QueryParser.java

/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * JBoss, Home of Professional Open Source
 * Copyright 2013 Red Hat Inc. and/or its affiliates and other contributors
 * as indicated by the @authors tag. All rights reserved.
 * See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU Lesser General Public License, v. 2.1.
 * This program is distributed in the hope that it will be useful, but WITHOUT A
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
 * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
 * You should have received a copy of the GNU Lesser General Public License,
 * v.2.1 along with this distribution; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA  02110-1301, USA.
 */
package org.hibernate.hql;

import java.util.List;

import org.antlr.runtime.ANTLRStringStream;
import org.antlr.runtime.CommonTokenStream;
import org.antlr.runtime.RecognitionException;
import org.antlr.runtime.Token;
import org.antlr.runtime.tree.CommonTree;
import org.hibernate.hql.ast.origin.hql.parse.HQLLexer;
import org.hibernate.hql.ast.origin.hql.parse.HQLParser;
import org.hibernate.hql.ast.spi.AstProcessingChain;
import org.hibernate.hql.ast.spi.AstProcessor;
import org.hibernate.hql.internal.logging.Log;
import org.hibernate.hql.internal.logging.LoggerFactory;

/**
 * A parser for HQL/JPQL queries. Parsing comprises these steps:
 * <ul>
 * <li>lexing the query</li>
 * <li>parsing the query, building up an AST while doing so</li>
 * <li>transforming the resulting parse tree using an {@link AstProcessingChain}</li>
 * </ul>
 *
 * @author Gunnar Morling
 */
public class QueryParser {

	private static final Log log = LoggerFactory.make();

	/**
	 * Parses the given query string.
	 *
	 * @param queryString the query string to parse
	 * @param processingChain one or more {@link AstProcessor}s which traverse the query parse tree in order to
	 * normalize/validate it and create the parsing result
	 * @return the result of this parsing as created by the given processing chain
	 * @throws ParsingException in case any exception occurs during parsing
	 */
	public <T> T parseQuery(String queryString, AstProcessingChain<T> processingChain) throws ParsingException {
		HQLLexer lexer = new HQLLexer( new ANTLRStringStream( queryString ) );
		CommonTokenStream tokens = new CommonTokenStream( lexer );
		HQLParser parser = new HQLParser( tokens );

		try {
			// parser#statement() is the entry point for evaluation of any kind of statement
			HQLParser.statement_return r = parser.statement();

			if ( parser.hasErrors() ) {
				throw log.getInvalidQuerySyntaxException( queryString, parser.getErrorMessages() );
			}

			String unconsumedTokens = getUnconsumedTokens( tokens );
			if ( unconsumedTokens != null ) {
				throw log.getInvalidQuerySyntaxDueToUnconsumedTokensException( queryString, unconsumedTokens );
			}

			CommonTree tree = (CommonTree) r.getTree();

			final boolean debugEnabled = log.isDebugEnabled();
			for ( AstProcessor processor : processingChain ) {
				tree = processor.process( tokens, tree );

				if ( debugEnabled ) {
					log.debug( "Processed tree: " + tree.toStringTree() );
				}
			}

			return processingChain.getResult();
		}
		catch (RecognitionException e) {
			throw log.getInvalidQuerySyntaxException( queryString, e );
		}
	}

	private String getUnconsumedTokens(CommonTokenStream tokens) {
		// ensure we've buffered all tokens from the underlying TokenSource
		tokens.fill();
		if ( tokens.index() == tokens.size() - 1 ) {
			return null;
		}

		StringBuilder nonEofEndingTokens = new StringBuilder();

		@SuppressWarnings("unchecked")
		List<Token> unconsumed = (List<Token>) tokens.getTokens( tokens.index(), tokens.size() - 1 );
		for ( Token endToken : unconsumed ) {
			// Ignore <EOF> tokens as they might be inserted by the parser
			if ( endToken.getType() != Token.EOF ) {
				nonEofEndingTokens.append( endToken.getText() );
			}
		}

		return nonEofEndingTokens.length() > 0 ? nonEofEndingTokens.toString() : null;
	}
}