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• How to sort a list so that managers are always ahead of their subordinates (How do I do a topologica

  - by James Black

  I am working on a project using Groovy, and I would like to take an array of employees, so that no manager follows their subordinates in the array. The reason being that I need to add people to a database and I would prefer not to do it in two passes. So, I basically have: <employees> <employee> <employeeid>12</employeeid> <manager>3</manager> </employee> <employee> <employeeid>1</employeeid> <manager></manager> </employee> <employee> <employeeid>3</employeeid> <manager>1</manager> </employee> </employees> So, it should be sorted as such: employeeid = 1 employeeid = 3 employeeid = 12 The first person should have a null for managers. I am thinking about a binary tree representation, but I expect it will be very unbalanced, and I am not certain the best way to do this using Groovy properly. Is there a way to do this that isn't going to involve using nested loops?

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• Getting unhandled error and connection get lost when a client tries to communicate with chat server in twisted

  - by user2433888

  from twisted.internet.protocol import Protocol,Factory from twisted.internet import reactor class ChatServer(Protocol): def connectionMade(self): print "A Client Has Connected" self.factory.clients.append(self) print"clients are ",self.factory.clients self.transport.write('Hello,Welcome to the telnet chat to sign in type aim:YOUR NAME HERE to send a messsage type msg:YOURMESSAGE '+'\n') def connectionLost(self,reason): self.factory.clients.remove(self) self.transport.write('Somebody was disconnected from the server') def dataReceived(self,data): #print "data is",data a = data.split(':') if len(a) > 1: command = a[0] content = a[1] msg="" if command =="iam": self.name + "has joined" elif command == "msg": ma=sg = self.name + ":" +content print msg for c in self.factory.clients: c.message(msg) def message(self,message): self.transport.write(message + '\n') factory = Factory() factory.protocol = ChatServer factory.clients = [] reactor.listenTCP(80,factory) print "Iphone Chat server started" reactor.run() The above code is running succesfully...but when i connect the client (by typing telnet localhost 80) to this chatserver and try to write message ,connection gets lost and following errors occurs : Iphone Chat server started A Client Has Connected clients are [<__main__.ChatServer instance at 0x024AC0A8>] Unhandled Error Traceback (most recent call last): File "C:\Python27\lib\site-packages\twisted\python\log.py", line 84, in callWithLogger return callWithContext({"system": lp}, func, *args, **kw) File "C:\Python27\lib\site-packages\twisted\python\log.py", line 69, in callWithContext return context.call({ILogContext: newCtx}, func, *args, **kw) File "C:\Python27\lib\site-packages\twisted\python\context.py", line 118, in callWithContext return self.currentContext().callWithContext(ctx, func, *args, **kw) File "C:\Python27\lib\site-packages\twisted\python\context.py", line 81, in callWithContext return func(*args,**kw) --- --- File "C:\Python27\lib\site-packages\twisted\internet\selectreactor.py", line 150, in _doReadOrWrite why = getattr(selectable, method)() File "C:\Python27\lib\site-packages\twisted\internet\tcp.py", line 199, in doRead rval = self.protocol.dataReceived(data) File "D:\chatserverultimate.py", line 21, in dataReceived content = a[1] exceptions.IndexError: list index out of range Where am I going wrong?

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• MS Access (Jet) transactions, workspaces & scope

  - by Eric G

  I am having trouble with committing a transaction (using Access 2003 DAO). It's acting as if I never had called BeginTrans -- I get error 3034 on CommitTrans, "You tried to commit or rollback a transaction without first beginning a transaction"; and the changes are written to the database (presumably because they were never wrapped in a transaction). However, BeginTrans is run, if you step through it. I am running it within the Access environment using the DBEngine(0) workspace. The tables I'm updating are all opened via a Jet database connection (to the same database) and updated using DAO.Recordset.update. The connection is opened before starting BeforeTrans. I'm not doing anything weird in the middle of the transaction like closing/opening connections or multiple workspaces etc. There is one nested transaction level (basically it's wrapping multiple transacted updates in an outer transaction, so if any fail they all fail). The inner transactions run without errors, it's the outer transaction that doesn't work. Here are a few things I've looked into and ruled out: The transaction is spread across several methods and BeginTrans and CommitTrans (and Rollback) are all in different places. But when I tried a simple test of running a transaction this way, it doesn't seem like this should matter. I thought maybe the database connection gets closed when it goes out of local scope, even though I have another 'global' reference to it (I'm never sure what DAO does with dbase connections to be honest). But this seems not to be the case -- right before the commit, the connection and its recordsets are alive (I can check their properties, EOF = False, etc.) My CommitTrans and Rollback are done within event callbacks. (Very basically, a parser program is throwing an 'onLoad' or 'onLoadFail' event at the end of parsing, which I am handling by either committing or rolling back the inserts I made during processing.) However, again, trying a simple test, it doesn't seem like this should matter. Any ideas why this isn't working for me? Thanks.

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• Rails can't find my route but it exists!

  - by DJTripleThreat

  Ok I have events that I want to publish/unpublish with an extra action (nonRESTful) I watched Ryan Bates' railscast on this: http://railscasts.com/episodes/35-custom-rest-actions and it got me most of the way. I think the problem is that my route is nested in an /admin section so even though when I run rake routes and get: publish_admin_event PUT /admin/events/:id/publish(.:format) {:controller=>"event_services", :action=>"publish"} This won't work in my /views/admin/index.html.erb file: <%= link_to 'Publish', publish_admin_event(event), :method => :put %> because it claims that path doesn't exist! And neither will this: <%= link_to 'Publish', {:controller => :event_services, :action => :publish}, {:method => :put, :id => event} %> and says that "No route matches {:controller=>"event_services", :action=>"publish"}" so what gives? (And I've tried restarting my server so that isn't it.) EDIT: This DOES work: <%= link_to 'Publish', "/admin/events/" + event.id.to_s + "/publish", :method => :put %> But I'd rather NOT do this.

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• Very strange Application.ThreadException behaviour.

  - by Brann

  I'm using the Application.ThreadException event to handle and log unexpected exceptions in my winforms application. Now, somewhere in my application, I've got the following code (or rather something equivalent, but this dummy code is enough to reproduce my issue) : try { throw new NullReferenceException("test"); } catch (Exception ex) { throw new Exception("test2", ex); } I'm clearly expecting my Application_ThreadException handler to be passed the "test2" exception, but this is not always the case. Typically, if another thread marshals my code to the UI, my handler receives the "test" exception, exactly as if I hadn't caught "test" at all. Here is a short sample reproducing this behavior. I have omitted the designer's code. static class Program { [STAThread] static void Main() { Application.ThreadException += new System.Threading.ThreadExceptionEventHandler(Application_ThreadException); Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); Application.Run(new Form1()); } static void Application_ThreadException(object sender, System.Threading.ThreadExceptionEventArgs e) { Console.WriteLine(e.Exception.Message); } } public partial class Form1 : Form { public Form1() { InitializeComponent(); button1.Click+=new EventHandler(button1_Click); System.Threading.Thread t = new System.Threading.Thread(new System.Threading.ThreadStart(ThrowEx)); t.Start(); } private void button1_Click(object sender, EventArgs e) { try { throw new NullReferenceException("test"); } catch (Exception ex) { throw new Exception("test2", ex); } } void ThrowEx() { this.BeginInvoke(new EventHandler(button1_Click)); } } The output of this program on my computer is : test ... here I click button1 test2 I've reproduced this on .net 2.0,3.5 and 4.0. Does someone have a logical explanation ?

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• Best way to catch a WCF exception in Silverlight?

  - by wahrhaft

  I have a Silverlight 2 application that is consuming a WCF service. As such, it uses asynchronous callbacks for all the calls to the methods of the service. If the service is not running, or it crashes, or the network goes down, etc before or during one of these calls, an exception is generated as you would expect. The problem is, I don't know how to catch this exception. Because it is an asynchronous call, I can't wrap my begin call with a try/catch block and have it pick up an exception that happens after the program has moved on from that point. Because the service proxy is automatically generated, I can't put a try/catch block on each and every generated function that calls EndInvoke (where the exception actually shows up). These generated functions are also surrounded by External Code in the call stack, so there's nowhere else in the stack to put a try/catch either. I can't put the try/catch in my callback functions, because the exception occurs before they would get called. There is an Application_UnhandledException function in my App.xaml.cs, which captures all unhandled exceptions. I could use this, but it seems like a messy way to do it. I'd rather reserve this function for the truly unexpected errors (aka bugs) and not end up with code in this function for every circumstance I'd like to deal with in a specific way. Am I missing an obvious solution? Or am I stuck using Application_UnhandledException? [Edit] As mentioned below, the Error property is exactly what I was looking for. What is throwing me for a loop is that the fact that the exception is thrown and appears to be uncaught, yet execution is able to continue. It triggers the Application_UnhandledException event and causes VS2008 to break execution, but continuing in the debugger allows execution to continue. It's not really a problem, it just seems odd.

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• Logging to a file on Android

  - by Greg B

  Is there any way of retrieving log messages from an Android handset. I'm building an application which uses the GPS of my HTC Hero. I can run and debug the application from eclipse but this isn't a good use case of GPS, sat at my desk. When I fire the app up when I am walking around, I get an intermittent exception. Is there anyway I can output these exceptions to a text file on the SD card or output calls to Log.x("") to a text file so that I can see what the exception is. Thanks EDIT : Solution Here is the code I finally went with... Thread.currentThread().setUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() { @Override public void uncaughtException(Thread thread, Throwable ex) { PrintWriter pw; try { pw = new PrintWriter( new FileWriter(Environment.getExternalStorageDirectory()+"/rt.log", true)); ex.printStackTrace(pw); pw.flush(); pw.close(); } catch (IOException e) { e.printStackTrace(); } } }); I had to wrap the line pw = new PrintWriter(new FileWriter(Environment.getExternalStorageDirectory()+"/rt.log", true)); in a try/catch as Eclipse would not let me compile the app. It kept saying Unhandled exception type IOException 1 quick fix Sorround with try/catch So I did and it all works which is fine by me but it does make me wonder what Eclipse was on about...

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• Visitor Pattern can be replaced with Callback functions?

  - by getit

  Is there any significant benefit to using either technique? In case there are variations, the Visitor Pattern I mean is this: http://en.wikipedia.org/wiki/Visitor_pattern And below is an example of using a delegate to achieve the same effect (at least I think it is the same) Say there is a collection of nested elements: Schools contain Departments which contain Students Instead of using the Visitor pattern to perform something on each collection item, why not use a simple callback (Action delegate in C#) Say something like this class Department { List Students; } class School { List Departments; VisitStudents(Action<Student> actionDelegate) { foreach(var dep in this.Departments) { foreach(var stu in dep.Students) { actionDelegate(stu); } } } } School A = new School(); ...//populate collections A.Visit((student)=> { ...Do Something with student... }); *EDIT Example with delegate accepting multiple params Say I wanted to pass both the student and department, I could modify the Action definition like so: Action class School { List Departments; VisitStudents(Action<Student, Department> actionDelegate, Action<Department> d2) { foreach(var dep in this.Departments) { d2(dep); //This performs a different process. //Using Visitor pattern would avoid having to keep adding new delegates. //This looks like the main benefit so far foreach(var stu in dep.Students) { actionDelegate(stu, dep); } } } }

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• How can I recurse up a DOM tree?

  - by smartdirt

  So I have a series of nested ul elements as part of a tree like below: <ul> <li> <ul> <li>1.1</li> <li>1.2</li> </ul> <ul> <li>2.1</li> <li> <ul> <li>2.2</li> </ul> </li> </ul> <ul> <li>3.1</li> <li>3.2</li> </ul> </li> </ul> Let's say when 3.1 is the selected node and when the user clicks previous the selected node should then be 2.2. The bad news is that there could be any number of levels deep. How can I find the previous node (li) in relationship to the currently selected node using jquery?

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• Why does C# not provide the C++ style 'friend' keyword?

  - by Ash

  The C++ friend keyword allows a class A to designate class B as it's friend. This allows Class B to access the private/protected members of class A. I've never read anything as to why this was left out of C# (and VB.NET). Most answers to this earlier StackOverflow question seem to be saying it is a useful part of C++ and there are good reasons to use it. In my experience I'd have to agree. Another question seems to me to be really asking how to do something similar to friend in a C# application. While the answers generally revolve around nested classes, it doesn't seem quite as elegant as using the friend keyword. The original Design Patterns book uses the friend keyword regularly throughout its examples. So in summary, why is friend missing from C#, and what is the "best practice" way (or ways) of simulating it in C#? (By the way, the "internal" keyword is not the same thing, it allows ALL classes within the entire assembly to access internal members, friend allows you to give access to a class to just one other class.)

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• Robust DateTime parser library for .NET

  - by Frank Krueger

  Hello, I am writing an RSS and Mail reader app in C# (technically MonoTouch). I have run into the issue of parsing DateTimes. I see a lot of variance in how dates are presented in the wild and have begun writing a function like this: public static DateTime ParseTime(string timeStr) { var formats = new string[] { "ddd, d MMM yyyy H:mm:ss \"GMT+00:00\"", "d MMM yyyy H:mm:ss \"EST\"", "yyyy-MM-dd\"T\"HH:mm:ss\"Z\"", "ddd MMM d HH:mm:ss \"+0000\" yyyy", }; try { return DateTime.Parse(timeStr); } catch (Exception) { } foreach (var f in formats) { try { var t = DateTime.ParseExact(timeStr, f, CultureInfo.InvariantCulture); return t; } catch (Exception) { } } return DateTime.MinValue; } This, well, makes me sick. Three points. (1) It's silly of me to think that I can actually collect a format list that will cover everything out there. (2) It's wrong! Notice that I'm treating an EST date time as UTC (since .NET seems oblivious to time zones). (3) I don't like using exceptions for logic. I am looking for an existing library (source only please) that is known to handle a bunch of these formats. Also, I would like to keep using UTC DateTimes throughout my code so whatever library is suggested should be able to produce DateTimes. Is there anything out there like this?

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• Polling servers at the same port - Threads and Java

  - by John

  Hi there. I'm currently busy working on an IP ban tool for the early versions of Call of Duty 1. (Apparently such a feature wasn't implemented in these versions). I've finished a single threaded application but it won't perform well enough for multiple servers, which is why I am trying to implement threading. Right now, each server has its own thread. I have a Networking class, which has a method; "GetStatus" -- this method is synchronized. This method uses a DatagramSocket to communicate with the server. Since this method is static and synchronized, I shouldn't get in trouble and receive a whole bunch of "Address already in use" exceptions. However, I have a second method named "SendMessage". This method is supposed to send a message to the server. How can I make sure "SendMessage" cannot be invoked when there's already a thread running in "GetStatus", and the other way around? If I make both synchronized, I will still get in trouble if Thread A is opening a socket on Port 99999 and invoking "SendMessage" while Thread B is opening a socket on the same port and invoking "GetStatus"? (Game servers are usually hosted on the same ports) I guess what I am really after is a way to make an entire class synchronized, so that only one method can be invoked and run at a time by a single thread. Hope that what I am trying to accomplish/avoid is made clear in this text. Any help is greatly appreciated.

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• Java - How to declare table[i][j] elements as instance variables?

  - by JDelage

  All, I am trying to code a Connect4 game. For this, I have created a P4Game class and a P4Board class which represents the i X j dimensions of the Connect4 board. In P4Game, I have the following: public class P4Game{ //INSTANCE VARIABLES private int nbLines; private int nbColumns; private P4Board [][] position; //CONSTRUCTOR public P4Game(int nbLines, int nbColumns){ this.nbColumns = nbColumns; this.nbLines = nbLines; P4Board [][] position = new P4Board [nbLines][nbColumns]; //Creates the table to receive the instances of the P4Board object.*/ for (int i=0; i<nbLines; i++){ for (int j=0; j<nbColumns; j++){ this.position[i][j] = new P4Board(i,j); //Meant to create each object at (line=i, column=j) } } } This causes a NullPointerException in the nested loops where I mention this.position[i][j]. I reference those objects in other methods of this class so I need them to be instance variables. I suppose the exception is due to the fact that I have not listed the table element position[i][j] as an instance variable at the beginning of the class. my question to people here is (1) is my assumption correct, and if so (2) what would be the syntax to declare instance variables of this form? Thank you all for your help with what I realize is a very basic question. Hopefully it will also benefit other newbies. Cheers, JDelage

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• Dojo StackContainer children are not resizing on browser maximise/restore

  - by Andy

  Hi. I have the following nested layout in a dojo 1.4 app: BorderContainer 1 -- Stack Container 1 ----BorderContainer 2 ----BorderContainer 3 The StackContainer is sized with width and height 100%. When I resize the browser window using maximise/restore, the StackContainer correctly resizes to the center region of it's parent BorderContainer. The problem I have is that the StackContainer children (BorderContainer 2 and 3) do not get resized to the StackContainer's contentBox. Is there something special you have to do to force a resize of StackContainer children? I have tried calling StackContainer1.resize() but this makes no difference. Thanks in advance. Additional information: Thanks for the reply peller. The widget hierachy that contains the StackContainer is actually a custom widget, so the StackContainer is not actually in a BorderContainer directly, but has its height and width explicitly set to 100%. This works and the StackContainer is resized correctly on browser maximise. The direct children of the stackcontainer are BorderContainers and it is these BorderContainers that do not get resized when the StackContainer is resized. One point to note is that when the StackContainer is created in markup, the stackcontainer children are empty divs. These divs are then used as placeholders for custom widget creation, e.g. var widget = new com.company.widget(params, placeholderDiv); where placeholderDiv is a direct child of the StackContainer in markup. Should I be adding the programatically created 'widget' to the stackcontainer using addChild instead?

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• How to write this snippet in Python?

  - by morpheous

  I am learning Python (I have a C/C++ background). I need to write something practical in Python though, whilst learning. I have the following pseudocode (my first attempt at writing a Python script, since reading about Python yesterday). Hopefully, the snippet details the logic of what I want to do. BTW I am using python 2.6 on Ubuntu Karmic. Assume the script is invoked as: script_name.py directory_path import csv, sys, os, glob # Can I declare that the function accepts a dictionary as first arg? def getItemValue(item, key, defval) return !item.haskey(key) ? defval : item[key] dirname = sys.argv[1] # declare some default values here weight, is_male, default_city_id = 100, true, 1 # fetch some data from a database table into a nested dictionary, indexed by a string curr_dict = load_dict_from_db('foo') #iterate through all the files matching *.csv in the specified folder for infile in glob.glob( os.path.join(dirname, '*.csv') ): #get the file name (without the '.csv' extension) code = infile[0:-4] # open file, and iterate through the rows of the current file (a CSV file) f = open(infile, 'rt') try: reader = csv.reader(f) for row in reader: #lookup the id for the code in the dictionary id = curr_dict[code]['id'] name = row['name'] address1 = row['address1'] address2 = row['address2'] city_id = getItemValue(row, 'city_id', default_city_id) # insert row to database table finally: f.close() I have the following questions: Is the code written in a Pythonic enough way (is there a better way of implementing it)? Given a table with a schema like shown below, how may I write a Python function that fetches data from the table and returns is in a dictionary indexed by string (name). How can I insert the row data into the table (actually I would like to use a transaction if possible, and commit just before the file is closed) Table schema: create table demo (id int, name varchar(32), weight float, city_id int); BTW, my backend database is postgreSQL

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• Why is my PHP upload script not working?

  - by Turner

  Hello all, I am doing some simple work with uploading a file. I am ignoring error checking and exceptions at this point just to get my uploads working. I have this HTML form: <form action='addResult.php' method='post' enctype='multipart/form-data' target='results_iFrame' onsubmit='startUpload();'> Entry: <input type='text' id='entry' /> Stop: <input type='text' id='stop' /> Final: <input type='text' id='final' /> Chart: <input type='file' id='chart' /> <input type='submit' value='Add' /></form> As you can see, it calls 'addResult.php' within the iFrame 'results_iFrame'. The Javascript is just for animation purposes and to tell me when things are finished. addResult.php has this code in it (along with processing the other inputs): $upload_dir = "../img/"; $chart_loc = $upload_dir.basename($_FILES['chart']['name']); move_uploaded_file($_FILES['chart']['tmp_name'], $chart_loc); print_r($_FILES); It uses the 'chart' input from the form and tries to upload it. I have the print_r() function to display some information on $_FILES, but the array is empty, thus making this fail. What could I be doing wrong?

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• Why does GetWindowThreadProcessId return 0 when called from a service

  - by Marve

  When using the following class in a console application, and having at least one instance of Notepad running, GetWindowThreadProcessId correctly returns a non-zero thread id. However, if the same code is included in a Windows Service, GetWindowThreadProcessId always returns 0 and no exceptions are thrown. Changing the user the service launches under to be the same as the one running the console application didn't alter the result. What causes GetWindowThreadProcessId to return 0 even if it is provided with a valid hwnd? And why does it function differently in the console application and the service? Note: I am running Windows 7 32-bit and targeting .NET 3.5. public class TestClass { [DllImport("user32.dll")] static extern uint GetWindowThreadProcessId(IntPtr hWnd, IntPtr ProcessId); public void AttachToNotepad() { var processesToAttachTo = Process.GetProcessesByName("Notepad") foreach (var process in processesToAttachTo) { var threadID = GetWindowThreadProcessId(process.MainWindowHandle, IntPtr.Zero); .... } } } Console Code: class Program { static void Main(string[] args) { var testClass = new TestClass(); testClass.AttachToNotepad(); } } Service Code: public class TestService : ServiceBase { private TestClass testClass = new TestClass(); static void Main() { ServiceBase.Run(new TestService()); } protected override void OnStart(string[] args) { testClass.AttachToNotepad(); base.OnStart(args); } protected override void OnStop() { ... } }

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• php: autoload exception handling.

  - by YuriKolovsky

  Hello again, I'm extending my previous question (Handling exceptions within exception handle) to address my bad coding practice. I'm trying to delegate autoload errors to a exception handler. <?php function __autoload($class_name) { $file = $class_name.'.php'; try { if (file_exists($file)) { include $file; }else{ throw new loadException("File $file is missing"); } if(!class_exists($class_name,false)){ throw new loadException("Class $class_name missing in $file"); } }catch(loadException $e){ header("HTTP/1.0 500 Internal Server Error"); $e->loadErrorPage('500'); exit; } return true; } class loadException extends Exception { public function __toString() { return get_class($this) . " in {$this->file}({$this->line})".PHP_EOL ."'{$this->message}'".PHP_EOL . "{$this->getTraceAsString()}"; } public function loadErrorPage($code){ try { $page = new pageClass(); echo $page->showPage($code); }catch(Exception $e){ echo 'fatal error: ', $code; } } } $test = new testClass(); ?> the above script is supposed to load a 404 page if the testClass.php file is missing, and it works fine, UNLESS the pageClass.php file is missing as well, in which case I see a "Fatal error: Class 'pageClass' not found in D:\xampp\htdocs\Test\PHP\errorhandle\index.php on line 29" instead of the "fatal error: 500" message I do not want to add a try/catch block to each and every class autoload (object creation), so i tried this. What is the proper way of handling this?

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• How to get at JSON in grails 2.0

  - by Mikey

  I am sending myself JSON like so with jQuery: $.ajax ({ type: "POST", url: 'http://localhost:8080/myproject/myController/myAction', dataType: 'json', async: false, //json object to sent to the authentication url data: {"stuff":"yes", "listThing":[1,2,3], "listObjects":[{"one":"thing"},{"two":"thing2"}]}, success: function () { alert("Thanks!"); } }) I send this to a controller and do println params And I know I'm already in trouble... [stuff:yes, listObjects[1][two]:thing2, listObjects[0][one]:thing, listThing[]:[1, 2, 3], action:myAction, controller:myController] I cannot figure out how to get at most of these values... I can get "yes" with params.stuff, but I cant do params.listThing.each{} or params.listObjects.each{} What am I doing wrong? UPDATE: I make the controller do this to try the two suggestions so far: println params println params.stuff println params.list('listObjects') println params.listThing def thisWontWork = JSON.parse(params.listThing) render("omg l2json") look how weird the parameters look at the end of the null pointer exception when I try the answers: [stuff:yes, listObjects[1][two]:thing2, listObjects[0][one]:thing, listThing[]:[1, 2, 3], action:l2json, controller:rateAPI] yes [] null | Error 2012-03-25 22:16:13,950 ["http-bio-8080"-exec-7] ERROR errors.GrailsExceptionResolver - NullPointerException occurred when processing request: [POST] /myproject/myController/myAction - parameters: stuff: yes listObjects[1][two]: thing2 listObjects[0][one]: thing listThing[]: 1 listThing[]: 2 listThing[]: 3 UPDATE 2 I am learning things, but this can't be right: println params['listThing[]'] println params['listObjects[0][one]'] prints [1, 2, 3] thing It seems like this is some part of grails new JSON marshaling. This is somewhat inconvenient for my purposes of hacking around with the values. How would I get all these individual params back into a big groovy object of nested maps and lists? Maybe I am not doing what I want with jQuery?

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• How do I serialise a graph in Java without getting StackOverflowException?

  - by Tim Cooper

  I have a graph structure in java, ("graph" as in "edges and nodes") and I'm attempting to serialise it. However, I get "StackOverflowException", despite significantly increasing the JVM stack size. I did some googling, and apparently this is a well known limitation of java serialisation: that it doesn't work for deeply nested object graphs such as long linked lists - it uses a stack record for each link in the chain, and it doesn't do anything clever such as a breadth-first traversal, and therefore you very quickly get a stack overflow. The recommended solution is to customise the serialisation code by overriding readObject() and writeObject(), however this seems a little complex to me. (It may or may not be relevant, but I'm storing a bunch of fields on each edge in the graph so I have a class JuNode which contains a member ArrayList<JuEdge> links;, i.e. there are 2 classes involved, rather than plain object references from one node to another. It shouldn't matter for the purposes of the question). My question is threefold: (a) why don't the implementors of Java rectify this limitation or are they already working on it? (I can't believe I'm the first person to ever want to serialise a graph in java) (b) is there a better way? Is there some drop-in alternative to the default serialisation classes that does it in a cleverer way? (c) if my best option is to get my hands dirty with low-level code, does someone have an example of graph serialisation java source-code that can use to learn how to do it?

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• How do I get Spotlight attributes to display in the get info window?

  - by Alexander Rauchfuss

  I have created a spotlight importer for comic files. The attributes are successfully imported and searchable. The one thing that remains is getting the attributes to display in a file's get info window. It seems that this should be a simple matter of editing the schema.xml file so the attributes are nested inside displayattrs tags. Unfortunately this does not seem to be working. I simplified the plugin for testing. The following are all of the important files. schema.xml <types> <type name="cx.c3.cbz-archive"> <allattrs> kMDItemTitle kMDItemAuthors </allattrs> <displayattrs> kMDItemTitle kMDItemAuthors </displayattrs> </type> <type name="cx.c3.cbr-archive"> <allattrs> kMDItemTitle kMDItemAuthors </allattrs> <displayattrs> kMDItemTitle kMDItemAuthors </displayattrs> </type> GetMetadataForFile.m Boolean GetMetadataForFile(void* thisInterface, CFMutableDictionaryRef attributes, CFStringRef contentTypeUTI, CFStringRef pathToFile) { NSAutoreleasePool * pool = [NSAutoreleasePool new]; NSString * file = (NSString *)pathToFile; NSArray * authors = [[UKXattrMetadataStore stringForKey: @"com_opencomics_authors" atPath: file traverseLink: NO] componentsSeparatedByString: @","]; [(NSMutableDictionary *)attributes setObject: authors forKey: (id)kMDItemAuthors]; NSString * title = [UKXattrMetadataStore stringForKey: @"com_opencomics_title" atPath: file traverseLink: NO]; [(NSMutableDictionary *)attributes setObject: title forKey: (id)kMDItemTitle]; [pool release]; return true; }

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• Dealing with SQLException with spring,hibernate & Postgres

  - by mad

  Hi im working on a project using HibernateDaoSUpport from my Daos from Spring & spring-ws & hibernate & postgres who will be used in a national application (means a lot of users) Actually, every exception from hibernate is automatically transformed into some specific Spring dataAccesException. I have a table with a keyword on the dabatase & a unique constraint on the keywords : no duplicate keywords is allowed. I have found twows ways to deal with with that in the Insert Dao: 1- Check for the duplicate manually (with a select) prior to doing your insert. I means that the spring transaction will have a SERIALIZABLE isolation level. The obvious drawback is that we have now 2 queries for a simple insert.Advantage: independent of the database 2-let the insert gone & catch the SqlException & convert it to a userfriendly message & errorcode to the final consumer of our webservices. Solution 2: Spring has developped a way to translate specific exeptions into customized exceptions. see http://www.oracle.com/technology/pub/articles/marx_spring.html In my case i would have a ConstraintViolationException. Ideally i would like to write a custom SQLExceptionTranslator to map the duplicate word constraint in the database with a DuplicateWordException. But i can have many unique constraints on the same table. So i have to get the message of the SQLEXceptions in order to find the name of the constraint declared in the create table "uq_duplicate-constraint" for example. Now i have a strong dependency with the database. Thanks in advance for your answers & excuse me for my poor english (it is not my mother tongue)

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• Validations for a has_many/belongs_to relationship

  - by Craig Walker

  I have a Recipe model which has_many Ingredients (which in turn belongs_to Recipe). I want Ingredient to be existent dependent on Recipe; an Ingredient should never exist without a Recipe. I'm trying to enforce the presence of a valid Recipe ID in the Ingredient. I've been doing this with a validates :recipe, :presence => true (Rails 3) statement in Ingredient. This works fine if I save the Recipe before adding an Ingredient to it's ingredients collection. However, if I don't have explicit control over the saving (such as when I'm creating a Recipe and its Ingredients from a nested form) then I get an error: Ingredients recipe can't be blank I can get around this simply by dropping the presence validation on Ingredient.recipe. However, I don't particularly like this, as it means I'm working without a safety net. What is the best way to enforce existence-dependence in Rails? Things I'm considering (please comment on the wisdom of each): Adding a not-null constraint on the ingredients.recipe_id database column, and letting the database do the checking for me. A custom validation that somehow checks whether the Ingredient is in an unsaved recipe's ingredient collection (and thus can't have a recipe_id but is still considered valid).

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• Java Socket Returns True

  - by ikurtz

  I hope you can help. Im fairly new to progamming and Im playing around with java Sockets. The problem is the code below. for some reason commSocket = new Socket(hostName, portNumber); is returning true even when it has not connected with the server (server not implemented yet!). Any ideas regarding this situation? For hostName Im passing my local machine IP and for port a manually selected port. public void networkConnect(String hostName, int portNumber){ try { networkConnected = false; netMessage = "Attempting Connection"; NetworkMessage networkMessage = new NetworkMessage(networkConnected, netMessage); commSocket = new Socket(hostName, portNumber); // this returns true!! System.out.println(commSocket.isConnected()); networkConnected = true; netMessage = "Connected: "; System.out.println("hellooo"); } catch (UnknownHostException e){ System.out.println(e.getMessage()); } catch (IOException e){ System.out.println(e.getMessage()); } } Many thanks. EDIT: new Socket(.., ..); is blocking isnt it? i thought in that case if that was processed without exceptions then we have a true connection?

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• What makes an effective UI for displaying versioning of structured hierarchical data

  - by Fadrian Sudaman

  Traditional version control system are displaying versioning information by grouping Projects-Folders-Files with Tree view on the left and details view on the right, then you will click on each item to look at revision history for that configuration history. Assuming that I have all the historical versioning information available for a project from Object-oriented model perspective (e.g. classes - methods - parameters and etc), what do you think will be the most effective way to present such information in UI so that you can easily navigate and access the snapshot view of the project and also the historical versioning information? Put yourself in the position that you are using a tool like this everyday in your job like you are currently using SVN, SS, Perforce or any VCS system, what will contribute to the usability, productivity and effectiveness of the tool. I personally find the classical way for display folders and files like above are very restrictive and less effective for displaying deep nested logical models. Assuming that this is a greenfield project and not restricted by specific technology, how do you think I should best approach this? I am looking for idea and input here to add values to my research project. Feel free to make any suggestions that you think is valuable. Thanks again for anyone that shares their thoughts.

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