Weaknesses in Java

Maker QR Code 2d barcode in Java Weaknesses
Weaknesses
QR Code Maker In Java
Using Barcode maker for Java Control to generate, create QR image in Java applications.
Although the preceding design is functional, it has a lot of weaknesses Here are just a few: 1 There's no check to be sure two users aren't using the same username Eventually, the system should include usernames and passwords, and only allow one person to use a particular account name 2 The amount of money you have and your car's items should be stored on the server in a database Otherwise, it's easy for a hacker to pretend to have limitless amounts of money 3 If items were in a database, then the store could be persistent You wouldn't have to remain logged in to sell your items Rather, the system could sell items for you and notify you via e-mail when a purchase succeeds 4 All buy and sell operations should be discrete transactions that is, a database should "lock" each object whenever a deal is made, to ensure that only one person is buying or selling it at a time 5 There's no real interaction It would be nice to have some chat or other social functionality so people can express themselves, and allow the player to get an idea of the other players' personalities
Bar Code Drawer In Java
Using Barcode drawer for Java Control to generate, create barcode image in Java applications.
The Client Side
Read Bar Code In Java
Using Barcode scanner for Java Control to read, scan read, scan image in Java applications.
It then sends this number to a server Note that for the sake of testing, it's a good idea to set the server to localhost that way you can run the server and the client from the comfort of your desktop machine Eventually, however, you will want to run the servlet on a live Web site and your MIDlet should connect to that URL Different application servers allow you to set up servlets in different ways A typical servlet setup will look like this: http://localhost:8080/servlet/GarageServlet Note that we created a ServerCallback interface with one method:
Draw QR Code 2d Barcode In Visual C#.NET
Using Barcode drawer for .NET Control to generate, create QR Code ISO/IEC18004 image in .NET applications.
public void serverResponse( String response);
QR Code ISO/IEC18004 Encoder In .NET Framework
Using Barcode generation for ASP.NET Control to generate, create Quick Response Code image in ASP.NET applications.
Every major game message is given its own class, each implementing ServerCallback Each message connects to the server and passes in itself as the callback That way, when the servlet issues a response, it can be handled by the appropriate class The full code listing is as follows:
Painting Quick Response Code In VS .NET
Using Barcode drawer for .NET framework Control to generate, create QR-Code image in .NET applications.
import javautil*; import javaio*; import javaxmicroeditionio*; import javaxmicroeditionlcdui*; import javaxmicroeditionmidlet*; public class GarageClient extends MIDlet implements CommandListener { private Display display; private Form loginform; private Form mainform; private Form detailform; private Form sellform; private Form sellform2; private Form itemsoldform; // Hard-coded for now I have 200 dollars public int mybalance = 200; // For now, just hard code the item data // TODO: Grab this from the database public String[] myitemname = {"Turbo Boost","Oil Slick","Wide Tires"}; public String[] myitemdescript = {"Add 2 To Speed","Releases Oil On Track","Add 1 To Control"}; // commands static final Command LOGIN = new Command("Log In",CommandSCREEN, 1); static final Command EXIT = new Command("Exit",CommandEXIT, 2); static static static 2); static 2); final Command BUY = new Command("Buy",CommandSCREEN, 1); final Command SELL = new Command("Sell",CommandSCREEN, 1); final Command LOGOUT = new Command("Log Out",CommandSCREEN, final Command REFRESH = new Command("Refresh",CommandSCREEN,
Generate QR Code In VB.NET
Using Barcode generation for .NET Control to generate, create QR image in .NET framework applications.
static final Command BUYIT = new Command("Buy It",CommandSCREEN, 1); static final Command SELLIT = new Command("Sell It",CommandSCREEN, 1); static final Command BACK = new Command("Back",CommandBACK, 2); private TextField usernamefield; private TextField pricefield; private ChoiceGroup itemgroup; String username; private Vector itemvector; private Vector solditemvector; private int price; private String usershere; Timer timer; // Point to the servlet here String url = "http://localhost:8080/servlet/GarageServlet"; public GarageClient() { display = DisplaygetDisplay(this); }
Drawing DataMatrix In Java
Using Barcode encoder for Java Control to generate, create Data Matrix image in Java applications.
public void startApp() { loginform = new Form("The Garage"); loginformappend("Log In Now"); usernamefield = new TextField("Username:", "", 10, TextFieldANY); loginformappend(usernamefield); loginformaddCommand(LOGIN); loginformaddCommand(EXIT); loginformsetCommandListener(this); displaysetCurrent(loginform); } public void pauseApp() { }
Generate UPC-A In Java
Using Barcode maker for Java Control to generate, create UPC Symbol image in Java applications.
public void destroyApp(boolean unconditional) { } public void commandAction(Command c, Displayable s) { if (s instanceof Form) { Form obj = (Form) s; if (obj == loginform) { if (c == EXIT) { notifyDestroyed(); } else if (c == LOGIN) { username = usernamefieldgetString(); Login l = new Login(); } } else if (obj == mainform) { if (c == BUY) buydetail(itemgroupgetSelectedIndex()); else if (c == SELL) sell(); else if (c == LOGOUT) { Logout lo = new Logout(); } else if (c == REFRESH) { Login l = new Login(); } } else if (obj == sellform || obj == detailform || obj == itemsoldform) { if (c == BACK) displaysetCurrent(mainform); else if (c == BUYIT) { BuyIt bi = new BuyIt(itemgroupgetSelectedIndex()); } else if (c == SELLIT) pickprice(); }
Encode Barcode In Java
Using Barcode generator for Java Control to generate, create bar code image in Java applications.
else if (obj == sellform2) { if (c == BACK) displaysetCurrent(sellform); else if (c == SELLIT) { String price = pricefieldgetString(); int i = itemgroupgetSelectedIndex(); // Be sure item wasn't already put up for sale if (myitemname[i]equals("")) return; // Marshal data for item in a String String theitem = myitemname[i]+"!"+myitemdescript[i]+"!"+price; // Remove the item from the local list of my items myitemname[i] = ""; myitemdescript[i] = ""; SellIt si = new SellIt(theitem); } } } } void CreateMainform() { mainform = new Form("Items For Sale"); mainformaddCommand(BUY); mainformaddCommand(SELL); mainformaddCommand(LOGOUT); mainformaddCommand(REFRESH); mainformsetCommandListener(this); mainformappend("Also Here: "+usershere+"\n"); mainformappend("My Balance: $"+mybalance+"\n"); if (itemvectorsize() == 0) { mainformappend("No Items For Sale"); mainformappend("Come Back Later"); // Remove the buy button mainformremoveCommand(BUY); } else { String items[] = new String[itemvectorsize()]; // Now parse out the item name for (int i=0; i < itemvectorsize(); i++) items[i] = ItemName((String)itemvectorelementAt(i)); itemgroup = new ChoiceGroup("Exclusive",ChoiceGroup EXCLUSIVE,items,null); mainformappend(itemgroup); } } void CreateItemsoldform()
Code-39 Maker In Java
Using Barcode printer for Java Control to generate, create Code-39 image in Java applications.
{ itemsoldform = new Form("Item Sold!"); itemsoldformaddCommand(BACK); itemsoldformsetCommandListener(this); }
Generate Barcode In Java
Using Barcode drawer for Java Control to generate, create barcode image in Java applications.
class Login implements ServerCallback { Login() { ConnectServer("login",null,this); } public void serverResponse(String response) { if (CheckForError(response)) return; // Parse out the user list and items for sale int uindex = responseindexOf("users"); int findex = responseindexOf("forsale"); if (uindex == -1 || findex == -1) { ShowError("Bad User List or For Sale List Returned"); return; } usershere = responsesubstring(6,findex-1); String forsale = responsesubstring(findex+8); // Now parse through the for sale list itemvector = new Vector(); CreateItemVector(forsale,itemvector); boolean canbuy = true; CreateMainform(); displaysetCurrent(mainform); } } private void buydetail(int at) { detailform = new Form("Ready To Buy"); detailformaddCommand(BUYIT); detailformaddCommand(BACK); detailformsetCommandListener(this);
EAN 8 Encoder In Java
Using Barcode generator for Java Control to generate, create GTIN - 8 image in Java applications.
detailformappend(ItemName((String)itemvectorelementAt(at))+"\n"); // Show the description detailformappend(ItemDescription((String)itemvectorelementAt(at))+" \n"); // Show the price String iprice = ItemPrice((String)itemvectorelementAt(at)); detailformappend("For $"+iprice+"\n"); try {
Make Barcode In Visual Basic .NET
Using Barcode creation for VS .NET Control to generate, create barcode image in .NET framework applications.
price = IntegerparseInt(iprice); } catch (NumberFormatException nfe) { price = 0; } // Do we have enough money if (price > mybalance) { detailformappend("You Can't Afford This!"); detailformremoveCommand(BUYIT); } displaysetCurrent(detailform); } class BuyIt implements ServerCallback { int index; BuyIt(int itemindex) { index = itemindex; ConnectServer("buy",itemgroupgetString(itemindex),this); } public void serverResponse(String response) { if (CheckForError(response)) return; if (responseequals("")) { // Charge your account mybalance -= price; // TODO: Add item to your personal database // Remove item from local list itemvectorremoveElementAt(index); CreateMainform(); displaysetCurrent(mainform); } else ShowError(response); } } private void sell() { sellform = new Form("Your Items"); sellformaddCommand(SELLIT); sellformaddCommand(BACK); sellformsetCommandListener(this); itemgroup = new ChoiceGroup("Exclusive",ChoiceGroup EXCLUSIVE,myitemname,null); sellformappend(itemgroup); displaysetCurrent(sellform); } private void pickprice()
Code128 Maker In Visual Basic .NET
Using Barcode creation for VS .NET Control to generate, create ANSI/AIM Code 128 image in Visual Studio .NET applications.
{ sellform2 = new Form("Choose Sale Price"); sellform2addCommand(SELLIT); sellform2addCommand(BACK); sellform2setCommandListener(this);
Paint Barcode In Visual Basic .NET
Using Barcode creator for .NET Control to generate, create barcode image in Visual Studio .NET applications.
sellform2append(itemgroupgetString(itemgroupgetSelectedIndex())+"\ n"); pricefield = new TextField("Price:", "", 3, TextFieldNUMERIC); sellform2append(pricefield); displaysetCurrent(sellform2); } class SellIt implements ServerCallback { SellIt(String item) { ConnectServer("sell", item, this); } public void serverResponse(String response) { if (CheckForError(response)) return; // Begin polling the server for any updates if (timer == null) { timer = new Timer(); CheckInTimer ci = new CheckInTimer(); timerschedule(ci,(long)10000,10000); } displaysetCurrent(mainform); } } class Logout implements ServerCallback { Logout() { if (timer != null) timercancel(); ConnectServer("logout",null,this); } public void serverResponse(String response) { if (CheckForError(response)) return; displaysetCurrent(loginform); } } class CheckIn implements ServerCallback CheckIn() { ConnectServer("checkin",null,this); {
Printing Bar Code In VS .NET
Using Barcode creation for Visual Studio .NET Control to generate, create bar code image in Visual Studio .NET applications.
} public void serverResponse(String response) { if (CheckForError(response)) return; int rindex = responseindexOf("sold"); if (rindex != -1) { String items = responsesubstring(rindex+5); if (!itemsequals("")) { CreateItemsoldform(); solditemvector = new Vector(); CreateItemVector(items,solditemvector); // Now parse out the item name for (int i=0; i < solditemvectorsize(); i++) { String itemname = ItemName((String)solditemvectorelementAt(i)); String itemprice = ItemPrice((String)solditemvectorelementAt(i)); int price = 0; try { price = IntegerparseInt(itemprice); } catch (NumberFormatException nfe) { } // TODO: Remove the item from the database itemsoldformappend(itemname+" sold for $"+itemprice); // Add money to your balance mybalance += price; CreateMainform(); displaysetCurrent(itemsoldform); } } } } } void CreateItemVector(String items,Vector iv) { // Parse through the list of items int start = 0; int end = 0; String item = ""; end = itemsindexOf(','); while (end != -1) { item = itemssubstring(start,end); ivaddElement(item); start = end+1; end = itemsindexOf(',',start); } item = itemssubstring(start); if (!itemequals("")) ivaddElement(item); }
Code39 Drawer In C#.NET
Using Barcode printer for .NET framework Control to generate, create Code 3 of 9 image in VS .NET applications.
private boolean CheckForError(String response) { Systemoutprintln("RESP:"+response); int ecode = responseindexOf("error"); if (ecode != -1) { String therror = responsesubstring(ecode+6); ShowError(therror); return true; } return false; } private void ShowError(String err) { Alert errorAlert = new Alert("Alert",err,null, AlertTypeERROR); errorAlertsetTimeout(AlertFOREVER); displaysetCurrent(errorAlert); } private String ItemName(String item) { int end = itemindexOf('!'); if (end == -1) { ShowError("Bad Item Format"); return ""; } return itemsubstring(0,end); // Horse!mean!669 } private String ItemDescription(String item) { int start = itemindexOf('!'); int end = itemindexOf('!',start+1); if (end == -1 || start == -1) { ShowError("Bad Item Format"); return ""; } return itemsubstring(start+1,end); } private String ItemPrice(String item) { int start = itemindexOf('!'); int end = itemindexOf('!',start+1); if (end == -1 || start == -1) { ShowError("Bad Item Format"); return ""; } return itemsubstring(end+1); } void ConnectServer(String action,String item,ServerCallback callback) { ConnectNow cn = new ConnectNow(action,item,callback); cnstart(); }
USS Code 39 Recognizer In VS .NET
Using Barcode decoder for VS .NET Control to read, scan read, scan image in Visual Studio .NET applications.
public interface ServerCallback { public void serverResponse( String response); } class ConnectNow implements Runnable { String action; String item; ServerCallback callback; ConnectNow( String a,String i,ServerCallback c) { action = a; item = i; callback = c; } public void run() { HttpConnection c InputStream is = DataOutputStream StringBuffer b = if (item == null) item = ""; try { c = (HttpConnection)Connectoropen(url); csetRequestMethod(HttpConnectionPOST); csetRequestProperty("User-Agent","Profile/MIDP-10 Configuration/CLDC-10"); csetRequestProperty("Content-Language", "en-US"); os = new DataOutputStream(copenOutputStream()); oswriteUTF(username); oswriteUTF(action); oswriteUTF(item); Systemoutprintln(username+","+action+","+item); int rc = cgetResponseCode(); if( rc == HttpConnectionHTTP_OK ) { is = copenDataInputStream(); int ch; while ((ch = isread()) != -1) bappend((char) ch); } else { Systemoutprintln("Response Code: "+rc); ShowError("Bad Server Response!"); } } catch (Exception e) { ShowError("Problem Connecting to Network"); } finally
Bar Code Generator In Visual C#.NET
Using Barcode drawer for .NET framework Control to generate, create barcode image in VS .NET applications.
= null; null; os = null; new StringBuffer();
{ try { if (is != null) isclose(); if (c != null) cclose(); if (os != null) osclose(); } catch (Exception e) { ShowError("Problem Closing Network Connection"); } } if (b != null) callbackserverResponse(btoString()); else callbackserverResponse(null); } void start() { Thread t = new Thread( this ); try { tstart(); } catch( Exception e ) { ShowError(etoString()); } } } class CheckInTimer extends TimerTask { CheckInTimer() { } public void run() { try { CheckIn ci = new CheckIn(); } catch (Exception ex) { } } } }