com.github.haixing_hu.criteria.parser.SqlCriterionParser.java Source code

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/******************************************************************************
 *
 * Copyright (c) 2014  Haixing Hu
 *
 * Licensed 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 com.github.haixing_hu.criteria.parser;

import org.antlr.v4.runtime.ANTLRInputStream;
import org.antlr.v4.runtime.CommonTokenStream;
import org.antlr.v4.runtime.tree.ParseTree;

import com.github.haixing_hu.antlr.AntlrParseException;
import com.github.haixing_hu.antlr.ThrowExceptionErrorListener;
import com.github.haixing_hu.criteria.Criterion;
import com.github.haixing_hu.criteria.formatter.SqlCriterionFormatter;
import com.github.haixing_hu.criteria.parser.sql.CriterionLexer;
import com.github.haixing_hu.criteria.parser.sql.CriterionParser;
import com.github.haixing_hu.criteria.parser.sql.CriterionParsingVisitor;
import com.github.haixing_hu.text.Parser;
import com.github.haixing_hu.text.ParsingException;

/**
 * A parser used to parse a criterion from its SQL representation.
 * <p>
 * <b>NOTE:</b> This parser can only recognize the string representation of
 * criteria formatted by the {@link SqlCriterionFormatter} class.
 * <p>
 * <b>NOTE:</b> In order to distinguish between character literal and string
 * literal, we make the following conventions:
 * <ul>
 * <li>the character literals are quoted by single quotation marks, and</li>
 * <li>the string literals are quoted by double quotation marks.</li>
 * </ul>
 *
 * @author Haixing Hu
 */
public final class SqlCriterionParser implements Parser<String, Criterion> {

    @Override
    public Criterion parse(final String input) throws ParsingException {
        final ANTLRInputStream is = new ANTLRInputStream(input);
        final ThrowExceptionErrorListener listener = new ThrowExceptionErrorListener();
        final CriterionLexer lexer = new CriterionLexer(is);
        lexer.removeErrorListeners();
        lexer.addErrorListener(listener);
        final CommonTokenStream tokens = new CommonTokenStream(lexer);
        final CriterionParser parser = new CriterionParser(tokens);
        parser.removeErrorListeners();
        parser.addErrorListener(listener);
        try {
            final ParseTree tree = parser.line().criterion();
            final CriterionParsingVisitor visitor = new CriterionParsingVisitor();
            final Criterion result = visitor.visit(tree);
            if (result == null) {
                throw new ParsingException(input, 0, "Failed to parse the SQL representation.");
            }
            return result;
        } catch (final AntlrParseException e) {
            throw new ParsingException(e.getInput(), e.getPosition(), e.getMessage());
        }
    }

}