org.apache.drill.common.parser.LogicalExpressionParser.java Source code

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Here is the source code for org.apache.drill.common.parser.LogicalExpressionParser.java

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/*
 * 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.drill.common.parser;

import org.antlr.v4.runtime.CharStreams;
import org.antlr.v4.runtime.CommonTokenStream;
import org.apache.drill.common.expression.LogicalExpression;
import org.apache.drill.common.expression.parser.ExprLexer;
import org.apache.drill.common.expression.parser.ExprParser;

/**
 * Helper class for parsing logical expression.
 */
public class LogicalExpressionParser {

    private static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(LogicalExpressionParser.class);

    /**
     * Initializes logical expression lexer and parser, add error listener that converts all
     * syntax error into {@link org.apache.drill.common.exceptions.ExpressionParsingException}.
     * Parses given expression into logical expression instance.
     *
     * @param expr expression to be parsed
     * @return logical expression instance
     */
    public static LogicalExpression parse(String expr) {
        ExprLexer lexer = new ExprLexer(CharStreams.fromString(expr));
        lexer.removeErrorListeners(); // need to remove since default listener will output warning
        lexer.addErrorListener(ErrorListener.INSTANCE);
        CommonTokenStream tokens = new CommonTokenStream(lexer);

        ExprParser parser = new ExprParser(tokens);
        parser.removeErrorListeners(); // need to remove since default listener will output warning
        parser.addErrorListener(ErrorListener.INSTANCE);
        ExprParser.ParseContext parseContext = parser.parse();
        logger.trace("Tokens: [{}]. Parsing details: [{}].", tokens.getText(), parseContext.toInfoString(parser));
        return parseContext.e;
    }

}