www.pudn.com > town-1[1].0.4.rar > QueryDataSet.java

package com.workingdogs.town; 
 
import java.sql.*; 
import java.util.*; 
 
/* 
Town, a Java JDBC abstraction layer 
Copyright (C) 1999  Serge Knystautas, Jon S. Stevens 
 
This library is free software; you can redistribute it and/or 
modify it under the terms of the GNU Library General Public 
License as published by the Free Software Foundation; either 
version 2 of the License, or (at your option) any later version. 
 
This library 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 
Library General Public License for more details. 
 
You should have received a copy of the GNU Library General Public 
License along with this library; if not, write to the 
Free Software Foundation, Inc., 59 Temple Place - Suite 330, 
Boston, MA  02111-1307, USA. 
*/ 
 
/** 
This class is used for doing SQL select statements on the database. It 
should not be used for doing modifications via update/delete/insert statements. 
If you would like to perform those functions, please use a 
TableDataSet. 
 
Here is some example code for using a QueryDataSet. 
 
QueryDataSet qds = new QueryDataSet ( connection, "SELECT * from my_table" ); 
qds.fetchRecords(10); // fetch only the first 10 records 
for ( int i = 0; i < qds.size(); i++ ) 
{ 
  Record rec = qds.getRecord(i); 
  int value = rec.getValue("column").asInt(); 
  System.out.println ( "The value is: " + value ); 
} 
qds.close(); 
 
 
It is important to always remember to close() a QueryDataSet in order to 
free the allocated resources. 
 
 
@author Jon S. Stevens jon@working-dogs.com 
@author Serge Knystautas sergek@lokitech.com 
@version 1.0 
*/ 
public class QueryDataSet extends DataSet 
{ 
    protected String selectString; 
    /** 
       * Creates a new QueryDataSet based on a connection and a select string 
       * 
       * @param   conn 
       * @param   selectStmt 
       * @exception   ConnectionException 
       * @exception   DataSetException 
       */ 
    public QueryDataSet(String driver, String connString, 
            String selectStmt) throws ConnectionException, DataSetException 
    { 
        this (driver, connString, null, null, selectStmt); 
    } 
    /** 
       * Creates a new QueryDataSet based on a connection and a select string 
       * 
       * @param   conn 
       * @param   selectStmt 
       * @exception   ConnectionException 
       * @exception   DataSetException 
       */ 
    public QueryDataSet(String driver, String connString, 
            String username, String password, 
            String selectStmt) throws ConnectionException, DataSetException 
    { 
        super (driver, connString, username, password); 
        try 
        { 
            //this.conn = conn; 
            //if (! (selectStmt.startsWith ("select") || 
            //        selectStmt.startsWith ("SELECT"))) 
            //    throw new DataSetException ("QueryDataSet must be a SELECT string"); 
 
            selectString = selectStmt; 
            stmt = dbconn.createStatement(); 
            resultSet = stmt.executeQuery (selectStmt); 
            schema = new Schema(); 
            schema.populate (resultSet.getMetaData()); 
        } 
        catch (SQLException sqle) 
        { 
            throw new ConnectionException (sqle); 
        } 
    } 
    /** 
      * This method was created in VisualAge. 
      */ 
    public Record addRecord () throws ConnectionException, DataSetException 
    { 
        throw new DataSetException ("Cannot add a record to a QueryDataSet"); 
    } 
    /** 
      * Return the KeyDef for this dataset 
      * @return com.workingdogs.town.KeyDef 
      */ 
    public KeyDef getKeyDef () throws DataSetException 
    { 
        throw new DataSetException ("QueryDataSet does not support a KeyDef for now."); 
    } 
    /** 
       * get the Select String that was used to create this QueryDataSet 
       * 
       * @return     a select string 
       */ 
    protected String getSelectString () throws ConnectionException, 
    DataSetException 
    { 
        return selectString; 
    } 
    /** 
        Gets the tableName upon table data set creation 
        @return string 
      */ 
    public String getTableName() throws DataSetException, 
    ConnectionException 
    { 
        throw new DataSetException ("QueryDataSet does not support table names now."); 
    } 
}