package JBExamples.database.applets;

public interface ITransportClient {
  public String executeQuery(String query) throws Exception ;
}

package JBExamples.database.applets;

import java.util.*;
import java.net.*;
import java.io.*;

public class HTTPTransportClient implements ITransportClient {
  String servletLoc;

  public HTTPTransportClient(String servletLoc) {
    this.servletLoc = servletLoc;
  }

  /**
   * This method illustrates how to communicate to the JDBCServlet using
   * the HTTP transport.
   * This method also illustrates how general applet to servlet communication
   * can be carried out.
   */
  public String executeQuery(String queryString) throws Exception {
    StringBuffer results = new StringBuffer();

    //The value of dbquery has to be urlencoded to be passed through http.
    String postData   = "dbQuery="+URLEncoder.encode(queryString);

    URL action = new URL(servletLoc);
    URLConnection url = action.openConnection();

    url.setDoInput(true);
    url.setDoOutput(true);
    url.setUseCaches(false);
    url.setRequestProperty("Content-type", "application/x-www-form-urlencoded");
    url.setRequestProperty("Content-length", "" + postData.length());

    // Write out post data
    DataOutputStream out = new DataOutputStream(url.getOutputStream());
    out.writeBytes(postData);
    out.flush();
    out.close();

    // Get response
    DataInputStream in = new DataInputStream(new BufferedInputStream(url.getInputStream()));

    String line;
    while(null != ((line = in.readLine())))
      results.append(line + "\n");

    return results.toString();
  }

}

package JBExamples.database.applets;

//Packages for RMI support
import java.rmi.registry.*;
import java.rmi.server.UnicastRemoteObject;
import java.rmi.*;

//RMI objects
import JBExamples.database.servlets.rmi.IDBQuerier;
import JBExamples.database.servlets.rmi.IDataTable;

public class RMITransportClient implements ITransportClient {
  String serverName;
  IDBQuerier dbQuerier = null;

  public RMITransportClient(String serverName) throws Exception {
    this.serverName = serverName;

   //Install a security manager.  Doing this will allow this client to load
   //stubs remotely.
    if (System.getSecurityManager() == null)
      System.setSecurityManager(new RMISecurityManager());

    //Get a remote reference to the JDBCRmiServlet object
    dbQuerier = (JBExamples.database.servlets.rmi.IDBQuerier)Naming.lookup(serverName);
  }

  /**
   * This method illustrates how to communicate to the JDBCRmiServlet using
   * the RMI transport.
   */
  public String executeQuery(String queryString) throws Exception
  {
    if( dbQuerier == null ) return "DBQuerier is null";

    StringBuffer results = new StringBuffer();
    //Try to fetch an IDataTable object from the IDBQuerier. IDataTable
    //should contain the results of the query.
    IDataTable dataTable = dbQuerier.getResultTable(queryString);

    if( dataTable == null ) return "Data is null";

    return dataTable.toTableString();

  }

} 

package JBExamples.database.applets;

//Packages for CORBA support
import org.omg.CORBA.*;
import JBExamples.database.servlets.corba.IDBQuerierHelper;

//CORBA objects
import JBExamples.database.servlets.corba.IDataTable;
import JBExamples.database.servlets.corba.IDBQuerier;

public class CORBATransportClient implements ITransportClient
{
  //Server's identifier
  String serverName;
  IDBQuerier dbQuerier = null;

  public CORBATransportClient(String serverName) throws Exception {
    this.serverName = serverName;

    //Inititialize the orb
    String[] args = new String[0];
    ORB orb = ORB.init(args, null);

    //Get a remote reference to the JDBCCorbaServlet object
    dbQuerier = IDBQuerierHelper.bind(orb, serverName);
  }

  public String executeQuery(String queryString) throws Exception {
    StringBuffer results = new StringBuffer();

    if( dbQuerier == null ) return "DBQuerier is null";

    //Try to fetch an IDataTable object from the IDBQuerier. IDataTable
    //should contain the results of the query.
    IDataTable dataTable = dbQuerier.getResultTable(queryString);

    if( dataTable == null ) return "Data is null";

    return dataTable.toTableString();
  }
  
}

package JBExamples.database.applets;

import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.net.*;
import java.io.*;
import java.util.Hashtable;


/*
 * A class that shows how to access an RMI or CORBA servlet from an    
 * applet.
 * Since both objects are also servlets they both can be accessed via the
 * HTTP transport.
 */
public class JDBCApplet extends Applet implements Runnable {
  Thread t = null;
  TextArea textArea;
  TextField textField;
  Button queryButton;
  Choice jdbcClients;

  Hashtable transportClients = new Hashtable();

  String HTTP  = "HTTP";
  String RMI   = "RMI";
  String CORBA = "CORBA";

  //A variable that specifies the name of the servlet to be accessed using
  //the HTTP transport.  The servlet is accessed using the servlet's alias.
  //Servlet aliasing can be set through the servlet runners admin tool.
  //The alias to the JDBCRmiServlet is assumed to be set to RMIServlet
  //The alias to the JDBCCorbaServlet is assumed to be set to CORBAServlet
  //String servletName = "CORBAServlet"; //Use the corba servlet as the plain servlet
  String servletName  = "RMIServlet"; //Use the rmi servlet as the plain servlet

  //Construct the applet
  public JDBCApplet() {
  }
  
  //Initialize the applet
  public void init() {
    super.init();
    try {
      jbInit();

      //Initialize transport clients
      transportClients.put( HTTP,  new HTTPTransportClient(getCodeRoot()+"/servlet/"+servletName));
      transportClients.put( RMI,   new CORBATransportClient("DBQuerier") );
      transportClients.put( CORBA, new RMITransportClient("DBQuerier") );

    } catch (Exception e) { e.printStackTrace(); }
  }

  //Component initialization
  private void jbInit() throws Exception {
    setSize(new Dimension(300, 300));
    setLayout(new BorderLayout());

    //Build the mainPanel
    Panel mainPanel = new Panel();
    mainPanel.setLayout(new BorderLayout());

    //Build north part of mainPanel
    Panel northPanel = new Panel();
    northPanel.setLayout(new GridLayout(2,2) );
    northPanel.add(new Label("Query String: "));

    textField = new TextField();
    textField.setColumns(25);
    northPanel.add(textField);

    jdbcClients = new Choice();
    jdbcClients.add(HTTP);
    jdbcClients.add(RMI);
    jdbcClients.add(CORBA);

    northPanel.add(new Label("JDBC Client Call Through:"));
    northPanel.add(jdbcClients);

    mainPanel.add("North", northPanel);

    //Build a blank textArea and center in the panel
    textArea = new TextArea();
    textArea.setEditable(false);
    mainPanel.add("Center", textArea);

    //Build the button panel
    Panel buttonPanel = new Panel();
    this.queryButton = new Button("Query");
    this.queryButton.addActionListener(
      new ActionListener()
      {
        public void actionPerformed(ActionEvent event)
        {
          try {
            String selectedClient = jdbcClients.getSelectedItem();

            //Get the correct transport client
            ITransportClient client = (ITransportClient)transportClients.get(selectedClient);
            doQuery(client);
          }
          catch(Throwable e) {
            e.printStackTrace();
            textArea.setText("An exception occured trying to locate the server.\n"+
              "Here it is: "+e.toString());
            textArea.show();
          }
        }
      }
    );

    buttonPanel.add("Center", queryButton);
    mainPanel.add("South", buttonPanel);

    add("Center", mainPanel);
  }

  public void run() {
    if( t == null ) {
      this.t = new Thread(this);
      t.start();
    }
  }

  public void stop() {
    if( t != null ) {
      t.stop();
      t = null;
    }
  }

  public Insets insets() {
    return new Insets(10,10,10,10);
  }

  /**
   * Execute the query using the given ITransportClient
   */
  public void doQuery(ITransportClient client) {
    String queryString = textField.getText();

    try {
      String results = client.executeQuery(queryString);
      textArea.setText( results );
    }
    catch(Exception e) {
      e.printStackTrace();
      textArea.setText("An exception occured trying to execute the query.\n"+
        "Here it is: "+e.toString() );
    }
    
    textArea.show();
  }

  /**
   * Get Applet information
   */
  public String getAppletInfo() {
    return "Applet Information";
  }

  /**
   * Get parameter info
   */
  public String[][] getParameterInfo() {
    return null;
  }

  /**
   * Find the code root.
   */
  private String getCodeRoot() {
    String codeRoot;
    String codeBase = getCodeBase().toString();
    int i=0, count=0;
    while(count < 3) {
      if(codeBase.charAt(i++) == '/')
        count++;
      if(i > codeBase.length())
        break;
    }

    if(i < codeBase.length())
      codeRoot = codeBase.substring(0, i);
    else
      codeRoot = codeBase;
            
    while(codeRoot.endsWith("/"))
      codeRoot = codeRoot.substring(0, codeRoot.length()-1);
            
    if(codeRoot.startsWith("http://") == false && codeRoot.startsWith("file://") == false )
      codeRoot = "http://" + codeRoot;

    return codeRoot;
  }


}

<TITLE>
JDBC Applet Page
</TITLE>
</HEAD>
<BODY>
JDBCApplet will appear below in a Java enabled browser work<BR>
<APPLET
  CODEBASE = "."
  CODE     = "JBExamples.database.applets.JDBCApplet.class"
  NAME     = "JDBCApplet"
  WIDTH    = 400
  HEIGHT   = 300
  HSPACE   = 0
  VSPACE   = 0
  ALIGN    = middle
>
</APPLET>
</BODY>
</HTML>