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• Pro ASP.Net MVC 3 Entity Framework Sports Store tutorial

  - by gary7

  Following the tutorial in the book "Pro ASP.Net MVC 3 Entity Framework" in Chapter 9 - Image Uploads section; asks that the Product class be updated with two new columns - public byte ImageData, and public string ImageType. It also directs that the database be updated with these two columns via the server explorer. After these updates, the discussion directs that the Entity Framework Conceptual Model be updated via the SportsStore.EDMX file. This file does not exist in the source code for the project, and was not used in the project to begin with. Obvious errata for the book. Adding the ADO.NET Entity Data Model to the Project then overrides the EFProduct reposistory (conceptual model used throughout the project) which inherits from the interface IProductsRepository; and results in errors within the mapping. If the project is debugged after the columns are added, an error is thrown related to the new added columns. Has anyone resolved this issue in the project? I haven't found any solutions so far. Thanks!

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• Best way to transfer an Entity Framework object over the web and back via JSON

  - by AVH

  I've got some MVC code that serializes an EF 3.5 object into an anonymous type for return as a JSON result to an AJAX call on my page. The hurdle I have is that when I send the object back to the server via JSON, (and let the ModelBinder deserialize it for me into my EF type), I have to update it in my Entity Framework context manually. Or at least that's what I'm doing now. It has no EntityKey, so attaching it fails. I end up having to look up the old object and update it property by property. Any ideas around this? Is the solution to pass the EntityKey around with my object? Here's what I have: public void Update(Album album) { using (var db = new BandSitesMasterEntities()) { var albumToUpdate = db.Album.First(x => x.ID == album.ID); albumToUpdate.AlbumTitle = album.AlbumTitle; albumToUpdate.Description = album.Description; albumToUpdate.ReleaseYear = album.ReleaseYear; albumToUpdate.ImageURL = album.ImageURL; albumToUpdate.OtherURL = album.OtherURL; db.SaveChanges(); } } And here's what I'd like to do, or something similar: public void Update(Album album) { using (var db = new BandSitesMasterEntities()) { db.Attach(album) db.SaveChanges(); } }

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• multiple definition in header file

  - by Jérôme

  Here is a small code-example from which I'd like to ask a question : complex.h : #ifndef COMPLEX_H #define COMPLEX_H #include <iostream> class Complex { public: Complex(float Real, float Imaginary); float real() const { return m_Real; }; private: friend std::ostream& operator<<(std::ostream& o, const Complex& Cplx); float m_Real; float m_Imaginary; }; std::ostream& operator<<(std::ostream& o, const Complex& Cplx) { return o << Cplx.m_Real << " i" << Cplx.m_Imaginary; } #endif // COMPLEX_H complex.cpp : #include "complex.h" Complex::Complex(float Real, float Imaginary) { m_Real = Real; m_Imaginary = Imaginary; } main.cpp : #include "complex.h" #include <iostream> int main() { Complex Foo(3.4, 4.5); std::cout << Foo << "\n"; return 0; } When compiling this code, I get the following error : multiple definition of operator<<(std::ostream&, Complex const&) I've found that making this fonction inline solves the problem, but I don't understand why. Why does the compiler complain about multiple definition ? My header file is guarded (with #define COMPLEX_H). And, if complaining about the operator<< fonction, why not complain about the public real() fonction, which is defined in the header as well ? And is there another solution as using the inline keyword ?

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• How do virtual destructors work?

  - by Prabhu

  Few hours back I was fiddling with a Memory Leak issue and it turned out that I really got some basic stuff about virtual destructors wrong! Let me put explain my class design. class Base { virtual push_elements() {} }; class Derived:public Base { vector<int> x; public: void push_elements(){ for(int i=0;i <5;i++) x.push_back(i); } }; void main() { Base* b = new Derived(); b->push_elements(); delete b; } The bounds checker tool reported a memory leak in the derived class vector. And I figured out that the destructor is not virtual and the derived class destructor is not called. And it surprisingly got fixed when I made the destructor virtual. Isn't the vector deallocated automatically even if the derived class destructor is not called? Is that a quirk in BoundsChecker tool or is my understanding of virtual destructor wrong?

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• Class initialization and synchronized class method

  - by nybon

  Hi there, In my application, there is a class like below: public class Client { public synchronized static print() { System.out.println("hello"); } static { doSomething(); // which will take some time to complete } } This class will be used in a multi thread environment, many threads may call the Client.print() method simultaneously. I wonder if there is any chance that thread-1 triggers the class initialization, and before the class initialization complete, thread-2 enters into print method and print out the "hello" string? I see this behavior in a production system (64 bit JVM + Windows 2008R2), however, I cannot reproduce this behavior with a simple program in any environments. In Java language spec, section 12.4.1 (http://java.sun.com/docs/books/jls/second_edition/html/execution.doc.html), it says: A class or interface type T will be initialized immediately before the first occurrence of any one of the following: T is a class and an instance of T is created. T is a class and a static method declared by T is invoked. A static field declared by T is assigned. A static field declared by T is used and the reference to the field is not a compile-time constant (§15.28). References to compile-time constants must be resolved at compile time to a copy of the compile-time constant value, so uses of such a field never cause initialization. According to this paragraph, the class initialization will take place before the invocation of the static method, however, it is not clear if the class initialization need to be completed before the invocation of the static method. JVM should mandate the completion of class initialization before entering its static method according to my intuition, and some of my experiment supports my guess. However, I did see the opposite behavior in another environment. Can someone shed me some light on this? Any help is appreciated, thanks.

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• How do I correcly handle ZoneLocalMapping.ResultType.Ambiguous?

  - by RWC

  In my code I try to handle ZoneLocalMapping.ResultType.Ambiguous. The line unambiguousLocalDateTime = localDateTimeMapping.EarlierMapping; throws an InvalidOperationException with message "EarlierMapping property should not be called on a result of type Ambiguous". I have no clue how I should handle it. Can you give me an example? This is what my code looks like: public Instant getInstant(int year, int month, int day, int hour, int minute) { var localDateTime = new LocalDateTime(year, month, day, hour, minute); //invalidated, might be not existing var timezone = DateTimeZone.ForId(TimeZoneId); //TimeZone is set elsewhere, example "Brazil/East" var localDateTimeMapping = timezone.MapLocalDateTime(localDateTime); ZonedDateTime unambiguousLocalDateTime; switch (localDateTimeMapping.Type) { case ZoneLocalMapping.ResultType.Unambiguous: unambiguousLocalDateTime = localDateTimeMapping.UnambiguousMapping; break; case ZoneLocalMapping.ResultType.Ambiguous: unambiguousLocalDateTime = localDateTimeMapping.EarlierMapping; break; case ZoneLocalMapping.ResultType.Skipped: unambiguousLocalDateTime = new ZonedDateTime(localDateTimeMapping.ZoneIntervalAfterTransition.Start, timezone); break; default: throw new InvalidOperationException(string.Format("Unexpected mapping result type: {0}", localDateTimeMapping.Type)); } return unambiguousLocalDateTime.ToInstant(); } If I look at class ZoneLocalMapping I see the following code: /// <summary> /// In an ambiguous mapping, returns the earlier of the two ZonedDateTimes which map to the original LocalDateTime. /// </summary> /// <exception cref="InvalidOperationException">The mapping isn't ambiguous.</exception> public virtual ZonedDateTime EarlierMapping { get { throw new InvalidOperationException("EarlierMapping property should not be called on a result of type " + type); } } That's why I am receiving the exception, but what should I do to get the EarlierMapping?

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• getSharedPreferences not working for me with concerns to ListPreferences and Integers

  - by ideagent

  I'm stuck at a point where I'm trying to get my project to read a preference value (from a ListPreference listing) and then use that value in a basic mathematical subtraction instance. The problem is that the "seek" preference is not being seen by my Java code, and yet the default value is (I've tried the default value with 3000 and now 0). Am i missing something, is there a bug here, known or unknown? Java code chunk where the issues manifests itself: public static final String PREF_FILE_NAME = "preferences"; seekback.setOnClickListener(new Button.OnClickListener() { @Override public void onClick(View view) { try { SharedPreferences preferences = getSharedPreferences(PREF_FILE_NAME, MODE_PRIVATE); Integer storedPreference = preferences.getInt("seek", 0); (mediaPlayer.getCurrentPosition()-storedPreference); } catch (Exception e) { e.printStackTrace(); } } }); Here are some other code bits for my project: From preferences file: <ListPreference android:entries="@array/seconds" android:entryValues="@array/seconds_values" android:summary="sets the seek interval for the seekback and seekforward buttons" android:title="Seek Interval" android:defaultValue="5000" android:key="@string/seek" From strings file: seek From an array file: Five seconds Fifteen seconds Thirty seconds Sixty seconds 5000 15000 30000 60000 let me know if you need to see more code to figure this one out Thanks in advance for any help that can be offered. I've worked over this issue now for a few hours and I'm burnt, a second pair of eyes on it would be very much appreciated. Arg, not sure how to get the code and plain text to format nicely here, even tried the options, like Code Sample, no luck AndroidCoder

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• Why is this linq extension method hit the database twice?

  - by Pure.Krome

  Hi folks, I have an extension method called ToListIfNotNullOrEmpty(), which is hitting the DB twice, instead of once. The first time it returns one result, the second time it returns all the correct results. I'm pretty sure the first time it hits the database, is when the .Any() method is getting called. here's the code. public static IList<T> ToListIfNotNullOrEmpty<T>(this IEnumerable<T> value) { if (value.IsNullOrEmpty()) { return null; } if (value is IList<T>) { return (value as IList<T>); } return new List<T>(value); } public static bool IsNullOrEmpty<T>(this IEnumerable<T> value) { if (value != null) { return !value.Any(); } return true; } I'm hoping to refactor it so that, before the .Any() method is called, it actually enumerates through the entire list. If i do the following, only one DB call is made, because the list is already enumerated. var pewPew = (from x in whatever select x) .ToList() // This enumerates. .ToListIsNotNullOrEmpty(); // This checks the enumerated result. I sorta don't really want to call ToList() then my extension method. Any ideas, folks?

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• Style first 2 TextViews in Android ListView differently

  - by Kurtis Nusbaum

  I have a ListView and I want the first two entries in it to be displayed differently than the rest. Nothing fancy, I want them all to just be text views. But the first two entries need to have different sizes and weights than the rest. I tried modifying the ArrayAdapter class like so: private class BusStopAdapter<T> extends ArrayAdapter<T>{ public BusStopAdapter( Context context, int textViewResourceId, List<T> objects) { super(context, textViewResourceId, objects); } public View getView(int position, View convertView, ViewGroup parent) { TextView toReturn = (TextView)super.getView(position, convertView, parent); if(position == 0){ toReturn.setTextSize(12); toReturn.setText("Previous Bus: " + toReturn.getText()); toReturn.setPadding(0,0,0,0); } else if(position == 1){ toReturn.setTextSize(20); toReturn.setPadding( toReturn.getPaddingLeft(), 0, toReturn.getPaddingRight(), 0 ); toReturn.setText("Next Bus: " + toReturn.getText()); toReturn.setGravity(Gravity.CENTER_HORIZONTAL|Gravity.TOP); } return toReturn; } } But this inadvertantly causes some of the other textviews to take on these special attributes. I think it's because cause textviews get "recycled" in the AbsListAdapter class.

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• ControlCollection extension method optimization

  - by Johan Leino

  Hi, got question regarding an extension method that I have written that looks like this: public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance) where T : class { T control; foreach (Control ctrl in instance) { if ((control = ctrl as T) != null) { yield return control; } foreach (T child in FindControlsOfType<T>(ctrl.Controls)) { yield return child; } } } public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance, Func<T, bool> match) where T : class { return FindControlsOfType<T>(instance).Where(match); } The idea here is to find all controls that match a specifc criteria (hence the Func<..) in the controls collection. My question is: Does the second method (that has the Func) first call the first method to find all the controls of type T and then performs the where condition or does the "runtime" optimize the call to perform the where condition on the "whole" enumeration (if you get what I mean). secondly, are there any other optimizations that I can do to the code to perform better. An example can look like this: var checkbox = this.Controls.FindControlsOfType<MyCustomCheckBox>( ctrl => ctrl.CustomProperty == "Test" ) .FirstOrDefault();

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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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• Static Variables somehow maintaining state?

  - by gfoley

  I am working on an existing project, setup by another coder. I'm having some trouble understanding how state is being maintained between pages. There is a Class library which has some helper objects. Mostly these objects are just used for there static methods and rarely instantiated or inherited. This is an example class I'm testing with. public sealed class Application { public static string Test; } Now when i run something like the following in the base class of my page, I would expect the result to be "1: 2:Test" all the time (note that "1" is empty), but strangly its only this way the first time it is run. Then every time afterwards its "1:Test 2:Test". Somehow its maintaining the state of the static variable between pages and being refreshed?? Response.Write("1:" + SharedLibrary.Application.Test); SharedLibrary.Application.Test = "Test"; Response.Write(" 2:" + SharedLibrary.Application.Test); I need to create more classes like this, but want to understand why this is occurring in the first place. Many Thanks

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• Basic PHP OOPS Query

  - by appu

  Ok. I am starting out OOPS in PHP. Created a couple of classes: customer(parent) and sales(child) class that inherits from parent class. Created another testcustomer.php in which a new sales object is created however the salesprint() function defined in the sales class does not echo out customer's name though it is set to be "Jane" in the class.customer.php(parent). My thinking is that when sales class extends customer class PHP automatically includes all the code from class.customer.php to sales.customer.php and therefore the constructor in parent class set $name to "Jane". Here is the code: class.customer.php <?php class customer{ private $name; private $cust_no; public function __construct($customerid) { $this->name = 'Jane'; $this->cust_no = $customerid; } } ?> class.sales.php <?php require_once('class.customer.php'); class sales extends customer{ public function salesprint($customerid) { echo "Hello $this->name this is a print of your purchased products"; } } ?> testcustomer.php require_once('class.sales.php'); $objsales = new sales(17); $objsales->salesprint(17); ?> The Output I get Hello this is a print of your purchased products. What am i doing wrong ? thanks romesh

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• WCF Async callback setup for polled device

  - by Mark Pim

  I have a WCF service setup to control a USB fingerprint reader from our .Net applications. This works fine and I can ask it to enroll users and so on. The reader allows identification (it tells you that a particular user has presented their finger, as opposed to asking it to verify that a particular user's finger is present), but the device must be constantly polled while in identification mode for its status - when a user is detected the status changes. What I want is for an interested application to notify the service that it wants to know when a user is identified, and provide a callback that gets triggered when this happens. The WCF service will return immediately and spawn a thread in the background to continuously poll the device. This polling could go on for hours at a time if no one tries to log in. What's the best way to acheive this? My service contract is currently defined as follows: [ServiceContract (CallbackContract=typeof(IBiometricCallback))] public interface IBiometricWcfService { ... [OperationContract (IsOneWay = true)] void BeginIdentification(); ... } public interface IBiometricCallback { ... [OperationContract(IsOneWay = true)] void IdentificationFinished(int aUserId, string aMessage, bool aSuccess); ... } In my BeginIdentification() method can I easily spawn a worker thread to poll the device, or is it easier to make the WCF service asynchronous?

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• Spring 3 MVC validation BindingResult doesn't contain any errors

  - by Travelsized

  I'm attempting to get a Spring 3.0.2 WebMVC project running with the new annotated validation support. I have a Hibernate entity annotated like this: @Entity @Table(name = "client") public class Client implements Serializable { private static final long serialVersionUID = 1L; @Id @Basic(optional = false) @Column(name = "clientId", nullable = false) @NotEmpty private Integer clientId; @Basic(optional = false) @Column(name = "firstname", nullable = false, length = 45) @NotEmpty @Size(min=2, max=45) private String firstname; ... more fields, getters and setters } I've turned on mvc annotation support in my applicationContext.xml file: <mvc:annotation-driven /> And I have a method in my controller that responds to a form submission: @RequestMapping(value="/addClient.htm") public String addClient(@ModelAttribute("client") @Valid Client client, BindingResult result) { if(result.hasErrors()) { return "addClient"; } service.storeClient(client); return "clientResult"; } When my app loads in the server, I can see in the server log file that it loads a validator: 15 [http-8084-2] INFO org.hibernate.validator.util.Version - Hibernate Validator 4.0.2.GA The problem I'm having is that the validator doesn't seem to kick in. I turned on the debugger, and when I get into the controller method, the BindingResult contains 0 errors after I submit an empty form. (The BindingResult does show that it contains the Client object as a target.) It then proceeds to insert a record without an Id and throws an exception. If I fill out an Id but leave the name blank, it creates a record with the Id and empty fields. What steps am I missing to get the validation working?

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• C++: calling non-member functions with the same syntax of member ones

  - by peoro

  One thing I'd like to do in C++ is to call non-member functions with the same syntax you call member functions: class A { }; void f( A & this ) { /* ... */ } // ... A a; a.f(); // this is the same as f(a); Of course this could only work as long as f is not virtual (since it cannot appear in A's virtual table. f doesn't need to access A's non-public members. f doesn't conflict with a function declared in A (A::f). I'd like such a syntax because in my opinion it would be quite comfortable and would push good habits: calling str.strip() on a std::string (where strip is a function defined by the user) would sound a lot better than calling strip( str );. most of the times (always?) classes provide some member functions which don't require to be member (ie: are not virtual and don't use non-public members). This breaks encapsulation, but is the most practical thing to do (due to point 1). My question here is: what do you think of such feature? Do you think it would be something nice, or something that would introduce more issues than the ones it aims to solve? Could it make sense to propose such a feature to the next standard (the one after C++0x)? Of course this is just a brief description of this idea; it is not complete; we'd probably need to explicitly mark a function with a special keyword to let it work like this and many other stuff.

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• PHP Class Question

  - by Jerry

  Hi all I am trying to build a PHP class to check the username and password in MySql. I am getting "mysql_query(): supplied argument is not a valid MySQL-Link resource in D:\2010Portfolio\football\main.php on line 38" database has errors:" message. When I move my userQuery code out of my Class, it works fine. Only if it is inside my Class. I am not sure if the problem is that I don't build the connection to mysql inside my Class or not. Thanks for any helps!! Here is my code <?php $userName=$_POST['userName']; $userPw=$_POST['password']; class checkUsers { public $userName; public $userPw; function checkUsers($userName='', $userPw=''){ $this->userName=$userName; $this->userPw=$userPw; } function check1(){ if (empty($this->userName) || empty($this->userPw)){ $message="<strong>Please Enter Username and Password</strong>"; }else{ //line 38 is next line $userQuery=mysql_query("SELECT userName, userPw FROM user WHERE userName='$this->userName' and userPw='$this->userPw'", $connection); if (!$userQuery){ die("database has errors: ". mysql_error()); } if(mysql_num_rows($userQuery)==0){ $message="Please enter valid username and password"; } }//end empty check return $message; }//end check1 method }//end Class $checkUser=new checkUsers($userName, $userPw); echo $checkUser->check1(); ?> I appreciate any helps!!!!

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• How can change my code to can user insert numbers of year and days ?

  - by MANAL

  I make code to calculate the date of today and the date for two years ago before the day of today and also calculate day before 5 days. I want user insert the numbers of years and days to make compare between date of today . import java.util.Date; import java.util.Calendar; import java.text.SimpleDateFormat; import java.util.Scanner; public class Calendar1 { private static void doCalendarTime() { System.out.print("*************************************************"); Date now = Calendar.getInstance().getTime(); System.out.print(" \n Calendar.getInstance().getTime() : " + now); System.out.println(); } private static void doSimpleDateFormat() { System.out.print("*************************************************"); System.out.print("\n\nSIMPLE DATE FORMAT\n"); System.out.print("*************************************************"); // Get today's date Calendar now = Calendar.getInstance(); SimpleDateFormat formatter = new SimpleDateFormat("E yyyy.MM.dd 'at' hh:mm:ss a zzz"); System.out.print(" \n It is now : " + formatter.format(now.getTime())); System.out.println(); } private static void doAdd() { System.out.println("ADD / SUBTRACT CALENDAR / DATEs"); System.out.println("================================================================="); // Get today's date Calendar now = Calendar.getInstance(); Calendar working; SimpleDateFormat formatter = new SimpleDateFormat("E yyyy.MM.dd 'at' hh:mm:ss a zzz"); working = (Calendar) now.clone(); working.add(Calendar.DAY_OF_YEAR, - (365 * 2)); System.out.println (" Two years ago it was: " + formatter.format(working.getTime())); working = (Calendar) now.clone(); working.add(Calendar.DAY_OF_YEAR, + 5); System.out.println(" In five days it will be: " + formatter.format(working.getTime())); System.out.println(); } public static void main(String[] args) { System.out.println(); doCalendarTime(); doSimpleDateFormat(); doAdd(); } } help me .

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• Spring Security ACL: NotFoundException from JDBCMutableAclService.createAcl

  - by user340202

  Hello, I've been working on this task for too long to abandon the idea of using Spring Security to achieve it, but I wish that the community will provide with some support that will help reduce the regret that I have for choosing Spring Security. Enough ranting and now let's get to the point. I'm trying to create an ACL by using JDBCMutableAclService.createAcl as follows: [code] public void addPermission(IWFArtifact securedObject, Sid recipient, Permission permission, Class clazz) { ObjectIdentity oid = new ObjectIdentityImpl(clazz.getCanonicalName(), securedObject.getId()); this.addPermission(oid, recipient, permission); } @Override @Transactional(propagation = Propagation.REQUIRED, isolation = Isolation.READ_UNCOMMITTED, readOnly = false) public void addPermission(ObjectIdentity oid, Sid recipient, Permission permission) { SpringSecurityUtils.assureThreadLocalAuthSet(); MutableAcl acl; try { acl = this.mutableAclService.createAcl(oid); } catch (AlreadyExistsException e) { acl = (MutableAcl) this.mutableAclService.readAclById(oid); } // try { // acl = (MutableAcl) this.mutableAclService.readAclById(oid); // } catch (NotFoundException nfe) { // acl = this.mutableAclService.createAcl(oid); // } acl.insertAce(acl.getEntries().length, permission, recipient, true); this.mutableAclService.updateAcl(acl); } [/code] The call throws a NotFoundException from the line: [code] // Retrieve the ACL via superclass (ensures cache registration, proper retrieval etc) Acl acl = readAclById(objectIdentity); [/code] I believe this is caused by something related to Transactional, and that's why I have tested with many TransactionDefinition attributes. I have also doubted the annotation and tried with declarative transaction definition, but still with no luck. One important point is that I have used the statement used to insert the oid in the database earlier in the method directly on the database and it worked, and also threw a unique constraint exception at me when it tried to insert it in the method. I'm using Spring Security 2.0.8 and IceFaces 1.8 (which doesn't support spring 3.0 but definetely supprorts 2.0.x, specially when I keep caling SpringSecurityUtils.assureThreadLocalAuthSet()). My AppServer is Tomcat 6.0, and my DB Server is MySQL 6.0 I wish to get back a reply soon because I need to get this task off my way

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• virtual methods and template classes

  - by soxs060389

  Hi I got over a problem, I think a very specific one. I've got 2 classes, a B aseclass and a D erived class (from B aseclass). B is a template class ( or class template) and has a pure virtual method virutal void work(const T &dummy) = 0; The D erived class is supposed to reimplement this, but as D is Derived from B rather than D being another template class, the compiler spits at me that virtual functions and templates don't work at once. Any ideas how to acomplish what I want? I am thankfull for any thoughts and Ideas, especially if you allready worked out that problem this class is fixed aka AS IS, I can not edit this without breaking existing code base template <typename T> class B { public: ... virtual void work(const T &dummy) = 0; .. }; take int* as an example class D : public B<int*>{ ... virtual void work(const int* &dummy){ /* put work code here */ } .. }; Edit: The compiler tells me, that void B<T>::work(const T&) [with T = int*] is pure virtual within D

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• Why does GCC need extra declarations in templates when VS does not?

  - by Kyle

  template<typename T> class Base { protected: Base() {} T& get() { return t; } T t; }; template<typename T> class Derived : public Base<T> { public: Base<T>::get; // Line A Base<T>::t; // Line B void foo() { t = 4; get(); } }; int main() { return 0; } If I comment out lines A and B, this code compiles fine under Visual Studio 2008. Yet when I compile under GCC 4.1 with lines A and B commented, I get these errors: In member function ‘void TemplateDerived::foo()’: error: ‘t’ was not declared in this scope error: there are no arguments to ‘get’ that depend on a template parameter, so a declaration of ‘get’ must be available Why would one compiler require lines A and B while the other doesn't? Is there a way to simplify this? In other words, if derived classes use 20 things from the base class, I have to put 20 lines of declarations for every class deriving from Base! Is there a way around this that doesn't require so many declarations?

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• C# class can not disguise to be another class because GetType method cannot be override

  - by zinking

  there is a statement in the CLR via C# saying in C#, one class cannot disguise to be another, because GetType is virutal and thus it cannot be override but I think in C# we can still hide the parent implementation of GetType. I must missed something if I hide the base GetType implementation then I can disguise my class to be another class, is that correct? The key here is not whether GetType is virutal or not, the question is can we disguise one class to be another in C# Following is the NO.4 answer from the possible duplicate, so My question is more on this. is this kind of disguise possible, if so, how can we say that we can prevent class type disguise in C# ? regardless of the GetType is virtual or not While its true that you cannot override the object.GetType() method, you can use "new" to overload it completely, thereby spoofing another known type. This is interesting, however, I haven't figured out how to create an instance of the "Type" object from scratch, so the example below pretends to be another type. public class NotAString { private string m_RealString = string.Empty; public new Type GetType() { return m_RealString.GetType(); } } After creating an instance of this, (new NotAString()).GetType(), will indeed return the type for a string. share|edit|flag answered Mar 15 at 18:39 Dr Snooze 213 By almost anything that looks at GetType has an instance of object, or at the very least some base type that they control or can reason about. If you already have an instance of the most derived type then there is no need to call GetType on it. The point is as long as someone uses GetType on an object they can be sure it's the system's implementation, not any other custom definition. – Servy Mar 15 at 18:54 add comment

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• java gregorian calendar timer

  - by Ieyasu Sawada

  I have this java program which calculates the time that the person took to respond to the confirm dialog box. But it seems that both time1 and time 2 gets the same value. What have I done wrong here: import javax.swing.JOptionPane; import java.util.*; public class DialogTimer{ public static void main(String args[]){ int time1, time2, milli1, milli2, sec1, sec2, timeDifference; final int MILLISECSINSECOND =1000; JOptionPane.showConfirmDialog(null, "Is stealing ever justified? "); GregorianCalendar before=new GregorianCalendar(); GregorianCalendar after= new GregorianCalendar(); milli1=before.get(GregorianCalendar.MILLISECOND); milli2=after.get(GregorianCalendar.MILLISECOND); sec1=before.get(GregorianCalendar.SECOND); sec2=after.get(GregorianCalendar.SECOND); time1=MILLISECSINSECOND * sec1 + milli1; time2=MILLISECSINSECOND * sec2 + milli2; //timeDifference=time1 - time2; System.out.println(time1); System.out.println(time2); //JOptionPane.showMessageDialog(null, "It took " + (time1 - time2) + " milliseconds for you to answer"); } }

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• vlcj not displaying the video

  - by Cássio Eudardo

  I'm using vlcj to play video, but the video doesn't display on some computers(i tested in 4 and worked on 2, all windows), on 1 it displays the button but not the video and on the other it just display a gray background without the button. I tested .wmv and .avi files. I'm using the following code: public class Video extends JFrame implements WindowListener{ private JPanel contentPane; private JButton btnClose; private Dimension size; private float aspectRatio; private EmbeddedMediaPlayer mediaPlayer; public Video() { try { size = Toolkit.getDefaultToolkit().getScreenSize(); aspectRatio = (float)size.width/size.height; String file = "..."; btnClose = new JButton("X"); btnClose.addActionListener(new ActionListener() {...}); btnClose.setBounds(640 - 50, 10, 40, 40); setBounds(size.width/2 - 320, (int)(size.height - 40*aspectRatio) - 250, 640, 200); contentPane = new JPanel(); contentPane.setLayout(null); setContentPane(contentPane); WindowsCanvas surface = new WindowsCanvas(); contentPane.setBounds(0, 0, 640, 200); surface.setBounds(0, 0, 640, 200); MediaPlayerFactory factory = new MediaPlayerFactory(new String("--no-video-title-show")); mediaPlayer = factory.newEmbeddedMediaPlayer(); surface.addMouseListener(new MouseListener() {...}); contentPane.add(btnClose); contentPane.add(surface); setVisible(true); mediaPlayer.setVideoSurface(factory.newVideoSurface(surface)); mediaPlayer.setRepeat(true); mediaPlayer.playMedia(file); } catch(Exception e) { } }}

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• Providing custom database functionality to custom asp.net membership provider

  - by IrfanRaza

  Hello friends, I am creating custom membership provider for my asp.net application. I have also created a separate class "DBConnect" that provides database functionality such as Executing SQL statement, Executing SPs, Executing SPs or Query and returning SqlDataReader and so on... I have created instance of DBConnect class within Session_Start of Global.asax and stored to a session. Later using a static class I am providing the database functionality throughout the application using the same single session. In short I am providing a single point for all database operations from any asp.net page. I know that i can write my own code to connect/disconnect database and execute SPs within from the methods i need to override. Please look at the code below - public class SGI_MembershipProvider : MembershipProvider { ...... public override bool ChangePassword(string username, string oldPassword, string newPassword) { if (!ValidateUser(username, oldPassword)) return false; ValidatePasswordEventArgs args = new ValidatePasswordEventArgs(username, newPassword, true); OnValidatingPassword(args); if (args.Cancel) { if (args.FailureInformation != null) { throw args.FailureInformation; } else { throw new Exception("Change password canceled due to new password validation failure."); } } ..... //Database connectivity and code execution to change password. } .... } MY PROBLEM - Now what i need is to execute the database part within all these overriden methods from the same database point as described on the top. That is i have to pass the instance of DBConnect existing in the session to this class, so that i can access the methods. Could anyone provide solution on this. There might be some better techniques i am not aware of that. The approach i am using might be wrong. Your suggessions are always welcome. Thanks for sharing your valuable time.

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