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• How to use db4o IObjectContainer in a web application ? (Container lifetime ?)

  - by driis

  I am evaluating db4o for persistence for a ASP .NET MVC project. I am wondering how I should use the IObjectContainer in a web context with regards to object lifetime. As I see it, I can do one of the following: Create the IObjectContainer at application startup and keep the same instance for the entire application lifetime. Create one IObjectContainer per request. Start a server, and get a client IObjectContainer for each database interaction. What are the implications of these options, in terms of performance and concurrency ? Since the database is locked when an IObjectContainer is opened, I am pretty sure that option 2) would get me some problems with concurrency - would this also be the case for option 1 ? As I understand it, if I retrieve an object from an IObjectContainer, it must be saved by the same IObjectContainer instance - in order for db4o to identify it as being the same object. Therefore, If I choose option 3), I would have to retrieve the original object, make the necessary changes (copy data from a modified object), and then store it using the same IObjectContainer. Is this true ?

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• Request for advice about class design, inheritance/aggregation

  - by Lasse V. Karlsen

  I have started writing my own WebDAV server class in .NET, and the first class I'm starting with is a WebDAVListener class, modelled after how the HttpListener class works. Since I don't want to reimplement the core http protocol handling, I will use HttpListener for all its worth, and thus I have a question. What would the suggested way be to handle this: Implement all the methods and properties found inside HttpListener, just changing the class types where it matters (ie. the GetContext + EndGetContext methods would return a different class for WebDAV contexts), and storing and using a HttpListener object internally Construct WebDAVListener by passing it a HttpListener class to use? Create a wrapper for HttpListener with an interface, and constrct WebDAVListener by passing it an object implementing this interface? If going the route of passing a HttpListener (disguised or otherwise) to the WebDAVListener, would you expose the underlying listener object through a property, or would you expect the program that used the class to keep a reference to the underlying HttpListener? Also, in this case, would you expose some of the methods of HttpListener through the WebDAVListener, like Start and Stop, or would you again expect the program that used it to keep the HttpListener reference around for all those things? My initial reaction tells me that I want a combination. For one thing, I would like my WebDAVListener class to look like a complete implementation, hiding the fact that there is a HttpListener object beneath it. On the other hand, I would like to build unit-tests without actually spinning up a networked server, so some kind of mocking ability would be nice to have as well, which suggests I would like the interface-wrapper way. One way I could solve this would be this: public WebDAVListener() : WebDAVListener(new HttpListenerWrapper()) { } public WebDAVListener(IHttpListenerWrapper listener) { } And then I would implement all the methods of HttpListener (at least all those that makes sense) in my own class, by mostly just chaining the call to the underlying HttpListener object. What do you think? Final question: If I go the way of the interface, assuming the interface maps 1-to-1 onto the HttpListener class, and written just to add support for mocking, is such an interface called a wrapper or an adapter?

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• How to debug memory allocation issues?

  - by amitabh

  Hi I am writing an iPhone app that that is trying to create a second a view when the user clicks on an element in UITableView. The code looks like ReplyToViewController *reply = [[ReplyToViewController alloc] initWithNibName:@"ReplyTo" bundle:nil]; reply.delegate = self; Message *message = [resultData objectAtIndex:indexPath.row]; int dbid = [message.bizid intValue]; NSLog(@"dbid=%d",dbid); reply.currentMessage = message; reply.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal; [self presentModalViewController:reply animated:YES]; The reply object gets created properly and the view is proper. Last line in above code segment calls some framework code which eventually calls the viewDidLoad method of the ReplyToViewController. Address of the reply object in the above code and the address of the object in viewDidLoad is not same. Any idea where this new object is coming from? How do I debug? I also added init method the following method in ReplyToViewController hoping that it will get called and I can find who is creating this new object. But it does not stop in this method. Any help will be greatly appreciated. - (id) init { /* first initialize the base class */ self = [super init]; return self; } // Following gets called from the 1st code segment. - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) { // Custom initialization } return self; } - (void)viewDidLoad { [super viewDidLoad]; NSLog(currentMessage.text]; // THIS returns nil and the program fails later in the code. }

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• empty sharepoint user profile property throw an exception

  - by James123

  I have a user profile property. user not assigned any value that property. If I use below code. It is thorwing exception " object reference not set to an instance of an object " userprof["OptOut"].ToString() I tried all types like if (userprof["OptOut"] != null) OR if(userprof["OptOut"].Value != null) nothing worked out for me. Here userProf object has value. userprof["OptOut"].Value is null How to handle this?

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• C# DDD Populate Immutable Objects

  - by Russel

  Hi I have a immutable Customer class in my domain assembly. It contains the following GET properties : id, firstname and lastname. I have a CustomerRepository class in my persistence assembly. In turn, this CustomerRepository class should populate and return a Customer object using a remote web-serivce. My Customer class contains no setter properties and it contains a private constructor. The reason - I dont want the UI developer to get the wrong idea - He should not be able to create or change a Customer object. My question: How do I get my CustomerRepository to populate my Customer object. Reflection? Or should I sacrifice my design and enable a public constructor for constructing the customer object?

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• Storing Instances of Classes in Flex Shared Objects

  - by babyangel86

  Is it possible to store instances of a class in a cookie or in shared objects. Basically in my application I have an object "Diagram" that the user can create. If they hit save, I want to store the current instance as a cookie and allows them to reload it later. Alternatively, I could see about getting them to store the saved version on the hard disk. But even then, all I want to save and retreive is my actionscript object. Is this possible? I've tried storing the object to SharedObject.data.diag, but when I try to retrieve the object from the cookie doing SharedObject.data.diag as Diag returns null.

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• Why does this ActionFilterAttribute not import data to the ViewModel?

  - by Tomas Lycken

  I have the following attribute public class ImportStatusAttribute : ActionFilterAttribute { public override void OnActionExecuted(ActionExecutedContext filterContext) { var model = (IHasStatus)filterContext.Controller.ViewData.Model; model.Status = (StatusMessageViewModel)filterContext.Controller.TempData["status"]; filterContext.Controller.ViewData.Model = model; } } which I test with the following test method (the first of several I'll write when this one passes...) [TestMethod] public void OnActionExecuted_ImportsStatusFromTempDataToModel() { // Arrange Expect(new { Status = new StatusMessageViewModel() { Subject = "The test", Predicate = "has been tested" }, Key = "status" }); var filterContext = new Mock<ActionExecutedContext>(); var model = new Mock<IHasStatus>(); var tempData = new TempDataDictionary(); var viewData = new ViewDataDictionary(model.Object); var controller = new FakeController() { ViewData = viewData, TempData = tempData }; tempData.Add(expected.Key, expected.Status); filterContext.Setup(c => c.Controller).Returns(controller); var attribute = new ImportStatusAttribute(); // Act attribute.OnActionExecuted(filterContext.Object); // Assert Assert.IsNotNull(model.Object.Status, "The status was not exported"); Assert.AreEqual(model.Object.Status.ToString(), ((StatusMessageViewModel)expected.Status).ToString(), "The status was not the expected"); } (Expect() is a method that saves some expectations in the expected object...) When I run the test, it fails on the first assertion, and I can't get my head around why. Debugging, I can see that model is populated correctly, and that (StatusMessageViewModel)filterContext.Controller.TempData["status"] has the correct data. But after model.Status = (StatusMessageViewModel)filterContext.Controller.TempData["status"]; model.Status is still null in my watch window. Why can't I do this?

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• MVC binding form data problem.

  - by John

  I am using an object that matches all the fields in my form. I then use the default binding to populate the object in my action, like this; public ActionResult GetDivisionData(DivisionObj FormData) My DivisionObj initializes all it's values to string.empty in the constructor. The problem is that when the binder populates the model from the posted form data, any data that is not posted is set to null in the object, eventhough I initialized the object to contain empty strings. Is there a way to change this so that unposted data will be an empty string.

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• How to fire off a asych thread in a web application, and gaurantee only 1 thread fires?

  - by Blankman

  I want to cache a object in memory. Regenerating the object when the cache expires is fairly expensive, so I want to do the following: When the cache is "about" to expire, I want to fire off a asychronous thread that will go and rebuild the object and then reset the cache. One thing I am worry about is multiple threads firing to fetch the object to cache, I only want a single thread doing this, realizing many people will be hitting the website. This might not be the best use case to do this, but I want to know how to do this sort of thing.

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• In Java how do a read an input stream in to a string?

  - by Johnny Maelstrom

  If you have an java.io.InputStream object how should you process that object and produce a string.

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• multi-dimensional ArrayList

  - by wishi

  Hi! Just a very small question... I seem to run into too much complexity here: I have to realize an index-structure like {42, someString}. I tried: Object entry[][] = new Object[1][1]; ArrayList<Object> my_list = new ArrayList<Object>(); However that looks really strange. Isn't there a better much simpler solution to just store some Integer and a String? I need to perfrom search for the Strings and return the Integer... so I thought Collections and ArrayLists are good friends in the Java API.

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• Database for managing large volumes of (system) metrics

  - by symcbean

  Hi, I'm looking at building a system for managing and reporting stats on web page performance. I'll be collecting a lot more stats than are available in the standard log formats (approx 20 metrics) but compared to most types of database applications, the base data structure will be very simple. My problem is that I'll be accumulating a lot of data - in the region of 100,000 records (i.e. sets of metrics) per hour. Of course, resources are very limited! So that its possible to sensibly interact with the data, I'd need to consolidate each metric into one minute bins, broken down by URL, then for anything more than 1 day old, consolidated into 10 minute bins, then at 1 week, hourly bins. At the front end, I want to provide a view (prefereably as plots) of the last hour of data, with the facility for users to drill up/down through defined hierarchies of URLs (which do not always map directly to the hierarchy expressed in the path of the URL) and to view different time frames. Rather than coding all this myself and using a relational database, I was wondering if there were tools available which would facilitate both the management of the data and the reporting. I had a look at Mondrian however I can't see from the documentation I've looked at whether it's possible to drop the more granular information while maintaining the consolidated views of the data. RRDTool looks promising in terms of managing the data consolidation, but seems to be rather limited in terms of querying the dataset as a multi-dimensional/relational database. What else whould I be looking at?

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• Faulty to use memcache together with a php web-browser-game in this way?

  - by Crowye

  Background We are currently working on a strategy web-browser game based on php, html and javascript. The plan is to have 10,000+ users playing within the same world. Currently we are using memcached to: store json static data, language files store changeable serialized php class objects (such as armies, inventorys, unit-containers, buildings, etc) In the back we have a mysql server running and holding all the game data aswell. When a object is loaded through our ObjectLoader it loads in this order: checks a static hashmap in the script for the object checks memcache if it has already been loaded into it otherwise loads from database, and saves it into memcache and the static temp hashmap We have built the whole game using a class-object-oriented approach where functionality is always made between objects. Beause of this we think we have managed to get a nice structure, and with the help of memcached we have received good request times from client-server when interacting with the game. I'm aware that memcache is not synchronized, and also is not commonly used for holding a full game in memory. In the beginning after a server's startup the load times when loading objects into memcache for the first time will be high, but after the server's been online for a while and most loads are from memcache, the loads will be well reduced. Currently we are saving changed objects into memcache and database at the same time. Earlier we had an idea to save objects into db only after a certain time or at intervals, but due to risk inconsistency if the memcache/server went down, we skipped it for now. Client requests to server often return object's status simple json-format without changing the object, which in turn is represented in the browser visually with images and javascript. But from time to time depending on when an object was last updated, it updates them with new information (e.g. a build-queue holding planned buildings time-progress is increased, and/or planned-queue-items-array has changed). Questions: Do you see how this could work or are we walking in blindness here? Do you expect us to have a lot of inconsistency issues if someone loads and updates the a memcache objects while someone else does the same? Is it even doable to do it in the way he have done it? Seems to be working fine atm, but so far we have only been 4 people online at the same time.. Is some other cache program more fit for this class-object approach than memcached? Is there any other tips you have for this situation? UPDATE Since it is simply a "normal webpage" (no applet, flash, etc), we are implementing the game so that the server is the only one holding a "real game-state".. the state of the different javascript-objects on the client is more like a approximative version of the server's game state. From time to time and before you do certain things important things, the client's visual state is updated to the server's state (e.g. the client things he can afford a barracks, asks the server to build a barracks, server updates current resources according to income-data on server and then tries to build a barracks or casts an error-message, and then sends the current server-state on resources, buildings back to the client).. It is not a fast-paced game lika real strategy game. More like a quite slow 3-4 months playtime game, where buildings can take +1 minute up to several days to complete.

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• Strange Java Socket Behavior (Connects, but Doesn't Send)

  - by Donald Campbell

  I have a fairly complex project that boils down to a simple Client / Server communicating through object streams. Everything works flawlessly for two consecutive connections (I connect once, work, disconnect, then connect again, work, and disconnect). The client connects, does its business, and then closes. The server successfully closes both the object output stream and the socket, with no IO errors. When I try to connect a third time, the connection appears to go through (the ServerSocket.accept() method goes through and an ObjectOutputStream is successfully created). No data is passed, however. The inputStream.readUnshared() method simply blocks. I have taken the following memory precautions: When it comes time to close the sockets, all running threads are stopped, and all objects are nulled out. After every writeUnshared() method call, the ObjectOutputBuffer is flushed and reset. Has anyone encountered a similar problem, or does anyone have any suggestions? I'm afraid my project is rather large, and so copying code is problematic. The project boils down to this: SERVER MAIN ServerSocket serverSocket = new ServerSocket(port); while (true) { new WorkThread(serverSocket.accept()).start(); } WORK THREAD (SERVER) public void run() { ObjectInputBuffer inputBuffer = new ObjectInputBuffer(new BufferedInputStream(socket.getInputStream())); while (running) { try { Object myObject = inputBuffer.readUnshared(); // do work is not specified in this sample doWork(myObject); } catch (IOException e) { running = false; } } try { inputBuffer.close(); socket.close(); } catch (Exception e) { System.out.println("Could not close."); } } CLIENT public Client() { Object myObject; Socket mySocket = new Socket(address, port); try { ObjectOutputBuffer output = new ObjectOutputBuffer(new BufferedOutputStream(mySocket.getOutputStream())); output.reset(); output.flush(); } catch (Exception e) { System.out.println("Could not get an input."); mySocket.close(); return; } // get object data is not specified in this sample. it simply returns a serializable object myObject = getObjectData(); while (myObject != null) { try { output.writeUnshared(myObject); output.reset(); output.flush(); } catch (Exception e) { e.printStackTrace(); break; } // catch } // while try { output.close(); socket.close(); } catch (Exception e) { System.out.println("Could not close."); } } Thank you to everyone who may be able to help!

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• Map browser DOM using Javascript

  - by EddyR

  I'm trying to map a browsers DOM using javascript. It should list all the functions and attributes associated with it and it should also recurse through any object attributes. Now as I understand it 'window' is the most top-level node (although I've see a reference to 'top' as well in Chrome.) then 'document', etc. However I've never seen 'Node' under 'window' and yet I can call it. So where is 'Node' located? Is there a level above 'window' or is it a separate object (W3C says it's supposed to be inherited by 'document' only.)? I've been playing with a function to do this but I keep getting weird results so I'm not post it here. Alternatively - is it possible to get the properties from the object types instead of the object reference itself? for example 'DOMWindow' instead of 'window'. I think this would stop duplicating data from inherited objects.

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• python list/dict property best practice

  - by jterrace

  I have a class object that stores some properties that are lists of other objects. Each of the items in the list has an identifier that can be accessed with the id property. I'd like to be able to read and write from these lists but also be able to access a dictionary keyed by their identifier. Let me illustrate with an example: class Child(object): def __init__(self, id, name): self.id = id self.name = name class Teacher(object): def __init__(self, id, name): self.id = id self.name = name class Classroom(object): def __init__(self, children, teachers): self.children = children self.teachers = teachers classroom = Classroom([Child('389','pete')], [Teacher('829','bob')]) This is a silly example, but it illustrates what I'm trying to do. I'd like to be able to interact with the classroom object like this: #access like a list print classroom.children[0] #append like it's a list classroom.children.append(Child('2344','joe')) #delete from like it's a list classroom.children.pop(0) But I'd also like to be able to access it like it's a dictionary, and the dictionary should be automatically updated when I modify the list: #access like a dict print classroom.childrenById['389'] I realize I could just make it a dict, but I want to avoid code like this: classroom.childrendict[child.id] = child I also might have several of these properties, so I don't want to add functions like addChild, which feels very un-pythonic anyway. Is there a way to somehow subclass dict and/or list and provide all of these functions easily with my class's properties? I'd also like to avoid as much code as possible.

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• Unit testing with serialization mock objects in C++

  - by lhumongous

  Greetings, I'm fairly new to TDD and ran across a unit test that I'm not entirely sure how to address. Basically, I'm testing a couple of legacy class methods which read/write a binary stream to a file. The class functions take a serializable object as a parameter, which handles the actual reading/writing to the file. For testing this, I was thinking that I would need a serialization mock object that I would pass to this function. My initial thought was to have the mock object hold onto a (char*) which would dynamically allocate memory and memcpy the data. However, it seems like the mock object might be doing too much work, and might be beyond the scope of this particular test. Is my initial approach correct, or can anyone think of another way of correctly testing this? Thanks!

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• Check for state change in objects using serialization?

  - by sev7n

  I have a form that is bind to an object, and when the user trying to leave the form, I want to warn them if anything on the form has been changed, and prompt them to save. My question is, is there any way to achieve this without implementing IComparar for all my classes in the binded object? I was thinking if there is a way I can serialize my object when loading the form, and do a simple comparison against the change object that also get serialized. Something like a string comparison. Hope that make sense, Thanks

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• Django model help

  - by dotty

  Does anyone have any clue why this doesn't work as expected. If i use the python shell and do team.game_set or team.games It returns an error AttributeError: 'Team' object has no attribute 'game' If i create a Game object and call game.home_team it returns the correct team object Heres my model class Team(models.Model): name = models.CharField(blank=True, max_length=100) class Game(models.Model): home_team = models.ForeignKey(Team, related_name="home_team")

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• Php code not executing - dies out when trying to refer to member of static class - no error displaye

  - by Ali

  I'm having some problems with this piece of code. I've included a class declaration and trying to create an object of that class but my code dies out. It doesn't seem to be an include issue as all the files are being included even the files called for inclusion within the class file itself. However the object is not created - I tried to put an echo statement in the __construct function but nothing it just doesn't run infact doesn't create the object and the code won't continue from there - plus no error is reported or displayed and I have error reporting set to E_ALL and display errors set to true WHats happening here :( =============EDIT SOrry I checked again the error is prior to teh object creation thing - it dies out when it tries to refer to a constant in a static class like so: $v = Zend_Oauth::REQUEST_SCHEME_HEADER; THis is the class or part of it - it has largely static functions its the Zend Oauth class: class Zend_Oauth { const REQUEST_SCHEME_HEADER = 'header'; const REQUEST_SCHEME_POSTBODY = 'postbody'; const REQUEST_SCHEME_QUERYSTRING = 'querystring'; // continued LIke I said no error is being reported at all :(

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• how to save a fitted R model for later use

  - by ahala

  Sorry for this novice question: if I fit a lm() model or loess() model, and save the model somewhere in a file or in database, for later using by third party with predict() method, do I have to save the entire model object? Since returned model object contains orginal raw data, this returned object can be huge.

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• creating BeanInfo objects in NetBeans 6.1 does not work for some objects

  - by Coder

  I have recently learned about BeanInfo classes in Java, and have successfully used them to add icons to my custom GUI components which extend swing components such as JTextField, however i have a more specialized GUI component which extends from another one of my GUI components, which then extends from JTextField. Ie. the class hierarchy is of the form "A - B - JTextField". I can create a bean info object that works for class B, but when i click on the bean info editor option in netbeans to create a bean info object for class A, nothing happens. Ie. there is no error pop-up and a bean info object is not created. There isn't much difference between class A and B. Both A and B have default no argument constructors and they are very similar to each other. The only thing i can really think of is that A uses generics and B does not. I would like to create a beaninfo object for class A so that i can add custom icons for that component. Any help would be appreciated. Thanks.

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• How can I inherit an ASP.NET MVC controller and change only the view?

  - by AlexWalker

  I have a controller that's inheriting from a base controller, and I'm wondering how I can utilize all of the logic from the base controller, but return a different view than the base controller uses. The base controller populates a model object and passes that model object to its view, but I'm not sure how I can access that model object in the child controller so that I can pass it to the child controller's view.

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• Compare class objects

  - by reto

  I have to compare a class object against a list of pre defined classes. Is it safe to use == or should I use equals()? if (klass == KlassA.class) { } else if (klass == KlassB.class) { } else if (klass == KlassC.class) { } else { } Note: I cannot use instanceof, I don't have an object, I just have the class object. I (mis)use it like an enum in this situation! Thanks!

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• Multithreaded linked list traversal

  - by Rob Bryce

  Given a (doubly) linked list of objects (C++), I have an operation that I would like multithread, to perform on each object. The cost of the operation is not uniform for each object. The linked list is the preferred storage for this set of objects for a variety of reasons. The 1st element in each object is the pointer to the next object; the 2nd element is the previous object in the list. I have solved the problem by building an array of nodes, and applying OpenMP. This gave decent performance. I then switched to my own threading routines (based off Windows primitives) and by using InterlockedIncrement() (acting on the index into the array), I can achieve higher overall CPU utilization and faster through-put. Essentially, the threads work by "leap-frog'ing" along the elements. My next approach to optimization is to try to eliminate creating/reusing the array of elements in my linked list. However, I'd like to continue with this "leap-frog" approach and somehow use some nonexistent routine that could be called "InterlockedCompareDereference" - to atomically compare against NULL (end of list) and conditionally dereference & store, returning the dereferenced value. I don't think InterlockedCompareExchangePointer() will work since I cannot atomically dereference the pointer and call this Interlocked() method. I've done some reading and others are suggesting critical sections or spin-locks. Critical sections seem heavy-weight here. I'm tempted to try spin-locks but I thought I'd first pose the question here and ask what other people are doing. I'm not convinced that the InterlockedCompareExchangePointer() method itself could be used like a spin-lock. Then one also has to consider acquire/release/fence semantics... Ideas? Thanks!

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