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  • How to model in J2EE / JEE?

    - by Harry
    Let's say, I have decided to go with J(2)EE stack for my enterprise application. Now, for domain modelling (or: for designing the M of MVC), which APIs can I safely assume and use, and which I should stay away from... say, via a layer of abstraction? For example, Should I go ahead and litter my Model with calls to Hibernate/JPA API? Or, should I build an abstraction... a persistence layer of my own to avoid hard-coding against these two specific persistence APIs? Why I ask this: Few years ago, there was this Kodo API which got superseded by Hibernate. If one had designed a persistence layer and coded the rest of the model against this layer (instead of littering the Model with calls to specific vendor API), it would have allowed one to (relatively) easily switch from Kodo to Hibernate to xyz. Is it recommended to make aggressive use of the *QL provided by your persistence vendor in your domain model? I'm not aware of any real-world issues (like performance, scalability, portability, etc) arising out of a heavy use of an HQL-like language. Why I ask this: I would like to avoid, as much as possible, writing custom code when the same could be accomplished via query language that is more portable than SQL. Sorry, but I'm a complete newbie to this area. Where could I find more info on this topic? Many thanks in advance. /HS

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  • Subclassing and adding data members

    - by Marius
    I have an hierarchy of classes that looks like the following: class Critical { public: Critical(int a, int b) : m_a(a), m_b(b) { } virtual ~Critical() { } int GetA() { return m_a; } int GetB() { return m_b; } void SetA(int a) { m_a = a; } void SetB(int b) { m_b = b; } protected: int m_a; int m_b; }; class CriticalFlavor : public Critical { public: CriticalFlavor(int a, int b, int flavor) : Critical(a, b), m_flavor(flavor) { } virtual ~CriticalFlavor() { } int GetFlavor() { return m_flavor; } void SetFlavor(int flavor) { m_flavor = flavor; } protected: int m_flavor; }; class CriticalTwist : public Critical { public: CriticalTwist(int a, int b, int twist) : Critical(a, b), m_twist(twist) { } virtual ~CriticalTwist() { } int GetTwist() { return m_twist; } void SetTwist(int twist) { m_twist = twist; } protected: int m_twist; }; The above does not seem right to me in terms of the design and what bothers me the most is the fact that the addition of member variables seems to drive the interface of these classes (the real code that does the above is a little more complex but still embracing the same pattern). That will proliferate when in need for another "Critical" class that just adds some other property. Does this feel right to you? How could I refactor such code? An idea would be to have just a set of interfaces and use composition when it comes to the base object like the following: class Critical { public: virtual int GetA() = 0; virtual int GetB() = 0; virtual void SetA(int a) = 0; virtual void SetB(int b) = 0; }; class CriticalImpl { public: CriticalImpl(int a, int b) : m_a(a), m_b(b) { } ~CriticalImpl() { } int GetA() { return m_a; } int GetB() { return m_b; } void SetA(int a) { m_a = a; } void SetB(int b) { m_b = b; } private: int m_a; int m_b; }; class CriticalFlavor { public: virtual int GetFlavor() = 0; virtual void SetFlavor(int flavor) = 0; }; class CriticalFlavorImpl : public Critical, public CriticalFlavor { public: CriticalFlavorImpl(int a, int b, int flavor) : m_flavor(flavor), m_critical(new CriticalImpl(a, b)) { } ~CriticalFlavorImpl() { delete m_critical; } int GetFlavor() { return m_flavor; } void SetFlavor(int flavor) { m_flavor = flavor; } int GetA() { return m_critical-GetA(); } int GetB() { return m_critical-GetB(); } void SetA(int a) { m_critical-SetA(a); } void SetB(int b) { m_critical-SetB(b); } private: int m_flavor; CriticalImpl* m_critical; };

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  • Binary Search Tree can't delete the root

    - by Ali Zahr
    Everything is working fine in this function, but the problem is that I can't delete the root, I couldn't figure out what's the bug here.I've traced the "else part" it works fine until the return, it returns the old value I don't know why. Plz Help! node *removeNode(node *Root, int key) { node *tmp = new node; if(key > Root->value) Root->right = removeNode(Root->right,key); else if(key < Root->value) Root->left = removeNode(Root->left, key); else if(Root->left != NULL && Root->right != NULL) { node *minNode = findNode(Root->right); Root->value = minNode->value; Root->right = removeNode(Root->right,Root->value); } else { tmp = Root; if(Root->left == NULL) Root = Root->right; else if(Root->right == NULL) Root = Root->left; delete tmp; } return Root; }

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  • I have data about deadlocks, but I can't understand why they occur

    - by Alex
    I am receiving a lot of deadlocks in my big web application. http://stackoverflow.com/questions/2941233/how-to-automatically-re-run-deadlocked-transaction-asp-net-mvc-sql-server Here I wanted to re-run deadlocked transactions, but I was told to get rid of the deadlocks - it's much better, than trying to catch the deadlocks. So I spent the whole day with SQL Profiler, setting the tracing keys etc. And this is what I got. There's a Users table. I have a very high usable page with the following query (it's not the only query, but it's the one that causes troubles) UPDATE Users SET views = views + 1 WHERE ID IN (SELECT AuthorID FROM Articles WHERE ArticleID = @ArticleID) And then there's the following query in ALL pages: User = DB.Users.SingleOrDefault(u => u.Password == password && u.Name == username); That's where I get User from cookies. Very often a deadlock occurs and this second Linq-to-SQL query is chosen as a victim, so it's not run, and users of my site see an error screen. I read a lot about deadlocks... And I don't understand why this is causing a deadlock. So obviously both of this queries run very often. At least once a second. Maybe even more often (300-400 users online). So they can be run at the same time very easily, but why does it cause a deadlock? Please help. Thank you

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  • ASP.NET - Update progress while processing data

    - by Danny
    Hope I can explain this correctly. I have a process, that outputs step by step messages (i.e., Processing item 1... Error in item 2 etc etc). I want this to be outputted to the user during the process, and not at the end. I pretty sure i need to do this with threading, but can't find a decent example. Thanks in advanced.

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  • Rowwise iteration of a dictionay object

    - by mono
    I have a dictionary object like: Dictionary<string, HashSet<int>> dict = new Dictionary<string, HashSet<int>>(); dict.Add("foo", new HashSet<int>() { 15,12,16,18}); dict.Add("boo", new HashSet<int>() { 16,47,45,21 }); I have to print in such a way such that result would be as following at each iteration: It1: foo boo //only the key in a row It2: 15 16 It3: 16 47 Can anyone help me to achieve this. Thanks.

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  • Generate sample XML from composite hierarchical structure

    - by Jevgenij Nekrasov
    Let's say I have composite hierarchical structure. Each object in the structure has child collection of the same objects. Each object has XPath property, which stores the exact xpath to the element inside XML file. Right now I am trying to create an extension, which can generate XML string from that hierarchical structure, but first I want to make some sort of research what is the most efficient way to do that? ant what is the easiest way?

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  • how to select and group mysql data based on the follwoing table

    - by user1151680
    how can I achieve the desired result in mysql if my table looks like this. result|year 1 |2011 2 |2011 1 |2011 0 |2011 1 |2012 2 |2012 1 = Won, 2 = lost, 0 = draw Every year can have multiple values like this. Not sure how I can get the desired result like below. year won lost draw totalPlayed 2011 2 1 1 3 2012 1 1 0 2 I have tried the following query but does not get the desired result select year, league_types.league_name, sum(if(result = 1,1,0)) as won, sum(if(result = 0,1,0)) as draw, sum(if(result = 4,1,0)) as noResult, sum(if(result = 2,1,0)) as lost, sum(if(result = 3,1,0)) as tied, sum(if(result > 0 and result < 4,1,0)) as played from match_score_card inner join fixtures on match_score_card.match_id = fixtures.match_id inner join league_types on fixtures.league_id = league_types.league_id where team_id = 1 group by year order by year desc

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  • Matrix multiplication using pairs

    - by sc_ray
    Hi, I am looking into alternate ways to do a Matrix Multiplication. Instead of storing my matrix as a two-dimensional array, I am using a vector such as vector<pair<pair<int,int >,int > > to store my matrix. The pair within my pair (pair) stores my indices (i,j) and the other int stores the value for the given (i,j) pair. I thought I might have some luck implementing my sparse array this way. The problem is when I try to multiply this matrix with itself. If this was a 2-d array implementation, I would have multiplied the matrix as follows: for(i=0; i<row1; i++) { for(j=0; j<col1; j++) { C[i][j] = 0; for(k=0; k<col2; k++) C[i][j] += A[i][j] * A[j][k]; } } Can somebody point out a way to achieve the same result using my vector of 'pair of pairs'? Thanks

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  • Silverlight Image Data Binding

    - by Alexander
    I am new to Silverlight, and have an issue with binding. I have a class ItemsManager, that has inside its scope another class Item. class ItemsManager { ... class Item : INotifyPropertyChanged { ... private BitmapImage bitmapSource; public BitmapImage BitmapSource { get { return bitmapSource; } set { bitmapSource = value; if(PropertyChanged != null )PropertyChanged("BitmapSource") } } } } I do the following in code to test binding: { ItemsManager.Instance.AddItem("123"); //Items manager started downloading item visual //part (in my case bitmap image png) Binding b = new Binding("Source"); b.Source = ItemsManager.Instance.GetItem("123").BitmapSource; b.BindsDirectlyToSource = true; Image img = new Image(); img.SetBinding(Image.SourceProperty, b); img.Width = (double)100.0; img.Height = (double)100.0; LayoutRoot.Children.Add(img); } Once image is loaded, image doesn't appear. Though, if I set directly after image has been loaded its source, it displays well. I also noticed that PropertyChanged("BitmapSource") never fires, because PropertyChanged is null, like Image never binded to it. I am looking forward to hearing from you!

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  • iPhone app store approval - coredata design change

    - by satyam
    I created an app, uploaded to app store and approved by app store as well. Its ready for download. The app is based on coredata. Now I changed the design of the app to add new functionality. Changes include addition of new attributes to current entities, deletion of few entities etc. Now, if I upload the app to app store, does it approve or not? Do I have to put and Note saying that "Please uninstall old version and install new version?" Will my app be approved first of all or not.

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  • The C vs. C++ way

    - by amc
    Hi, So I have to write a program that will iterate through an image and record the pixel locations corresponding to each color pixel that appears in it. For example, given http://www.socuteurl.com/fishywishykissy I need to find the coordinates of all yellow, purple, dark pink, etc pixels. In C++ I would use a hash table to do this. I would iterate through the image, check each pixel's value, look up that value and either add to a vector of pixel coordinates if it were found or add a new entry to the table if the value were not already there. The problem is that I may need to write this program in pure C instead of C++. How would I go about doing this in C? I feel like implementing a hash table would be pretty obnoxious and error-prone: should I avoid doing that? I'm pretty inexperienced with C and have a fair amount of C++ experience, if that matters. Thanks.

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  • Algorithm Question.. Linked List..

    - by AGeek
    Hi, Scenario is as follows:- I want to reverse the direction of the singly linked list, In other words, after the reversal all pointers should now point backwards.. Well the algorithm should take linear time. The solution that i have thought of using another datastructure A Stack.. With the help of which the singly linked list would be easily reversed, with all pointers pointing backwards.. But i am in doubt, that whether the following implementation yeild linear time complexity.. Please comment on this.. And if any other efficient algorithm is in place, then please discuss.. Thanks.

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  • Identifying the parts of this typedef struct in C?

    - by Tommy
    Please help me identify the parts of this typdef struct and what each part does and how it can be used: typedef struct my_struct { int a; int b; int c; } struct_int, *p_s; struct_int struct_array[5]; my_struct is the...? struct_int is the...? *p_s is the...and can be used to point to what? struct_array is the...? Also, when creating the array of structs, why do we use struct_int instead of my_struct ? Thank You!

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  • Java: Is there a way to efficiently insert or remove many elements from the middle of a LinkedList?

    - by allyourcode
    I was expecting to find this in Java's LinkedList, since the point of linked lists is to be able to efficiently insert (and remove) anywhere (assuming you have some kind of pointer to the location where you want to insert or remove). I'm not finding anything in the API though. Am I overlooking something? The closest thing I can find to this are the add and remove method in ListIterator. This has some limitations though. In particular, other iterators become invalid as soon as the underlying LinkedList is modified via remove, according to the API. This is born out in my tests as well; the following program results in a IllegalStateException: import java.util.*; public class RemoveFromLinkedList { public static void main(String[] args) { LinkedList<Integer> myList= new LinkedList<Integer>(); for (int i = 0; i < 10; ++i) { myList.add(i); } ListIterator<Integer> i1 = myList.listIterator(); ListIterator<Integer> i2 = myList.listIterator(); for (int i = 0; i < 3; ++i) { i1.next(); i2.next(); } System.out.println("i1.next() should be 3: " + i1.next()); i1.remove(); i1.remove(); // Exception! System.out.println("i2.next() should be 5: " + i2.next()); } } Ideally, what I'm expecting is something like this: // In my imagination only. This is the way Java actually works, afaict. // Construct two insertion/deletion points in LinkedList myLinkedList. myIterator = myLinkedList.iterator(); for (...) { myIterator.next(); } start = myIterator.clone(); for (...) { myIterator.next(); } // Later... after = myLinkedList.spliceAfter(myIterator, someOtherLinkedList); // start, myIterator, and after are still all valid; thus, I can do this: // Removes everything I just spliced in, as well as some other stuff before that. myLinkedList.remove(start, after); // Now, myIterator is invalid, but not start, nor after. C++ has something like this for its list class (template). Only iterators pointing to moved elements become invalidated, not ALL iterators.

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  • Return REF CURSOR to procedure generated data

    - by ThaDon
    I need to write a sproc which performs some INSERTs on a table, and compile a list of "statuses" for each row based on how well the INSERT went. Each row will be inserted within a loop, the loop iterates over a cursor that supplies some values for the INSERT statement. What I need to return is a resultset which looks like this: FIELDS_FROM_ROW_BEING_INSERTED.., STATUS VARCHAR2 The STATUS is determined by how the INSERT went. For instance, if the INSERT caused a DUP_VAL_ON_INDEX exception indicating there was a duplicate row, I'd set the STATUS to "Dupe". If all went well, I'd set it to "SUCCESS" and proceed to the next row. By the end of it all, I'd have a resultset of N rows, where N is the number of insert statements performed and each row contains some identifying info for the row being inserted, along with the "STATUS" of the insertion Since there is no table in my DB to store the values I'd like to pass back to the user, I'm wondering how I can return the info back? Temporary table? Seems in Oracle temporary tables are "global", not sure I would want a global table, are there any temporary tables that get dropped after a session is done?

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  • Parsing plain data with Javascript (JQuery)

    - by Angelus
    Well , I have this text in a Javascript Var: GIMP Palette Name: Named Colors Columns: 16 # 255 250 250 snow (255 250 250) 248 248 255 ghost white (248 248 255) 245 245 245 white smoke (245 245 245) 220 220 220 gainsboro (220 220 220) 255 250 240 floral white (255 250 240) 253 245 230 old lace (253 245 230) 250 240 230 linen (250 240 230) 250 235 215 antique white (250 235 215) 255 239 213 papaya whip (255 239 213) And What I need is to cut it in lines and put them in one Array , after that i must separate each number and the rest in an string. I'm getting crazy searching functions to do that but now i can't see anyone in Javascript. modified End expected format will be first the next: array[0]='255 250 250 snow (255 250 250)' Then i wanna take it and extract each line into some vars to use them: colour[0]=255; colour[1]=250; colour[2]=250; string=snow (255 250 250); (the vars will be reused with each line)

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  • What's the point of having to provide a cacheName for NSFetchedResultsController?

    - by dontWatchMyProfile
    NSFetchedResultsController *frc = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:moc sectionNameKeyPath:nil cacheName:@"Root"]; Why do we have to think about a cacheName? How important is this decision? What would happen if there are two NSFetchedResultsController instances using the exact same cacheName? Does that matter? Is that some kind of singleton stuff? Thinking about Core Animation, there's also this strange animationID parameter, but setting it to the exact same thing for dozens of simultaneous animations doesn't hurt the animations at all. So I guess it's probably the same thing here...or not?

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  • How to merge existing row with new data in SQLite?

    - by CSharperWithJava
    I have a database full of simple note data, with columns for title, due date, priority, and details. There is also a _id column PRIMARY KEY int. Say I have a note in the table already with some data filled and the rest null. I also have a set of data that will fill all those fields. Is there a way that I can only write data to the fields that are NULL? I can't overwrite existing data, but I'd like to add data to NULL columns. I know the rowId of the target row. If my target row had rowId of 5, I could do something like this: UPDATE SET duedate='some date', priority='2', details='some text' WHERE _id=5 But that would overwrite all the data in that row, and I don't want to lose any data that might be there. How can I change this statement to avoid writing to non-null fields?

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