resultset.java

关系型数据库 Postgresql 6.5.2

package postgresql.jdbc1;

// IMPORTANT NOTE: This file implements the JDBC 1 version of the driver.
// If you make any modifications to this file, you must make sure that the
// changes are also made (if relevent) to the related JDBC 2 class in the
// postgresql.jdbc2 package.

import java.lang.*;
import java.io.*;
import java.math.*;
import java.text.*;
import java.util.*;
import java.sql.*;
import postgresql.Field;
import postgresql.largeobject.*;
import postgresql.util.*;

/**
 * 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.
 *
 * <P>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.
 *
 * <P>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.
 *
 * <P>For maximum portability, ResultSet columns within each row should be read
 * in left-to-right order and each column should be read only once.
 *
 *<P> 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.
 *
 * <P>Column names used as input to getXXX methods are case insenstive.  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.  The
 * column name option is designed to be used when column names are used in the
 * SQL Query.  For columns that are NOT explicitly named in the query, it is
 * best to use column numbers.  If column names were used there is no way for
 * the programmer to guarentee that they actually refer to the intended
 * columns.
 *
 * <P>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.
 *
 * <P>The number, types and properties of a ResultSet's columns are provided by
 * the ResultSetMetaData object returned by the getMetaData method.
 *
 * @see ResultSetMetaData
 * @see java.sql.ResultSet
 */
public class ResultSet extends postgresql.ResultSet implements java.sql.ResultSet 
{
  /**
   * Create a new ResultSet - Note that we create ResultSets to
   * represent the results of everything.
   *
   * @param fields an array of Field objects (basically, the
   *	ResultSet MetaData)
   * @param tuples Vector of the actual data
   * @param status the status string returned from the back end
   * @param updateCount the number of rows affected by the operation
   * @param cursor the positioned update/delete cursor name
   */
  public ResultSet(Connection conn, Field[] fields, Vector tuples, String status, int updateCount)
  {
      super(conn,fields,tuples,status,updateCount);
  }
  
  /**
   * 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.
   *
   * <p>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
   *
   * @return true if the new current is valid; false if there are no
   *	more rows
   * @exception SQLException if a database access error occurs
   */
  public boolean next() throws SQLException
  {
    if (++current_row >= rows.size())
      return false;
    this_row = (byte [][])rows.elementAt(current_row);
    return true;
  }
  
  /**
   * In some cases, it is desirable to immediately release a ResultSet
   * database and JDBC resources instead of waiting for this to happen
   * when it is automatically closed.  The close method provides this
   * immediate release.
   *
   * <p><B>Note:</B> A ResultSet is automatically closed by the Statement
   * 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.
   *
   * @exception SQLException if a database access error occurs
   */
  public void close() throws SQLException
  {
    // No-op
  }
  
  /**
   * 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 SQL NULL
   *
   * @return true if the last column read was SQL NULL
   * @exception SQLException if a database access error occurred
   */
  public boolean wasNull() throws SQLException
  {
    return wasNullFlag;
  }
  
  /**
   * Get the value of a column in the current row as a Java String
   *
   * @param columnIndex the first column is 1, the second is 2...
   * @return the column value, null for SQL NULL
   * @exception SQLException if a database access error occurs
   */
  public String getString(int columnIndex) throws SQLException
  {
    //byte[] bytes = getBytes(columnIndex);
    //
    //if (bytes == null)
    //return null;
    //return new String(bytes);
    if (columnIndex < 1 || columnIndex > fields.length)
      throw new PSQLException("postgresql.res.colrange");
    wasNullFlag = (this_row[columnIndex - 1] == null);
    if(wasNullFlag)
      return null;
    return new String(this_row[columnIndex - 1]);
  }
  
  /**
   * Get the value of a column in the current row as a Java boolean
   *
   * @param columnIndex the first column is 1, the second is 2...
   * @return the column value, false for SQL NULL
   * @exception SQLException if a database access error occurs
   */
  public boolean getBoolean(int columnIndex) throws SQLException
  {
    String s = getString(columnIndex);
    
    if (s != null)
      {
	int c = s.charAt(0);
	return ((c == 't') || (c == 'T'));
      }
    return false;		// SQL NULL
  }
  
  /**
   * 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; 0 if SQL NULL
   * @exception SQLException if a database access error occurs
   */
  public byte getByte(int columnIndex) throws SQLException
  {
    String s = getString(columnIndex);
    
    if (s != null)
      {
	try
	  {
	    return Byte.parseByte(s);
	  } catch (NumberFormatException e) {
	    throw new PSQLException("postgresql.res.badbyte",s);
	  }
      }
    return 0;		// SQL NULL
  }
  
  /**
   * Get the value of a column in the current row as a Java short.
   *
   * @param columnIndex the first column is 1, the second is 2,...
   * @return the column value; 0 if SQL NULL
   * @exception SQLException if a database access error occurs
   */
  public short getShort(int columnIndex) throws SQLException
  {
    String s = getString(columnIndex);
    
    if (s != null)
      {
	try
	  {
	    return Short.parseShort(s);
	  } catch (NumberFormatException e) {
	    throw new PSQLException("postgresql.res.badshort",s);
	  }
      }
    return 0;		// SQL NULL
  }
  
  /**
   * Get the value of a column in the current row as a Java int.
   *
   * @param columnIndex the first column is 1, the second is 2,...
   * @return the column value; 0 if SQL NULL
   * @exception SQLException if a database access error occurs
   */
  public int getInt(int columnIndex) throws SQLException
  {
    String s = getString(columnIndex);
    
    if (s != null)
      {
	try
	  {
	    return Integer.parseInt(s);
	  } catch (NumberFormatException e) {
	    throw new PSQLException ("postgresql.badint",s);
	  }
      }
    return 0;		// SQL NULL
  }
  
  /**
   * Get the value of a column in the current row as a Java long.
   *
   * @param columnIndex the first column is 1, the second is 2,...
   * @return the column value; 0 if SQL NULL
   * @exception SQLException if a database access error occurs
   */
  public long getLong(int columnIndex) throws SQLException
  {
    String s = getString(columnIndex);
    
    if (s != null)
      {
	try
	  {
	    return Long.parseLong(s);
	  } catch (NumberFormatException e) {
	    throw new PSQLException ("postgresql.res.badlong",s);
	  }
      }
    return 0;		// SQL NULL
  }
  
  /**
   * Get the value of a column in the current row as a Java float.
   *
   * @param columnIndex the first column is 1, the second is 2,...
   * @return the column value; 0 if SQL NULL
   * @exception SQLException if a database access error occurs
   */
  public float getFloat(int columnIndex) throws SQLException
  {
    String s = getString(columnIndex);
    
    if (s != null)
      {
	try
	  {
	    return Float.valueOf(s).floatValue();
	  } catch (NumberFormatException e) {
	    throw new PSQLException ("postgresql.res.badfloat",s);
	  }
      }
    return 0;		// SQL NULL
  }
  
  /**
   * Get the value of a column in the current row as a Java double.
   *
   * @param columnIndex the first column is 1, the second is 2,...
   * @return the column value; 0 if SQL NULL
   * @exception SQLException if a database access error occurs
   */
  public double getDouble(int columnIndex) throws SQLException
  {
    String s = getString(columnIndex);
    
    if (s != null)
      {
	try
	  {
	    return Double.valueOf(s).doubleValue();
	  } catch (NumberFormatException e) {
	    throw new PSQLException ("postgresql.res.baddouble",s);
	  }
      }
    return 0;		// SQL NULL
  }
  
  /**
   * Get the value of a column in the current row as a 
   * java.lang.BigDecimal object
   *
   * @param columnIndex  the first column is 1, the second is 2...
   * @param scale the number of digits to the right of the decimal
   * @return the column value; if the value is SQL NULL, null
   * @exception SQLException if a database access error occurs
   */
  public BigDecimal getBigDecimal(int columnIndex, int scale) throws SQLException
  {
    String s = getString(columnIndex);
    BigDecimal val;
    
    if (s != null)
      {
	try
	  {
	    val = new BigDecimal(s);
	  } catch (NumberFormatException e) {
	    throw new PSQLException ("postgresql.res.badbigdec",s);
	  }
	  try
	    {
	      return val.setScale(scale);
	    } catch (ArithmeticException e) {
		throw new PSQLException ("postgresql.res.badbigdec",s);
	    }
      }
    return null;		// SQL NULL
  }
  
  /**
   * Get the value of a column in the current row as a Java byte array.
   *
   * <p>In normal use, the bytes represent the raw values returned by the
   * backend. However, if the column is an OID, then it is assumed to
   * refer to a Large Object, and that object is returned as a byte array.
   *
   * <p><b>Be warned</b> If the large object is huge, then you may run out
   * of memory.
   *
   * @param columnIndex the first column is 1, the second is 2, ...
   * @return the column value; if the value is SQL NULL, the result
   *	is null
   * @exception SQLException if a database access error occurs
   */
  public byte[] getBytes(int columnIndex) throws SQLException
  {
    if (columnIndex < 1 || columnIndex > fields.length)
      throw new PSQLException("postgresql.res.colrange");
    wasNullFlag = (this_row[columnIndex - 1] == null);
    
    // Handle OID's as BLOBS
    if(!wasNullFlag)
      if( fields[columnIndex - 1].getOID() == 26) {
	LargeObjectManager lom = connection.getLargeObjectAPI();
	LargeObject lob = lom.open(getInt(columnIndex));
	byte buf[] = lob.read(lob.size());
	lob.close();
	return buf;
      }
    
    return this_row[columnIndex - 1];
  }
  
  /**
   * Get the value of a column in the current row as a java.sql.Date
   * object
   *
   * @param columnIndex the first column is 1, the second is 2...
   * @return the column value; null if SQL NULL
   * @exception SQLException if a database access error occurs
   */
  public java.sql.Date getDate(int columnIndex) throws SQLException
  {