Platinum Edition Using HTML 4, XML, and Java 1.2
(Publisher: Macmillan Computer Publishing)
Author(s): Eric Ladd
ISBN: 078971759x
Publication Date: 11/01/98

Listing 37.10 DBDemo.java—This Test Program Opens a Database and Reads and Writes Data Interactively

import java.awt.*;
import java.applet.*;
import java.util.Properties;
import java.util.Enumeration;
import COM.odi.*;
import COM.odi.util.*;

public class DBDemo extends Applet
{
    private Database fDb;
    private Transaction fTrans;

    // indicates that ObjectStore has been initialized
    private Thread fInitialized;
    private Session fSession;

        public void init()
        {
               // Take out this line if you don’t use
⇒symantec.itools.net.RelativeURL or
⇒symantec.itools.awt.util.StatusScroller
               symantec.itools.lang.Context.setApplet(this);

               // This code is automatically generated by Visual Cafe
⇒when you add
               // components to the visual environment.
⇒It instantiates and initializes
               // the components. To modify the code,
⇒only use code syntax that matches
               // what Visual Cafe can generate,
⇒or Visual Cafe may be unable to back
               // parse your Java file into its visual environment.
               //{{INIT_CONTROLS

               setLayout(null);
               setSize(426,400);
               theAddNurseLabel = new java.awt.Label(“Add Nurse to Database”);
               theAddNurseLabel.setBounds(48,192,360,32);
               theAddNurseLabel.setFont(new Font(“Dialog”, Font.BOLD, 18));
               add(theAddNurseLabel);
               theNursesInDatabaseLabel = new java.awt.Label(“Nurses in Database”);
               theNursesInDatabaseLabel.setBounds(24,12,360,32);
               theNursesInDatabaseLabel.setFont(new Font(“Dialog”, Font.BOLD, 18));
               add(theNursesInDatabaseLabel);
               theNurseIDLabel = new java.awt.Label(“ID”);
               theNurseIDLabel.setBounds(48,240,40,36);
               add(theNurseIDLabel);
               theNurseNameLabel = new java.awt.Label(“Last Name”);
               theNurseNameLabel.setBounds(48,276,72,54);
               add(theNurseNameLabel);
               theNurseIDField = new java.awt.TextField();
               theNurseIDField.setText(“the nurse ID”);
               theNurseIDField.setBounds(120,240,225,26);
               add(theNurseIDField);
               theNurseNameField = new java.awt.TextField();
               theNurseNameField.setText(“the nurse name”);
               theNurseNameField.setBounds(120,288,225,28);
               add(theNurseNameField);
               theAddButton = new java.awt.Button();
               theAddButton.setLabel(“Add”);
               theAddButton.setBounds(228,324,113,30);
               theAddButton.setFont(new Font(“Dialog”, Font.BOLD, 12));
               theAddButton.setBackground(java.awt.Color.lightGray);
               add(theAddButton);
               theNurseList = new java.awt.List(0,false);
               add(theNurseList);
               theNurseList.setBounds(36,60,329,103);
               //}}
             
               setupDatabase();
       
               //{{REGISTER_LISTENERS
               SymAction lSymAction = new SymAction();
               theAddButton.addActionListener(lSymAction);
               //}}
        }
       
        public void start()
        {
               reload(theNurseList, TNurse.getAll());
        }


        public void destroy() {
            // save everything to the database
            if (fDb == null) {
                System.out.println(“Database not open.”);
                return;
            }
            fTrans.commit();

            // and close the database
            if (fDb == null) {
                System.out.println(“No database to close.”);
                return;
            }
            fDb.close();
            fDb = null;
        }

        private void maybeInitialize() {
            if (fInitialized != null) {
                return;
            }
            Properties properties = new Properties();
            String user = getParameter(“user”);
            if (user != null) {
                properties.put(“COM.odi.user”, user);
            }
            String password = getParameter(“password”);
            if (password != null) {
                properties.put(“COM.odi.password”, password);
            }
            ObjectStore.initialize(null, properties);
            fInitialized = Thread.currentThread();
        }

        public String[][] getParameterInfo() {
             String pinfo[][] = {
               {“user”,    “String”,    “username for database”},
               {“password”, “String”, “password for database”}
         };
     return pinfo;
    }
   
    public void setupDatabase()
    {
    vvvv// Here begins the ObjectStore connection
                       fDb = null;
                       fTrans = null;
                       fInitialized = null;
                       fSession = null;

                       if (fDb != null) {
                   System.out.println(“Database already open.”);
                   return;
                      }

                      String theDbname = new String(“demo.odb”);

      // The following line starts a nonglobal session and joins this

      // thread to the new session. This allows the thread to use
      // the ObjectStore API.
                      Session.create(null, null).join();
      fSession = Session.getCurrent();
                      try {
                   //db = Database.create(dbname, 0664);
                   System.out.println(“Opening database”);
                   fDb = Database.open(theDbname, ObjectStore.OPEN_UPDATE);
                   System.out.println(“1a.Database open is “ + fDb.isOpen());

                  // Enable this code if you want a new database each time
                  /* db.destroy();
                        System.out.println(“Replacing database.”);
                         db = Database.create(dbname, ObjectStore.ALL_READ |
⇒ObjectStore.ALL_WRITE);
                   System.out.println(“1b.Database open is “ + db.isOpen());
                  */
                       } catch (AccessViolationException e) {
                   System.out.println(“File system access violation.”);
                   return;
                      } catch (DatabaseAlreadyExistsException e) {
                   System.out.println(“Database already exists.”);
                       } catch (DatabaseNotFoundException e) {
                                System.out.println(“Making new database.”);
                          fDb = Database.create(theDbname, ObjectStore.ALL_READ |
⇒ObjectStore.ALL_WRITE);
                      } catch (DatabaseException e) {
                  System.out.println(“Invalid database: “ + theDbname);
                  return;
                      }

                      if (fDb != null) {
                   fTrans = Transaction.begin(ObjectStore.UPDATE);
                   System.out.println(“Made new transaction.”);
                   System.out.println(“2.Database open is “ + fDb.isOpen());
                      }

                      System.out.println(“About to initialize TNurse”);
                      System.out.println(“3.Database open is “ + fDb.isOpen());
                      TNurse.initialize(fDb);
               }
              
               public void reload(java.awt.List theList, Enumeration e)
               {
                      // copy the elements of the enumeration into the list
                       for ( ; e.hasMoreElements();) {
                              theList.add((String) e.nextElement().toString());
                      }
               }
                          
    public static void main(String args[])
    {
        System.out.println(“Starting. . . “);
        DBDemo theApplet = new DBDemo();
        System.out.println(“setting up database”);
        theApplet.setupDatabase();
       
        System.out.println(“populating database”);
        try {
                        TNurse nurseSmith = TNurse.add(“123S”, “Smith”);
                        TNurse nurseJones = TNurse.add(“234J”, “Jones”);
                        TNurse nurseBrown = TNurse.add(“345B”, “Brown”);
                      } catch (Exception e) {
                              System.out.println(“Exception: “ + e);
                      }
                     
        System.out.println(“destroying”);
        theApplet.destroy();
        System.out.println(“done”);
        System.exit(0);
    }

        //{{DECLARE_CONTROLS
        java.awt.Label theAddNurseLabel;
        java.awt.Label theNursesInDatabaseLabel;
        java.awt.Label theNurseIDLabel;
        java.awt.Label theNurseNameLabel;
        java.awt.TextField theNurseIDField;
        java.awt.TextField theNurseNameField;
        java.awt.Button theAddButton;
        java.awt.List theNurseList;
        //}}

        class SymAction implements java.awt.event.ActionListener
        {
               public void actionPerformed(java.awt.event.ActionEvent event)
               {
                      Object object = event.getSource();
                      if (object == theAddButton)
                              theAddButton_Action(event);
               }
       }

        void theAddButton_Action(java.awt.event.ActionEvent event)
        {
               if (Session.getCurrent() == null)
      fSession.join();
     
    TNurse.initialize(fDb);
     
               String theID = theNurseIDField.getText();
               String theName = theNurseNameField.getText();
               try {
                 TNurse aNurse = TNurse.add(theID, theName);
               } catch (Exception e) {
                      System.out.println(“Exception: “ + e);
               }

               fTrans.commit();
          fTrans = Transaction.begin(ObjectStore.UPDATE);
          TNurse.initialize(fDb);
                      
               //{{CONNECTION
               // Clear the text for TextField
               theNurseIDField.setText(“”);
               //}}
                       
               //{{CONNECTION
               // Clear the text for TextField
               theNurseNameField.setText(“”);
               //}}
                       
               //{{CONNECTION
               // Clear the List
               theNurseList.removeAll();
               reload(theNurseList, TNurse.getAll());
               //}}
        }
}