rawdatarecordset.java

openmap java写的开源数字地图程序. 用applet实现,可以像google map 那样放大缩小地图.

// **********************************************************************
// 
// <copyright>
// 
//  BBN Technologies
//  10 Moulton Street
//  Cambridge, MA 02138
//  [phone]
// 
//  Copyright (C) BBNT Solutions LLC. All rights reserved.
// 
// </copyright>
// **********************************************************************
// 
// $Source: /cvs/distapps/openmap/src/openmap/com/bbn/openmap/layer/location/db/RawDataRecordSet.java,v $
// $RCSfile: RawDataRecordSet.java,v $
// $Revision: 1.2.2.1 $
// $Date: 2004/10/14 18:27:10 $
// $Author: dietrick $
// 
// **********************************************************************

package com.bbn.openmap.layer.location.db;

import java.sql.*;
import java.io.*;
import java.util.Hashtable;
import java.util.Properties;

/**
 * This class is responsible for retrieving Raw Data from a table in a
 * Database given a key. Users of this class should provide Database
 * connection, Table name, Column name that has the key and column
 * name that has the actual data.
 * <P>
 * If you are going to use this, there are a couple of properties to
 * set: <BR>
 * prefix.rawDataTableName=table name <BR>
 * prefix.rawDataColumnName=data column name <BR>
 * prefix.rawDataKeyColumnName=data key name <BR>
 *  
 */
public class RawDataRecordSet {
    /** Connection object that will be used to retrieve data */
    protected Connection connection;
    /** Table name from which data would be retrieved */
    protected String tableName;
    /** Column name in the above table that has Raw Data */
    protected String rawDataColumnName;
    /** Column name which has the key to lookup above data */
    protected String rawDataKeyColumnName;

    /**
     * A hashtable to keep track of the byte arrays, using the key.
     * This will reduce the calls to the database.
     */
    protected Hashtable byteCache = new Hashtable();

    public static final String tableNameProperty = "rawDataTableName";
    public static final String rawDataColumnNameProperty = "rawDataColumnName";
    public static final String rawDataKeyColumnNameProperty = "rawDataKeyColumnName";

    public RawDataRecordSet() {}

    public RawDataRecordSet(Connection inConnection) {
        setConnection(inConnection);
    }

    public RawDataRecordSet(Connection inconnection, String prefix,
            Properties properties) {

        if (prefix != null) {
            prefix = prefix + ".";
        } else {
            prefix = "";
        }

        setConnection(inconnection);
        setTableName(properties.getProperty(prefix + tableNameProperty));
        setRawDataColumnName(properties.getProperty(prefix
                + rawDataColumnNameProperty));
        setRawDataKeyColumnName(properties.getProperty(prefix
                + rawDataKeyColumnNameProperty));
    }

    /** Returns a byte[] array if successfull, null otherwise */
    public byte[] getRawData(String lookUpKey) throws SQLException {

        byte[] foundit = (byte[]) byteCache.get(lookUpKey.toLowerCase()
                .intern());

        if (foundit != null) {
            return foundit;
        }

        String query = "Select " + rawDataColumnName + " from " + tableName
                + " where " + rawDataKeyColumnName + " = '"
                + lookUpKey.toLowerCase() + "' ";

        try {
            Statement stmt = connection.createStatement();
            ResultSet rset = stmt.executeQuery(query);
            rset.next();

            // This is the only(first hence 1)
            InputStream dbis = rset.getBinaryStream(1);
            int chunksize = 4096;
            byte barr[] = new byte[chunksize];
            int imagelength = 0;
            ;

            try {
                imagelength = dbis.read(barr);
            } catch (IOException ioE) {
                System.err.println("ERROR - while reading raw data\n"
                        + ioE.getMessage());
            }
            //          System.out.println("image length = " + imagelength);
            byte image[] = new byte[imagelength];
            System.arraycopy(barr, 0, image, 0, imagelength);

            // close the resultSet
            rset.close();
            // Close the statement
            stmt.close();
            byteCache.put(lookUpKey.toLowerCase().intern(), image);
            return image;

        } catch (SQLException sqlE) {
            //          throw new SQLException(sqlE.getMessage() + "\n"+
            //                                 "SQL String " + query);
            System.err.println("ERROR - " + sqlE.getMessage() + "\n"
                    + "SQL String: " + query);
            return null;
        }
    }

    public Connection getConnection() {
        return connection;
    }

    public void setConnection(Connection inConnection) {
        connection = inConnection;
    }

    public String getTableName() {
        return tableName;
    }

    public void setTableName(String inTableName) {
        tableName = inTableName;
    }

    public String getRawDataColumnName() {
        return rawDataColumnName;
    }

    public void setRawDataColumnName(String inrawDataColumnName) {
        rawDataColumnName = inrawDataColumnName;
    }

    public String getRawDataKeyColumnName() {
        return rawDataKeyColumnName;
    }

    public void setRawDataKeyColumnName(String inrawDataKeyColumnName) {
        rawDataKeyColumnName = inrawDataKeyColumnName;
    }
}