exportabstract.java

derby database source code.good for you.

/*

   Derby - Class org.apache.derby.impl.load.ExportAbstract

   Copyright 1998, 2004 The Apache Software Foundation or its licensors, as applicable.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

 */

package org.apache.derby.impl.load;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Types;
import java.util.Date;

/**
 * 
 * <P>
 */
abstract class ExportAbstract {

  protected ControlInfo controlFileReader;
  protected ExportResultSetForObject exportResultSetForObject;
  protected ExportWriteDataAbstract exportWriteData;
  protected Connection con;
  protected String entityName;  //this can be a plain table name or qualified with schema also
  protected String schemaName;
  protected String selectStatement ;
  

  //following makes the resultset using select * from entityName
  protected ResultSet resultSetForEntity() throws Exception {
    exportResultSetForObject = new ExportResultSetForObject(con, schemaName,
															entityName, 
															selectStatement);

    ResultSet rs = exportResultSetForObject.getResultSet();
    return rs;
  }

  //convert resultset data to string array
  public String[] getOneRowAtATime(ResultSet rs) throws Exception {
    int columnCount = exportResultSetForObject.getColumnCount();

	ResultSetMetaData rsm=rs.getMetaData();
    if (rs.next()){
       String[] rowObjects = new String[columnCount];
       for (int colNum = 0; colNum < columnCount; colNum++) {
       		rowObjects[colNum]=rs.getString(colNum + 1);
       }
       return rowObjects;
    }
    rs.close();
	exportResultSetForObject.close();
    return null;
  }

  //returns the control file reader corresponding to the control file passed
  protected ControlInfo getControlFileReader(){
	  return controlFileReader; 
  }

  protected abstract ExportWriteDataAbstract getExportWriteData() throws Exception;

  protected void doAllTheWork() throws Exception {

	ResultSet rs = null;
	try {
    	rs = resultSetForEntity();
    	if (rs != null) {
			ResultSetMetaData rsmeta = rs.getMetaData();
			int ncols = rsmeta.getColumnCount();
			boolean[] isNumeric = new boolean[ncols];
			for (int i = 0; i < ncols; i++) {
				int ctype = rsmeta.getColumnType(i+1);
				if (ctype == Types.BIGINT || ctype == Types.DECIMAL || ctype == Types.DOUBLE ||
						ctype == Types.FLOAT ||ctype == Types.INTEGER || ctype == Types.NUMERIC ||
						ctype == Types.REAL ||ctype == Types.SMALLINT || ctype == Types.TINYINT)
    				isNumeric[i] = true;
				else
					isNumeric[i] = false;
			}
			exportWriteData = getExportWriteData();
			exportWriteData.writeColumnDefinitionOptionally(
						exportResultSetForObject.getColumnDefinition(),
						exportResultSetForObject.getColumnTypes());
			exportWriteData.setColumnLengths(controlFileReader.getColumnWidths());

       		//get one row at a time and write it to the output file
       		String[] oneRow = getOneRowAtATime(rs);
       		while (oneRow != null) {
         		exportWriteData.writeData(oneRow, isNumeric);
         		oneRow = getOneRowAtATime(rs);
       		}
		}
	} finally {
		//cleanup work after no more rows
		if (exportWriteData != null)
			exportWriteData.noMoreRows();
		if (rs != null)
			rs.close();
    }
  }


}