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• web application with secured sections, sessions and related trouble

  - by spirytus

  I would like to create web application with admin/checkout sections being secured. Assuming I have SSL set up for subdomain.mydomain.com I would like to make sure that all that top-secret stuff ;) like checkout pages and admin section is transferred securely. Would it be ok to structure my application as below? subdomain.mydomain.com adminSectionFolder adminPage1.php adminPage2.php checkoutPagesFolder checkoutPage1.php checkoutPage2.php checkoutPage3.php homepage.php loginPage.php someOtherPage.php someNonSecureFolder nonSecurePage1.php nonSecurePage2.php nonSecurePage3.php imagesFolder image1.jpg image2.jpg image3.jpg Users would access my web application via http as there is no need for SSL for homepage and similar. Checkout/admin pages would have to be accessed via https though (that I would ensure via .htaccess redirects). I would also like to have login form on every page of the site, including non-secure pages. Now my questions are: if I have form on non-secure page e.g http://subdomain.mydomain.com/homepage.php and that form sends data to http://subdomain.mydomain.com/loginPage.php, is data being send encrypted as if it were sent from https://subdomain.mydomain.com/homepage.php? I do realize users will not see padlock, but browser still should encrypt it, is it right? If on secure page loginPage.php (or any other accessed via https for that instance) I created session, session ID would be assigned, and in case of my web app. something like username of the logged in user. Would I be able to access these session variable from http://subdomain.mydomain.com/homepage.php to for example display greeting message? If session ID is stored in cookies then it would be trouble I assume, but could someone clarify how it should be done? It seems important to have username and password send over SSL. Related to above question I think.. would it actually make any sense to have login secured via SSL so usenrame/password would be transferred securely, and then session ID being transferred with no SSL? I mean wouldnt it be the same really if someone caught username and password being transferred, or caught session ID? Please let me know if I make sense here cause it feels like I'm missing something important. EDIT: I came up with idea but again please let me know if that would work. Having above, so assuming that sharing session between http and https is as secure as login in user via plain http (not https), I guess on all non secure pages, like homepage etc. I could check if user is already logged in, and if so from php redirect to https version of same page. So user fills in login form from homepage.php, over ssl details are send to backend so probably https://.../homepage.php. Trying to access http://.../someOtherPage.php script would always check if session is created and if so redirect user to https version of this page so https://.../someOtherPage.php. Would that work? 4.To avoid browser popping message "this page contains non secure items..." my links to css, images and all assets, e.g. in case of http://subdomain.mydomain.com/checkoutPage1.php should be absolute so "/images/image1.jpg" or relative so "../images/image1.jpg"? I guess one of those would have to work :) wow that's long post, thanks for your patience if you got that far and any answers :) oh yeh and I use php/apache on shared hosting

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• Nothing happen when refreshing the main Frame (JAVA)

  - by Ams

  Hello everyone, I try to show a ( Logged in ) message when a user is succefully connected but nothing happen when a do a repaint(). you can take a look to the code : public class MainFrame extends JFrame implements ActionListener{ private static final long serialVersionUID = 1L; private static final int FRAME_HEIGHT = 400; private static final int FRAME_WIDTH = 250; private static final String TITLE = new String("TweeX"); private static String TWITTERID = new String(); private static String TWITTERPW = new String(); private boolean logged = false; private JTextField loginField = new JTextField(10); private JPasswordField passField = new JPasswordField(10); private JButton login = new JButton("Connect"); private GridBagConstraints c = new GridBagConstraints(); private String UserStatus = new String("Please login..."); /* * Constructor ! */ MainFrame() { setSize(FRAME_WIDTH, FRAME_HEIGHT); setTitle(TITLE); setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); setResizable(false); loginUser(); } /* * Login Forms */ protected void loginUser(){ this.setLayout(new GridBagLayout()); //add Login Fiels + Label c.fill = GridBagConstraints.HORIZONTAL; c.gridx = 0; c.insets = new Insets(5,5,5,20); c.gridy = 0; add(new JLabel("Username:"),c); c.fill = GridBagConstraints.HORIZONTAL; c.gridx = 1; c.gridy = 0; add(loginField,c); //add Password Fiels + Label c.fill = GridBagConstraints.HORIZONTAL; c.gridx = 0; c.gridy = 1; add(new JLabel("Password:"),c); c.fill = GridBagConstraints.HORIZONTAL; c.gridx = 1; c.gridy = 1; add(passField,c); //add Login button c.fill = GridBagConstraints.HORIZONTAL; c.gridx = 1; c.gridy = 2; add(login,c); //add listener to login button login.addActionListener((ActionListener) this); c.fill = GridBagConstraints.HORIZONTAL; c.gridx = 1; c.gridy = 3; add(new JLabel(UserStatus),c); setVisible(true); } @Override public void actionPerformed(ActionEvent e) { TWITTERID = loginField.getText(); TWITTERPW = passField.getText(); Twitter twitter = new TwitterFactory().getInstance(TWITTERID,TWITTERPW); logged = true; try { twitter.verifyCredentials(); } catch (TwitterException e1) { logged = false; } } protected void connect(){ if(logged){ UserStatus = "Loged In :)"; repaint(); } } static public void main(String[] argv) { new MainFrame(); } }

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• What does a WinForm application need to be designed for usability, and be robust, clean, and profess

  - by msorens

  One of the principal problems impeding productivity in software implementation is the classic conundrum of “reinventing the wheel”. Of late I am a .NET developer and even the wonderful wizardry of .NET and Visual Studio covers only a portion of this challenging issue. Below I present my initial thoughts both on what is available and what should be available from .NET on a WinForm, focusing on good usability. That is, aspects of an application exposed to the user and making the user experience easier and/or better. (I do include a couple items not visible to the user because I feel strongly about them, such as diagnostics.) I invite you to contribute to these lists. LIST A: Components provided by .NET These are substantially complete components provided by .NET, i.e. those requiring at most trivial coding to use. “About” dialog -- add it with a couple clicks then customize. Persist settings across invocations -- .NET has the support; just use a few lines of code to glue them together. Migrate settings with a new version -- a powerful one, available with one line of code. Tooltips (and infotips) -- .NET includes just plain text tooltips; third-party libraries provide richer ones. Diagnostic support -- TraceSources, TraceListeners, and more are built-in. Internationalization -- support for tailoring your app to languages other than your own. LIST B: Components not provided by .NET These are not supplied at all by .NET or supplied only as rudimentary elements requiring substantial work to be realized. Splash screen -- a small window present during program startup with your logo, loading messages, etc. Tip of the day -- a mini-tutorial presented one bit at a time each time the user starts your app. Check for available updates -- facility to query a server to see if the user is running the latest version of your app, then provide a simple way to upgrade if a new version is found. Maximize to multiple monitors -- the canonical window allows you to maximize to a single monitor only; in my apps I allow maximizing across multiple monitors with a click. Taskbar notifier -- flash the taskbar when your backgrounded app has new info for the user. Options dialogs -- multi-page dialogs letting the user customize the app settings to his/her own preferences. Progress indicator -- for long running operations give the user feedback on how far there is left to go. Memory gauge -- an indicator (either absolute or percentage) of how much memory is used by your app. LIST C: Stylistic and/or tiny bits of functionality This list includes bits of functionality that are too tiny to merit being called a component, along with stylistic concerns (that admittedly do overlap with the Windows User Experience Interaction Guidelines). Design a form for resizing -- unless you are restricting your form to be a fixed size, use anchors and docking so that it does what is reasonable when enlarged or shrunk by the user. Set tab order on a form -- repeated tab presses by the user should advance from field to field in a logical order rather than the default order in which you added fields. Adjust controls to be aware of operating modes -- When starting a background operation with, for example, a “Go” button, disable that “Go” button until the operation completes. Provide access keys for all menu items (per UXGuide). Provide shortcut keys for commonly used menu items (per UXGuide). Set up some (global or important or common) shortcut keys without associating to menu items. Allow some menu items to be invoked with or without modifier keys (shift, control, alt) where the modifier key is useful to vary the operation slightly. Hook up Escape and Enter on child forms to do what is reasonable. Decorate any library classes with documentation-comments and attributes -- this allows Visual Studio to leverage them for Intellisense and property descriptions. Spell check your code! What else would you include?

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• How to figure out who owns a worker thread that is still running when my app exits?

  - by Dave

  Not long after upgrading to VS2010, my application won't shut down cleanly. If I close the app and then hit pause in the IDE, I see this: The problem is, there's no context. The call stack just says [External code], which isn't too helpful. Here's what I've done so far to try to narrow down the problem: deleted all extraneous plugins to minimize the number of worker threads launched set breakpoints in my code anywhere I create worker threads (and delegates + BeginInvoke, since I think they are labeled "Worker Thread" in the debugger anyway). None were hit. set IsBackground = true for all threads While I could do the next brute force step, which is to roll my code back to a point where this didn't happen and then look over all of the change logs, this isn't terribly efficient. Can anyone recommend a better way to figure this out, given the notable lack of information presented by the debugger? The only other things I can think of include: read up on WinDbg and try to use it to stop anytime a thread is started. At least, I thought that was possible... :) comment out huge blocks of code until the app closes properly, then start uncommenting until it doesn't. UPDATE Perhaps this information will be of use. I decided to use WinDbg and attach to my application. I then closed it, and switched to thread 0 and dumped the stack contents. Here's what I have: ThreadCount: 6 UnstartedThread: 0 BackgroundThread: 1 PendingThread: 0 DeadThread: 4 Hosted Runtime: no PreEmptive GC Alloc Lock ID OSID ThreadOBJ State GC Context Domain Count APT Exception 0 1 1c70 005a65c8 6020 Enabled 02dac6e0:02dad7f8 005a03c0 0 STA 2 2 1b20 005b1980 b220 Enabled 00000000:00000000 005a03c0 0 MTA (Finalizer) XXXX 3 08504048 19820 Enabled 00000000:00000000 005a03c0 0 Ukn XXXX 4 08504540 19820 Enabled 00000000:00000000 005a03c0 0 Ukn XXXX 5 08516a90 19820 Enabled 00000000:00000000 005a03c0 0 Ukn XXXX 6 08517260 19820 Enabled 00000000:00000000 005a03c0 0 Ukn 0:008> ~0s eax=c0674960 ebx=00000000 ecx=00000000 edx=00000000 esi=0040f320 edi=005a65c8 eip=76c37e47 esp=0040f23c ebp=0040f258 iopl=0 nv up ei pl nz na po nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000202 USER32!NtUserGetMessage+0x15: 76c37e47 83c404 add esp,4 0:000> !clrstack OS Thread Id: 0x1c70 (0) Child SP IP Call Site 0040f274 76c37e47 [InlinedCallFrame: 0040f274] 0040f270 6baa8976 DomainBoundILStubClass.IL_STUB_PInvoke(System.Windows.Interop.MSG ByRef, System.Runtime.InteropServices.HandleRef, Int32, Int32)*** WARNING: Unable to verify checksum for C:\Windows\assembly\NativeImages_v4.0.30319_32\WindowsBase\d17606e813f01376bd0def23726ecc62\WindowsBase.ni.dll 0040f274 6ba924c5 [InlinedCallFrame: 0040f274] MS.Win32.UnsafeNativeMethods.IntGetMessageW(System.Windows.Interop.MSG ByRef, System.Runtime.InteropServices.HandleRef, Int32, Int32) 0040f2c4 6ba924c5 MS.Win32.UnsafeNativeMethods.GetMessageW(System.Windows.Interop.MSG ByRef, System.Runtime.InteropServices.HandleRef, Int32, Int32) 0040f2dc 6ba8e5f8 System.Windows.Threading.Dispatcher.GetMessage(System.Windows.Interop.MSG ByRef, IntPtr, Int32, Int32) 0040f318 6ba8d579 System.Windows.Threading.Dispatcher.PushFrameImpl(System.Windows.Threading.DispatcherFrame) 0040f368 6ba8d2a1 System.Windows.Threading.Dispatcher.PushFrame(System.Windows.Threading.DispatcherFrame) 0040f374 6ba7fba0 System.Windows.Threading.Dispatcher.Run() 0040f380 62e6ccbb System.Windows.Application.RunDispatcher(System.Object)*** WARNING: Unable to verify checksum for C:\Windows\assembly\NativeImages_v4.0.30319_32\PresentationFramewo#\7f91eecda3ff7ce478146b6458580c98\PresentationFramework.ni.dll 0040f38c 62e6c8ff System.Windows.Application.RunInternal(System.Windows.Window) 0040f3b0 62e6c682 System.Windows.Application.Run(System.Windows.Window) 0040f3c0 62e6c30b System.Windows.Application.Run() 0040f3cc 001f00bc MyApplication.App.Main() [C:\code\trunk\MyApplication\obj\Debug\GeneratedInternalTypeHelper.g.cs @ 24] 0040f608 66c421db [GCFrame: 0040f608] EDIT -- not sure if this helps, but the main thread's call stack looks like this: [Managed to Native Transition] > WindowsBase.dll!MS.Win32.UnsafeNativeMethods.GetMessageW(ref System.Windows.Interop.MSG msg, System.Runtime.InteropServices.HandleRef hWnd, int uMsgFilterMin, int uMsgFilterMax) + 0x15 bytes WindowsBase.dll!System.Windows.Threading.Dispatcher.GetMessage(ref System.Windows.Interop.MSG msg, System.IntPtr hwnd, int minMessage, int maxMessage) + 0x48 bytes WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrameImpl(System.Windows.Threading.DispatcherFrame frame = {System.Windows.Threading.DispatcherFrame}) + 0x85 bytes WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrame(System.Windows.Threading.DispatcherFrame frame) + 0x49 bytes WindowsBase.dll!System.Windows.Threading.Dispatcher.Run() + 0x4c bytes PresentationFramework.dll!System.Windows.Application.RunDispatcher(object ignore) + 0x17 bytes PresentationFramework.dll!System.Windows.Application.RunInternal(System.Windows.Window window) + 0x6f bytes PresentationFramework.dll!System.Windows.Application.Run(System.Windows.Window window) + 0x26 bytes PresentationFramework.dll!System.Windows.Application.Run() + 0x1b bytes I did a search on it and found some posts related to WPF GUIs hanging, and maybe that'll give me some more clues.

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• Applying Unity in dynamic menu

  - by Rajarshi

  I was going through Unity 2.0 to check if it has an effective use in our new application. My application is a Windows Forms application and uses a traditional bar menu (at the top), currently. My UIs (Windows Forms) more or less support Dependency Injection pattern since they all work with a class (Presentation Model Class) supplied to them via the constructor. The form then binds to the properties of the supplied P Model class and calls methods on the P Model class to perform its duties. Pretty simple and straightforward. How P Model reacts to the UI actions and responds to them by co-ordinating with the Domain Class (Business Logic/Model) is irrelevant here and thus not mentioned. The object creation sequence to show up one UI from menu then goes like this - Create Business Model instance Create Presentation Model instance with Business Model instance passed to P Model constructor. Create UI instance with Presentation Model instance passed to UI constructor. My present solution: To show an UI in the method above from my menu I would have to refer all assemblies (Business, PModel, UI) from my Menu class. Considering I have split the modules into a number of physical assemblies, that would be a dificult task to add references to about 60 different assemblies. Also the approach is not very scalable since I would certainly need to release more modules and with this approach I would have to change the source code every time I release a new module. So primarily to avoid the reference of so many assemblies from my Menu class (assembly) I did as below - Stored all the dependency described above in a database table (SQL Server), e.g. ModuleShortCode | BModelAssembly | BModelFullTypeName | PModelAssembly | PModelFullTypeName | UIAssembly | UIFullTypeName Now used a static class named "Launcher" with a method "Launch" as below - Launcher.Launch("Discount") Launcher.Launch("Customers") The Launcher internally uses data from the dependency table and uses Activator.CreateInstance() to create each of the objects and uses the instance as constructor parameter to the next object being created, till the UI is built. The UI is then shown as a modal dialog. The code inside Launcher is somewhat like - Form frm = ResolveForm("Discount"); frm.ShowDialog(); The ResolveForm does the trick of building the chain of objects. Can Unity help me here? Now when I did that I did not have enough information on Unity and now that I have studied Unity I think I have been doing more or less the same thing. So I tried to replace my code with Unity. However, as soon as I started I hit a block. If I try to resolve UI forms in my Menu as Form customers = myUnityContainer.Resolve(); or Form customers = myUnityContainer.Resolve(typeof(Customers)); Then either way, I need to refer to my UI assembly from my Menu assembly since the target Type "Customers" need to be known for Unity to resolve it. So I am back to same place since I would have to refer all UI assemblies from the Menu assembly. I understand that with Unity I would have to refer fewer assemblies (only UI assemblies) but those references are needed which defeats my objectives below - Create the chain of objects dynamically without any assembly reference from Menu assembly. This is to avoid Menu source code changing every time I release a new module. My Menu also is built dynamically from a table. Be able to supply new modules just by supplying the new assemblies and inserting the new Dependency row in the table by a database patch. At this stage, I have a feeling that I have to do it the way I was doing, i.e. Activator.CreateInstance() to fulfil all my objectives. I need to verify whether the community thinks the same way as me or have a better suggestion to solve the problem. The post is really long and I sincerely thank you if you come til this point. Waiting for your valuable suggestions. Rajarshi

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• change password code error.....

  - by shimaTun

  I've created a code to change a password. Now it seem contain an error.before i fill the form. the page display the error message: Parse error: parse error, unexpected $end in C:\Program Files\xampp\htdocs\e-Complaint(FYP)\userChangePass.php on line 222 this the code: <?php # userChangePass.php //this page allows logged in user to change their password. $page_title='Change Your Password'; //if no first_name variable exists, redirect the user if(!isset($_SESSION['nameuser'])){ header("Location: http://" .$_SERVER['HTTP_HOST']. dirname($_SERVER['PHP_SELF'])."/index.php"); ob_end_clean(); exit(); }else{ if(isset($_POST['submit'])) {//handle form. require_once('connectioncomplaint.php'); //connec to the database //check for a new password and match againts the confirmed password. if(eregi ("^[[:alnum:]]{4,20}$", stripslashes(trim($_POST['password1'])))){ if($_POST['password1'] == $_POST['password2']){ $p =escape_data($_POST['password1']); }else{ $p=FALSE; echo'<p><font color="red" size="+1"> Your password did not match the confirmed password!</font></p>'; } }else{ $p=FALSE; echo'<p><font color="red" size="+1"> Please Enter a valid password!</font></p>'; } if($p){ //if everything OK. //make the query $query="UPDATE access SET password=PASSWORD('$p') WHERE userid={$_SESSION['userid']}"; $result=@mysql_query($query);//run the query. if(mysql_affected_rows() == 1) {//if it run ok. //send an email,if desired. echo '<p><b>your password has been changed.</b></p>'; //include('templates/footer.inc');//include the HTML footer. exit(); }else{//if it did not run ok $message= '<p>Your password could not be change due to a system error.We apolpgize for any inconvenience.</p><p>' .mysql_error() .'</p>'; } mysql_close();//close the database connection. }else{//failed the validation test. echo '<p><font color="red" size="+1"> Please try again.</font></p>'; } }//end of the main Submit conditional. ?> And code for form: <h1>Change Your Password</h1> <form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post"> <fieldset> <p><b>New Password:</b><input type="password" name="password1" size="20" maxlength="20" /> <small>Use only letters and numbers.Must be between 4 and 20 characters long.</small></p> <p><b>Confirm New Password:</b><input type="password" name="password2" size="20" maxlength="20" /></p> </fieldset> <div align="center"> <input type="submit" name="submit" value="Change My Password" /></div> </form><!--End Form-->

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• Application stops on back button in new activity

  - by Bruno Almeida

  I have this application, that have a listView, and when I click in a item on listView, it opens a new activity. That works fine! But, if I open the new activity and than press the "back button" the application "Unfortunately, has stopped". Is there something I'm doing wrong? Here is my code: First activity: public class AndroidSQLite extends Activity { private SQLiteAdapter mySQLiteAdapter; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); ListView listContent = (ListView)findViewById(R.id.contentlist); mySQLiteAdapter = new SQLiteAdapter(this); mySQLiteAdapter.openToRead(); Cursor cursor = mySQLiteAdapter.queueAll(); startManagingCursor(cursor); String[] from = new String[]{SQLiteAdapter.KEY_NOME,SQLiteAdapter.KEY_ID}; int[] to = new int[]{R.id.text,R.id.id}; SimpleCursorAdapter cursorAdapter = new SimpleCursorAdapter(this, R.layout.row, cursor, from, to); listContent.setAdapter(cursorAdapter); listContent.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> parent, View view, int position, long id) { Toast.makeText(getBaseContext(), id + "", Toast.LENGTH_LONG).show(); Intent details = new Intent(getApplicationContext(),DetailsPassword.class); startActivity(details); } }); mySQLiteAdapter.close(); } } Second Activity: public class DetailsPassword extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); TextView text = new TextView(getApplicationContext()); text.setText("Text to show"); setContentView(text); } } // ===== EDITED ===== here is the Stack Track 10-30 08:55:05.744: E/AndroidRuntime(28046): FATAL EXCEPTION: main 10-30 08:55:05.744: E/AndroidRuntime(28046): java.lang.RuntimeException: Unable to resume activity {com.example.sqliteexemple2/com.example.sqliteexemple2.AndroidSQLite}: java.lang.IllegalStateException: trying to requery an already closed cursor android.database.sqlite.SQLiteCursor@4180a370 10-30 08:55:05.744: E/AndroidRuntime(28046): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2701) 10-30 08:55:05.744: E/AndroidRuntime(28046): at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2729) 10-30 08:55:05.744: E/AndroidRuntime(28046): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1250) 10-30 08:55:05.744: E/AndroidRuntime(28046): at android.os.Handler.dispatchMessage(Handler.java:99) 10-30 08:55:05.744: E/AndroidRuntime(28046): at android.os.Looper.loop(Looper.java:137) 10-30 08:55:05.744: E/AndroidRuntime(28046): at android.app.ActivityThread.main(ActivityThread.java:4931) 10-30 08:55:05.744: E/AndroidRuntime(28046): at java.lang.reflect.Method.invokeNative(Native Method) 10-30 08:55:05.744: E/AndroidRuntime(28046): at java.lang.reflect.Method.invoke(Method.java:511) 10-30 08:55:05.744: E/AndroidRuntime(28046): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) 10-30 08:55:05.744: E/AndroidRuntime(28046): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:558) 10-30 08:55:05.744: E/AndroidRuntime(28046): at dalvik.system.NativeStart.main(Native Method) 10-30 08:55:05.744: E/AndroidRuntime(28046): Caused by: java.lang.IllegalStateException: trying to requery an already closed cursor android.database.sqlite.SQLiteCursor@4180a370 10-30 08:55:05.744: E/AndroidRuntime(28046): at android.app.Activity.performRestart(Activity.java:5051) 10-30 08:55:05.744: E/AndroidRuntime(28046): at android.app.Activity.performResume(Activity.java:5074) 10-30 08:55:05.744: E/AndroidRuntime(28046): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2691) 10-30 08:55:05.744: E/AndroidRuntime(28046): ... 10 more

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• Why does @PostConstruct callback fire every time even though bean is @ViewScoped? JSF

  - by Nitesh Panchal

  Hello, I am using datatable on page and using binding attribute to bind it to my backing bean. This is my code :- <?xml version='1.0' encoding='UTF-8' ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:h="http://java.sun.com/jsf/html" xmlns:p="http://primefaces.prime.com.tr/ui"> <h:head> <title>Facelet Title</title> </h:head> <h:body> <h:form prependId="false"> <h:dataTable var="item" value="#{testBean.stringCollection}" binding="#{testBean.dataTable}"> <h:column> <h:outputText value="#{item}"/> </h:column> <h:column> <h:commandButton value="Click" actionListener="#{testBean.action}"/> </h:column> </h:dataTable> </h:form> </h:body> </html> This is my bean :- package managedBeans; import java.io.Serializable; import java.util.ArrayList; import java.util.List; import javax.annotation.PostConstruct; import javax.faces.bean.ManagedBean; import javax.faces.bean.ViewScoped; import javax.faces.component.html.HtmlDataTable; @ManagedBean(name="testBean") @ViewScoped public class testBean implements Serializable { private List<String> stringCollection; public List<String> getStringCollection() { return stringCollection; } public void setStringCollection(List<String> stringCollection) { this.stringCollection = stringCollection; } private HtmlDataTable dataTable; public HtmlDataTable getDataTable() { return dataTable; } public void setDataTable(HtmlDataTable dataTable) { this.dataTable = dataTable; } @PostConstruct public void init(){ System.out.println("Post Construct fired!!"); stringCollection = new ArrayList<String>(); stringCollection.add("a"); stringCollection.add("b"); stringCollection.add("c"); } public void action(){ System.out.println("Clicked!!"); } } Please tell me why is the @PostConstruct firing each and every time i click on button? It should fire only once as long as i am on same page beacause my bean is @ViewScoped. Further, if i remove the binding attribute then everything works fine and @PostConstruct callback fires only once. Then why every time when i use binding attribute? I need binding attribute and want to perform initialisation tasks like fetching data from webservice, etc only once. What should i do? Where should i write my initialisation task?

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• Mbean registered but not found in mbean Server

  - by Prisco

  I have a problem about the mbeans. I have created a simple mbean and I have registered it on the default mBeanServer that is run (Via eclipse or java -jar mbean.jar) and in the same process if I try to fouund the mbean registered with a simple query: for (ObjectInstance instance : mbs.queryMBeans(ObjectNameMbean, null)) { System.out.println(instance.toString()); } the query retuerns my mbean, but if I start another process and try to search this mbean registered the mbeas is not found! why? The approch is : (Process that is running) public static void main(String[] args) throws Exception { MBeanServer mbeanServer =ManagementFactory.getPlatformMBeanServer(); ObjectName objectName = new ObjectName(ObjectNameMbean); Simple simple = new Simple (1, 0); mbeanServer.registerMBean(simple, objectName); while (true) { wait (Is this necessary?) } } So this is the first process that is running (that has the only pourpose to registry the mbean, because there is another process that want to read these informations. So I start another process to search this mbean but nothing. I 'm not using jboss but the local Java virtual Machine but my scope is to deploy this simple application in one ejb (autostart) and another ejb will read all informations. All suggestions are really apprecciated. This example should be more useful : Object Hello: public class Hello implements HelloMBean { public void sayHello() { System.out.println("hello, world"); } public int add(int x, int y) { return x + y; } public String getName() { return this.name; } public int getCacheSize() { return this.cacheSize; } public synchronized void setCacheSize(int size) { this.cacheSize = size; System.out.println("Cache size now " + this.cacheSize); } private final String name = "Reginald"; private int cacheSize = DEFAULT_CACHE_SIZE; private static final int DEFAULT_CACHE_SIZE = 200; } Interface HelloBean (implemented by Hello) public interface HelloMBean { public void sayHello(); public int add(int x, int y); public String getName(); public int getCacheSize(); public void setCacheSize(int size); } Simple Main import java.lang.management.ManagementFactory; import java.util.logging.Logger; import javax.management.MBeanServer; import javax.management.ObjectName; public class Main { static Logger aLog = Logger.getLogger("MBeanTest"); public static void main(String[] args) { try{ MBeanServer mbs = ManagementFactory.getPlatformMBeanServer(); ObjectName name = new ObjectName("ApplicationDomain:type=Hello"); Hello mbean = new Hello(); mbs.registerMBean(mbean, name); // System.out.println(mbs.getAttribute(name, "Name")); aLog.info("Waiting forever..."); Thread.sleep(Long.MAX_VALUE); } catch(Exception x){ x.printStackTrace(); aLog.info("exception"); } } } So now I have exported this project as jar file and run it as "java -jar helloBean.jar" and by eclipse I have modified the main class to read informations of this read (Example "Name" attribute) by using the same objectname used to registry it . Main to read : public static void main(String[] args) { try{ MBeanServer mbs = ManagementFactory.getPlatformMBeanServer(); ObjectName name = new ObjectName("ApplicationDomain:type=Hello"); System.out.println(mbs.getAttribute(name, "Name")); } catch(Exception x){ x.printStackTrace(); aLog.info("exception"); } } But nothing, the bean is not found.

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• How do I learn algorithms?

  - by Panthe

  Brief History: Just graduated high school, learned a bit of python and C++, have no friends with any helpful computer knowledge at all. Out of anyone i met in my school years I was probably the biggest nerd, but no one really knew. I consider my self to have a vast amount of knowledge on computers and tech then the average person. built/fixed tons of computers, and ability to troubleshoot pretty much any problem I came across. Now that high school is over, Ive really been thinking about my career. Loving, living computers for the past 15 years of my life I decided to take my ability's and try to learn computer programming, why I didn't start earlier I don't know, seems to be big mistake on my part... Doing some research I concluded that Python was the first programming language I should learn, since it was high level and easier to understand then C++ and Java. I also knew that to become good at what I did I needed to know more then just 2 or 3 languages, which didn't seem like a big problem considering once I learned the way Python worked, mainly syntax changed, and the rest would come naturally. I watched a couple of youtube videos, downloaded some book pdf's and snooped around from some tutorials here and there to get the hang of what to do. A two solid weeks had passed of trying to understand the syntax, create small programs that used the basic functions and understanding how it worked, I think i have got the hang of it. It breaks down into what ive been dealing with all this time (although i kinda knew) is that, input,output, loops, functions and other things derived from 0's and 1's storing data and recalling it, ect. (A VERY BASIC IDEA). Ive been able to create small programs, Hangman, file storing, temperature conversion, Caeser Cipher decode/encoding, Fibonacci Sequence and more, which i can create and understand how each work. Being 2 weeks into this, I have learned alot. Nothing at all compared to what i should be lear ning in the years to come if i get a grip on what I'm doing. While doing these programs I wont stop untill I've done doing a practice problem on a book, which embarresing enough will take me a couple hour depending on the complexity of it. I absolutly will not put aside the challenge until its complete, WHICH CAN BE EXTREMELY DRAINING, ive tried most problems without cheating and reached success, which makes me feel extremely proud of my self after completing something after much trial and error. After all this I have met the demon, alogrithm's which seem to be key to effiecent code. I cant seem to rap my head around some of the computer codes people put out there using numbers, and sometimes even basic functions, I have been able to understand them after a while but i know there are alot more complex things to come, considering my self smart, functions that require complex codes, actually hurt my brain. NOTHING EVER IN LIFE HURT MY BRAIN....... not even math classes in highschool, trying to understand some of the stuff people put out there makes me feel like i have a mental disadvantage lol... i still walk forward though, crossing my fingers that the understanding will come with time. Sorry if is this is long i just wish someone takes all these things into consideration when answering my question. even through all these downsides im still pushing through and continuing to try and get good at this, i know reading these tutorials wont make me any good unless i can become creative and make my own, understand other peoples programs, so this leads me to the simple question i could have asked in the beginning..... WHERE IN THE WORLD DO I START ? Ive been trying to find out how to understand some of the open source projects, how i can work with experianced coders to learn from them and help them, but i dont think thats even possible by the way how far people's knowledge is compared to me, i have no freinds who i can learn from, can someone help me and guide me into the right direction.. i have a huge motivation to get good at coding, anything information would be extremely helpful

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• wordexp followed by strcpy = EXC_BAD_ACCESS + sharedlibrary apply-load-rules-all

  - by fyngyrz

  The implication is a memory problem. I have static allocations for these: char akdir[400]; char homedir[400]; This crashes on the first strcpy(): void setuplibfoo() { long ii; double x; wordexp_t result; // This obtains the user's home directory // -------------------------------------- homedir[0]=0; // in case wordexp fails switch (wordexp("~/",&result,0)) { case 0: // Successful. We'll fall into deallocate when done. { strcpy(homedir,result.we_wordv[0]); // <<--- CRASH! strcpy(akdir,homedir); strcat(akdir,"ak-plugins/"); vs_status(akdir); } case WRDE_NOSPACE: // If the error was WRDE_NOSPACE, then { // perhaps part of the result was allocated. wordfree (&result); } default: // all other errors do not require deallocation { break; } } ...additional code clipped.. doesn't get there on crash. This is in a shared library I've written that is linked to my application, also something I've written. In this case, it doesn't get very far, although if it starts, it's fine. ...I've read the wordexp docs several times; they say they allocate new objects, so you just set up that type and call them with the address. The switch error model is right from the wordexp docs: http://www.gnu.org/s/libc/manual/html_mono/libc.html#Wordexp-Example It doesn't always crash. Just sometimes, and just under 10.6. Never under 10.5 I'm building debug mode with XCode 3.1.1, under OSX 10.5.8 it seems to run ok, I've not seen a crash -- under 10.6, it crashes... sometimes. But always with that same exception, and always in the same place. The Google has it that this actually means, somehow, that it's too soon to allocate memory. But all the instances I could find were memory errors on the part of the programmer. Overruns, etc. And I can't find any docs on when it IS safe to allocate memory. Now, the path that expands there is nowhere near 400 characters. it's this (it it completes): /Users/flake/ak-plugins/ and this: /Users/flake/ ...if it doesn't. the strcpy... copies 2nd param to first. Theirs to mine. And it works! under 10.5. :/ So is wordexp broke? Is 10.6 broke? Am I cRaZy? Here's the debugger output: 0x00013446 <+0049> call 0xc98da <dyld_stub_wordexp> 0x0001344b <+0054> test %eax,%eax 0x0001344d <+0056> je 0x13454 <setuplibfoo+63> 0x0001344f <+0058> jmp 0x134da <setuplibfoo+197> 0x00013454 <+0063> mov -0x1c(%ebp),%eax 0x00013457 <+0066> mov (%eax),%eax 0x00013459 <+0068> mov %eax,0x4(%esp) 0x0001345d <+0072> lea 0xb6cc2(%ebx),%eax 0x00013463 <+0078> mov (%eax),%eax 0x00013465 <+0080> mov %eax,(%esp) 0x00013468 <+0083> call 0xc9898 <dyld_stub_strcpy> 0x0001346d <+0088> lea 0xb6cc2(%ebx),%eax <<--CRASH!

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• "didChangeSection:" NSfetchedResultsController delegate method not being called

  - by robenk

  I have a standard split view controller, with a detail view and a table view. Pressing a button in the detail view can cause the an object to change its placement in the table view's ordering. This works fine, as long as the resulting ordering change doesn't result in a section being added or removed. I.e. an object can change it's ordering in a section or switch from one section to another. Those ordering changes work correctly without problems. But, if the object tries to move to a section that doesn't exist yet, or is the last object to leave a section (therefore requiring the section its leaving to be removed), then the application crashes. NSFetchedResultsControllerDelegate has methods to handle sections being added and removed that should be called in those cases. But those delegate methods aren't being called for some reason. The code in question, is boilerplate: - (void)controllerWillChangeContent:(NSFetchedResultsController *)controller { NSLog(@"willChangeContent"); [self.tableView beginUpdates]; } - (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type { NSLog(@"didChangeSection"); switch(type) { case NSFetchedResultsChangeInsert: [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade]; break; case NSFetchedResultsChangeDelete: [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade]; break; } } - (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath { NSLog(@"didChangeObject"); UITableView *tableView = self.tableView; switch(type) { case NSFetchedResultsChangeInsert: [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade]; break; case NSFetchedResultsChangeDelete: [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade]; break; case NSFetchedResultsChangeUpdate: [self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath]; break; case NSFetchedResultsChangeMove: [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade]; [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]withRowAnimation:UITableViewRowAnimationFade]; break; } } - (void)controllerDidChangeContent:(NSFetchedResultsController *)controller { NSLog(@"didChangeContent"); [self.tableView endUpdates]; [detailViewController.reminderView update]; } Starting the application, and then causing the last object to leave a section results in the following output: 2011-01-08 23:40:18.910 Reminders[54647:207] willChangeContent 2011-01-08 23:40:18.912 Reminders[54647:207] didChangeObject 2011-01-08 23:40:18.914 Reminders[54647:207] didChangeContent 2011-01-08 23:40:18.915 Reminders[54647:207] *** Assertion failure in -[UITableView _endCellAnimationsWithContext:], /SourceCache/UIKit_Sim/UIKit-1145.66/UITableView.m:825 2011-01-08 23:40:18.917 Reminders[54647:207] Serious application error. Exception was caught during Core Data change processing: Invalid update: invalid number of sections. The number of sections contained in the table view after the update (5) must be equal to the number of sections contained in the table view before the update (6), plus or minus the number of sections inserted or deleted (0 inserted, 0 deleted). with userInfo (null) As you can see, "willChangeContent", "didChangeObject" (moving the object in question), and "didChangeContent" were all called properly. Based on the Apple's NSFetchedResultsControllerDelegate documentation "didChangeSection" should have been called before "didChangeObject", which would have prevented the exception causing the crash. So I guess the question is how do I assure that didChangeSection gets called? Thanks in advance for any help!

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• how to user ajax with json in ruby on rails

  - by fenec

  I am implemeting a facebook application in rails using facebooker plugin, therefore it is very important to use this architecture if i want to update multiple DOM in my page. if my code works in a regular rails application it would work in my facebook application. i am trying to use ajax to let the user know that the comment was sent, and update the comments bloc. migration: class CreateComments < ActiveRecord::Migration def self.up create_table :comments do |t| t.string :body t.timestamps end end def self.down drop_table :comments end end controller: class CommentsController < ApplicationController def index @comments=Comment.all end def create @comment=Comment.create(params[:comment]) if request.xhr? @comments=Comment.all render :json=>{:ids_to_update=>[:all_comments,:form_message], :all_comments=>render_to_string(:partial=>"comments" ), :form_message=>"Your comment has been added." } else redirect_to comments_url end end end view: <script> function update_count(str,message_id) { len=str.length; if (len < 200) { $(message_id).innerHTML="<span style='color: green'>"+ (200-len)+" remaining</span>"; } else { $(message_id).innerHTML="<span style='color: red'>"+ "Comment too long. Only 200 characters allowed.</span>"; } } function update_multiple(json) { for( var i=0; i<json["ids_to_update"].length; i++ ) { id=json["ids_to_update"][i]; $(id).innerHTML=json[id]; } } </script> <div id="all_comments" > <%= render :partial=>"comments/comments" %> </div> Talk some trash: <br /> <% remote_form_for Comment.new, :url=>comments_url, :success=>"update_multiple(request)" do |f|%> <%= f.text_area :body, :onchange=>"update_count(this.getValue(),'remaining');" , :onkeyup=>"update_count(this.getValue(),'remaining');" %> <br /> <%= f.submit 'Post'%> <% end %> <p id="remaining" >&nbsp;</p> <p id="form_message" >&nbsp;</p> <br><br> <br> if i try to do alert(json) in the first line of the update_multiple function , i got an [object Object]. if i try to do alert(json["ids_to_update"][0]) in the first line of the update_multiple function , there is no dialog box displayed. however the comment got saved but nothing is updated. questions: 1.how can javascript and rails know that i am dealing with json objects? 2.how can i debug this problem? 3.how can i get it to work?

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• Agile: User Stories for Machine Learning Project?

  - by benjismith

  I've just finished up with a prototype implementation of a supervised learning algorithm, automatically assigning categorical tags to all the items in our company database (roughly 5 million items). The results look good, and I've been given the go-ahead to plan the production implementation project. I've done this kind of work before, so I know how the functional components of the software. I need a collection of web crawlers to fetch data. I need to extract features from the crawled documents. Those documents need to be segregated into a "training set" and a "classification set", and feature-vectors need to be extracted from each document. Those feature vectors are self-organized into clusters, and the clusters are passed through a series of rebalancing operations. Etc etc etc etc. So I put together a plan, with about 30 unique development/deployment tasks, each with time estimates. The first stage of development -- ignoring some advanced features that we'd like to have in the long-term, but aren't high enough priority to make it into the development schedule yet -- is slated for about two months worth of work. (Keep in mind that I already have a working prototype, so the final implementation is significantly simpler than if the project was starting from scratch.) My manager said the plan looked good to him, but he asked if I could reorganize the tasks into user stories, for a few reasons: (1) our project management software is totally organized around user stories; (2) all of our scheduling is based on fitting entire user stories into sprints, rather than individually scheduling tasks; (3) other teams -- like the web developers -- have made great use of agile methodologies, and they've benefited from modelling all the software features as user stories. So I created a user story at the top level of the project: As a user of the system, I want to search for items by category, so that I can easily find the most relevant items within a huge, complex database. Or maybe a better top-level story for this feature would be: As a content editor, I want to automatically create categorical designations for the items in our database, so that customers can easily find high-value data within our huge, complex database. But that's not the real problem. The tricky part, for me, is figuring out how to create subordinate user stories for the rest of the machine learning architecture. Case in point... I know that the algorithm requires two major architectural subdivisions: (A) training, and (B) classification. And I know that the training portion of the architecture requires construction of a cluster-space. All the Agile Development literature I've read seems to indicate that a user story should be the "smallest possible implementation that provides any business value". And that makes a lot of sense when designing a piece of end-user software. Start small, and then incrementally add value when users demand additional functionality. But a cluster-space, in and of itself, provides zero business value. Nor does a crawler, or a feature-extractor. There's no business value (not for the end-user, or for any of the roles internal to the company) in a partial system. A trained cluster-space is only possible with the crawler and feature extractor, and only relevant if we also develop an accompanying classifier. I suppose it would be possible to create user stories where the subordinate components of the system act as the users in the stories: As a supervised-learning cluster-space construction routine, I want to consume data from a feature extractor, so that I can exist. But that seems really weird. What benefit does it provide me as the developer (or our users, or any other stakeholders, for that matter) to model my user stories like that? Although the main story can be easily divided along architectural-component boundaries (crawler, trainer, classifier, etc), I can't think of any useful decomposition from a user's perspective. What do you guys think? How do you plan Agile user stories for sophisticated, indivisible, non-user-facing components?

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• Learning to implement DIC in MVC

  - by Tom

  I am learning to apply DIC to MVC project. So, I have sketched this DDD-ish DIC-ready-ish layout to my best understanding. I have read many blogs articles wikis for the last few days. However, I am not confident about implementing it correctly. Could you please demonstrate to me how to put them into DIC the proper way? I prefer Ninject or Windsor after all the readings, but anyDIC will do as long as I can get the correct idea how to do it. Web controller... public class AccountBriefingController { //create private IAccountServices accountServices { get; set; } public AccountBriefingController(IAccountServices accsrv) accountServices = accsrv; } //do work public ActionResult AccountBriefing(string userid, int days) { //get days of transaction records for this user BriefingViewModel model = AccountServices.GetBriefing(userid, days); return View(model); } } View model ... public class BriefingViewModel { //from user repository public string UserId { get; set; } public string AccountNumber {get; set;} public string FirstName { get; set; } public string LastName { get; set; } //from account repository public string Credits { get; set; } public List<string> Transactions { get; set; } } Service layer ... public interface IAccountServices { BriefingViewModel GetBriefing(); } public class AccountServices { //create private IUserRepository userRepo {get; set;} private IAccountRepository accRepo {get; set;} public AccountServices(UserRepository ur, AccountRepository ar) { userRepo = ur; accRepo = ar; } //do work public BriefingViewModel GetBriefing(string userid, int days) { var model = new BriefingViewModel(); //<---is that okay to new a model here?? var user = userRepo.GetUser(userid); if(user != null) { model.UserId = userid; model.AccountNumber = user.AccountNumber; model.FirstName = user.FirstName; model.LastName = user.LastName; //account records model.Credits = accRepo.GetUserCredits(userid); model.Transactions = accRepo.GetUserTransactions(userid, days); } return model; } } Domain layer and data models... public interface IUserRepository { UserDataModel GetUser(userid); } public interface IAccountRepository { List<string> GetUserTransactions(userid, days); int GetUserCredits(userid); } // Entity Framework DBContext goes under here Please point out if my implementation is wrong, e.g.I can feel in AccountServices-GetBriefing - new BriefingViewModel() seems wrong to me, but I don't know how to fit the stud into DIC? Thank you very much for your help!

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• Trying to sentinel loop this program. [java]

  - by roger34

  Okay, I spent all this time making this for class but I have one thing that I can't quite get: I need this to sentinel loop continuously (exiting upon entering x) so that the System.out.println("What type of Employee? Enter 'o' for Office " + "Clerical, 'f' for Factory, or 's' for Saleperson. Enter 'x' to exit." ); line comes back up after they enter the first round of information. Also, I can't leave this up long on the (very) off chance a classmate might see this and steal the code. Full code following: import java.util.Scanner; public class Project1 { public static void main (String args[]){ Scanner inp = new Scanner( System.in ); double totalPay; System.out.println("What type of Employee? Enter 'o' for Office " + "Clerical, 'f' for Factory, or 's' for Saleperson. Enter 'x' to exit." ); String response= inp.nextLine(); while (!response.toLowerCase().equals("o")&&!response.toLowerCase().equals("f") &&!response.toLowerCase().equals("s")&&!response.toLowerCase().equals("x")){ System.out.print("\nInvalid selection,please enter your choice again:\n"); response=inp.nextLine(); } char choice = response.toLowerCase().charAt( 0 ); switch (choice){ case 'o': System.out.println("Enter your hourly rate:"); double officeRate=inp.nextDouble(); System.out.println("Enter the number of hours worked:"); double officeHours=inp.nextDouble(); totalPay = officeCalc(officeRate,officeHours); taxCalc(totalPay); break; case 'f': System.out.println("How many Widgets did you produce during the week?"); double widgets=inp.nextDouble(); totalPay=factoryCalc(widgets); taxCalc(totalPay); break; case 's': System.out.println("What were your total sales for the week?"); double totalSales=inp.nextDouble(); totalPay=salesCalc(totalSales); taxCalc(totalPay); break; } } public static double taxCalc(double totalPay){ double federal=totalPay*.22; double state =totalPay*.055; double netPay = totalPay - federal - state; federal =federal*Math.pow(10,2); federal =Math.round(federal); federal= federal/Math.pow(10,2); state =state*Math.pow(10,2); state =Math.round(state); state= state/Math.pow(10,2); totalPay =totalPay*Math.pow(10,2); totalPay =Math.round(totalPay); totalPay= totalPay/Math.pow(10,2); netPay =netPay*Math.pow(10,2); netPay =Math.round(netPay); netPay= netPay/Math.pow(10,2); System.out.printf("\nTotal Pay \t: %1$.2f.\n", totalPay); System.out.printf("State W/H \t: %1$.2f.\n", state); System.out.printf("Federal W/H : %1$.2f.\n", federal); System.out.printf("Net Pay \t: %1$.2f.\n", netPay); return totalPay; } public static double officeCalc(double officeRate,double officeHours){ double overtime=0; if (officeHours>=40) overtime = officeHours-40; else overtime = 0; if (officeHours >= 40) officeHours = 40; double otRate = officeRate * 1.5; double totalPay= (officeRate * officeHours) + (otRate*overtime); return totalPay; } public static double factoryCalc(double widgets){ double totalPay=widgets*.35 +300; return totalPay; } public static double salesCalc(double totalSales){ double totalPay = totalSales * .05 + 500; return totalPay; } }

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• Android onClickListener options and help on creating a non-static array adapter

  - by CoderInTraining

  I am trying to make an application that gets data dynamically and displays it in a listView. Here is my code that I have with static data. There are a couple of things I want to try and do and can't figure out how. MainActivity.java package text.example.project; import java.util.ArrayList; import java.util.Arrays; import java.util.Collections; import android.app.ListActivity; import android.os.Bundle; import android.view.View; import android.widget.AdapterView; import android.widget.AdapterView.OnItemClickListener; import android.widget.ArrayAdapter; import android.widget.ListView; import android.widget.TextView; import android.widget.Toast; public class MainActivity extends ListActivity { //declarations private boolean isItem; private ArrayAdapter<String> item1Adapter; private ArrayAdapter<String> item2Adapter; private ArrayAdapter<String> item3Adapter; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Collections.sort(ITEM1); Collections.sort(ITEM2); Collections.sort(ITEM3); item1Adapter = new ArrayAdapter<String>(this, R.layout.list_item, ITEM1); item2Adapter = new ArrayAdapter<String>(this, R.layout.list_item, ITEM2); item3Adapter = new ArrayAdapter<String>(this, R.layout.list_item, ITEM3); setListAdapter(item1Adapter); isItem = true; ListView lv = getListView(); lv.setTextFilterEnabled(true); lv.setOnItemClickListener(new OnItemClickListener() { @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { // When clicked, show a toast with the TextView text if (isItem) { //ITEM1.add("another\n\t" + Calendar.getInstance().getTime()); Collections.sort(ITEM1); item2Adapter.notifyDataSetChanged(); setListAdapter(item2Adapter); isItem = false; } else { item1Adapter.notifyDataSetChanged(); setListAdapter(item1Adapter); isItem = true; } Toast.makeText(getApplicationContext(), ((TextView) view).getText(), Toast.LENGTH_SHORT).show(); } }); } // need to turn dynamic static ArrayList<String> ITEM1 = new ArrayList<String> (Arrays.asList( "ITEM1-1", "ITEM1-2" )); static ArrayList<String> ITEM2 = new ArrayList<String> (Arrays.asList( "ITEM2-1", "ITEM2-2" )); static ArrayList<String> ITEM3 = new ArrayList<String> (Arrays.asList("ITEM3-1", "ITEM3-2")); } list_item.xml <?xml version="1.0" encoding="utf-8"?> <TextView xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:padding="10dp" android:textSize="16sp" > </TextView> What I want to do is first pull from a dynamic source. I need to do what is almost exactly like this tutorial... http://androiddevelopement.blogspot.in/2011/06/android-xml-parsing-tutorial-using.html ... however, I can't get the tutorial to work... I also would like to know how I can make the list item clicks so that if I click on "ITEM1-1" it goes to the menu "ITEM2-1" and "ITEM2-2". and if "ITEM1-2" is clicked, then it goes to the menu with "ITEM3-1" and "ITEM3-2"... I am totally a noob at this whole android development thing. So any suggestions would be great!

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• Servlet response wrapper has encoding problem

  - by John O

  A servlet response wrapper is being used in a Servlet Filter. The idea is that the response is manipulated, with a 'nonce' value being injected into forms, as part of defence against CSRF attacks. The web app is using UTF-8 everywhere. When the Servlet Filter is absent, no problems. When the filter is added, encoding issues occur. (It seems as if the response is reverting to 8859-1.) The guts of the code : final class CsrfResponseWrapper extends AbstractResponseWrapper { ... byte[] modifyResponse(byte[] aInputResponse){ ... String originalInput = new String(aInputResponse, encoding); String modifiedResult = addHiddenParamToPostedForms(originalInput); result = modifiedResult.getBytes(encoding); ... } ... } As I understand it, the transition between byte-land and String-land should specify an encoding. That is done here, as you can see, in two places. The value of the 'encoding' variable is 'UTF-8'; the alteration of the String itself is standard string manipulation (with a regex), and never specifies an encoding (addHiddenParamToPostedForms). Where am I in error about the encoding? EDIT: Here is the base class (sorry it's rather long): package hirondelle.web4j.security; import javax.servlet.ServletOutputStream; import javax.servlet.ServletResponse; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpServletResponseWrapper; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.PrintWriter; /** Abstract Base Class for altering response content. (May be useful in future contexts as well. For now, keep package-private.) */ abstract class AbstractResponseWrapper extends HttpServletResponseWrapper { AbstractResponseWrapper(ServletResponse aServletResponse) throws IOException { super((HttpServletResponse)aServletResponse); fOutputStream = new ModifiedOutputStream(aServletResponse.getOutputStream()); fWriter = new PrintWriter(fOutputStream); } /** Return the modified response. */ abstract byte[] modifyResponse(byte[] aInputResponse); /** Standard servlet method. */ public final ServletOutputStream getOutputStream() { //fLogger.fine("Modified Response : Getting output stream."); if ( fWriterReturned ) { throw new IllegalStateException(); } fOutputStreamReturned = true; return fOutputStream; } /** Standard servlet method. */ public final PrintWriter getWriter() { //fLogger.fine("Modified Response : Getting writer."); if ( fOutputStreamReturned ) { throw new IllegalStateException(); } fWriterReturned = true; return fWriter; } // PRIVATE /* Well-behaved servlets return either an OutputStream or a PrintWriter, but not both. */ private PrintWriter fWriter; private ModifiedOutputStream fOutputStream; /* These items are used to implement conformance to the javadoc for ServletResponse, regarding exceptions being thrown. */ private boolean fWriterReturned; private boolean fOutputStreamReturned; /** Modified low level output stream. */ private class ModifiedOutputStream extends ServletOutputStream { public ModifiedOutputStream(ServletOutputStream aOutputStream) { fServletOutputStream = aOutputStream; fBuffer = new ByteArrayOutputStream(); } /** Must be implemented to make this class concrete. */ public void write(int aByte) { fBuffer.write(aByte); } public void close() throws IOException { if ( !fIsClosed ){ processStream(); fServletOutputStream.close(); fIsClosed = true; } } public void flush() throws IOException { if ( fBuffer.size() != 0 ){ if ( !fIsClosed ) { processStream(); fBuffer = new ByteArrayOutputStream(); } } } /** Perform the core processing, by calling the abstract method. */ public void processStream() throws IOException { fServletOutputStream.write(modifyResponse(fBuffer.toByteArray())); fServletOutputStream.flush(); } // PRIVATE // private ServletOutputStream fServletOutputStream; private ByteArrayOutputStream fBuffer; /** Tracks if this stream has been closed. */ private boolean fIsClosed = false; } }

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• How to select table column names in a view and pass to controller in rails?

  - by zachd1_618

  So I am new to Rails, and OO programming in general. I have some grasp of the MVC architecture. My goal is to make a (nearly) completely dynamic plug-and-play plotting web server. I am fairly confused with params, forms, and select helpers. What I want to do is use Rails drop downs to basically pass parameters as strings to my controller, which will use the params to select certain column data from my database and plot it dynamically. I have the latter part of the task working, but I can't seem to pass values from my view to controller. For simplicity's sake, say my database schema looks like this: --------------Plot--------------- |____x____|____y1____|____y2____| | 1 | 1 | 1 | | 2 | 2 | 4 | | 3 | 3 | 9 | | 4 | 4 | 16 | | 5 | 5 | 25 | ... and in my Model, I have dynamic selector scopes that will let me select just certain columns of data: in Plot.rb class Plot < ActiveRecord::Base scope :select_var, lambda {|varname| select(varname)} scope :between_x, lambda {|x1,x2| where("x BETWEEN ? and ?","#{x1}","#{x2}")} So this way, I can call: irb>>@p1 = Plot.select_var(['x','y1']).between_x(1,3) and get in return a class where @p1.x and @p1.y1 are my only attributes, only for values between x=1 to x=4, which I dynamically plot. I want to start off in a view (plot/index), where I can dynamically select which variable names (table column names), and which rows from the database to fetch and plot. The problem is, most select helpers don't seem to work with columns in the database, only rows. So to select columns, I first get an array of column names that exist in my database with a function I wrote. Plots Controller def index d=Plot.first @tags = d.list_vars end So @tags = ['x','y1','y2'] Then in my plot/index.html.erb I try to use a drop down to select wich variables I send back to the controller. index.html.erb <%= select_tag( :variable, options_for_select(@plots.first.list_vars,:name,:multiple=>:true) )%> <%= button_to 'Plot now!', :controller =>"plots/plot_vars", :variable => params[:variable]%> Finally, in the controller again Plots controller ... def plot_vars @plot_data=Plot.select_vars([params[:variable]]) end The problem is everytime I try this (or one of a hundred variations thereof), the params[:variable] is nill. How can I use a drop down to pass a parameter with string variable names to the controller? Sorry its so long, I have been struggling with this for about a month now. :-( I think my biggest problem is that this setup doesn't really match the Rails architecture. I don't have "users" and "articles" as individual entities. I really have a data structure, not a data object. Trying to work with the structure in terms of data object speak is not necessarily the easiest thing to do I think. For background: My actual database has about 250 columns and a couple million rows, and they get changed and modified from time to time. I know I can make the database smarter, but its not worth it on my end. I work at a scientific institute where there are a ton of projects with databases just like this. Each one has a web developer that spends months setting up a web interface and their own janky plotting setups. I want to make this completely dynamic, as a plug-and-play solution so all you have to do is specify your database connection, and this rails setup will automatically show and plot which data you want in it. I am more of a sequential programmer and number cruncher, as are many people here. I think this project could be very helpful in the end, but its difficult to figure out for me right now.

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• Calculate the number of ways to roll a certain number

  - by helloworld

  I'm a high school Computer Science student, and today I was given a problem to: Program Description: There is a belief among dice players that in throwing three dice a ten is easier to get than a nine. Can you write a program that proves or disproves this belief? Have the computer compute all the possible ways three dice can be thrown: 1 + 1 + 1, 1 + 1 + 2, 1 + 1 + 3, etc. Add up each of these possibilities and see how many give nine as the result and how many give ten. If more give ten, then the belief is proven. I quickly worked out a brute force solution, as such int sum,tens,nines; tens=nines=0; for(int i=1;i<=6;i++){ for(int j=1;j<=6;j++){ for(int k=1;k<=6;k++){ sum=i+j+k; //Ternary operators are fun! tens+=((sum==10)?1:0); nines+=((sum==9)?1:0); } } } System.out.println("There are "+tens+" ways to roll a 10"); System.out.println("There are "+nines+" ways to roll a 9"); Which works just fine, and a brute force solution is what the teacher wanted us to do. However, it doesn't scale, and I am trying to find a way to make an algorithm that can calculate the number of ways to roll n dice to get a specific number. Therefore, I started generating the number of ways to get each sum with n dice. With 1 die, there is obviously 1 solution for each. I then calculated, through brute force, the combinations with 2 and 3 dice. These are for two: There are 1 ways to roll a 2 There are 2 ways to roll a 3 There are 3 ways to roll a 4 There are 4 ways to roll a 5 There are 5 ways to roll a 6 There are 6 ways to roll a 7 There are 5 ways to roll a 8 There are 4 ways to roll a 9 There are 3 ways to roll a 10 There are 2 ways to roll a 11 There are 1 ways to roll a 12 Which looks straightforward enough; it can be calculated with a simple linear absolute value function. But then things start getting trickier. With 3: There are 1 ways to roll a 3 There are 3 ways to roll a 4 There are 6 ways to roll a 5 There are 10 ways to roll a 6 There are 15 ways to roll a 7 There are 21 ways to roll a 8 There are 25 ways to roll a 9 There are 27 ways to roll a 10 There are 27 ways to roll a 11 There are 25 ways to roll a 12 There are 21 ways to roll a 13 There are 15 ways to roll a 14 There are 10 ways to roll a 15 There are 6 ways to roll a 16 There are 3 ways to roll a 17 There are 1 ways to roll a 18 So I look at that, and I think: Cool, Triangular numbers! However, then I notice those pesky 25s and 27s. So it's obviously not triangular numbers, but still some polynomial expansion, since it's symmetric. So I take to Google, and I come across this page that goes into some detail about how to do this with math. It is fairly easy(albeit long) to find this using repeated derivatives or expansion, but it would be much harder to program that for me. I didn't quite understand the second and third answers, since I have never encountered that notation or those concepts in my math studies before. Could someone please explain how I could write a program to do this, or explain the solutions given on that page, for my own understanding of combinatorics? EDIT: I'm looking for a mathematical way to solve this, that gives an exact theoretical number, not by simulating dice

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• File Segmentation when trying to write in a file

  - by user1286390

  I am trying in C language to use the method of bisection to find the roots of some equation, however when I try to write every step of this process in a file I get the problem "Segmentation fault". This might be an idiot fault that I did, however I have been trying to solve this for a long time. I am compiling using gcc and that is the code: #include <stdio.h> #include <stdlib.h> #include <math.h> #define R 1.0 #define h 1.0 double function(double a); void attractor(double *a1, double *a2, double *epsilon); void attractor(double *a1, double *a2, double *epsilon) { FILE* bisection; double a2_copia, a3, fa1, fa2; bisection = fopen("bisection-part1.txt", "w"); fa1 = function(*a1); fa2 = function(*a2); if(function(*a1) - function(*a2) > 0.0) *epsilon = function(*a1) - function(*a2); else *epsilon = function(*a2) - function(*a1); fprintf(bisection, "a1 a2 fa1 fa2 epsilon\n"); a2_copia = 0.0; if(function(*a1) * function(*a2) < 0.0 && *epsilon >= 0.00001) { a3 = *a2 - (*a2 - *a1); a2_copia = *a2; *a2 = a3; if(function(*a1) - function(*a2) > 0.0) *epsilon = function(*a1) - function(*a2); else *epsilon = function(*a2) - function(*a1); if(function(*a1) * function(*a2) < 0.0 && *epsilon >= 0.00001) { fprintf(bisection, "%.4f %.4f %.4f %.4f %.4f\n", *a1, *a2, function(*a1), function(*a1), *epsilon); attractor(a1, a2, epsilon); } else { *a2 = a2_copia; *a1 = a3; if(function(*a1) - function(*a2) > 0) *epsilon = function(*a1) - function(*a2); else *epsilon = function(*a2) - function(*a1); if(function(*a1) * function(*a2) < 0.0 && *epsilon >= 0.00001) { fprintf(bisection, "%.4f %.4f %.4f %.4f %.4f\n", *a1, *a2, function(*a1), function(*a1), *epsilon); attractor(a1, a2, epsilon); } } } fa1 = function(*a1); fa2 = function(*a2); if(function(*a1) - function(*a2) > 0.0) *epsilon = function(*a1) - function(*a2); else *epsilon = function(*a2) - function(*a1); fprintf(bisection, "%.4f %.4f %.4f %.4f %.4f\n", a1, a2, fa1, fa2, epsilon); } double function(double a) { double fa; fa = (a * cosh(h / (2 * a))) - R; return fa; } int main() { double a1, a2, fa1, fa2, epsilon; a1 = 0.1; a2 = 0.5; fa1 = function(a1); fa2 = function(a2); if(fa1 - fa2 > 0.0) epsilon = fa1 - fa2; else epsilon = fa2 - fa1; if(epsilon >= 0.00001) { fa1 = function(a1); fa2 = function(a2); attractor(&a1, &a2, &epsilon); fa1 = function(a1); fa2 = function(a2); if(fa1 - fa2 > 0.0) epsilon = fa1 - fa2; else epsilon = fa2 - fa1; } if(epsilon < 0.0001) printf("Vanish at %f", a2); else printf("ERROR"); return 0; } Thanks anyway and sorry if this question is not suitable.

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• What is the best practice when coding math class/functions ?

  - by Isaac Clarke

  Introductory note : I voluntarily chose a wide subject. You know that quote about learning a cat to fish, that's it. I don't need an answer to my question, I need an explanation and advice. I know you guys are good at this ;) Hi guys, I'm currently implementing some algorithms into an existing program. Long story short, I created a new class, "Adder". An Adder is a member of another class representing the physical object actually doing the calculus , which calls adder.calc() with its parameters (merely a list of objects to do the maths on). To do these maths, I need some parameters, which do not exist outside of the class (but can be set, see below). They're neither config parameters nor members of other classes. These parameters are D1 and D2, distances, and three arrays of fixed size : alpha, beta, delta. I know some of you are more comfortable reading code than reading text so here you go : class Adder { public: Adder(); virtual Adder::~Adder(); void set( float d1, float d2 ); void set( float d1, float d2, int alpha[N_MAX], int beta[N_MAX], int delta[N_MAX] ); // Snipped prototypes float calc( List& ... ); // ... inline float get_d1() { return d1_ ;}; inline float get_d2() { return d2_ ;}; private: float d1_; float d2_; int alpha_[N_MAX]; // A #define N_MAX is done elsewhere int beta_[N_MAX]; int delta_[N_MAX]; }; Since this object is used as a member of another class, it is declared in a *.h : private: Adder adder_; By doing that, I couldn't initialize the arrays (alpha/beta/delta) directly in the constructor ( int T[3] = { 1, 2, 3 }; ), without having to iterate throughout the three arrays. I thought of putting them in static const, but I don't think that's the proper way of solving such problems. My second guess was to use the constructor to initialize the arrays Adder::Adder() { int alpha[N_MAX] = { 0, -60, -120, 180, 120, 60 }; int beta[N_MAX] = { 0, 0, 0, 0, 0, 0 }; int delta[N_MAX] = { 0, 0, 180, 180, 180, 0 }; set( 2.5, 0, alpha, beta, delta ); } void Adder::set( float d1, float d2 ) { if (d1 > 0) d1_ = d1; if (d2 > 0) d2_ = d2; } void Adder::set( float d1, float d2, int alpha[N_MAX], int beta[N_MAX], int delta[N_MAX] ) { set( d1, d2 ); for (int i = 0; i < N_MAX; ++i) { alpha_[i] = alpha[i]; beta_[i] = beta[i]; delta_[i] = delta[i]; } } My question is : Would it be better to use another function - init() - which would initialize arrays ? Or is there a better way of doing that ? My bonus question is : Did you see some mistakes or bad practice along the way ?

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• destructor and copy-constructor calling..(why does it get called at these times)

  - by sil3nt

  Hello there, I have the following code #include <iostream> using namespace std; class Object { public: Object(int id){ cout << "Construct(" << id << ")" << endl; m_id = id; } Object(const Object& obj){ cout << "Copy-construct(" << obj.m_id << ")" << endl; m_id = obj.m_id; } Object& operator=(const Object& obj){ cout << m_id << " = " << obj.m_id << endl; m_id = obj.m_id; return *this; } ~Object(){ cout << "Destruct(" << m_id << ")" << endl; } private: int m_id; }; Object func(Object var) { return var; } int main(){ Object v1(1); cout << "( a )" << endl; Object v2(2); v2 = v1; cout << "( b )" << endl; Object v4 = v1; Object *pv5; pv5 = &v1; pv5 = new Object(5); cout << "( c )" << endl; func(v1); cout << "( d )" << endl; delete pv5; } which outputs Construct(1) ( a ) Construct(2) 2 = 1 ( b ) Copy-construct(1) Construct(5) ( c ) Copy-construct(1) Copy-construct(1) Destruct(1) Destruct(1) ( d ) Destruct(5) Destruct(1) Destruct(1) Destruct(1) I have some issues with this, firstly why does Object v4 = v1; call the copy constructor and produce Copy-construct(1) after the printing of ( b ). Also after the printing of ( c ) the copy-constructor is again called twice?, Im not certain of how this function works to produce that Object func(Object var) { return var; } and just after that Destruct(1) gets called twice before ( d ) is printed. sorry for the long question, I'm confused with the above.

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• connection between two android phones

  - by user1770346

  I m not able to connect my android device to other device(either android or non-android)via bluetooth.After detecting the devices from my android phone,i m not able to connect it to selected device from the list.The main problem is it not showing connectivity conformation message in selected device from list.How can i recover from this problem. please help me.Thanks My code for searching device is:(BluetoothSearchActivity.java) public class BluetoothSearchActivity extends Activity { ArrayAdapter<String> btArrayAdapter; BluetoothAdapter mBluetoothAdapter; TextView stateBluetooth; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ImageView BluetoothSearchImageView=new ImageView(this); BluetoothSearchImageView.setImageResource(R.drawable.inner1); setContentView(BluetoothSearchImageView); setContentView(R.layout.activity_bluetooth_search); mBluetoothAdapter=BluetoothAdapter.getDefaultAdapter(); ListView listDevicesFound=(ListView) findViewById(R.id.myList); btArrayAdapter=new ArrayAdapter<String> (BluetoothSearchActivity.this,android.R.layout.simple_list_item_1); listDevicesFound.setAdapter(btArrayAdapter); registerReceiver(ActionFoundReceiver,new IntentFilter(BluetoothDevice.ACTION_FOUND)); btArrayAdapter.clear(); mBluetoothAdapter.startDiscovery(); listDevicesFound.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> parent,View view,int position,long id) { Intent i6=new Intent(getApplicationContext(),AcceptThread.class); startActivity(i6); } }); } private final BroadcastReceiver ActionFoundReceiver=new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { // TODO Auto-generated method stub String action=intent.getAction(); if(BluetoothDevice.ACTION_FOUND.equals(action)) { BluetoothDevice device=intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE); btArrayAdapter.add(device.getName()+"\n"+device.getAddress()); btArrayAdapter.notifyDataSetChanged(); Log.d("BluetoothSearchActivity",device.getName()+"\n"+device.getAddress()); } } }; @Override protected void onDestroy() { super.onDestroy(); unregisterReceiver(ActionFoundReceiver); } @Override public boolean onCreateOptionsMenu(Menu menu) { getMenuInflater().inflate(R.menu.activity_bluetooth_search, menu); return true; } } and my connectivity code is:(AcceptThread.java) class ConnectThread extends Thread { private static final UUID MY_UUID=UUID.fromString("fa87c0d0-afac-11de-8a39-0800200c9a66"); private static final String ConnectThread = null; BluetoothSocket mSocket; BluetoothDevice mDevice; BluetoothAdapter mBluetoothAdapter; public ConnectThread(BluetoothDevice device) { BluetoothSocket temp=null; mDevice=device; try{ temp=mDevice.createRfcommSocketToServiceRecord(MY_UUID); }catch(IOException e) { } mSocket=temp; } public void run() { mBluetoothAdapter.cancelDiscovery(); try{ Log.i(ConnectThread,"starting to connect"); mSocket.connect(); }catch(IOException connectException) { Log.e(ConnectThread,"connection Failed"); try{ mSocket.close(); }catch(IOException closeException){ } return; } } public void cancel() { try{ mSocket.close(); }catch(IOException e) { } } } public class AcceptThread extends Thread{ private static final String NAME="BluetoothAcceptThread"; private static final UUID MY_UUID=UUID.fromString("fa87c0d0-afac-11de-8a39-0800200c9a66"); BluetoothServerSocket mServerSocket; BluetoothAdapter mBluetoothAdapter; public AcceptThread() { BluetoothServerSocket temp=null; try{ temp=mBluetoothAdapter.listenUsingRfcommWithServiceRecord(NAME,MY_UUID); }catch(IOException e){ } mServerSocket=temp; } public void run() { BluetoothSocket socket=null; while(true) { try{ socket=mServerSocket.accept(); }catch(IOException e) { break; } if(socket!=null) { try { mServerSocket.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } break; } } } public void cancel() { try{ mServerSocket.close(); }catch(IOException e) { } } }

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• Reordering Variadic Parameters

  - by void-pointer

  I have come across the need to reorder a variadic list of parameters that is supplied to the constructor of a struct. After being reordered based on their types, the parameters will be stored as a tuple. My question is how this can be done so that a modern C++ compiler (e.g. g++-4.7) will not generate unnecessary load or store instructions. That is, when the constructor is invoked with a list of parameters of variable size, it efficiently pushes each parameter into place based on an ordering over the parameters' types. Here is a concrete example. Assume that the base type of every parameter (without references, rvalue references, pointers, or qualifiers) is either char, int, or float. How can I make it so that all the parameters of base type char appear first, followed by all of those of base type int (which leaves the parameters of base type float last). The relative order in which the parameters were given should not be violated within sublists of homogeneous base type. Example: foo::foo() is called with arguments float a, char&& b, const float& c, int&& d, char e. The tuple tupe is std::tuple<char, char, int, float, float>, and it is constructed like so: tuple_type{std::move(b), e, std::move(d), a, c}. Consider the struct defined below, and assume that the metafunction deduce_reordered_tuple_type is already implemented. How would you write the constructor so that it works as intended? If you think that the code for deduce_reodered_tuple_type, would be useful to you, I can provide it; it's a little long. template <class... Args> struct foo { // Assume that the metafunction deduce_reordered_tuple_type is defined. typedef typename deduce_reordered_tuple_type<Args...>::type tuple_type; tuple_type t_; foo(Args&&... args) : t_{reorder_and_forward_parameters<Args>(args)...} {} }; Edit 1 The technique I describe above does have applications in mathematical frameworks that make heavy use of expression templates, variadic templates, and metaprogramming in order to perform aggressive inlining. Suppose that you wish to define an operator that takes the product of several expressions, each of which may be passed by reference, reference to const, or rvalue reference. (In my case, the expressions are conditional probability tables and the operation is the factor product, but something like matrix multiplication works suitably as well.) You need access to the data provided by each expression in order to evaluate the product. Consequently, you must move the expressions passed as rvalue references, copy the expressions passed by reference to const, and take the addresses of expressions passed by reference. Using the technique I describe above now poses several benefits. Other expressions can use uniform syntax to access data elements from this expression, since all of the heavy-lifting metaprogramming work is done beforehand, within the class. We can save stack space by grouping the pointers together and storing the larger expressions towards the end of the tuple. Implementing certain types of queries becomes much easier (e.g. check whether any of the pointers stored in the tuple aliases a given pointer). Thank you very much for your help!

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