jdbcapplet.java

数据库连接包括连接池。很有用的资料

/*
 * This sample applet just selects 'Hello World' and the date from the database
 */

// Import the JDBC classes
import java.sql.*;

// Import the java classes used in applets
import java.awt.*;
import java.io.*;
import java.util.*;

public class JdbcApplet extends java.applet.Applet
{

  // The connect string 
  static final String connect_string = 
                  "jdbc:oracle:thin:scott/tiger@dlsun511:1721:dbms733";

  // This is the kind of string you would use if going through the 
  // Oracle 8 connection manager which lets you run the database on a 
  // different host than the Web Server.  See the on-line documentation
  // for more information.
  // static final String connect_string = "jdbc:oracle:thin:scott/tiger@(description=(address_list=(address=(protocol=tcp)(host=dlsun511)(port=1610))(address=(protocol=tcp)(host=pkrishna-pc2)(port=1521)))(source_route=yes)(connect_data=(sid=orcl)))";

  // The query we will execute
  static final String query = "select 'Hello JDBC: ' || sysdate from dual";
  

  // The button to push for executing the query
  Button execute_button;

  // The place where to dump the query result
  TextArea output;

  // The connection to the database
  Connection conn;

  // Create the User Interface
  public void init ()
  {
    this.setLayout (new BorderLayout ());
    Panel p = new Panel ();
    p.setLayout (new FlowLayout (FlowLayout.LEFT));
    execute_button = new Button ("Hello JDBC");
    p.add (execute_button);
    this.add ("North", p);
    output = new TextArea (10, 60);
    this.add ("Center", output);
  }

  // Do the work
  public boolean action (Event ev, Object arg)
  {
    if (ev.target == execute_button)
    {
      try
      {

	// See if we need to open the connection to the database
	if (conn == null)
	{
	  // Load the JDBC driver
    DriverManager.registerDriver (new oracle.jdbc.driver.OracleDriver());

	  // Connect to the databse
	  output.appendText ("Connecting to " + connect_string + "\n");
	  conn = DriverManager.getConnection (connect_string);
	  output.appendText ("Connected\n");
	}

	// Create a statement
	Statement stmt = conn.createStatement ();

	// Execute the query
	output.appendText ("Executing query " + query + "\n");
	ResultSet rset = stmt.executeQuery (query);

	// Dump the result
	while (rset.next ())
	  output.appendText (rset.getString (1) + "\n");

	// We're done
	output.appendText ("done.\n");
      }
      catch (Exception e)
      {
	// Oops
	output.appendText (e.getMessage () + "\n");
      }
      return true;
    }
    else
      return false;
  }
}