rowdatadynamic.java

jsp数据库系统

/*
   Copyright (C) 2002 MySQL AB

      This program is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published by
      the Free Software Foundation; either version 2 of the License, or
      (at your option) any later version.

      This program is distributed in the hope that it will be useful,
      but WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      GNU General Public License for more details.

      You should have received a copy of the GNU General Public License
      along with this program; if not, write to the Free Software
      Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 */
package com.mysql.jdbc;

import java.io.IOException;

import java.sql.SQLException;


/**
 * Allows streaming of MySQL data.
 *
 * @author dgan
 * @version $Id: RowDataDynamic.java,v 1.8.2.6 2003/12/24 05:16:24 mmatthew Exp $
 */
public class RowDataDynamic implements RowData {
    private MysqlIO io;
    private byte[][] nextRow;
    private boolean isAfterEnd = false;
    private boolean isAtEnd = false;
    private boolean streamerClosed = false;
    private int columnCount;
    private int index = -1;
    private long lastSuccessfulReadTimeMs = 0;
    private long netWriteTimeoutMs = 0;
    private ResultSet owner;

    /**
     * Creates a new RowDataDynamic object.
     *
     * @param io DOCUMENT ME!
     * @param colCount DOCUMENT ME!
     *
     * @throws SQLException DOCUMENT ME!
     */
    public RowDataDynamic(MysqlIO io, int colCount) throws SQLException {
        this.io = io;
        this.columnCount = colCount;
        nextRecord();
    }

    /**
     * Returns true if we got the last element.
     *
     * @return true if after last row
     *
     * @throws SQLException if a database error occurs
     */
    public boolean isAfterLast() throws SQLException {
        return isAfterEnd;
    }

    /**
     * Only works on non dynamic result sets.
     *
     * @param index row number to get at
     *
     * @return row data at index
     *
     * @throws SQLException if a database error occurs
     */
    public byte[][] getAt(int index) throws SQLException {
        notSupported();

        return null;
    }

    /**
     * Returns if iteration has not occured yet.
     *
     * @return true if before first row
     *
     * @throws SQLException if a database error occurs
     */
    public boolean isBeforeFirst() throws SQLException {
        return index < 0;
    }

    /**
     * Moves the current position in the result set to the given row number.
     *
     * @param rowNumber row to move to
     *
     * @throws SQLException if a database error occurs
     */
    public void setCurrentRow(int rowNumber) throws SQLException {
        notSupported();
    }
    
	/**
	 * @see com.mysql.jdbc.RowData#setOwner(com.mysql.jdbc.ResultSet)
	 */
	public void setOwner(ResultSet rs) {
		this.owner = rs;
	}
	
	/**
	 * @see com.mysql.jdbc.RowData#getOwner()
	 */
	public ResultSet getOwner() {
		return this.owner;
	}

    /**
     * Returns the current position in the result set as a row number.
     *
     * @return the current row number
     *
     * @throws SQLException if a database error occurs
     */
    public int getCurrentRowNumber() throws SQLException {
        notSupported();

        return -1;
    }

    /**
     * Returns true if the result set is dynamic. This means that move back and
     * move forward won't work because we do not hold on to the records.
     *
     * @return true if this result set is streaming from the server
     */
    public boolean isDynamic() {
        return true;
    }

    /**
     * Has no records.
     *
     * @return true if no records
     *
     * @throws SQLException if a database error occurs
     */
    public boolean isEmpty() throws SQLException {
        notSupported();

        return false;
    }

    /**
     * Are we on the first row of the result set?
     *
     * @return true if on first row
     *
     * @throws SQLException if a database error occurs
     */
    public boolean isFirst() throws SQLException {
        notSupported();

        return false;
    }

    /**
     * Are we on the last row of the result set?
     *
     * @return true if on last row
     *
     * @throws SQLException if a database error occurs
     */
    public boolean isLast() throws SQLException {
        notSupported();

        return false;
    }

    /**
     * Adds a row to this row data.
     *
     * @param row the row to add
     *
     * @throws SQLException if a database error occurs
     */
    public void addRow(byte[][] row) throws SQLException {
        notSupported();
    }

    /**
     * Moves to after last.
     *
     * @throws SQLException if a database error occurs
     */
    public void afterLast() throws SQLException {
        notSupported();
    }

    /**
     * Moves to before first.
     *
     * @throws SQLException if a database error occurs
     */
    public void beforeFirst() throws SQLException {
        notSupported();
    }

    /**
     * Moves to before last so next el is the last el.
     *
     * @throws SQLException if a database error occurs
     */
    public void beforeLast() throws SQLException {
        notSupported();
    }

    /**
     * We're done.
     *
     * @throws SQLException if a database error occurs
     */
    public void close() throws SQLException {
        //drain the rest of the records.
        int count = 0;
        
        while (this.hasNext()) {
            this.next();
            
            count++;
            
            if (count == 100) {
            	Thread.yield();
            	count = 0;
            }
        }
    }

    /**
     * Returns true if another row exsists.
     *
     * @return true if more rows
     *
     * @throws SQLException if a database error occurs
     */
    public boolean hasNext() throws SQLException {
        boolean hasNext = (nextRow != null);

        if (!hasNext && !streamerClosed) {
            io.closeStreamer(this);
            streamerClosed = true;
        }

        return hasNext;
    }

    /**
     * Moves the current position relative 'rows' from the current position.
     *
     * @param rows the relative number of rows to move
     *
     * @throws SQLException if a database error occurs
     */
    public void moveRowRelative(int rows) throws SQLException {
        notSupported();
    }

    /**
     * Returns the next row.
     *
     * @return the next row value
     *
     * @throws SQLException if a database error occurs
     */
    public byte[][] next() throws SQLException {
        index++;

        byte[][] ret = nextRow;
        nextRecord();

        return ret;
    }

    /**
     * Removes the row at the given index.
     *
     * @param index the row to move to
     *
     * @throws SQLException if a database error occurs
     */
    public void removeRow(int index) throws SQLException {
        notSupported();
    }

    /**
     * Only works on non dynamic result sets.
     *
     * @return the size of this row data
     */
    public int size() {
        return RESULT_SET_SIZE_UNKNOWN;
    }

    private void nextRecord() throws SQLException {
        try {
            if (!isAtEnd) {
                nextRow = io.nextRow((int) columnCount);

                if (nextRow == null) {
                    isAtEnd = true;
                }
                
                this.lastSuccessfulReadTimeMs = System.currentTimeMillis();
            } else {
                isAfterEnd = true;
            }
        } catch (SQLException sqlEx) {
            // don't wrap SQLExceptions
            throw sqlEx;
        } catch (IOException ioEx) {
        	long timeSinceLastReadMs = System.currentTimeMillis() - this.lastSuccessfulReadTimeMs;
        	
            String exceptionType = ioEx.getClass().getName();
            String exceptionMessage = ioEx.getMessage();

            exceptionMessage += "\n\nNested Stack Trace:\n";
            exceptionMessage += Util.stackTraceToString(ioEx);

            throw new java.sql.SQLException(
                "IOException while retrieving next record in streaming result set."
                + "(Check for deadlock "
                + " or retrieval exceeding 'net_write_timeout' seconds. Last "
                + "successful record read was " + timeSinceLastReadMs + " ms ago, and"
                + "'net_write_timeout' is configured in the server as " + this.netWriteTimeoutMs 
                + " ms.) : "
                + exceptionType + " message given: " + exceptionMessage, SQLError.SQL_STATE_GENERAL_ERROR);
        } catch (Exception ex) {
            String exceptionType = ex.getClass().getName();
            String exceptionMessage = ex.getMessage();

            exceptionMessage += "\n\nNested Stack Trace:\n";
            exceptionMessage += Util.stackTraceToString(ex);

            throw new java.sql.SQLException(
                "Error retrieving record: Unexpected Exception: "
                + exceptionType + " message given: " + exceptionMessage, SQLError.SQL_STATE_GENERAL_ERROR);
        }
    }

    private void notSupported() throws SQLException {
        throw new OperationNotSupportedException();
    }

    class OperationNotSupportedException extends SQLException {
        OperationNotSupportedException() {
            super("Operation not supported for streaming result sets", SQLError.SQL_STATE_ILLEGAL_ARGUMENT);
        }
    }
}