simpletextresultset.java

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//----------------------------------------------------------------------------
//
// Module:      SimpleTextResultSet.java
//
// Description: Implementation of the JDBC ResultSet interface
//
// Author:      Karl Moss
//
// Copyright:   (C) 1996,1997 Karl Moss.  All rights reserved.
//              You may study, use, modify and distribute this example
//              for any purpose, provided that this copyright notice
//              appears in all copies.  This example is provided WITHOUT
//              WARRANTY either expressed or implied.
//----------------------------------------------------------------------------

package jdbc.SimpleText;

//----------------------------------------------------------------------------
// A ResultSet provides access to a table of data generated by
// executing a Statement. The table rows are retrieved in
// sequence. Within a row its column values can be accessed in any
// order.
//
// A ResultSet maintains a cursor pointing to its current row of
// data.  Initially the cursor is positioned before the first row.
// The 'next' method moves the cursor to the next row.
//
// The getXXX methods retrieve column values for the current
// row.  You can retrieve values either using the index number of the
// column, or by using the name of the column.  In general using the
// column index will be more efficient.  Columns are numbered from 1.
//
// For maximum portability, ResultSet columns within each row should be
// read in left-to-right order and each column should be read only once.
//
// For the getXXX methods, the JDBC driver attempts to convert the
// underlying data to the specified Java type and returns a suitable
// Java value.  See the JDBC specification for allowable mappings
// from SQL types to Java types with the ResultSet.getXXX methods.
//
// Column names used as input to getXXX methods are case insensitive.
// When performing a getXXX using a column name if several columns have
// the same name then the value of the first matching column will be
// returned.
//
// A ResultSet is automatically closed by the Statement that
// generated it when that Statement is closed, re-executed, or is used
// to retrieve the next result from a sequence of multiple results.
//
// The number, types and properties of a ResultSet's columns are
// provided by the ResulSetMetaData object returned by the getMetaData
// method.
//----------------------------------------------------------------------------
// NOTE - this is an implementation of the JDBC API version 1.20
//---------------------------------------------------------------------------

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

public class SimpleTextResultSet
    extends        SimpleTextObject
    implements    ResultSet
{

    //------------------------------------------------------------------------
    // initialize
    //------------------------------------------------------------------------

    public void initialize(
        SimpleTextIStatement statement,
        String catalog,
        String table,
        Hashtable columns,
        SimpleTextFilter filter)
        throws SQLException
    {
        // Save the owning statement object

        ownerStatement = statement;
        ownerConnection = ownerStatement.getConnection();

        // Save the in-memory column definitions

        inMemoryColumns = columns;

        // Save the select WHERE filter

        selectFilter = filter;

        // If a table was given, open it now

        if (table != null) {
            openSDF(catalog, table);
        }
    }

    public void initialize(
        SimpleTextIStatement statement,
        Hashtable columns,
        Hashtable rows)
        throws SQLException
    {
        // Save the in-memory rows (used for catalog functions)

        inMemoryRows = rows;
        rowNum = 0;

        initialize(statement, null, null, columns, null);
    }

    //------------------------------------------------------------------------
    // next - JDBC API
    // A ResultSet is initially positioned before its first row; the
    // first call to next makes the first row the current row; the
    // second call makes the second row the current row, etc.
    //
    // If an input stream from the previous row is open it is
    // implicitly closed. The ResultSet's warning chain is cleared
    // when a new row is read.
    //
    // Returns true if the new current row is valid; false if there
    // are no more rows
    //------------------------------------------------------------------------

    public boolean next()
        throws SQLException
    {
        boolean rc = true;
        boolean validRow = false;

        // In memory result set, get the next row

        if (inMemoryRows != null) {
            rowNum++;

            // No more rows, return end-of-file

            if (rowNum > inMemoryRows.size()) {
                rc = false;
            }
        }
        else {

            // Not in-memory, read the next line from the file until a
            // valid row has been found

            while (!validRow) {

                currentLine = readLine(rafSDF);

                if (currentLine == null) {
                    rc = false;
                    break;
                }

                // We'll cheat a little bit here.  We'll use the SQL
                // parser to break the line up, then treat it as a
                // comma separated list (much like a select list)

                String data[] = ownerConnection.parseSQL(currentLine);

                Hashtable dataList = new Hashtable();

                ownerStatement.buildList(data, 0, "", dataList);

                // Now go through each data element and create a
                // CommonValue object.  Then, put the CommonValue object
                // on our columnValues list

                SimpleTextColumn column;
                columnValues = new Hashtable();
                String s;
                CommonValue value;

                for (int i = 1; i <= dataList.size(); i++) {
                    column = (SimpleTextColumn) dataList.get(new Integer(i));

                    // Get the data item

                    s = column.name;

                    // Remove any quotes
                    if (s.startsWith("'") &&
                        s.endsWith("'")) {
                        s = s.substring(1, s.length() - 1);
                    }

                    // Create a CommonValue object using the string

                    value = new CommonValue(s);

                    // Create a CommonValue object

                    columnValues.put(new Integer(i), value);

                }

                // Filter the row, if necessary

                validRow = filterRow(columnValues, selectFilter);

            }
        }
        return rc;
    }


    //------------------------------------------------------------------------
    // close - JDBC API
    // In some cases, it is desirable to immediately release a
    // ResultSet's database and JDBC resources instead of waiting for
    // this to happen when it is automatically closed; the close
    // method provides this immediate release.
    //
    // Note:  A ResultSet is automatically closed by the
    // Statement that generated it when that Statement is closed,
    // re-executed, or is used to retrieve the next result from a
    // sequence of multiple results. A ResultSet is also automatically
    // closed when it is garbage collected.
    //------------------------------------------------------------------------

    public void close()
        throws SQLException
    {
        try {
            if (rafSDF != null) {
                rafSDF.close();
            }
            if (rafSBF != null) {
                rafSBF.close();
            }
        }
        catch (Exception ex) {
        }
    }

    //------------------------------------------------------------------------
    // wasNull - JDBC API
    // A column may have the value of SQL NULL; wasNull reports whether
    // the last column read had this special value.
    // Note that you must first call getXXX on a column to try to read
    // its value and then call wasNull() to find if the value was
    // the SQL NULL.
    //
    // Returns true if last column read was SQL NULL
    //------------------------------------------------------------------------

    public boolean wasNull()
        throws SQLException
    {
        return lastNull;
    }

    //------------------------------------------------------------------------
    // getString - JDBC API
    // Get the value of a column in the current row as a Java String.
    //
    //    columnIndex        the first column is 1, the second is 2, ...
    //
    // Returns the column value; if the value is SQL NULL the result is null
    //------------------------------------------------------------------------

    public String getString(
        int columnIndex)
        throws SQLException
    {

        // Verify the column

        verify(columnIndex);

        String s = null;

        if (inMemoryRows != null) {
            s = (getColumn(rowNum, columnIndex)).getString();
        }
        else {
            CommonValue value = getValue(columnIndex);

            if (value != null) {
                s = value.getString();
            }
        }

        if (s == null) {
            lastNull = true;
        }

        return s;
    }

    //------------------------------------------------------------------------
    // getBoolean - JDBC API
    // Get the value of a column in the current row as a Java boolean.
    //
    //    columnIndex        the first column is 1, the second is 2, ...
    //
    // Returns the column value; if the value is SQL NULL the result is false
    //------------------------------------------------------------------------

    public boolean getBoolean(
        int columnIndex)
        throws SQLException
    {
        // We could coerce the data, but for now an exception is thrown

        throw DataTypeNotSupported();
    }

    //------------------------------------------------------------------------
    // getByte - JDBC API
    // Get the value of a column in the current row as a Java byte.
    //
    //    columnIndex        the first column is 1, the second is 2, ...
    // Returns the column value; if the value is SQL NULL the result is 0
    //------------------------------------------------------------------------

    public byte getByte(
        int columnIndex)
        throws SQLException
    {
        // We could coerce the data, but for now an exception is thrown

        throw DataTypeNotSupported();
    }

    //------------------------------------------------------------------------
    // getShort - JDBC API
    // Get the value of a column in the current row as a Java short.
    //
    //    columnIndex        the first column is 1, the second is 2, ...
    //
    // Returns the column value; if the value is SQL NULL the result is 0
    //------------------------------------------------------------------------

    public short getShort(
        int columnIndex)
        throws SQLException
    {
        // We could coerce the data, but for now an exception is thrown

        throw DataTypeNotSupported();
    }

    //------------------------------------------------------------------------
    // getInt - JDBC API
    // Get the value of a column in the current row as a Java int.
    //
    //    columnIndex        the first column is 1, the second is 2, ...
    //
    // Returns the column value; if the value is SQL NULL the result is 0
    //------------------------------------------------------------------------

    public int getInt(
        int columnIndex)
        throws SQLException
    {
        // Verify the column

        verify(columnIndex);

        CommonValue value;

        if (inMemoryRows != null) {
            value = getColumn(rowNum, columnIndex);
        }
        else {
            value = getValue(columnIndex);
        }

        // Check for a null value

        if (value == null) {
            lastNull = true;
            return 0;
        }

        if (value.isNull()) {
            lastNull = true;
            return 0;
        }

        return value.getInt();
    }

    //------------------------------------------------------------------------
    // getLong - JDBC API
    // Get the value of a column in the current row as a Java long.
    //
    //    columnIndex        the first column is 1, the second is 2, ...
    //
    // Returns the column value; if the value is SQL NULL the result is 0
    //------------------------------------------------------------------------

    public long getLong(
        int columnIndex)
        throws SQLException
    {
        // We could coerce the data, but for now an exception is thrown

        throw DataTypeNotSupported();
    }

    //------------------------------------------------------------------------