QueryParser.java

/**
 *  Copyright 2012 Universitat Pompeu Fabra.
 *
 *  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 org.onexus.collection.query.parser.internal;

import org.antlr.runtime.ANTLRStringStream;
import org.antlr.runtime.CommonTokenStream;
import org.antlr.runtime.RecognitionException;
import org.antlr.runtime.TokenStream;
import org.onexus.collection.api.query.Filter;
import org.onexus.collection.api.query.IQueryParser;
import org.onexus.collection.api.query.OrderBy;
import org.onexus.collection.api.query.Query;
import org.onexus.resource.api.ORI;

import java.util.List;
import java.util.Map;

public class QueryParser implements IQueryParser {

    @Override
    public Map<String, ORI> parseDefine(String expression) {
        OqlParser parser = newParser("DEFINE " + expression);

        try {
            parser.defineClause();
        } catch (RecognitionException e) {
            return null;
        }

        return parser.getQuery().getDefine();
    }


    @Override
    public Map<String, List<String>> parserSelect(String expression) {

        OqlParser parser = newParser("SELECT " + expression);
        try {
            parser.selectClause();
        } catch (RecognitionException e) {
            return null;
        }

        return parser.getQuery().getSelect();

    }


    @Override
    public Filter parseWhere(String expression) {

        OqlParser parser = newParser("WHERE " + expression);
        try {
            parser.whereClause();
        } catch (RecognitionException e) {
            return null;
        }

        return parser.getQuery().getWhere();

    }

    @Override
    public List<OrderBy> parseOrder(String expression) {

        OqlParser parser = newParser("ORDER BY " + expression);
        try {
            parser.orderbyClause();
        } catch (RecognitionException e) {
            return null;
        }

        return parser.getQuery().getOrders();

    }

    @Override
    public Query parseQuery(String expression) {

        if (expression == null) {
            return null;
        }

        OqlParser parser = newParser(expression);

        try {
            parser.oql();
        } catch (RecognitionException e) {
            e.printStackTrace();
        }

        return parser.getQuery();
    }

    private OqlParser newParser(String expression) {

        //lexer splits input into tokens
        ANTLRStringStream input = new ANTLRStringStream(expression);
        OqlLexer lexer = new OqlLexer(input);
        TokenStream tokens = new CommonTokenStream(lexer);

        //parser generates abstract syntax tree
        OqlParser parser = new OqlParser(tokens);

        return parser;
    }

}