org.protempa.backend.dsb.relationaldb.JDBCDateTimeTimestampPositionParser Maven / Gradle / Ivy

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Implements support for retrieving data from relational databases.
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/*
 * #%L
 * Protempa Commons Backend Provider
 * %%
 * Copyright (C) 2012 - 2013 Emory University
 * %%
 * 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.
 * #L%
 */
package org.protempa.backend.dsb.relationaldb;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;
import java.util.Date;
import org.protempa.proposition.value.AbsoluteTimeGranularity;
import org.protempa.proposition.value.AbsoluteTimeGranularityUtil;

/**
 * Implements parsing of dates/times into a PROTEMPA position using an
 * appropriate call to {@link ResultSet}.
 *
 * @author Andrew Post
 */
public final class JDBCDateTimeTimestampPositionParser
        implements JDBCPositionFormat {

    private final Long defaultDate;

    /**
     * Constructs a date-time "parser" that calls the appropriate date, time
     * or timestamp result set getter.
     */
    public JDBCDateTimeTimestampPositionParser() {
        this(null);
    }

    /**
     * Constructs a JDBC date-time parser. Optionally allows specifying a
     * default date to use when the date column of interest has value 
     * null.
     * 
     * @param defaultDate default date to use when the date column of interest
     * is null.
     */
    public JDBCDateTimeTimestampPositionParser(Date defaultDate) {
        if (defaultDate != null) {
            this.defaultDate = defaultDate.getTime();
        } else {
            this.defaultDate = null;
        }
    }

    /**
     * Parses a date/time into a PROTEMPA position. For types date, time and
     * timestamp it calls the corresponding method in {@link ResultSet}. For
     * other types, it calls {@link ResultSet#getTimestamp(int)} and lets the
     * JDBC driver attempt to parse a date.
     *
     * @param resultSet a {@link ResultSet}. Cannot be null.
     * @param columnIndex the index of the column to retrieve from the result
     * set.
     * @param colType the SQL type of the column as a {@link Types}.
     * @return a PROTEMPA position or null if the column in the
     * database is NULL.
     *
     * @throws SQLException if there is an error accessing the result set or the
     * column cannot be parsed into a date.
     */
    @Override
    public Long toPosition(ResultSet resultSet, int columnIndex, int colType)
            throws SQLException {
        Date result;
        switch (colType) {
            case Types.DATE:
                result = resultSet.getDate(columnIndex);
                break;
            case Types.TIME:
                result = resultSet.getTime(columnIndex);
                break;
            default:
                /*
                 * We'll end up here for Types.TIMESTAMP and non-date SQL data
                 * types. For the latter, we'll let the JDBC driver try to 
                 * parse a date.
                 */
                result = resultSet.getTimestamp(columnIndex);
        }
        if (result != null) {
            return AbsoluteTimeGranularityUtil.asPosition(result);
        } else {
            return this.defaultDate;
        }

    }

    /**
     * Formats a PROTEMPA long as a JDBC timestamp string suitable for inclusion
     * in a SELECT statement executed via JDBC.
     *
     * @param position a PROTEMPA position.
     * @return a JDBC timestamp {@link String}.
     */
    @Override
    public String format(Long position) {
        return "{ts '" + AbsoluteTimeGranularity.toSQLString(
                position) + "'}";
    }
}