variableNames = new LinkedHashSet<String>();

		public Set<String> getVariableNames() {
			return variableNames;
		}

		@Override
		public Object visit(ASTVar node, Object data)
			throws VisitorException
		{
			if (!node.isAnonymous()) {
				variableNames.add(node.getName());
			}
			return super.visit(node, data);
		}
	}
}