movingcursorexample.java

java 完全探索的随书源码

import java.sql.*;

public class MovingCursorExample
{
  // Private reference to an instance of the Connection
  Connection connection = null;

  // Default Constructor
  public MovingCursorExample( Connection conn )
  {
    super();
    connection = conn;
  }

  // Private accessor for the connection
  private Connection getConnection()
  {
    return connection;
  }

  // Print out the Employee Records backwards using a scrollable
  // ResultSet
  public void performExample()
  {
    Statement stmt = null;
    ResultSet rs = null;

    try
    {
      // These two variables are used throughout this example
      String name = null;
      int cursorPosition = 0;

      // Get a scrollable ResultSet
      Connection conn = getConnection();
      stmt = conn.createStatement(
                                  ResultSet.TYPE_SCROLL_INSENSITIVE,
                                  ResultSet.CONCUR_READ_ONLY );

      // Get some fields from the employee table
      String sqlQuery =
          "SELECT EMPNO, EName, Job, MGR, HIREDATE FROM EMP";

      rs = stmt.executeQuery( sqlQuery );

      // Let's count the rows
      int rowSize = 0;
      while( rs.next() )
      {
        rowSize++;
      }

      System.out.println( "Number of Rows in ResultSet is: " + rowSize );
      if ( rowSize == 0 )
      {
        System.out.println( "Since there are no rows, exiting..." );
        System.exit( 0 );
      }


      // Let's go to the half way point in the ResultSet
      cursorPosition = Math.round( rowSize /  2 );

      System.out.println( "Moving to position: " + cursorPosition );
      // Get the name at the half way position
      rs.absolute( cursorPosition );
      System.out.println( "Name: " + rs.getString( 2 ) );

      // Try to go back one row relative from the current position
      rs.relative( -1 );

      cursorPosition = rs.getRow();
      System.out.println( "Moving to position: " + cursorPosition );
      System.out.println( "Name: " + rs.getString( 2 ) );

      System.out.println( "Moving to the first row" );
      // Move to the first row backwards, one row at a time
      while( !rs.isFirst() )
      {
        rs.previous();
      }
      System.out.println( "Name: " + rs.getString( 2 ) );

      rs.close();
    }
    catch( SQLException ex )
    {
      ex.printStackTrace();
    }
  }

  public static void main(String[] args)
  {
     // Use the previous DatabaseManager
    Connection conn = DatabaseManager.getConnection();
    MovingCursorExample example = new MovingCursorExample( conn );
    example.performExample();

    // Always make sure to close the connection when you are finished
    try
    {
      conn.close();
    }
    catch( SQLException ex )
    {
      ex.printStackTrace();
    }
    catch( Exception ex )
    {
      ex.printStackTrace();
    }
  }
}