The following source illustrates one way that your ToolboxME for iSeries™ application can use the Mobile Information Device Profile (MIDP) and JDBC to access a database and store information offline.
This example demonstrates how a real estate agent might be able to view and bid on properties that are currently for sale. The agent uses a Tier0 device to access information for the properties, which is stored in the iSeries server database.
When built as a working program, the example code below connects to a database created for this purpose.
To create a working version of the source code and to obtain the source for creating and populating the required database, you must download the example. You also may want to review the instructions for creating and running the example program.
//////////////////////////////////////////////////////////////////////////////////
//
// ToolboxME for iSeries example. This program is an example MIDlet that shows how
// you might code a JdbcMe application for the MIDP profile. Refer to the
// startApp, pauseApp, destroyApp and commandAction methods to see how it handles
// each requested transition.
//
//////////////////////////////////////////////////////////////////////////////////
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import java.sql.*;
import javax.microedition.rms.*;
import com.ibm.as400.micro.*;
public class JdbcMidpBid extends MIDlet implements CommandListener
{
private static int BID_PROPERTY = 0;
private Display display;
private TextField urlText = new TextField("urltext",
"jdbc:as400://mySystem;user=myUid;password=myPwd;",
65,
TextField.ANY);
private TextField jdbcmeText = new TextField("jdbcmetext", "meserver=myMEServer", 40, TextField.ANY);
private TextField jdbcmeTraceText = new TextField("jdbcmetracetext", "0", 10, TextField.ANY);
private final static String GETBIDS = "No bids are available, select here to download bids";
private List main = new List("JdbcMe Bid Demo", Choice.IMPLICIT);
private List listings = null;
private Form aboutBox;
private Form bidForm;
private Form settingsForm;
private int bidRow = 0;
private String bidTarget = null;
private String bidTargetKey = null;
private TextField bidText = new TextField("bidtext", "", 10, TextField.NUMERIC);
private Form errorForm = null;
private Command exitCommand = new Command("Exit", Command.SCREEN, 0);
private Command backCommand = new Command("Back", Command.SCREEN, 0);
private Command cancelCommand = new Command("Cancel", Command.SCREEN, 0);
private Command goCommand = new Command("Go", Command.SCREEN, 1);
private Displayable onErrorGoBackTo = null;
/*
* Construct a new JdbcMidpBid.
*/
public JdbcMidpBid()
{
display = Display.getDisplay(this);
}
/**
* Show the main screen
*/
public void startApp()
{
main.append("Show Bids", null);
main.append("Get New Bids", null);
main.append("Settings", null);
main.append("About", null);
main.addCommand(exitCommand);
main.setCommandListener(this);
display.setCurrent(main);
}
public void commandAction(Command c, Displayable s)
{
// All exitCommand processing is the same.
if (c == exitCommand)
{
destroyApp(false);
notifyDestroyed();
return;
}
if (s instanceof List)
{
List current = (List)s;
// An action occurred on the main page
if (current == main)
{
int idx = current.getSelectedIndex();
switch (idx)
{
case 0: // Show current bids
showBids();
break;
case 1: // Get New Bids
getNewBids();
break;
case 2: // Settings
doSettings();
break;
case 3: // About
aboutBox();
break;
default :
break;
}
return;
} // current == main
// An action occurred on the listings page
if (current == listings)
{
if (c == backCommand)
{
display.setCurrent(main);
return;
}
if (c == List.SELECT_COMMAND)
{
int idx = listings.getSelectedIndex();
String stext = listings.getString(idx);
if (stext.equals(GETBIDS))
{
getNewBids();
return;
}
int commaIdx = stext.indexOf(',');
bidTargetKey = stext.substring(0, commaIdx);
bidTarget = stext.substring(commaIdx+1) + "\n";
// Also keep track of which offline result set row
// This is. It happens to be the same as the index
// in the list.
bidRow = idx;
bidOnProperty();
}
} // current == listings
return;
} // instanceof List
if (s instanceof Form)
{
Form current = (Form)s;
if (current == errorForm)
{
if (c == backCommand)
display.setCurrent(onErrorGoBackTo);
return;
} // errorForm
if (current == settingsForm)
{
if (c == backCommand)
{
// Done with settings.
display.setCurrent(main);
settingsForm = null;
return;
}
} // settingsForm
if (current == aboutBox)
{
if (c == backCommand)
{
// Done with about box.
display.setCurrent(main);
aboutBox = null;
return;
}
}
if (current == bidForm)
{
if (c == cancelCommand)
{
display.setCurrent(listings);
bidForm = null;
return;
}
if (c == goCommand)
{
submitBid();
if (display.getCurrent() != bidForm)
{
// If we're no longer positioned at the
// bidForm, we will get rid of it.
bidForm = null;
}
return;
}
return;
} // current == bidForm
} // instanceof Form
}
public void aboutBox()
{
aboutBox = new Form("aboutbox");
aboutBox.setTitle("About");
aboutBox.append(new StringItem("", "Midp RealEstate example for JdbcMe "));
aboutBox.addCommand(backCommand);
aboutBox.setCommandListener(this);
display.setCurrent(aboutBox);
}
/**
* The settings form.
*/
public void doSettings()
{
settingsForm = new Form("settingsform");
settingsForm.setTitle("Settings");
settingsForm.append(new StringItem("", "DB URL"));
settingsForm.append(urlText);
settingsForm.append(new StringItem("", "JdbcMe server"));
settingsForm.append(jdbcmeText);
settingsForm.append(new StringItem("", "Trace"));
settingsForm.addCommand(backCommand);
settingsForm.setCommandListener(this);
display.setCurrent(settingsForm);
}
/**
* Show the bid screen for the bid target
* that we selected.
*/
public void bidOnProperty()
{
StringItem item = new StringItem("", bidTarget);
bidText = new TextField("bidtext", "", 10, TextField.NUMERIC);
bidText.setString("");
bidForm = new Form("bidform");
bidForm.setTitle("Submit a bid for:");
BID_PROPERTY = 0;
bidForm.append(item);
bidForm.append(new StringItem("", "Your bid:"));
bidForm.append(bidText);
bidForm.addCommand(cancelCommand);
bidForm.addCommand(goCommand);
bidForm.setCommandListener(this);
display.setCurrent(bidForm);
}
/**
* Update the listings card with the
* current list of bids that we are interested in.
*/
public void getNewBids()
{
// Reset the old listing
listings = null;
listings = new List("JdbcMe Bids", Choice.IMPLICIT);
java.sql.Connection conn = null;
Statement stmt = null;
try
{
conn = DriverManager.getConnection(urlText.getString() + ";" + jdbcmeText.getString());
stmt = conn.createStatement();
// Since we do not want the prepared statement to persist,
// a normal statement is really better in this environemnt.
String sql = "select mls, address, currentbid from qjdbcme.realestate where currentbid <> 0";
boolean results =((JdbcMeStatement)stmt).executeToOfflineData(sql,
"JdbcMidpBidListings",
0,
0);
if (results)
{
setupListingsFromOfflineData();
}
else
{
listings.append("No bids found", null);
listings.addCommand(backCommand);
listings.setCommandListener(this);
}
}
catch (Exception e)
{
// Currently no valid listings retrieved, so lets
// reset it to empty.
listings = new List("JdbcMe Bids", Choice.IMPLICIT);
listings.append(GETBIDS, null);
listings.addCommand(backCommand);
listings.setCommandListener(this);
// Return to main after showing the error.
showError(main, e);
return;
}
finally
{
if (conn != null)
{
try
{
conn.close();
}
catch (Exception e)
{
}
}
conn = null;
stmt = null;
}
showBids();
}
public void setupListingsFromOfflineData()
{
// Skip the first four rows in the record store
// (eyecatcher, version, num columns, sql column
// types)
// and each subsequent row in the record store is
// a single column. Our query returns 3 columns which
// we will return concatenated as a single string.
ResultSet rs = null;
listings.addCommand(backCommand);
listings.setCommandListener(this);
try
{
int i = 5;
int max = 0;
StringBuffer buf = new StringBuffer(20);
// Creator and dbtype unused in MIDP
rs = new JdbcMeOfflineResultSet("JdbcMidpBidListings", 0, 0);
if (rs == null)
{
// New listings...
listings = new List("JdbcMe Bids", Choice.IMPLICIT);
listings.append(GETBIDS, null);
listings.addCommand(backCommand);
listings.setCommandListener(this);
return;
}
i = 0;
String s = null;
while (rs.next())
{
++i;
s = rs.getString(1);
buf.append(s);
buf.append(",");
s = rs.getString(2);
buf.append(s);
buf.append(", $");
s = rs.getString(3);
buf.append(s);
listings.append(buf.toString(), null);
buf.setLength(0);
}
if (i == 0)
{
listings.append("No bids found", null);
return;
}
}
catch (Exception e)
{
// Currently no valid listings retrieved, so lets
// reset it to empty.
listings = new List("JdbcMe Bids", Choice.IMPLICIT);
listings.append(GETBIDS, null);
listings.addCommand(backCommand);
listings.setCommandListener(this);
// Return to main after showing the error.
showError(main, e);
return;
}
finally
{
if (rs != null)
{
try
{
rs.close();
}
catch (Exception e)
{
}
rs = null;
}
System.gc();
}
}
/**
* Update the listings card with the
* current list of bids that we are interested in.
*/
public void submitBid()
{
java.sql.Connection conn = null;
Statement stmt = null;
try
{
conn = DriverManager.getConnection(urlText.getString() + ";" + jdbcmeText.getString());
stmt = conn.createStatement();
// Since we do not want the prepared statement to persist,
// a normal statement is really better in this environemnt.
StringBuffer buf = new StringBuffer(100);
buf.append("Update QJdbcMe.RealEstate Set CurrentBid = ");
buf.append(bidText.getString());
buf.append(" Where MLS = '");
buf.append(bidTargetKey);
buf.append("' and CurrentBid < ");
buf.append(bidText.getString());
String sql = buf.toString();
int updated = stmt.executeUpdate(sql);
if (updated == 1)
{
// BID Accepted.
String oldS = listings.getString(bidRow);
int commaIdx = bidTarget.indexOf(',');
String bidAddr = bidTarget.substring(0, commaIdx);
String newS = bidTargetKey + "," + bidAddr + ", $" + bidText.getString();
ResultSet rs = null;
try
{
// Creator and dbtype unused in MIDP
rs = new JdbcMeOfflineResultSet("JdbcMidpBidListings", 0, 0);
rs.absolute(bidRow+1);
rs.updateString(3, bidText.getString());
rs.close();
}
catch (Exception e)
{
if (rs != null)
rs.close();
}
// Also update our live list of that result set.
listings.set(bidRow, newS, null);
display.setCurrent(listings);
conn.commit();
}
else
{
conn.rollback();
throw new SQLException("Failed to bid, someone beat you to it");
}
}
catch (SQLException e)
{
// Return to the bid form after showing the error.
showError(bidForm, e);
return;
}
finally
{
if (conn != null)
{
try
{
conn.close();
}
catch (Exception e)
{
}
}
conn = null;
stmt = null;
}
// Exit without exception, then show the current bids
showBids();
}
/**
* Show an error condition.
*/
public void showError(Displayable d, Exception e)
{
String s = e.toString();
onErrorGoBackTo = d;
errorForm = new Form("Error");
errorForm.setTitle("SQL Error");
errorForm.append(new StringItem("", s));
errorForm.addCommand(backCommand);
errorForm.setCommandListener(this);
display.setCurrent(errorForm);
}
/**
* Show the current bids.
*/
public void showBids()
{
if (listings == null)
{
// If we have no current listings, lets set
// them up.
listings = new List("JdbcMe Bids", Choice.IMPLICIT);
setupListingsFromOfflineData();
}
display.setCurrent(listings);
}
/**
* Time to pause, free any space we do not need right now.
*/
public void pauseApp()
{
display.setCurrent(null);
}
/**
* Destroy must cleanup everything.
*/
public void destroyApp(boolean unconditional)
{
}
}