resultsettablemodel.java

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import java.sql.*;
import java.util.*;
import javax.swing.table.*;

/**
 *ResultSet rows and columns are counted from 1 and JTable
 *rows and columns are counted from 0. When processing
 *ResultSet rows or columns for use in a JTable, it is
 *necessary to add 1 to the row or column number to manipulate
 *the appropriate ResultSet column (i.e., JTable column 0 is
 *ResultSet column 1 and JTable row 0 is ResultSet row 1)
 */
public class ResultSetTableModel extends AbstractTableModel{
	private Connection connection;
	private Statement statement;
	private ResultSet resultSet;
	private ResultSetMetaData metaData;
	private int numberOfRows;
	// keep track of database connection status 
	private boolean connectedToDatabase = false;

	// initialize resultSet and obtain its meta data object;
	// determine number of rows
	public ResultSetTableModel(String driver,String url,String query)throws SQLException,ClassNotFoundException{
		Class.forName(driver); // load database driver class
		connection = DriverManager.getConnection(url); // connect to database
		// create Statement to query database
		statement = connection.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
		connectedToDatabase = true; // update database connection status
		setQuery(query); // set query and execute it
	}
	// get class that represents column type
	public Class getColumnClass(int column)throws IllegalStateException{
		// ensure database connection is available
		if(!connectedToDatabase)throw new IllegalStateException("Not Connected to Database");
		// determine Java class of column
		try{
			String className = metaData.getColumnClassName(column + 1);
			return Class.forName(className); // return Class object that represents className
		}
		// catch SQLExceptions and ClassNotFoundExceptions
		catch(Exception exception){
			exception.printStackTrace();
		}
		// if problems occur above, assume type Object 
		return Object.class;
	}
	// get number of columns in ResultSet
	public int getColumnCount()throws IllegalStateException{
		// ensure database connection is available
		if(!connectedToDatabase)throw new IllegalStateException("Not Connected to Database");
		// determine number of columns
		try{
			return metaData.getColumnCount();
		}
		// catch SQLExceptions and print error message
		catch(SQLException sqlException){
			sqlException.printStackTrace();
		}
		// if problems occur above, return 0 for number of columns
		return 0;
	}
	// get name of a particular column in ResultSet
	public String getColumnName(int column)throws IllegalStateException{
		// ensure database connection is available
		if(!connectedToDatabase)throw new IllegalStateException("Not Connected to Database");
		// determine column name
		try{
			return metaData.getColumnName(column + 1);
		}
		// catch SQLExceptions and print error message
		catch(SQLException sqlException){
			sqlException.printStackTrace();
		}
		// if problems, return empty string for column name
		return "";
	}
	// return number of rows in ResultSet
	public int getRowCount()throws IllegalStateException{
		// ensure database connection is available
		if(!connectedToDatabase)throw new IllegalStateException("Not Connected to Database");
			return numberOfRows;
	}
	// obtain value in particular row and column
	public Object getValueAt(int row, int column)throws IllegalStateException{
		// ensure database connection is available
		if(!connectedToDatabase)throw new IllegalStateException("Not Connected to Database");
		// obtain a value at specified ResultSet row and column
		try{
			resultSet.absolute(row + 1);
			return resultSet.getObject(column + 1);
		}
		// catch SQLExceptions and print error message
		catch(SQLException sqlException){
			sqlException.printStackTrace();
		}
		// if problems, return empty string object
		return "";
	}
	// set new database query string
	public void setQuery(String query)throws SQLException, IllegalStateException{
		// ensure database connection is available
		if(!connectedToDatabase)throw new IllegalStateException("Not Connected to Database");
		// specify query and execute it
		resultSet = statement.executeQuery(query);
		// obtain meta data for ResultSet
		metaData = resultSet.getMetaData();
		// determine number of rows in ResultSet
		resultSet.last(); // move to last row
		numberOfRows = resultSet.getRow(); // get row number
		fireTableStructureChanged(); // notify JTable that model has changed
	}
	// close Statement and Connection
	public void disconnectFromDatabase(){
		// close Statement and Connection
		try{
			statement.close();
			connection.close();
		}
		// catch SQLExceptions and print error message
		catch(SQLException sqlException){
			sqlException.printStackTrace();
		}
		// update database connection status
		finally{
			connectedToDatabase = false;
		}
	}
} // end class ResultSetTableModel