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  • Partially constructed object / Multi threading

    - by reto
    Heya! I'm using joda due to it's good reputation regarding multi threading. It goes great distances to make multi threaded date handling efficient, for example by making all Date/Time/DateTime objects immutable. But here's a situation where I'm not sure if Joda is really doing the right thing. It probably is correct, but I'd be very interested to see the explanation for it. When a toString() of a DateTime is being called Joda does the following: /* org.joda.time.base.AbstractInstant */ public String toString() { return ISODateTimeFormat.dateTime().print(this); } All formatters are thread safe, as they are as well ready-only. But what's about the formatter-factory: private static DateTimeFormatter dt; /* org.joda.time.format.ISODateTimeFormat */ public static DateTimeFormatter dateTime() { if (dt == null) { dt = new DateTimeFormatterBuilder() .append(date()) .append(tTime()) .toFormatter(); } return dt; } This is a common pattern in single threaded applications. I see the following dangers: Race condition during null check -- worst case: two objects get created. No Problem, as this is solely a helper object (unlike a normal singleton pattern situation), one gets saved in dt, the other is lost and will be garbage collected sooner or later. the static variable might point to a partially constructed object before the objec has been finished initialization (before calling me crazy, read about a similar situation in this Wikipedia article. So how does Joda ensure that not partially created formatter gets published in this static variable? Thanks for your explanations! Reto

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  • C++ data member initializer is not allowed

    - by user1435915
    I totally new to C++ so bear with me. I want to make a class with a static array, and access to this array from the main. Here is what i want to do in C#. namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Class a = new Class(); Console.WriteLine(a.arr[1]); } } } ===================== namespace ConsoleApplication1 { class Class { public static string[] s_strHands = new string[]{"one","two","three"}; } } Here is what i have tried: // justfoolin.cpp : Defines the entry point for the console application. // #include "stdafx.h" #include <string> #include <iostream> using namespace std; class Class { public: static string arr[3] = {"one", "two", "three"}; }; int _tmain(int argc, _TCHAR* argv[]) { Class x; cout << x.arr[2] << endl; return 0; } But i got: IntelliSense: data member initializer is not allowed

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  • No Hibernate Exception on the same insert of data

    - by Mark Estrada
    Hi All, Hibernate Newbie here. I am quite unsure why I am not getting any exception when I am executing below code. On first attempt, this code creates the Book Entry on my Book Table. But my concern is that when I execute below code again, no error was pop out by Hibernate. I was in fact expecting some sort of Violation of Primary Key Constraints as what I have bee doing in JDBC code. public class BookDao { public void createBook(Book bookObj) { Session session = HibernateUtil.getSessionFactory() .getCurrentSession(); session.beginTransaction(); session.saveOrUpdate(bookObj); session.getTransaction().commit(); } } public class HibernateUtil { private static final SessionFactory sessionFactory = buildSessionFactory(); private static SessionFactory buildSessionFactory() { try { // Create the SessionFactory from hibernate.cfg.xml return new AnnotationConfiguration().configure() .buildSessionFactory(); } catch (Throwable ex) { // Make sure you log the exception, as it might be swallowed ex.printStackTrace(); throw new ExceptionInInitializerError(ex); } } public static SessionFactory getSessionFactory() { return sessionFactory; } } public class BookDBStarter { public static void main(String[] args) { Book bookHF = new Book(); bookHF.setIsbn("HF-12345"); bookHF.setName("Head First HTML"); bookHF.setPublishDate(new Date()); BookDao daoBook = new BookDao(); daoBook.createBook(bookHF); } } Is this normal hibernate way? And how will I know if my insert is successful? Any thoughts?

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  • Destructor - does it get called if the app crashes

    - by Antonio Nakic Alfirevic
    Does a destructor get called if the app crashes? If it's an unhandled exception I'm guessing it does, but what about more serious errors, or something like a user killing the application process? And a few more potentially dumb questions: what happens to all the objects in an app when the app exits and all finalizers have been executed - do the objects get garbage collected or are they somehow all "unloaded" with the process or appdomain? is the garbage collector part of each application (runs in the same process) or is it independent?

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  • Why is my GUI unresponsive while a SwingWorker thread runs?

    - by Starchy
    Hello, I have a SwingWorker thread with an IOBound task which is totally locking up the interface while it runs. Swapping out the normal workload for a counter loop has the same result. The SwingWorker looks basically like this: public class BackupWorker extends SwingWorker<String, String> { private static String uname = null; private static String pass = null; private static String filename = null; static String status = null; BackupWorker (String uname, String pass, String filename) { this.uname = uname; this.pass = pass; this.filename = filename; } @Override protected String doInBackground() throws Exception { BackupObject bak = newBackupObject(uname,pass,filename); return "Done!"; } } The code that kicks it off lives in a class that extends JFrame: public void actionPerformed(ActionEvent event) { String cmd = event.getActionCommand(); if (BACKUP.equals(cmd)) { SwingUtilities.invokeLater(new Runnable() { public void run() { final StatusFrame statusFrame = new StatusFrame(); statusFrame.setVisible(true); SwingUtilities.invokeLater(new Runnable() { public void run () { statusFrame.beginBackup(uname,pass,filename); } }); } }); } } Here's the interesting part of StatusFrame: public void beginBackup(final String uname, final String pass, final String filename) { worker = new BackupWorker(uname, pass, filename); worker.execute(); try { System.out.println(worker.get()); } catch (InterruptedException e) { e.printStackTrace(); } catch (ExecutionException e) { e.printStackTrace(); } } } So far as I can see, everything "long-running" is handled by the worker, and everything that touches the GUI on the EDT. Have I tangled things up somewhere, or am I expecting too much of SwingWorker?

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  • Comparing against NSLocalizedString safe?

    - by George
    Hi, Sometimes I need to compare interface elements to other objects. At the moment I'm doing it by comparing their titles against a localized string. Am I right that I better compare my objects against IBOutlets? Tags are out of the question because I'm using NSMenu.

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  • Java - Calling all methods of a class

    - by Thomas Eschemann
    I'm currently working on an application that has to render several Freemarker templates. So far I have a Generator class that handles the rendering. The class looks more or less like this: public class Generator { public static void generate(…) { renderTemplate1(); renderTemplate2(); renderTemplate3(); } private static void render(…) { // renders the template } private static void renderTemplate1() { // Create config object for the rendering // and calls render(); }; private static void renderTemplate1() { // Create config object for the rendering // and calls render(); }; … } This works, but it doesn't really feel right. What I would like to do is create a class that holds all the renderTemplate...() methods and then call them dynamically from my Generator class. This would make it cleaner and easier to extend. I was thinking about using something like reflection, but it doesn't really feel like a good solution either. Any idea on how to implement this properly ?

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  • In Sphinx, can I register a bunch of keywords that should always be translated into links?

    - by Ross Rogers
    My doc strings have references to other python classes that I've defined. Every time Sphinx encounters one of these classes, I want it to insert a link to the documentation for that other class. Is this possible in Sphinx? Specifically, I have a doc string like: '''This class contains a bunch of Foo objects''' I could write: '''This class contains a bunch of :class:`~foo.Foo` objects''' but I would prefer that Sphinx finds all text matching Foo and makes it seem as though I had typed :class:~foo.Foo

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  • Querying with foreign key

    - by theactiveactor
    Say I have 2 tables whose structures are as follows: tableA id | A1 | A2 tableB id | tableA_id (foreign key) | B1 Entries in A have a one-to-many relationship with entries in B. What kind of query operation would I need to achieve "something like this: select all objects from table B where A1="foo""? Basically, apply a query on tableA and from those result, find corresponding dependent objects in tableB

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  • Type classe, generic memoization

    - by nicolas
    Something quite odd is happening with y types and I quite dont understand if this is justified or not. I would tend to think not. This code works fine : type DictionarySingleton private () = static let mutable instance = Dictionary<string*obj, obj>() static member Instance = instance let memoize (f:'a -> 'b) = fun (x:'a) -> let key = f.ToString(), (x :> obj) if (DictionarySingleton.Instance).ContainsKey(key) then let r = (DictionarySingleton.Instance).[key] r :?> 'b else let res = f x (DictionarySingleton.Instance).[key] <- (res :> obj) res And this ones complains type DictionarySingleton private () = static let mutable instance = Dictionary<string*obj, _>() static member Instance = instance let memoize (f:'a -> 'b) = fun (x:'a) -> let key = f.ToString(), (x :> obj) if (DictionarySingleton.Instance).ContainsKey(key) then let r = (DictionarySingleton.Instance).[key] r :?> 'b else let res = f x (DictionarySingleton.Instance).[key] <- (res :> obj) res The difference is only the underscore in the dictionary definition. The infered types are the same, but the dynamic cast from r to type 'b exhibits an error. 'this runtime coercition ... runtime type tests are not allowed on some types, etc..' Am I missing something or is it a rough edge ?

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  • MVC4 Model in View has nested data - cannot get data in model

    - by Taersious
    I have a Model defined that gets me a View with a list of RadioButtons, per IEnumerable. Within that Model, I want to display a list of checkboxes that will vary based on the item selected. Finally, there will be a Textarea in the same view once the user has selected from the available checkboxes, with some dynamic text there based on the CheckBoxes that are selected. What we should end up with is a Table-per-hierarchy. The layout is such that the RadioButtonList is in the first table cell, the CheckBoxList is in the middle table cell, and the Textarea is ini the right table cell. If anyone can guide me to what my model-view should be to achieve this result, I'll be most pleased... Here are my codes: // // View Model for implementing radio button list public class RadioButtonViewModel { // objects public List<RadioButtonItem> RadioButtonList { get; set; } public string SelectedRadioButton { get; set; } } // // Object for handling each radio button public class RadioButtonItem { // this object public string Name { get; set; } public bool Selected { get; set; } public int ObjectId { get; set; } // columns public virtual IEnumerable<CheckBoxItem> CheckBoxItems { get; set; } } // // Object for handling each checkbox public class CheckBoxViewModel { public List<CheckBoxItem> CheckBoxList { get; set; } } // // Object for handling each check box public class CheckBoxItem { public string Name { get; set; } public bool Selected { get; set; } public int ObjectId { get; set; } public virtual RadioButtonItem RadioButtonItem { get; set; } } and the view @model IEnumerable<EF_Utility.Models.RadioButtonItem> @{ ViewBag.Title = "Connect"; ViewBag.Selected = Request["name"] != null ? Request["name"].ToString() : ""; } @using (Html.BeginForm("Objects" , "Home", FormMethod.Post) ){ @Html.ValidationSummary(true) <table> <tbody> <tr> <td style="border: 1px solid grey; vertical-align:top;"> <table> <tbody> <tr> <th style="text-align:left; width: 50px;">Select</th> <th style="text-align:left;">View or Table Name</th> </tr> @{ foreach (EF_Utility.Models.RadioButtonItem item in @Model ) { <tr> <td> @Html.RadioButton("RadioButtonViewModel.SelectedRadioButton", item.Name, ViewBag.Selected == item.Name ? true : item.Selected, new { @onclick = "this.form.action='/Home/Connect?name=" + item.Name + "'; this.form.submit(); " }) </td> <td> @Html.DisplayFor(i => item.Name) </td> </tr> } } </tbody> </table> </td> <td style="border: 1px solid grey; width: 220px; vertical-align:top; @(ViewBag.Selected == "" ? "display:none;" : "")"> <table> <tbody> <tr> <th>Column </th> </tr> <tr> <td><!-- checkboxes will go here --> </td> </tr> </tbody> </table> </td> <td style="border: 1px solid grey; vertical-align:top; @(ViewBag.Selected == "" ? "display:none;" : "")"> <textarea name="output" id="output" rows="24" cols="48"></textarea> </td> </tr> </tbody> </table> } and the relevant controller public ActionResult Connect() { /* TEST SESSION FIRST*/ if( Session["connstr"] == null) return RedirectToAction("Index"); else { ViewBag.Message = ""; ViewBag.ConnectionString = Server.UrlDecode( Session["connstr"].ToString() ); ViewBag.Server = ParseConnectionString( ViewBag.ConnectionString, "Data Source" ); ViewBag.Database = ParseConnectionString( ViewBag.ConnectionString, "Initial Catalog" ); using( var db = new SysDbContext(ViewBag.ConnectionString)) { var objects = db.Set<SqlObject>().ToArray(); var model = objects .Select( o => new RadioButtonItem { Name = o.Name, Selected = false, ObjectId = o.Object_Id, CheckBoxItems = Enumerable.Empty<EF_Utility.Models.CheckBoxItem>() } ) .OrderBy( rb => rb.Name ); return View( model ); } } } What I am missing it seems, is the code in my Connect() method that will bring the data context forward; at that point, it should be fairly straight-forward to set up the Html for the View. EDIT ** So I am going to need to bind the RadioButtonItem to the view with something like the following, except my CheckBoxList will NOT be an empty set. // // POST: /Home/Connect/ [HttpPost] public ActionResult Connect( RadioButtonItem rbl ) { /* TEST SESSION FIRST*/ if ( Session["connstr"] == null ) return RedirectToAction( "Index" ); else { ViewBag.Message = ""; ViewBag.ConnectionString = Server.UrlDecode( Session["connstr"].ToString() ); ViewBag.Server = ParseConnectionString( ViewBag.ConnectionString, "Data Source" ); ViewBag.Database = ParseConnectionString( ViewBag.ConnectionString, "Initial Catalog" ); using ( var db = new SysDbContext( ViewBag.ConnectionString ) ) { var objects = db.Set<SqlObject>().ToArray(); var model = objects .Select( o => new RadioButtonItem { Name = o.Name, Selected = false, ObjectId = o.Object_Id, CheckBoxItems = Enumerable.Empty<EF_Utility.Models.CheckBoxItem>() } ) .OrderBy( rb => rb.Name ); return View( model ); } } }

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  • Ninject: Shared DI/IoC container

    - by joblot
    Hi I want to share the container across various layers in my application. I started creating a static class which initialises the container and register types in the container. public class GeneralDIModule : NinjectModule { public override void Load() { Bind().To().InSingletonScope(); } } public abstract class IoC { private static IKernel _container; public static void Initialize() { _container = new StandardKernel(new GeneralDIModule(), new ViewModelDIModule()); } public static T Get<T>() { return _container.Get<T>(); } } I noticed there is a Resolve method as well. What is the difference between Resolve and Get? In my unit tests I don’t always want every registered type in my container. Is there a way of initializing an empty container and then register types I need. I’ll be mocking types as well in unit test so I’ll have to register them as well. There is an Inject method, but it says lifecycle of instance is not managed? Could someone please set me in right way? How can I register, unregister objects and reset the container. Thanks

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  • UML diagram for application architecture?

    - by fayer
    i'm trying to map my whole application in a UML diagram and i wonder what diagram type i should use. im not doing this in class level, rather from a bird eye's perspective. single application object (patterns: singleton)(examples: CodeIgniter application) that composes multiple module objects (patterns: singleton, facades)(examples: guestbook, addressbook) that compose multiple low level stand alone objects (examples: mysql mapper, doctrine mapper) that compose various 3rd and in-house libraries (examples: doctrine, solr, xml-parser) what UML diagram is suited for this kind of overview presentation? thanks

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  • More efficient method for grabbing all child units

    - by Hazior
    I have a table in SQL that links to itself through parentID. I want to find the children and their children and so forth until I find all the child objects. I have a recursive function that does this but it seems very ineffective. Is there a way to get sql to find all child objects? If so how?

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  • Migrating from hand-written persistence layer to ORM

    - by Sergey Mikhanov
    Hi community, We are currently evaluating options for migrating from hand-written persistence layer to ORM. We have a bunch of legacy persistent objects (~200), that implement simple interface like this: interface JDBC { public long getId(); public void setId(long id); public void retrieve(); public void setDataSource(DataSource ds); } When retrieve() is called, object populates itself by issuing handwritten SQL queries to the connection provided using the ID it received in the setter (this usually is the only parameter to the query). It manages its statements, result sets, etc itself. Some of the objects have special flavors of retrive() method, like retrieveByName(), in this case a different SQL is issued. Queries could be quite complex, we often join several tables to populate the sets representing relations to other objects, sometimes join queries are issued on-demand in the specific getter (lazy loading). So basically, we have implemented most of the ORM's functionality manually. The reason for that was performance. We have very strong requirements for speed, and back in 2005 (when this code was written) performance tests has shown that none of mainstream ORMs were that fast as hand-written SQL. The problems we are facing now that make us think of ORM are: Most of the paths in this code are well-tested and are stable. However, some rarely-used code is prone to result set and connection leaks that are very hard to detect We are currently squeezing some additional performance by adding caching to our persistence layer and it's a huge pain to maintain the cached objects manually in this setup Support of this code when DB schema changes is a big problem. I am looking for an advice on what could be the best alternative for us. As far as I know, ORMs has advanced in last 5 years, so it might be that now there's one that offers an acceptable performance. As I see this issue, we need to address those points: Find some way to reuse at least some of the written SQL to express mappings Have the possibility to issue native SQL queries without the necessity to manually decompose their results (i.e. avoid manual rs.getInt(42) as they are very sensitive to schema changes) Add a non-intrusive caching layer Keep the performance figures. Is there any ORM framework you could recommend with regards to that?

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  • Jython saying "No visible constructors for class"

    - by clutch
    I have a jython servlet as part of a large application running in tomcat5. I tested a few Spring Framework classes and create the objects in the Jython servlet. When I try to create objects of classes in the application I catch an Exception message "No visible constructors for class". These java classes do have a public constructor class, such as: public SchoolImpl() { } I create the object in python: from com.dc.sports.entity import SchoolImpl ... school = SchoolImpl() What am I doing wrong?

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  • View list of all JavaScript variables in Google Chrome Console

    - by GRboss
    Hello everyone. In Firebug the DOM tab shows a list of all your public variables and objects. In Chrome's console you have to type the name of the public variable or object you want to explore. Is there a way - or at least a command - for Chrome's console to display a list all the public variables and objects? It will save a lot of typing. Thank you all Stefanos

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  • problems with retrieving data that was saved outside of a grails webflow

    - by callie16
    Hi, this is actually connected to an earlier question of mine here. Anyway, I have 3 domains that look like this: class A { ... static hasMany = [ b : B ] ... } class B { ... static belongsTo = [ a : A ] static hasMany = [ c : C ] ... } class C { ... static belongsTo = [ b : B ] ... } In my GSP page, I call an action in the Controller via a remote function in a javascript block (I'm using Dojo so I'm passing data to be saved this way... it's not a form per se so I use JSON for now to pass the data to the Controller). Let's say, I'm calling something like this: def someAction = { def jsonArr = [parse the JSON here] def tmpA = A.get(params.id) ... def tmpB = new B() b.someParam = jsonArr.someParam ... def tmpC = new C() tmpC.cParam = jsonArr.cParam tmpB.addToC(tmpC) tmpB.save(flush: true) //this may or may not be here but I'm adding it for the sake of completeness tmpA.addToB(tmpB) tmpA.save(flush: true) // NOTE: If I check here via println or whatnot, tmpA has a tmpB which has a tmpC... in other words, the data got saved. It's also in the DB. redirect(action: 'order' ...) } Then comes the fun part. Here's the webflow sample: def orderFlow = { ... someStateIShouldEndUpIn { on("next") { // or on previous... doesn't matter def anId = params.id def currA = A.get(anId) // this does NOT return a null value def testB = currA.b // this DOES return a null value }.to("somePage") ... } ... } Any ideas on why this happens? Moreover, when I dump the data of currA, b=null... instead of b=[] or b=[contents of tmpB]. Any help would be seriously appreciated... been at this for a couple of days now... Thanks!

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  • Android WVGA800 and 854

    - by Droidy
    Although my relativelayout looks very similar on WVGA800 and WVGA854 on the emulator, theres different spacing on some of the objects because I'm going off of marginleft or marginright. Since the 854 is a greater width, its pushing some objects differently. Is there any way I could target either one to adjust for the different margins?

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  • Declaration, allocation and assignment of an array of pointers to function pointers

    - by manneorama
    Hello Stack Overflow! This is my first post, so please be gentle. I've been playing around with C from time to time in the past. Now I've gotten to the point where I've started a real project (a 2D graphics engine using SDL, but that's irrelevant for the question), to be able to say that I have some real C experience. Yesterday, while working on the event system, I ran into a problem which I couldn't solve. There's this typedef, //the void parameter is really an SDL_Event*. //but that is irrelevant for this question. typedef void (*event_callback)(void); which specifies the signature of a function to be called on engine events. I want to be able to support multiple event_callbacks, so an array of these callbacks would be an idea, but do not want to limit the amount of callbacks, so I need some sort of dynamic allocation. This is where the problem arose. My first attempt went like this: //initial size of callback vector static const int initial_vecsize = 32; //our event callback vector static event_callback* vec = 0; //size static unsigned int vecsize = 0; void register_event_callback(event_callback func) { if (!vec) __engine_allocate_vec(vec); vec[vecsize++] = func; //error here! } static void __engine_allocate_vec(engine_callback* vec) { vec = (engine_callback*) malloc(sizeof(engine_callback*) * initial_vecsize); } First of all, I have omitted some error checking as well as the code that reallocates the callback vector when the number of callbacks exceed the vector size. However, when I run this code, the program crashes as described in the code. I'm guessing segmentation fault but I can't be sure since no output is given. I'm also guessing that the error comes from a somewhat flawed understanding on how to declare and allocate an array of pointers to function pointers. Please Stack Overflow, guide me.

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  • How many times can you randomly generate a GUID before you risk duplicates? (.NET)

    - by SLC
    Mathematically I suppose it's possible that even two random GUIDs generated using the built in method in the .NET framework are identical, but roughly how likely are they to clash if you generate hundreds or thousands? If you generated one for every copy of Windows in the world, would they clash? The reason I ask is because I have a program that creates a lot of objects, and destroys some too, and I am wondering about the likelihood of any of those objects (including the destroyed ones) having identical GUIDs.

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