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  • Improving field get and set performance with ASM or Javassist

    - by ng
    I would like to avoid reflection in an open source project I am developing. Here I have classes like the following. public class PurchaseOrder { @Property private Customer customer; @Property private String name; } I scan for the @Property annotation to determine what I can set and get from the PurchaseOrder reflectively. There are many such classes all using java.lang.reflect.Field.get() and java.lang.reflect.Field.set(). Ideally I would like to generate for each property an invoker like the following. public interface PropertyAccessor<S, V> { public void set(S source, V value); public V get(S source); } Now when I scan the class I can create a static inner class of PurchaseOrder like so. static class customer_Field implements PropertyAccessor<PurchaseOrder, Customer> { public void set(PurchaseOrder order, Customer customer) { order.customer = customer; } public Customer get(PurchaseOrder order) { return order.customer; } } With these I totally avoid the cost of reflection. I can now set and get from my instances with native performance. Can anyone tell me how I would do this. A code example would be great. I have searched the net for a good example but can find nothing like this. The ASM and Javasist examples are pretty poor also. The key here is that I have an interface that I can pass around. So I can have various implementations, perhaps one with Java Reflection as a default, one with ASM, and one with Javassist? Any help would be greatly appreciated.

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  • Serialize Object

    - by Mark Pearl
    Hi.. I am new to serialization and I cannot for the life of me figure out how to fix this exception I am getting... I have an object that has the following structure [XmlRoot("MaxCut2")] public class MaxCut2File : IFile { public MaxCut2File() { MyJob = new Job(); Job.Reference = "MyRef"; } [XmlElement("JobDetails", typeof(Job))] public IJob MyJob { get; set; } } An inteferface... public interface IJob { string Reference { get; set; } } And an class [Serializable()] public class Job : IJob { [XmlElement("Reference")] public string Reference { get; set; } } When I try to serialize an instance of the MaxCut2File object I get an error {"Cannot serialize member 'MaxCut2File.MaxCut2File.MyJob' of type 'MaxCut2BL.Interfaces.IJob', see inner exception for more details."} "There was an error reflecting type 'MaxCut2File.MaxCut2File'." However if I change my property MyJob from the IJob type to the Job type it works fine... Any ideas?

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  • Java assignment issues - Is this atomic?

    - by Bob
    Hi, I've got some questions about Java's assigment. Strings I've got a class: public class Test { private String s; public synchronized void setS(String str){ s = s + " - " + str; } public String getS(){ return s; } } I'm using "synchronized" in my setter, and avoiding it in my getter, because in my app, there are a tons of data gettings, and very few settings. Settings must be synchronized to avoid inconsistency. My question is: is getting and setting a variable atomic? I mean, in a multithreaded environment, Thread1 is about to set variable s, while Thread2 is about to get "s". Is there any way the getter method could get something different than the s's old value or the s's new value (suppose we've got only two threads)? In my app it is not a problem to get the new value, and it is not a problem to get the old one. But could I get something else? What about HashMap's getting and putting? considering this: public class Test { private Map<Integer, String> map = Collections.synchronizedMap(new HashMap<Integer, String>()); public synchronized void setMapElement(Integer key, String value){ map.put(key, value); } public String getValue(Integer key){ return map.get(key); } } Is putting and getting atomic? How does HashMap handle putting an element into it? Does it first remove the old value and put the now one? Could I get other than the old value or the new value? Thanks in advance!

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  • CustomProfile is not saving?

    - by Xaisoft
    I created a class that extends ProfileBase: public class CustomerProfile : ProfileBase { public int CustomerID { get; set; } public string CustomerName { get; set; } public static CustomerProfile GetProfile() { return Create(Membership.GetUser().UserName) as CustomerProfile; } public static CustomerProfile GetProfile(string userName) { return Create(userName) as CustomerProfile; } } If I do: CustomerProfile p = CustomerProfile.GetProfile(); p.CustomerID = 1; p.Save(); The next time I try to access the value for the current user, it is not 1, it is 0, so it appears it is not saving it in the database. In my web.config file I have the following snippet: <profile inherits="PortalBLL.CustomerProfile"> <providers> <add name="CustomerProfile" type="System.Web.Profile.SqlProfileProvider" applicationName="/" connectionStringName="LocalSqlServer"/> </providers> </profile> I tried the following and it worked, I am curious why it doesn't save it using the automatic properties. [SettingsAllowAnonymous(false)] public int CustomerID { get { return (int)base.GetPropertyValue("CustomerID");} set { base.SetPropertyValue("CustomerID",value);} }

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  • Strange GWT serialization exception when overiding method of serialized object

    - by Flueras Bogdan
    Hi there! I have a GWT serializable class, lets call it Foo. Foo implements IsSerializable, has primitive and serializable members as well as other transient members and a no-arg constructor. class Foo implements IsSerializable { // transient members // primitive members public Foo() {} public void bar() {} } Also a Service which handles RPC comunication. // server code public interface MyServiceImpl { public void doStuff(Foo foo); } public interface MyServiceAsync { void doStuff(Foo foo, AsyncCallback<Void> async); } How i use this: private MyServiceAsync myService = GWT.create(MyService.class); Foo foo = new Foo(); ... AsyncCallback callback = new new AsyncCallback {...}; myService.doStuff(foo, callback); In the above case the code is running, and the onSuccess() method of callback instance gets executed. But when I override the bar() method on foo instance like this: Foo foo = new Foo() { public void bar() { //do smthng different } } AsyncCallback callback = new new AsyncCallback {...}; myService.doStuff(foo, callback); I get the GWT SerializationException. Please enlighten me, because I really don't understand why.

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  • How to Elegantly convert switch+enum with polymorphism

    - by Kyle
    I'm trying to replace simple enums with type classes.. that is, one class derived from a base for each type. So for example instead of: enum E_BASE { EB_ALPHA, EB_BRAVO }; E_BASE message = someMessage(); switch (message) { case EB_ALPHA: applyAlpha(); case EB_BRAVO: applyBravo(); } I want to do this: Base* message = someMessage(); message->apply(this); // use polymorphism to determine what function to call. I have seen many ways to do this which all seem less elegant even then the basic switch statement. Using dyanimc_pointer_cast, inheriting from a messageHandler class that needs to be updated every time a new message is added, using a container of function pointers, all seem to defeat the purpose of making code easier to maintain by replacing switches with polymorphism. This is as close as I can get: (I use templates to avoid inheriting from an all-knowing handler interface) class Base { public: template<typename T> virtual void apply(T* sandbox) = 0; }; class Alpha : public Base { public: template<typename T> virtual void apply(T* sandbox) { sandbox->applyAlpha(); } }; class Bravo : public Base { public: template<typename T> virtual void apply(T* sandbox) { sandbox->applyBravo(); } }; class Sandbox { public: void run() { Base* alpha = new Alpha; Base* bravo = new Bravo; alpha->apply(this); bravo->apply(this); delete alpha; delete bravo; } void applyAlpha() { // cout << "Applying alpha\n"; } void applyBravo() { // cout << "Applying bravo\n"; } }; Obviously, this doesn't compile but I'm hoping it gets my problem accross.

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  • Conversion type

    - by Ruben
    Hi, I've got the following question. I've got one class "Instellingen" that's a property in 3 other classes public class Instellingen { private int _ID; } public class Class1: Label { private Instellingen _Instellingen; } public class Class2 : Label { private Instellingen _Instellingen; } public class Class3 : Label { private Instellingen _Instellingen; } If I've got another class, that uses the other classes (but it can be anyone of this 3 classes) Do i have to use a switch? or is there an easier way? public class AnotherClass { public AnotherClass () { GetInstellingenFromClass(new Class1()); GetInstellingenFromClass(new Class2()); GetInstellingenFromClass(new Class3()); } private void GetInstellingenFromClass(Control c) { switch (c.GetType.ToString()) { case "Class1": Class1 klasse = (Class1) c; //Do something with the _Instellingen of this class break; case "Class2": Class2 klasse2 = (Class2) c; //Do something with the _Instellingen of this class break; case "Class3": Class3 klasse3 = (Class3)c; //Do something with the _Instellingen of this class break; } } } (does there exists something so i can just do something like c._Instellingen -- without converting it first to the right type, where it doesn't matter what type c is?) I hope you understand my question. Thanks

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  • User entered value validation and level of error catching

    - by Terry
    May I ask should the error catching code be placed at the lowest level or at the top as I am not sure what is the best practice? I prefer placing at the bottom, example a, as Example a public static void Main(string[] args) { string operation = args[0]; int value = Convert.ToInt32(args[1]); if (operation == "date") { DoDate(value); } else if (operation == "month") { DoMonth(value); } } public static void DoMonth(int month) { if (month < 1 || month > 12) { throw new Exception(""); } } public static void DoDate(int date) { if (date < 1 || date > 31) { throw new Exception(""); } } or example b public static void Main(string[] args) { string operation = args[0]; int value = Convert.ToInt32(args[1]); if (operation == "date" && (date < 1 || date > 12)) { throw new Exception(""); } else if (operation == "month" && (month < 1 || month > 31)) { throw new Exception(""); } if (operation == "date") { DoDate(value); } else if (operation == "month") { DoMonth(value); } } public static void DoMonth(int month) { } public static void DoDate(int date) { }

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  • Which view will be resolved, code from spring's docs

    - by Blankman
    So when you go to /appointments the get() action is called, so then would the view be get.jsp (assuming you are using .jsp, and assuming you are mapping action names to views)? And what about the getnewform? It seems to be returning an object? Is that basically passed into the view? @Controller @RequestMapping("/appointments") public class AppointmentsController { private final AppointmentBook appointmentBook; @Autowired public AppointmentsController(AppointmentBook appointmentBook) { this.appointmentBook = appointmentBook; } @RequestMapping(method = RequestMethod.GET) public Map<String, Appointment> get() { return appointmentBook.getAppointmentsForToday(); } @RequestMapping(value="/{day}", method = RequestMethod.GET) public Map<String, Appointment> getForDay(@PathVariable @DateTimeFormat(iso=ISO.DATE) Date day, Model model) { return appointmentBook.getAppointmentsForDay(day); } @RequestMapping(value="/new", method = RequestMethod.GET) public AppointmentForm getNewForm() { return new AppointmentForm(); } @RequestMapping(method = RequestMethod.POST) public String add(@Valid AppointmentForm appointment, BindingResult result) { if (result.hasErrors()) { return "appointments/new"; } appointmentBook.addAppointment(appointment); return "redirect:/appointments"; } } In the example, the @RequestMapping is used in a number of places. The first usage is on the type (class) level, which indicates that all handling methods on this controller are relative to the /appointments path. The get() method has a further @RequestMapping refinement: it only accepts GET requests, meaning that an HTTP GET for /appointments invokes this method. The post() has a similar refinement, and the getNewForm() combines the definition of HTTP method and path into one, so that GET requests for appointments/new are handled by that method.

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  • How do I use Google's Gson API to deserialize JSON properly?

    - by FK82
    Hi, In short, this is a sketch of the JSON object I want to parse in JAVA: { object1: { item1: //[String | Array | Object] , item2: // ... //<> more items object2: { // } //<> more objects } These are the POJO s I created for parsing (I'll leave out the import statements for brevity's sake): (1) The representation of the complete JSON object public class JObjectContainer { private List<JObject> jObjects ; public JObjectContainer() { // } //get & set methods } (2) The representation of the nested objects: public class JObject { private String id ; private List<JNode> jObjects ; public JObject() { // } //get & set methods } (3) The representation of the items: public class JNode { private JsonElement item1 ; private JsonElement item2 ; //<> more item fields public JNode() { // } //get & set methods } Now, creating a Gson instance (FileReader for importing the jsonFile), Gson gson = new Gson() ; JObjectContainer joc = gson(jsonFile,JObjectContainer.class) ; I get a NullPointerException whenever I try to access the parseable object (e.g. through a ListIterator). Gson does however create an object of the class I specified and does not throw any subsequent errors. I know that this has been done before. So, what am I missing? TIA

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  • A linked list with multiple heads in Java

    - by Emile
    Hi, I have a list in which I'd like to keep several head pointers. I've tried to create multiple ListIterators on the same list but this forbid me to add new elements in my list... (see Concurrent Modification exception). I could create my own class but I'd rather use a built-in implementation ;) To be more specific, here is an inefficient implementation of two basic operations and the one wich doesn't work : class MyList <E { private int[] _heads; private List<E _l; public MyList ( int nbHeads ) { _heads = new int[nbHeads]; _l = new LinkedList<E(); } public void add ( E e ) { _l.add(e); } public E next ( int head ) { return _l.get(_heads[head++]); // ugly } } class MyList <E { private Vector<ListIterator<E _iters; private List<E _l; public MyList ( int nbHeads ) { _iters = new Vector<ListIterator<E(nbHeads); _l = new LinkedList<E(); for( ListIterator<E iter : _iters ) iter = _l.listIterator(); } public void add ( E e ) { _l.add(e); } public E next ( int head ) { // ConcurrentModificationException because of the add() return _iters.get(head).next(); } } Emile

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  • Lightweight alternative to Manual/AutoResetEvent in C#

    - by sweetlilmre
    Hi, I have written what I hope is a lightweight alternative to using the ManualResetEvent and AutoResetEvent classes in C#/.NET. The reasoning behind this was to have Event like functionality without the weight of using a kernel locking object. Although the code seems to work well in both testing and production, getting this kind of thing right for all possibilities can be a fraught undertaking and I would humbly request any constructive comments and or criticism from the StackOverflow crowd on this. Hopefully (after review) this will be useful to others. Usage should be similar to the Manual/AutoResetEvent classes with Notify() used for Set(). Here goes: using System; using System.Threading; public class Signal { private readonly object _lock = new object(); private readonly bool _autoResetSignal; private bool _notified; public Signal() : this(false, false) { } public Signal(bool initialState, bool autoReset) { _autoResetSignal = autoReset; _notified = initialState; } public virtual void Notify() { lock (_lock) { // first time? if (!_notified) { // set the flag _notified = true; // unblock a thread which is waiting on this signal Monitor.Pulse(_lock); } } } public void Wait() { Wait(Timeout.Infinite); } public virtual bool Wait(int milliseconds) { lock (_lock) { bool ret = true; // this check needs to be inside the lock otherwise you can get nailed // with a race condition where the notify thread sets the flag AFTER // the waiting thread has checked it and acquires the lock and does the // pulse before the Monitor.Wait below - when this happens the caller // will wait forever as he "just missed" the only pulse which is ever // going to happen if (!_notified) { ret = Monitor.Wait(_lock, milliseconds); } if (_autoResetSignal) { _notified = false; } return (ret); } } }

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  • How to use reflection to call a method and pass parameters whose types are unknown at compile time?

    - by MandoMando
    I'd like to call methods of a class dynamically with parameter values that are "parsed" from a string input. For example: I'd like to call the following program with these commands: c:myprog.exe MethodA System.Int32 777 c:myprog.exe MethodA System.float 23.17 c:myprog.exe MethodB System.Int32& 777 c:myprog.exe MethodC System.Int32 777 System.String ThisCanBeDone static void Main(string[] args) { ClassA aa = new ClassA(); System.Type[] types = new Type[args.Length / 2]; object[] ParamArray = new object[types.Length]; for (int i=0; i < types.Length; i++) { types[i] = System.Type.GetType(args[i*2 + 1]); // LINE_X: this will obviously cause runtime error invalid type/casting ParamArray[i] = args[i*2 + 2]; MethodInfo callInfo = aa.GetType().GetMethod(args[0],types); callInfo.Invoke(aa, ParamArray); } // In a non-changeable classlib: public class ClassA { public void MethodA(int i) { Console.Write(i.ToString()); } public void MethodA(float f) { Console.Write(f.ToString()); } public void MethodB(ref int i) { Console.Write(i.ToString()); i++; } public void MethodC(int i, string s) { Console.Write(s + i.ToString()); } public void MethodA(object o) { Console.Write("Argg! Type Trapped!"); } } "LINE_X" in the above code is the sticky part. For one, I have no idea how to assign value to a int or a ref int parameter even after I create it using Activator.CreatInstance or something else. The typeConverter does come to mind, but then that requires an explicit compile type casting as well. Am I looking at CLR with JavaScript glasses or there is way to do this?

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  • How to make a thread that runs at x:00 x:15 x:30 and x:45 do something different at 2:00.

    - by rmarimon
    I have a timer thread that needs to run at a particular moments of the day to do an incremental replication with a database. Right now it runs at the hour, 15 minutes past the hour, 30 minutes past the hour and 45 minutes past the hour. This is the code I have which is working ok: public class TimerRunner implements Runnable { private static final Semaphore lock = new Semaphore(1); private static final ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor(); public static void initialize() { long delay = getDelay(); executor.schedule(new TimerRunner(), delay, TimeUnit.SECONDS); } public static void destroy() { executor.shutdownNow(); } private static long getDelay() { Calendar now = Calendar.getInstance(); long p = 15 * 60; // run at 00, 15, 30 and 45 minutes past the hour long second = now.get(Calendar.MINUTE) * 60 + now.get(Calendar.SECOND); return p - (second % p); } public static void replicate() { if (lock.tryAcquire()) { try { Thread t = new Thread(new Runnable() { public void run() { try { // here is where the magic happens } finally { lock.release(); } } }); t.start(); } catch (Exception e) { lock.release(); } } else { throw new IllegalStateException("already running a replicator"); } } public void run() { try { TimerRunner.replicate(); } finally { long delay = getDelay(); executor.schedule(new TimerRunner(), delay, TimeUnit.SECONDS); } } } This process is started by calling TimerRunner.initialize() when a server starts and calling TimerRunner.destroy(). I have created a full replication process (as opposed to incremental) that I would like to run at a certain moment of the day, say 2:00am. How would change the above code to do this? I think that it should be very simple something like if it is now around 2:00am and it's been a long time since I did the full replication then do it now, but I can't get the if right. Beware that sometimes the replicate process takes way longer to complete. Sometimes beyond the 15 minutes, posing a problem in running at around 2:00am.

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  • How to easily substitute a Base class

    - by JTom
    Hi, I have the following hierarchy of classes class classOne { virtual void abstractMethod() = 0; }; class classTwo : public classOne { }; class classThree : public classTwo { }; All classOne, classTwo and classThree are abstract classes, and I have another class that is defining the pure virtual methods class classNonAbstract : public classThree { void abstractMethod(); // Couple of new methods void doIt(); void doItToo(); }; And right now I need it differently...I need it like class classNonAbstractOne : public classOne { void abstractMethod(); // Couple of new methods void doIt(); void doItToo(); }; class classNonAbstractTwo : public classTwo { void abstractMethod(); // Couple of new methods void doIt(); void doItToo(); }; and class classNonAbstractThree : public classThree { void abstractMethod(); // Couple of new methods void doIt(); void doItToo(); }; But all the nonAbstract classes have the same new methods, with the same code...and I would like to avoid copying all the methods and it's code to every nonAbstract class. How could I accomplish that? Hopefully it's understandable...

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  • Why doesn't is operator take in consideration if the explicit operator is overriden when checking ty

    - by Galilyou
    Hey Guys, Consider this code sample: public class Human { public string Value { get; set;} } public class Car { public static explicit operator Human (Car c) { Human h = new Human(); h.Value = "Value from Car"; return h; } } public class Program { public static void Mani() { Car c = new Car(); Human h = (Human)c; Console.WriteLine("h.Value = {0}", h.Value); Console.WriteLine(c is Human); } } Up I provide a possibility of an explicit cast from Car to Human, though Car and Human hierarchically are not related! The above code simply means that "Car is convertible to human" However, if you run the snippet you will find the expression c is Human evaluates to false! I used to believe that the is operator is kinda expensive cause it attempts to do an actual cast that might result in an InvalidCastException. If the operator is trying to cast, then the cast should succeed as there's an operator logic that should perform the cast! What does "is" test? Does test a hierarchical "is-a" relationship? Does test whether a variable type is convertible to a type?

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  • Google Maps inside custom PODS page

    - by Sharath
    I have a custom pods page called addstory.php which uses a public form to display some input fields. For one of the fields, i have a input helper that displays a google map location which I can use to pick out a location which is stored in comma separated variable. Here is the input helper code... <div class="form pick <?php echo $location; ?>"> <div id="map" style="width:500; height:500"> </div> <script type="text/javascript"> $(function() { map=new GMap(document.getElementById("map")); map.centerAndZoom(new GPoint(77.595062,13.043359),6); map.setUIToDefault(); GEvent.addListener(map,"click",function(overlay,latlng) { map.clearOverlays(); var marker = new GMarker(latlng); map.addOverlay(marker); //Extra stuff here.. } ); }); </script> </div> And this is the code inside my addstory.php <?php get_header(); $rw = new Pod('rainwater'); $fields=array( 'name', 'email', 'location'=>array('input_helper'=>'gmap_location'), ); echo $rw->publicForm($fields); ?> I get the following error...and the google map doesn't load. a is null error source line: [Break on this error] function Qd(a){for(var b;b=a.firstChild;){Rg(b);a.removeChild(b)}}

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  • Intellisense on custom types in Iron Python

    - by Anish Patel
    Hi everybody, I'm just starting to play around with IronPython and am having a hard time using it with custom types created in C#. I can get IronPython to load in assemblies from C# classes, but I'm struggling without the help of intellisense. If I have a class in C# as defined below, how can I make it so that IronPython will be able to see the methods/properties that are available in it? public class Person { public string Name { get; set; } public int Age{ get; set; } public double Weight{ get; set; } public double Height { get; set; } public double CalculateBMI() { return Weight/Math.Pow(Height, 2); } } In Iron python I'd instance a Person object as follows: newPerson = Person() newPerson.Name = 'John' newPerson.Age = 25 newPerson.Weight = 75 newPerson.Height = 1.70 newPerson.CalculateBMI() The thing that is annoying me is that I want to be able to say newPerson = Person() And then be able to see all the methods and properties associated with the person object whenever I type: newPerson. Anyone have any ideas if this can be done?

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  • Incorporating Devise Authentication into an already existing user structure?

    - by Kevin
    I have a fully functional authentication system with a user table that has over fifty columns. It's simple but it does hash encryption with salt, uses email instead of usernames, and has two separate kinds of users with an admin as well. I'm looking to incorporate Devise authentication into my application to beef up the extra parts like email validation, forgetting passwords, remember me tokens, etc... I just wanted to see if anyone has any advice or problems they've encountered when incorporating Devise into an already existing user structure. The essential fields in my user model are: t.string :first_name, :null => false t.string :last_name, :null => false t.string :email, :null => false t.string :hashed_password t.string :salt t.boolean :is_userA, :default => false t.boolean :is_userB, :default => false t.boolean :is_admin, :default => false t.boolean :active, :default => true t.timestamps For reference sake, here's the Devise fields from the migration: t.database_authenticatable :null => false t.confirmable t.recoverable t.rememberable t.trackable That eventually turn into these actual fields in the schema: t.string "email", :default => "", :null => false t.string "encrypted_password", :limit => 128, :default => "", :null => false t.string "password_salt", :default => "", :null => false t.string "confirmation_token" t.datetime "confirmed_at" t.datetime "confirmation_sent_at" t.string "reset_password_token" t.string "remember_token" t.datetime "remember_created_at" t.integer "sign_in_count", :default => 0 t.datetime "current_sign_in_at" t.datetime "last_sign_in_at" t.string "current_sign_in_ip" t.string "last_sign_in_ip" t.datetime "created_at" t.datetime "updated_at" What do you guys recommend? Do I just remove email, hashed_password, and salt from my migration and put in the 5 Devise migration fields and everything will be OK or do I need to do something else?

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  • Why isn't componentHidden called for my JPopupMenu?

    - by heycam
    I want to be notified when my JPopupMenu is hidden — whether because an item was selected, the menu was dismissed, or setVisible(false) was called on it. Here is my test code: import javax.swing.*; import java.awt.*; import java.awt.event.*; public class A extends ComponentAdapter implements Runnable, ActionListener { private JButton b; public static void main(String[] args) { EventQueue.invokeLater(new A()); } public void run() { JFrame f = new JFrame("Test"); b = new JButton("Click me"); b.addActionListener(this); f.add(b); f.pack(); f.setVisible(true); } public void actionPerformed(ActionEvent e) { JPopupMenu pm = new JPopupMenu(); pm.addComponentListener(this); pm.add("Popup..."); pm.add("...menu!"); pm.show(b, 10, 10); } public void componentShown(ComponentEvent e) { System.out.println("componentShown"); } public void componentHidden(ComponentEvent e) { System.out.println("componentHidden"); } } Regardless of how I interact with the menu, neither of the two ComponentListener methods are being called. Why is that? Is there different/better/correct way of finding out when my JPopupMenu is hidden? Thanks, Cameron

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  • error LNK2001: unresolved external symbol

    - by numerical25
    I am receiving this error >GXRenderManager.obj : error LNK2001: unresolved external symbol "private: static class GXRenderer * GXRenderManager::renderDevice" (?renderDevice@GXRenderManager@@0PAVGXRenderer@@A) The following is my code... GXDX.h class GXDX: public GXRenderer { public: void Render(); void StartUp(); }; GXGL.h class GXGL: public GXRenderer { public: void Render(); void StartUp(); }; GXRenderer class GXRenderer { public: virtual void Render() = 0; virtual void StartUp() = 0; }; GXRenderManager.h #ifndef GXRM #define GXRM #include <windows.h> #include "GXRenderer.h" #include "GXDX.h" #include "GXGL.h" enum GXDEVICE { DIRECTX, OPENGL }; class GXRenderManager { public: static int Ignite(GXDEVICE); private: static GXRenderer *renderDevice; }; #endif GXRenderManager.cpp #include "GXRenderManager.h" int GXRenderManager::Ignite(GXDEVICE DeviceType) { switch(DeviceType) { case DIRECTX: GXRenderManager::renderDevice = new GXDX; return 1; break; case OPENGL: GXRenderManager::renderDevice = new GXGL; return 1; break; default: return 0; } } main.cpp #include "GXRenderManager.h" int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) { return 0; } I am not trying to get it to do anything. I am just trying to compile with no errors. I am new with all this so if anyone can give me a hand. that will be great. thanks

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  • Unboxing to unknown type

    - by Robert
    I'm trying to figure out syntax that supports unboxing an integral type (short/int/long) to its intrinsic type, when the type itself is unknown. Here is a completely contrived example that demonstrates the concept: // Just a simple container that returns values as objects struct DataStruct { public short ShortVale; public int IntValue; public long LongValue; public object GetBoxedShortValue() { return LongValue; } public object GetBoxedIntValue() { return LongValue; } public object GetBoxedLongValue() { return LongValue; } } static void Main( string[] args ) { DataStruct data; // Initialize data - any value will do data.LongValue = data.IntValue = data.ShortVale = 42; DataStruct newData; // This works if you know the type you are expecting! newData.ShortVale = (short)data.GetBoxedShortValue(); newData.IntValue = (int)data.GetBoxedIntValue(); newData.LongValue = (long)data.GetBoxedLongValue(); // But what about when you don't know? newData.ShortVale = data.GetBoxedShortValue(); // error newData.IntValue = data.GetBoxedIntValue(); // error newData.LongValue = data.GetBoxedLongValue(); // error } In each case, the integral types are consistent, so there should be some form of syntax that says "the object contains a simple type of X, return that as X (even though I don't know what X is)". Because the objects ultimately come from the same source, there really can't be a mismatch (short != long). I apologize for the contrived example, it seemed like the best way to demonstrate the syntax. Thanks.

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  • How to create a fully lazy singleton for generics

    - by Brendan Vogt
    I have the following code implementation of my generic singleton provider: public sealed class Singleton<T> where T : class, new() { Singleton() { } public static T Instance { get { return SingletonCreator.instance; } } class SingletonCreator { static SingletonCreator() { } internal static readonly T instance = new T(); } } This sample was taken from 2 articles and I merged the code to get me what I wanted: http://www.yoda.arachsys.com/csharp/singleton.html and http://www.codeproject.com/Articles/11111/Generic-Singleton-Provider. This is how I tried to use the code above: public class MyClass { public static IMyInterface Initialize() { if (Singleton<IMyInterface>.Instance == null // Error 1 { Singleton<IMyInterface>.Instance = CreateEngineInstance(); // Error 2 Singleton<IMyInterface>.Instance.Initialize(); } return Singleton<IMyInterface>.Instance; } } And the interface: public interface IMyInterface { } The error at Error 1 is: 'MyProject.IMyInterace' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method 'MyProject.Singleton<T>' The error at Error 2 is: Property or indexer 'MyProject.Singleton<MyProject.IMyInterface>.Instance' cannot be assigned to -- it is read only How can I fix this so that it is in line with the 2 articles mentioned above? Any other ideas or suggestions are appreciated.

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  • unable to compile a servlet in ubuntu

    - by codeomnitrix
    I am newbie to j2ee. I have download and installed j2eesdk-1_4_03-linux.bin in my ubuntu 10.04 distribution. and then i tried to code my first servlet in it as: import java.io.*; import javax.servelet.*; import javax.servelet.http.*; public class HowdyServelet extends HttpServelet{ public void doGet(HttpServeletRequest request, HttpServeletResponse response) throws IOException, ServeletException{ PrintWriter out = response.getWriter(); response.setContentType("text/html"); out.println("<html>"); out.println("<head><title>howdy</title></head>"); out.println("<body>"); out.println("<center><h1>Howdy</h1></center>"); out.println("</body>"); out.println("</html>"); } } and here are the environment variables i set after installation: 1. J2EE_HOME=/home/vinit/SUNWappserver 2. JAVA_HOME=/home/vinit/SUNWappserver/jdk 3. CLASSPATH=/home/vinit/SUNWappserver/lib and now i tried to compile the servlet using javac HowdyServelet.java But i got following errors: HowdyServelet.java:2: package javax.servelet does not exist import javax.servelet.*; ^ HowdyServelet.java:3: package javax.servelet.http does not exist import javax.servelet.http.*; ^ HowdyServelet.java:5: cannot find symbol symbol: class HttpServelet public class HowdyServelet extends HttpServelet{ ^ HowdyServelet.java:6: cannot find symbol symbol : class HttpServeletRequest location: class HowdyServelet public void doGet(HttpServeletRequest request, HttpServeletResponse response) throws IOException, ServeletException{ ^ HowdyServelet.java:6: cannot find symbol symbol : class HttpServeletResponse location: class HowdyServelet public void doGet(HttpServeletRequest request, HttpServeletResponse response) throws IOException, ServeletException{ ^ HowdyServelet.java:6: cannot find symbol symbol : class ServeletException location: class HowdyServelet public void doGet(HttpServeletRequest request, HttpServeletResponse response) throws IOException, ServeletException{ ^ 6 errors So how to compile this servlet. Thanks in advance.

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  • Entity Framework. Updating EntityCollection using disconnected objects via navigation property.

    - by yougotiger
    I have a question, much liket this unanswered one. I'm trying to work with the entity framework, and having a tough time getting my foreign tables to update. I have something basically like this in the DB: Incident (table): -ID -other fields Responses (table): -FK:Incident.ID -other fields And and entities that match: Incident (entity) -ID -Other fields -Responses (EntityCollection of Responses via navigation property) Each Incident can have 0 or more responses. In my Webpage, I have a form to allow the user to enter all the details of an Incident, including a list of responses. I can add everything to the database when a new Incident is created, however I'm having difficulty with editing the Incident. When the page loads for edit, I populate the form and then store the responses in the viewstate. When the user changes the list of responses (adds one, deletes one or edits one). I store this back into the viewstate. Then when the user clicks the save button, I'd like to save the changes to the Incident and the Responses back to the DB. I cannot figure out how to get the responses from the detached viewstate into the Incident object so that they can be updated together. Currently when the user clicks save, I'm getting the Incident to edit from the db, making changes to the Incident's fields and then saving it back to the DB. However I can't figure out how to have the detached list of responses from the viewstate attach to the Incident. I have tried the following without success: Clearning the Incident.Responses collection and adding the ones from the viewstate back in: Incident.Responses.Clear() for each objResponse in Viewstate("Responses") Incident.Responses.add(objResponse) next Creating an EntityCollection from my list and then assiging that to the Incident.Responses Incident.Responses = EntityCollectionFromViewstateList Iterating through the responses in Incident.Response and assigning the corresponding object from viewstate: for each ObjResponse in Incident.Responses objResponse = objCorrespondingModifedResonseFromViewState Next These all fail, I'd like to be able to merge the changes into the Inicdent object so that when the BLL calls SaveChanges on the changes to both the Incident and Responses will happen at the same time. Any suggestions? I keep finding lots of stuff about assigning foreign keys (singular), but I haven't found a great solution for doing a set of entities assigned to another entity in this manner.

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