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• Handling update errors in multiple records in the TClientDataset's ReconcileError method

  - by Fabio Gomes

  I'm trying to use the ReconcileError event to allow the user to correct the data after an update error which occurred in a specific record among others. Example: I have a dataset with one field and 3 records, this field have a unique constraint on the database, then I change one value to conflict when it reaches the database, then I call ApplyUpdates on the Dataset. This will generate an error (violation of unique constraint) in the provider and abort the applyupdates process, returning raAbort in the Action var of the ReconcileError method. In the ReconcileError method I tryied to use: Action := HandleReconcileError(aDataSet, UpdateKind, E); ** EDIT ** After debugging and dumping the DataSet records which were returned from the server, I noticed that there are 2 records in this Dataset, the first is the Old record and the second have all the changes I made to the first record. I'm a bit confused, will I always get this DataSet with 2 records? I thought that it should have only one record with the Old/New values. Thanks.

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• How do You Get a Specific Value From a System.Data.DataTable Object?

  - by Giffyguy

  I'm a low-level algorithm programmer, and databases are not really my thing - so this'll be a n00b question if ever there was one. I'm running a simple SELECT query through our development team's DAO. The DAO returns a System.Data.DataTable object containing the results of the query. This is all working fine so far. The problem I have run into now: I need to pull a value out of one of the fields of the first row in the resulting DataTable - and I have no idea where to even start. Microsoft is so confusing about this! Arrrg! Any advice would be appreciated. I'm not providing any code samples, because I believe that context is unnecessary here. I'm assuming that all DataTable objects work the same way, no matter how you run your queries - and therefore any additional information would just make this more confusing for everyone.

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• What are the "Navigation Properties" in this data model for?

  - by d03boy

  I've been wondering how to properly set up many-to-many relationships in ASP.NET MVC 2 using Linq2Sql for quite some time now. I found this blog post that seems to have a similar model layout as mine. If you take a look at the first screenshot showing the data model you can see that each model has "Navigation Properties" at the bottom of it. What exactly is this and why don't my models have them? I have the proper foreign keys put in to place. Most specifically, I am looking at the relationship between the Article and Category models since that is the only many-to-many relationship that I see and that's what I'm trying to model. Obviously I use an intermediary joining table between these two tables but I am having trouble understanding the proper methodology for modeling that relationship and I'm not finding this information anywhere on The Google.

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• Handling credit cards and IOS

  - by Susan Jackie

  I am using NSUrlConnection asyncronous request to transmit credit card information to a secure third party server. I do the following: I get the credit card number, cvv, etc from the uitextfields. Encode the credit card information into a json format. Set as httpd body of the nsurlconnection request as follows: NSURL * url = [[NSURL URLWithString: "https://www.example.com"]; NSMutableURLRequest * request = [[NSMutableURLRequest alloc] initWithURL: url]; [request setHTTPMethod: @"POST"]; [request setValue:@"application/json" forHTTPHeaderField:@"Accept"]; [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"]; [request setHTTPBody: [NSJSONSerialization dataWithJSONObject: params options: kNilOptions error: &parseError]]; Send this information via asynchronous request to a secure third party server: [NSURLConnection sendAsynchronousRequest:request queue: queue completionHandler:^(NSURLResponse *response, NSData *data, NSError * requestError) { What should I be considering to send user credit card information to a third party server using nsurlconnection asynchronous request?

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• loading data from file into 2d array

  - by Chris

  I am just starting with perl and would like some help with arrays please. I am reading lines from a data file and splitting the line into fields: open (INFILE, $infile); do { my $linedata = <INFILE>; my @data= split ',',$linedata; .... } until eof; I then want to store the individual field values (in @data) in and array so that the array looks like the input data file ie, the first "row" of the array contains the first line of data from INFILE etc. Each line of data from the infile contains 4 values, x,y,z and w and once the data are all in the array, I have to pass the array into another program which reads the x,y,z,w and displays the w value on a screen at the point determined by the x,y,z value. I can not pas the data to the other program on a row-by-row basis as the program expects the data to in a 2d matrtix format. Any help greatly appreciated. Chris

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• controlling if exceptions are swallowed by a static boolean

  - by sandis

  So we are a few guys developing this product that is communicating with a really unstable server. It often returns very strange and corrupt data. During testing we want the resulting crashes to be loud, so we discover them. But every other day we need to demonstrate our product for a potential customer. To the customer the errors will go undiscovered if we just swallow them. I am thinking about implementing something like this around all server communication to quickly switch between swallowing exceptions and crashing: try { apiCall(); } catch (Exception e) { if(!SWALLOW_EXCEPTION) { throw e; } } Is this an awesome idea, or can it be done in a better way?

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• Handling over-long UTF-8 sequences

  - by Grant McLean

  I've just been reworking my Encoding::FixLatin Perl module to handle over-long utf8 byte sequences and convert them to the shortest normal form. My question is quite simply "is this a bad idea"? A number of sources (including this RFC) suggest that any over-long utf8 should be treated as an error and rejected. They caution against "naive implementations" and leave me with the impression that these things are inherently unsafe. Since the whole purpose of my module is to clean up messy data files with mixed encodings and convert them to nice clean utf8, this seems like just one more thing I can clean up so the application layer doesn't have to deal with it. My code does not concern itself with any semantic meaning the resulting characters might have, it simply converts them into a normalised form. Am I missing something. Is there a hidden danger I haven't considered?

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• How to retrieve JSON Data Array from ExtJS Store

  - by user291928

  Is there a method allowing me to return my stored data in an ExtJS Grid Panel exactly the way I loaded it using: var data = ["value1", "value2"] Store.loadData(data); I would like to have a user option to reload the Grid, but changes to the store need to be taken into account. The user can make changes and the grid is dynamically updated, but if I reload the grid, the data that was originally loaded is shown even though the database has been updated with the new changes. I would prefer not to reload the page and just let them reload the grid data itself with the newly changed store. I guess im looking for something like this: var data = Store.getData(); //data = ["value1", "value2"] after its all said and done. Or is there a different way to refresh the grid with new data that I am not aware of. Even using the proxy still uses the "original" data, not the new store. Thanks in advance

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• Best way to store a large amount of game objects and update the ones onscreen

  - by user3002473

  Good afternoon guys! I'm a young beginner game developer working on my first large scale game project and I've run into a situation where I'm not quite sure what the best solution may be (if there is a lone solution). The question may be vague (if anyone can think of a better title after having read the question, please edit it) or broad but I'm not quite sure what to do and I thought it would help just to discuss the problem with people more educated in the field. Before we get started, here are some of the questions I've looked at for help in the past: Best way to keep track of game objects Elegant way to simulate large amounts of entities within a game world What is the most efficient container to store dynamic game objects in? I've also read articles about different data structures commonly used in games to store game objects such as this one about slot maps, but none of them are really what I'm looking for. Also, if it helps at all I'm using Python 3 to design the game. It has to be Python 3, if I could I would use C++ or Unityscript or something else, but I'm restricted to having to use Python 3. My game will be a form of side scroller shooter game. In said game the player will traverse large rooms with large amounts of enemies and other game objects to update (think some of the larger areas in Cave Story or Iji). The player obviously can't see the entire room all at once, so there is a viewport that follows the player around and renders only a selection of the room and the game objects that it contains. This is not a foreign concept. The part that's getting me confused has to do with how certain game objects are updated. Some of them are to be updated constantly, regardless of whether or not they can be seen. Other objects however are only to be updated when they are onscreen (for example, an enemy would only be updated to react to the player when it is onscreen or when it is in a certain range of the screen). Another problem is that game objects have to be easily referable by other game objects; something that happens in the player's update() method may affect another object in the world. Collision detection in games is always a serious problem. I need a way of containing the game objects such that it minimizes the number of cases when testing for collisions against one another. The final problem is that of creating and destroying game objects. I think this problem is pretty self explanatory. To store the game objects then I've considered a number of different methods. The original method I had was to simply store all the objects in a hash table by an id. This method was simple, and decently fast as it allows all the objects to be looked up in O(1) complexity, and also allows them to be deleted fairly easily. Hash collisions would not be a major problem; I wasn't originally planning on using computer generated ids to store the game objects I was going to rely on them all using ids given to them by the game designer (such names would be strings like 'Player' or 'EnemyWeapon4'), and even if I did use computer generated ids, if I used a decent hashing algorithm then the chances of collisions would be around 1 in 4 billion. The problem with using a hash table however is that it is inefficient in checking to see what objects are in range of the viewport. Considering the fact that certain game objects move (as well as the viewport itself), the only solution I could think of in order to only update objects that are in the viewport would be to iterate through every object in the hash table and check if it is in the viewport or not, updating only the ones that are in the valid area. This would be incredibly slow in scenarios where the amount of game objects exceeds 500, or even 200. The second solution was to store everything in a 2-d list. The world is partitioned up into cells (a tilemap essentially), where each cell or tile is the same size and is square. Each cell would contain a list of the game objects that are currently occupying it (each game object would be inserted into a cell depending on the center of the object's collision mask). A 2-d list would allow me to take the top-left and bottom-right corners of the viewport and easily grab a rectangular area of the grid containing only the cells containing entities that are in valid range to be updated. This method also solves the problem of collision detection; when I take an entity I can find the cell that it is currently in, then check only against entities in it's cell and the 8 cells around it. One problem with this system however is that it prohibits easy lookup of game objects. One solution I had would be to simultaneously keep a hash table that would contain all the positions of the objects in the 2-d list indexed by the id of said object. The major problem with a 2-d list is that it would need to be rebuilt every single game frame (along with the hash table of object positions), which may be a serious detriment to game speed. Both systems have ups and downs and seem to solve some of each other's problems, however using them both together doesn't seem like the best solution either. If anyone has any thoughts, ideas, suggestions, comments, opinions or solutions on new data structures or better implementations of the existing data structures I have in mind, please post, any and all criticism and help is welcome. Thanks in advance! EDIT: Please don't close the question because it has a bad title, I'm just bad with names!

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• how to format date when i load data from google-app-engine..

  - by zjm1126

  i use remote_api to load data from google-app-engine. appcfg.py download_data --config_file=helloworld/GreetingLoad.py --filename=a.csv --kind=Greeting helloworld the setting is: class AlbumExporter(bulkloader.Exporter): def __init__(self): bulkloader.Exporter.__init__(self, 'Greeting', [('author', str, None), ('content', str, None), ('date', str, None), ]) exporters = [AlbumExporter] and i download a.csv is : the date is not readable , and the date in appspot.com admin is : so how to get the full date ?? thanks i change this : class AlbumExporter(bulkloader.Exporter): def __init__(self): bulkloader.Exporter.__init__(self, 'Greeting', [('author', str, None), ('content', str, None), ('date', lambda x: datetime.datetime.strptime(x, '%m/%d/%Y').date(), None), ]) exporters = [AlbumExporter] but the error is :

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• How to handle concurrency control in ASP.NET Dynamic Data?

  - by Andrew

  I've been quite impressed with dynamic data and how easy and quick it is to get a simple site up and running. I'm planning on using it for a simple internal HR admin site for registering people's skills/degrees/etc. I've been watching the intro videos at www.asp.net/dynamicdata and one thing they never mention is how to handle concurrency control. It seems that DD does not handle it right out of the box (unless there is some setting I haven't seen) as I manually generated a change conflict exception and the app failed without any user friendly message. Anybody know if DD handles it out of the box? Or do you have to somehow build it into the site?

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• How does the iPhone SDK Core Data system store date types to sqlite?

  - by Andrew Arrow

  I used core data to do this: NSManagedObjectContext *m = [self managedObjectContext]; Foo *f = (Foo *)[NSEntityDescription insertNewObjectForEntityForName:@"Foo" inManagedObjectContext:m]; f.created_at = [NSDate date]; [m insertObject:f]; NSError *error; [m save:&error]; Where the created_at field is defined as type "Date" in the xcdatamodel. When I export the sql from the sqlite database it created, created_at is defined as type "timestamp" and the values look like: 290902422.72624 Nine digits before the . and then some fraction. What is this format? It's not epoch time and it's not julianday format. Epoch would be: 1269280338.81213 julianday would be: 2455278.236746875 (notice only 7 digits before the . not 9 like I have) How can I convert a number like 290902422.72624 to epoch time? Thanks!

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• The best way to display data in a table view?

  - by LawVS

  Hey guys, I'm trying to display nutritional information in a table view but am struggling about the best way to show the info. I don't want to create unique views for each page as that would take up a lot of space. My ideal avenue would be like a website having links to data pages instead of individual views for each page. How would I best implement that? For example, I would want the first page to be a list of restaurants, then as you press the restaurant it would list the different types of food...the next page would be a list of those foods and then the final page would be the nutrition info itself. Thanks

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• How do I display non-normalized data in a hierarchical structure?

  - by rofly

  My issue is that I want to display data in a hierarchal structure as so: Democrat County Clerk Candidate 1 Candidate 2 Magistrate Candidate 1 Candidate 2 Candidate 3 But I'm retrieving the dataset like this: Party | Office | Candidate Democrat | County Clerk | Candidate 1 Democrat | County Clerk | Candidate 2 Democrat | Magistrate | Candidate 1 Democrat | Magistrate | Candidate 2 Democrat | Magistrate | Candidate 3 I planned on using nested repeaters, but I need a distinct value of Party, and then distinct values of office name within that party in order to do it. Are there any .NET functions to easily do what I'm attempting to? Would there be a better way of displaying the information other than repeaters? Thanks in advance!

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• Handling Data Hierarchies in code

  - by Miau

  Hi there So, say I have a string to parse with a given format that maps to a tree like data structure. The string is kinda similar to a folder path, and the structure is similar to a file structure, except its got some rules so for something@cat1@otherSomething you would get /something/cat1/otherSomething for something@cat2@otherSomething you would get /something/cat2/otherSomething other examples /OtherThing/cat1/otherSomething/Blah /OtherThing/cat4/otherSomething Where something, cat1, otherSomethign, etc are some sort of instances of ICategory There are certain rules that control what subcategories are valid and which subcategories are not acceptable, at the moment I m considering a heavy Object hierachy, but I know this is not a flexible solution, I d prefer the categories to be a bit more general but again, since there are rules about what can go next I m not sure how to do this. An example of a rule can be: OtherThing can only have subcategories cat1 and cat4 ( anything else is invalid) An option would be to use some sort of convention based aproach to instantiate a particular class given a subsection of the string(like cat4) but it seems a bit too complex, I m all ears Thanks

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• What is the best data structure and algorithm for comparing a list of strings?

  - by Chiraag E Sehar

  I want to find the longest possible sequence of words that match the following rules: Each word can be used at most once All words are Strings Two strings sa and sb can be concatenated if the LAST two characters of sa matches the first two characters of sb. In the case of concatenation, it is performed by overlapping those characters. For example: sa = "torino" sb = "novara" sa concat sb = "torinovara" For example, I have the following input file, "input.txt": novara torino vercelli ravenna napoli liverno messania noviligure roma And, the output of the above file according to the above rules should be: torino novara ravenna napoli livorno noviligure since the longest possible concatenation is: torinovaravennapolivornovilligure Can anyone please help me out with this? What would be the best data structure for this?

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• C#: When should I use TryParse?

  - by zxcvbnm

  I understand it doesn't throw an Exception and because of that it might be sightly faster, but also, you're most likely using it to convert input to data you can use, so I don't think it's used so often to make that much of difference in terms of performance. Anyway, the examples I saw are all along the lines of an if/else block with TryParse, the else returning an error message. And to me, that's basically the same thing as using a try/catch block with the catch returning an error message. So, am I missing something? Is there a situation when this is actually useful?

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• Core Data: Fetch all entities in a to-many-relationship of a particular object?

  - by Björn Marschollek

  Hi there, in my iPhone application I am using simple Core Data Model with two entities (Item and Property): Item name properties Property name value item Item has one attribute (name) and one one-to-many-relationship (properties). Its inverse relationship is item. Property has two attributes the according inverse relationship. Now I want to show my data in table views on two levels. The first one lists all items; when one row is selected, a new UITableViewController is pushed onto my UINavigationController's stack. The new UITableView is supposed to show all properties (i.e. their names) of the selected item. To achieve this, I use a NSFetchedResultsController stored in an instance variable. On the first level, everything works fine when setting up the NSFetchedResultsController like this: -(NSFetchedResultsController *) fetchedResultsController { if (fetchedResultsController) return fetchedResultsController; // goal: tell the FRC to fetch all item objects. NSFetchRequest *fetch = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Item" inManagedObjectContext:self.moContext]; [fetch setEntity:entity]; NSSortDescriptor *sort = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES]; [fetch setSortDescriptors:[NSArray arrayWithObject:sort]]; [fetch setFetchBatchSize:10]; NSFetchedResultsController *frController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetch managedObjectContext:self.moContext sectionNameKeyPath:nil cacheName:@"cache"]; self.fetchedResultsController = frController; fetchedResultsController.delegate = self; [sort release]; [frController release]; [fetch release]; return fetchedResultsController; } However, on the second-level UITableView, I seem to do something wrong. I implemented the fetchedresultsController in a similar way: -(NSFetchedResultsController *) fetchedResultsController { if (fetchedResultsController) return fetchedResultsController; // goal: tell the FRC to fetch all property objects that belong to the previously selected item NSFetchRequest *fetch = [[NSFetchRequest alloc] init]; // fetch all Property entities. NSEntityDescription *entity = [NSEntityDescription entityForName:@"Property" inManagedObjectContext:self.moContext]; [fetch setEntity:entity]; // limit to those entities that belong to the particular item NSPredicate *predicate = [NSPredicate predicateWithFormat:[NSString stringWithFormat:@"item.name like '%@'",self.item.name]]; [fetch setPredicate:predicate]; // sort it. Boring. NSSortDescriptor *sort = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES]; [fetch setSortDescriptors:[NSArray arrayWithObject:sort]]; NSError *error = nil; NSLog(@"%d entities found.",[self.moContext countForFetchRequest:fetch error:&error]); // logs "3 entities found."; I added those properties before. See below for my saving "problem". if (error) NSLog("%@",error); // no error, thus nothing logged. [fetch setFetchBatchSize:20]; NSFetchedResultsController *frController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetch managedObjectContext:self.moContext sectionNameKeyPath:nil cacheName:@"cache"]; self.fetchedResultsController = frController; fetchedResultsController.delegate = self; [sort release]; [frController release]; [fetch release]; return fetchedResultsController; } Now it's getting weird. The above NSLog statement returns me the correct number of properties for the selected item. However, the UITableViewDelegate method tells me that there are no properties: -(NSInteger) tableView:(UITableView *)table numberOfRowsInSection:(NSInteger)section { id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section]; NSLog(@"Found %d properties for item \"%@\". Should have found %d.",[sectionInfo numberOfObjects], self.item.name, [self.item.properties count]); // logs "Found 0 properties for item "item". Should have found 3." return [sectionInfo numberOfObjects]; } The same implementation works fine on the first level. It's getting even weirder. I implemented some kind of UI to add properties. I create a new Property instance via Property *p = [NSEntityDescription insertNewObjectForEntityForName:@"Property" inManagedObjectContext:self.moContext];, set up the relationships and call [self.moContext save:&error]. This seems to work, as error is still nil and the object gets saved (I can see the number of properties when logging the Item instance, see above). However, the delegate methods are not fired. This seems to me due to the possibly messed up fetchRequest(Controller). Any ideas? Did I mess up the second fetch request? Is this the right way to fetch all entities in a to-many-relationship for a particular instance at all?

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• Handling input from a keyboard wedge

  - by JDibble

  Following on from the question asked by Mykroft Best way to handle input from a keyboard “wedge” http://stackoverflow.com/questions/42437/best-way-to-handle-input-from-a-keyboard-wedge. I need to write a class that intercepts key strokes, if the input is determined to be from the keyboard wedge (as described in the above post) the data will be directed to POS classes to handle, otherwise they keystrokes must be passed on to be handled in windows in the normal manner. This raises two questions How can I intercept key strokes when not in a WinForm. How can I pass on the keypresses to windows. Thanks JDibble

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• How do you delete a core data entry from the detail view?

  - by Sam

  I am working with an app similar to apple's core data recipes sample code. I want to be able to delete the entry from the detail view, much like apple's contacts app. The code below is deleting the 1st entry and not the selected entry. Not sure what I am doing wrong. NSIndexPath *indexPath = [myTableView indexPathForSelectedRow]; NSManagedObjectContext *context = [fetchedResultsController managedObjectContext]; [context deleteObject:[fetchedResultsController objectAtIndexPath:indexPath]]; [myTableView reloadData];

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• NSArrayController that is sorted and unique (no duplicates) for use in a pop-up in a core-data app

  - by Douglas Weaver

  I have core data app with an entity OBSERVATION that has as one of its attributes DEALNAME. I want to reference through Interface Builder or by making custom modifications to an NSArrayController a list of unique sorted dealnames so that I can use them in a pop-up. I have attempted to use @distinctUnionOfSets (and @distinctUnionOfArrays) but am unable to locate the proper key sequence. I can sort the ArrayController by providing a sort descriptor, but do not know how to eliminate duplicates. Are the @distinct... keys the right methodology? It would seem to provide the easiest way to optimize the use of IB. Is there a predicate form for removing duplicates? Or do I need to use my custom controller to extract an NSSet of the specific dealnames, put them back in an array and sort it and reference the custom array from IB? Any help would be appreciated. I am astounded that other have not tried to create a sorted-unique pop-up in tableviews.

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• Access data of a XSL file from a JSF...

  - by Asela

  Hi all, I'm having 2 simple XML & XSL files as follows. form_1.xml <?xml version="1.0" encoding="windows-1252"?> <?xml-stylesheet type="text/xsl" href="form_1.xsl"?> <myform> </myform> form_1.xsl <?xml version="1.0" encoding="windows-1252"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:template match="myform"> <html> <body> <form> <div align="center"> <h2>My first form in XSL</h2> <table cellspacing="1" cellpadding="1"> <tr> <td>First name : </td> <td> <input type="text"></input> </td> </tr> <tr> <td>Last name : </td> <td> <input type="text"></input> </td> </tr> <tr> <td>Address : </td> <td> <input type="text"></input> </td> </tr> </table> </div> </form> </body> </html> </xsl:template> </xsl:stylesheet> Now I have a JSF file where I have embeded the form_1.xml file inside an iFrame. Inside my JSF, I have submit & reset buttons as follows. myJsf.xhtml <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:h="http://java.sun.com/jsf/html" xmlns:f="http://java.sun.com/jsf/core" xmlns:ui="http://java.sun.com/jsf/facelets" xmlns:utils="http://java.sun.com/jsf/composite/utils"> <h:head> <title>::: The form filler application :::</title> <link href="./css/styles.css" rel="stylesheet" type="text/css" /> </h:head> <h:body> <div align="center"> <table cellspacing="2" cellpadding="2"> <tr> <th class="title">&nbsp; My form filler &nbsp;</th> </tr> </table> <br /> <fieldset><legend>Fill appropriate data in the following form</legend> <h:form> <div align="center"> <table> <tr> <td colspan="2"><iframe src="form_1.xml" frameborder="0" width="500px" height="500px"></iframe></td> </tr> <tr></tr> <tr> <td align="right"><h:commandButton value="Save data" action="#{myManagedBean.printValuesEnteredInTheForm}" /></td> <td align="left"><h:commandButton type="reset" value="Clear" /></td> </tr> </table> </div> </h:form></fieldset> </div> </h:body> </html> Now my question is that upon clicking the Submit button in my JSF, how do I access the values which I have entered in the XSL file? Any help is greatly appreciated. Thanks in advance. Reagrds, Asela.

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• handling activity destruction in multithreaded android app

  - by Jayesh

  Hi, I have a multithreded app where background threads are used to load data over network or from disk/db. Every once in a while user will perform some action e.g. fetch news over network, which will spawn a background AsyncTask, but for some reason user will quit the app (press back button so that activity gets destroyed). In most such scenarios, I make appropriate checks in the background thread after it returns from n/w i/o, so that it won't crash by accessing members of the activity that is destroyed by now. However some corner cases are left where crashes happen, because the background thread would access some member of activity that is now null. Do other Android developers have some generic/recommended framework to handle such scenarios? These are the times when I wish android would have guaranteed termination of all threads when activity destroys (in the same way that regular linux process cleans up when it's quit)... but I guess Android devs had good reasons for not exposing process lifetimes through the api.

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• Collaborative Whiteboard using WebSocket in GlassFish 4 - Text/JSON and Binary/ArrayBuffer Data Transfer (TOTD #189)

  - by arungupta

  This blog has published a few blogs on using JSR 356 Reference Implementation (Tyrus) as its integrated in GlassFish 4 promoted builds. TOTD #183: Getting Started with WebSocket in GlassFish TOTD #184: Logging WebSocket Frames using Chrome Developer Tools, Net-internals and Wireshark TOTD #185: Processing Text and Binary (Blob, ArrayBuffer, ArrayBufferView) Payload in WebSocket TOTD #186: Custom Text and Binary Payloads using WebSocket One of the typical usecase for WebSocket is online collaborative games. This Tip Of The Day (TOTD) explains a sample that can be used to build such games easily. The application is a collaborative whiteboard where different shapes can be drawn in multiple colors. The shapes drawn on one browser are automatically drawn on all other peer browsers that are connected to the same endpoint. The shape, color, and coordinates of the image are transfered using a JSON structure. A browser may opt-out of sharing the figures. Alternatively any browser can send a snapshot of their existing whiteboard to all other browsers. Take a look at this video to understand how the application work and the underlying code. The complete sample code can be downloaded here. The code behind the application is also explained below. The web page (index.jsp) has a HTML5 Canvas as shown: <canvas id="myCanvas" width="150" height="150" style="border:1px solid #000000;"></canvas> And some radio buttons to choose the color and shape. By default, the shape, color, and coordinates of any figure drawn on the canvas are put in a JSON structure and sent as a message to the WebSocket endpoint. The JSON structure looks like: { "shape": "square", "color": "#FF0000", "coords": { "x": 31.59999942779541, "y": 49.91999053955078 }} The endpoint definition looks like: @WebSocketEndpoint(value = "websocket",encoders = {FigureDecoderEncoder.class},decoders = {FigureDecoderEncoder.class})public class Whiteboard { As you can see, the endpoint has decoder and encoder registered that decodes JSON to a Figure (a POJO class) and vice versa respectively. The decode method looks like: public Figure decode(String string) throws DecodeException { try { JSONObject jsonObject = new JSONObject(string); return new Figure(jsonObject); } catch (JSONException ex) { throw new DecodeException("Error parsing JSON", ex.getMessage(), ex.fillInStackTrace()); }} And the encode method looks like: public String encode(Figure figure) throws EncodeException { return figure.getJson().toString();} FigureDecoderEncoder implements both decoder and encoder functionality but thats purely for convenience. But the recommended design pattern is to keep them in separate classes. In certain cases, you may even need only one of them. On the client-side, the Canvas is initialized as: var canvas = document.getElementById("myCanvas");var context = canvas.getContext("2d");canvas.addEventListener("click", defineImage, false); The defineImage method constructs the JSON structure as shown above and sends it to the endpoint using websocket.send(). An instant snapshot of the canvas is sent using binary transfer with WebSocket. The WebSocket is initialized as: var wsUri = "ws://localhost:8080/whiteboard/websocket";var websocket = new WebSocket(wsUri);websocket.binaryType = "arraybuffer"; The important part is to set the binaryType property of WebSocket to arraybuffer. This ensures that any binary transfers using WebSocket are done using ArrayBuffer as the default type seem to be blob. The actual binary data transfer is done using the following: var image = context.getImageData(0, 0, canvas.width, canvas.height);var buffer = new ArrayBuffer(image.data.length);var bytes = new Uint8Array(buffer);for (var i=0; i<bytes.length; i++) { bytes[i] = image.data[i];}websocket.send(bytes); This comprehensive sample shows the following features of JSR 356 API: Annotation-driven endpoints Send/receive text and binary payload in WebSocket Encoders/decoders for custom text payload In addition, it also shows how images can be captured and drawn using HTML5 Canvas in a JSP. How could this be turned in to an online game ? Imagine drawing a Tic-tac-toe board on the canvas with two players playing and others watching. Then you can build access rights and controls within the application itself. Instead of sending a snapshot of the canvas on demand, a new peer joining the game could be automatically transferred the current state as well. Do you want to build this game ? I built a similar game a few years ago. Do somebody want to rewrite the game using WebSocket APIs ? :-) Many thanks to Jitu and Akshay for helping through the WebSocket internals! Here are some references for you: JSR 356: Java API for WebSocket - Specification (Early Draft) and Implementation (already integrated in GlassFish 4 promoted builds) Subsequent blogs will discuss the following topics (not necessary in that order) ... Error handling Interface-driven WebSocket endpoint Java client API Client and Server configuration Security Subprotocols Extensions Other topics from the API

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• Sharepoint 2007 : Saving Form data with page redirection using custom parameters.

  - by Deepu

  HI Experts, After saving the form data I would like to REDIRECT to different pages based on the @Status value using the input type button. <input type="button" value="Save" name="btnSave" id="btnSave" onclick="{ddwrt:GenFireServerEvent('_commit;_redirect={*Confirm.aspx?ID=1}')};" /* if @Status == "Draft" url = "draft.aspx ? ID = " @ID else if @Status == "Save" url = "save.aspx ? ID = " @ID else url = "confirm.aspx ? ID = " @ID Here @ID and @Status are share point list column names Now I have hard-coded the url Confirm.aspx?ID=4. But I want to check the status value using XSLT condition and set different URL name with @ID value.. How do I achieve this.. any help would be appreciated.. thanks deepu

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