dbfinputstream.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/dataAccess/shape/input/DbfInputStream.java,v $
// $RCSfile: DbfInputStream.java,v $
// $Revision: 1.5.2.4 $
// $Date: 2005/08/12 14:25:11 $
// $Author: dietrick $
// 
// **********************************************************************

package com.bbn.openmap.dataAccess.shape.input;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.text.DecimalFormatSymbols;
import java.util.ArrayList;
import java.util.Locale;

import com.bbn.openmap.dataAccess.shape.DbfTableModel;
import com.bbn.openmap.util.Debug;

/**
 * Reads the contents of a DBF file and provides access to what it has
 * read through several get methods
 * 
 * @author Doug Van Auken
 */
public class DbfInputStream {
    /**
     * An input stream to process primitives in Little Endian or Big
     * Endian
     */
    private LittleEndianInputStream _leis = null;

    /**
     * An array of column names, as read from the field descripter
     * array
     */
    private String[] _columnNames = null;

    /**
     * An array of column lengths, as read from the field descripter
     * array
     */
    private int[] _lengths = null;

    /**
     * An array of decimal counts, as read from the field descripter
     * array
     */
    private byte[] _decimalCounts = null;

    /**
     * An array of column types, as read from the field descripter
     * array
     */
    private byte[] _types = null;

    /** The number of columns */
    private int _columnCount = -1;

    /** The number of rows */
    private int _rowCount = -1;

    /** The header length */
    private short _headerLength = -1;

    /** The record length */
    // private short _recordLength = -1; // Unused
    /**
     * An ArrayList with each element representing a record, which
     * itself is an ArrayList
     */
    private ArrayList _records = null;

    /**
     * Creates a LittleEndianInputStream then uses it to read the
     * contents of the DBF file
     * 
     * @param is An inputstream used to create a
     *        LittleEndianInputStream
     */
    public DbfInputStream(InputStream is) throws Exception {
        BufferedInputStream bis = new BufferedInputStream(is);
        _leis = new LittleEndianInputStream(bis);
        readHeader();
        readFieldDescripters();
        readData();
    }

    /**
     * Returns an array of column names
     * 
     * @return An array of column names
     */
    public String[] getColumnNames() {
        return _columnNames;
    }

    /**
     * Returns an array of character lengths
     * 
     * @return An array of character lengths
     */
    public int[] getLengths() {
        return _lengths;
    }

    /**
     * Returns an array of decimal counts
     * 
     * @return An array of decimal counts
     */
    public byte[] getDecimalCounts() {
        return _decimalCounts;
    }

    /**
     * Returns an array of field types
     * 
     * @return An array of field types
     */
    public byte[] getTypes() {
        return _types;
    }

    /**
     * Returns an ArrayList of records
     * 
     * @return An ArrayList of recrods
     */
    public ArrayList getRecords() {
        return _records;
    }

    /**
     * Returns the number of columns
     * 
     * @return The nunber of columns
     */
    public int getColumnCount() {
        return _columnCount;
    }

    /**
     * Returns the number of rows
     * 
     * @return The number of rows
     */
    public int getRowCount() {
        return _rowCount;

    }

    /**
     * Reads the header
     */
    private void readHeader() throws IOException {
        /* byte description = */_leis.readByte();
        /* byte year = */_leis.readByte();
        /* byte month = */_leis.readByte();
        /* byte day = */_leis.readByte();
        _rowCount = _leis.readLEInt();
        _headerLength = _leis.readLEShort();
        /* _recordLength = */_leis.readLEShort();
        _columnCount = (_headerLength - 32 - 1) / 32;
        _leis.skipBytes(20);
    }

    /**
     * Initializes arrays that hold column names, column types,
     * character lengths, and decimal counts, then populates them
     */
    private void readFieldDescripters() throws IOException {
        _columnNames = new String[_columnCount];
        _types = new byte[_columnCount];
        _lengths = new int[_columnCount];
        _decimalCounts = new byte[_columnCount];

        for (int n = 0; n <= _columnCount - 1; n++) {
            _columnNames[n] = _leis.readString(11);
            //
            // Some TIGER dbf files from ESRI have nulls
            // in the column names. Delete them.
            //
            int ix = _columnNames[n].indexOf((char) 0);
            if (ix > 0) {
                _columnNames[n] = _columnNames[n].substring(0, ix);
            }
            _types[n] = (byte) _leis.readByte();
            _leis.skipBytes(4);
            _lengths[n] = _leis.readUnsignedByte();
            _decimalCounts[n] = _leis.readByte();
            _leis.skipBytes(14);
        }
    }

    /**
     * Reads the data and places data in a class scope ArrayList of
     * records
     */
    public void readData() throws IOException {

        // Thanks to Bart Jourquin for the heads-up that some locales
        // may try to read this data incorrectly. DBF files have to
        // have '.' as decimal markers, not ','
        java.text.DecimalFormat df = new java.text.DecimalFormat();
        DecimalFormatSymbols dfs = new DecimalFormatSymbols(Locale.ENGLISH);
        df.setDecimalFormatSymbols(dfs);

        _leis.skipBytes(2);
        _records = new ArrayList();
        for (int r = 0; r <= _rowCount - 1; r++) {
            ArrayList record = new ArrayList();
            for (int c = 0; c <= _columnCount - 1; c++) {
                int length = _lengths[c];
                if (length == -1)
                    length = 255;
                int type = _types[c];
                String cell = _leis.readString(length);
                if (type == DbfTableModel.TYPE_NUMERIC && !cell.equals("")) {
                    try {
                        // record.add(c, new Double(cell));
                        record.add(c, new Double(df.parse(cell).doubleValue()));
                        // } catch (NumberFormatException nfe) {
                        // Debug.error("DbfInputStream: error reading
                        // column " + c + ", row " + r +
                        // ", expected number and got " + cell);
                        // record.add(c, new Double(0));
                    } catch (java.text.ParseException pe) {
                        Debug.error("DbfInputStream:  error parsing column "
                                + c + ", row " + r
                                + ", expected number and got " + cell);
                        record.add(c, new Double(0));
                    }
                } else {
                    record.add(c, cell);
                }
            }
            _records.add(record);
            _leis.skipBytes(1);
        }
    }
}