tinysqlresultset.java

有关JDBC的使用一些编程实例,有关与数据库连接的代码

/*
 *
 * The tinySQLResultSet class for the tinySQL JDBC Driver
 *
 * A lot of this code is based on or directly taken from
 * George Reese's ([e-mail]) mSQL driver.
 *
 * So, it's probably safe to say:
 *
 * Portions of this code Copyright (c) 1996 George Reese
 *
 * The rest of it:
 *
 * Copyright 1996, Brian C. Jepson
 *                 ([e-mail])
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

import java.sql.Date;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.SQLWarning;
import java.sql.Time;
import java.sql.Timestamp;
import java.sql.Types;
import java.text.SimpleDateFormat;
import java.util.Hashtable;
import java.text.ParsePosition;

public class tinySQLResultSet implements java.sql.ResultSet {

  /**
   *
   * The tsResultSet
   * 
   */
  private tsResultSet result;

  /**
   *
   * A tsRow object to hold the current row
   *
   */
  private tsRow current_row;
  
  /**
   *
   * The index of the current row
   *
   */
  private int current_row_index = 0;

  /**
   *
   * The meta data for this result set.
   *
   */
  private tinySQLResultSetMetaData meta;

  /**
   *
   * A Hashtable that maps column names to columns
   *
   */
  private Hashtable column_map = null;

  /**
   *
   * Given a tsResultSet, this will construct a new tinySQLResultSet
   * @param res the tsResultSet from a query
   *
   */
  public tinySQLResultSet(tsResultSet res) {
    result = res;
  }

  /**
   *
   * Advance to the next row in the result set. 
   * @see java.sql.ResultSet#next
   * @exception SQLException thrown in case of error
   * @return true if there are any more rows to process, otherwise false.
   *
   */
  public synchronized boolean next() throws SQLException {

    try {

      // automatically return false if the
      // result set is empty
      //
      if( result.size() < 1 ) {
	return false;
      }

      // return false if the index of the current row
      // is equal to the size of the result set
      //
      if( current_row_index == result.size() ) {
	return false;
      }

      // increment the current row index
      //
      current_row_index++;

      // retrieve the row at the current_row_index and store
      // it in the current_row field.
      //
      current_row = result.rowAt(current_row_index - 1);
      return true;

    } catch( Exception e ) {
      throw new SQLException(e.getMessage());
    }

  }
    
  /**
   *
   * Provides a method to close a ResultSet
   * 
   * @see java.sql.ResultSet#close
   *
   */
  public void close() throws SQLException {
  }

  /**
   *
   * Returns whether or not the last column read was null.
   * tinySQL doesn't have nulls, so this is inconsequential...
   * @see java.sql.ResultSet#wasNull
   * @return true if the column was null, false otherwise
   *
   */
  public boolean wasNull() throws SQLException {
    return false;
  }

  /**
   * 
   * Gets the value of a column (by index) as a String.
   * @see java.sql.ResultSet#getString
   * @exception SQLException thrown for bogus column index
   * @param column the column index
   * @return the column's String value
   *
   */
  public String getString(int column) throws SQLException {

    // retrieve the column at the specified index. tinySQL
    // has a column offset of zero, while JDBC uses one.
    // Because of this, I need to subtract one from the
    // index to get the tinySQL index.
    //
    tsColumn col = result.columnAtIndex(column-1);

    // return the column's value
    //
    return current_row.columnAsString(col);

  }

  /**
   *
   * Get the value of a column in the current row as a Java byte.
   *
   * @param columnIndex the first column is 1, the second is 2, ...
   * @return the column value
   *
   */
  public byte getByte(int column) throws SQLException {

    // get the column as a string
    //
    String str = getString(column);
   
    // if it's a blank string, return 0,
    // otherwise, cast the first character 
    // in the string to byte and return it.
    //
    if( str.equals("") ) {
      return 0;
    } else {
      return (byte)str.charAt(0);
    }

  }
  
  /**
   *
   * Get the value of a column in the current row as boolean
   * @see java.sql.ResultSet#getBoolean
   * @exception SQLException Harum Scarum's coming down fast, Clay...
   * @param column the column index
   * @return false for "", null, or "0"; true otherwise
   */
  public boolean getBoolean(int column) throws SQLException {

    try {
    
      // get the column as a string
      //
      String str = getString(column);
      
      // a blank string is false
      //
      if( str.equals("") ) return false;

      // a zero is false
      //
      if( str.equals("0") ) return false;

      // nothing is true... everything is permitted
      //
      return true;

    } catch( Exception e ) {
      throw new SQLException(e.getMessage());
    }
  }

  /**
   *
   * Get the value of a column in the current row as a short.
   * @see java.sql.ResultSet#getShort
   * @exception SQLException D'ohh!
   * @param column the column being retrieved
   * @return the column as a short
   *
   */
  public short getShort(int column) throws SQLException {
    
    // get the column as a string
    //
    String str = getString(column);

    // if it's null, return 0
    //
    if( str == null ) return 0;

    // try to convert it to an integer, and cast it to short
    //
    try {
      return (short)(Integer.valueOf(str).intValue());
    } catch( NumberFormatException e ) {
      throw new SQLException(e.getMessage());
    }

  }  

  /**
   *
   * Retrieve a column from the current row as an int
   * @see java.sql.ResultSet#getInt
   * @exception SQLException bad things... the wind began to howl...
   * @param column the column being retrieved
   * @return the column as an integer
   *
   */
  public int getInt(int column) throws SQLException {
    
    // get the column as a string
    //
    String str = getString(column);

    // if it's null, return 0
    //
    if( str == null ) return 0;

    // try to convert this string to integer
    //
    try {
      return Integer.valueOf(str).intValue();
    } catch( NumberFormatException e ) {
      throw new SQLException(e.getMessage());
    }
    
  }  
  
  /**
   * 
   * Get the value of a column in the current row as a long
   * @see java.sql.ResultSet#getLong
   * @exception SQLException in case of an error
   * @param column the column being retrieved
   * @return the column as a long
   *
   */
  public long getLong(int column) throws SQLException {
    
    // get the column as a string
    //
    String str = getString(column);

    // it it's null, return 0
    if( str == null ) return 0;

    // try to convert the String to a long
    //
    try {
      return Long.valueOf(str).longValue();
    } catch( NumberFormatException e ) {
      throw new SQLException(e.getMessage());
    }
    
  }  

  /**
   *
   * Return a column as a float.
   * @see java.sql.ResultSet#getFloat
   * @exception SQLException in case of error
   * @param column the column being retrieved
   * @return the column as a float
   *
   */
  public float getFloat(int column) throws SQLException {
    
    // get the column as a string
    //
    String str = getString(column);
   
    // if it's null, assume zero
    //
    if( str == null ) return 0;

    // try to perform the conversion
    //
    try {
      return Float.valueOf(str).floatValue();
    } catch( NumberFormatException e ) {
      throw new SQLException(e.getMessage());
    }

  }  

  /**
   *
   * Return a column as a double
   * @see java.sql.ResultSet#getDouble
   * @exception SQLException in case of error
   * @param column the column being retrieved
   * @return the column as a double
   *
   */
  public double getDouble(int column) throws SQLException {
    
    // get the column as a string
    //
    String str = getString(column);

    // it it's null, return zero
    //
    if( str == null ) return 0;

    // attempt the conversion
    //
    try {
      return Double.valueOf(str).doubleValue();
    } catch( NumberFormatException e ) {
      throw new SQLException(e.getMessage());
    }

  }  

  /**
   *
   * Return a column as a BigDecimal object
   * @see java.sql.ResultSet#getBigDecimal
   * @exception SQLException in case of a problem
   * @param column the column being retrieved
   * @param scale the number of digits to the right of the decimal
   * @return the column as a BigDecimal
   *
   */
  public BigDecimal getBigDecimal(int column, int scale)
       throws SQLException {
    
    // get the column as a string
    //
    String str = getString(column);

    // return null as zero, otherwise use the string
    //
    if( str == null ) {
      return new BigDecimal(new BigInteger("0"), scale);
    } else {
      return new BigDecimal(new BigInteger(str), scale);
    }

  }

  /**
   *
   * Get the value of a column in the current row as a Java byte array.
   * @see java.sql.ResultSet#getBytes
   * @exception SQLException thrown in case of trouble
   * @param column the column being retrieved
   * @return a byte array that is the value of the column
   *
   */
  public byte[] getBytes(int column) throws SQLException {
    
    // get the column as a string
    //
    String str = getString(column);

    if( str == null ) return null;
    try {
      return str.getBytes(str);
    }
    catch( java.io.UnsupportedEncodingException e ) {
      throw new java.sql.SQLException("Bad bytes!: " + e.getMessage());
    }

  }

  /**
   *
   * Get the value of a column in the current row as a java.sql.Date object.
   * @see java.sqlResultSet#getDate
   * @exception SQLException thrown in case of error
   * @param column the column being retrieved
   * @return the java.sql.Date object for the column
   *
   */
  public java.sql.Date getDate(int column)
       throws SQLException {
    
    // get the column as a string
    //
    String str = getString(column);

    // return null if the string is null
    //
    if( str == null ) return null;

    // try to use the string to instantiate a java.util.Date object,
    // then use that object to instantiate a java.sql.Date object.
    //
    try {
      SimpleDateFormat fmt = new SimpleDateFormat("EEE MMM dd hh:mm:ss z yyyy");
      java.util.Date d = fmt.parse(str, new ParsePosition(0));

      return new java.sql.Date(d.getTime());
    
    } catch( Exception e ) {
      throw new SQLException("Date format error: " + e.getMessage());
    }

  }

  /**
   *
   * Get the value of a column in the current row as a java.sql.Time object.
   *
   * @see java.sql.ResultSet#getTime
   * @exception SQLException thrown in the event of troubles
   * @param column the column being retrieved
   * @return the column as a java.sql.Time object
   *
   */
  public java.sql.Time getTime(int column)
       throws SQLException {
    
    // get the column as a string
    //
    String str = getString(column);

    // if the string is null, return null
    //
    if( str == null ) return null;

    // try to use the string to instantiate a java.util.Date object,
    // then use that object to instantiate a java.sql.Time object.
    //
    try {

      SimpleDateFormat fmt = new SimpleDateFormat("EEE MMM dd hh:mm:ss z yyyy");
      java.util.Date d = fmt.parse(str, new ParsePosition(0));

      return new java.sql.Time(d.getTime());
      
    } catch( Exception e ) {
      throw new SQLException("Data format error: " + e.getMessage());
    }
  }

  /**
   * Get the value of a column in the current row as a java.sql.Timestamp
   * @see java.sql.ResultSet#getTimestamp
   * @exception SQLException thrown in the event of troubles
   * @param column the column being retrieved
   * @return the column as a java.sql.Timestamp object
   */
  public java.sql.Timestamp getTimestamp(int column)
       throws SQLException {