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  • What is so bad about Singletons

    - by Ewan Makepeace
    The Singleton pattern is a fully paid up member of the GoF Patterns Book but lately seems rather orphaned by the developer world. I still use quite a lot of singletons, especially for Factory classes, and while you have to be a bit careful about multithreading issues (like any class actually) fail to see why they are so awful. This site especially seems to assume that everyone agrees that Singletons are evil. Why?

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  • C++ - Breaking code implementation into different parts

    - by Kotti
    Hi! The question plot (a bit abstract, but answering this question will help me in my real app): So, I have some abstract superclass for objects that can be rendered on the screen. Let's call it IRenderable. struct IRenderable { // (...) virtual void Render(RenderingInterface& ri) = 0; virtual ~IRenderable() { } }; And suppose I also have some other objects that derive from IRenderable, e.g. Cat and Dog. So far so good. I add some Cat and Dog specific methods, like SeekForWhiskas(...) and Bark(...). After that I add specific Render(...) method for them, so my code looks this way: class Cat : public IRenderable { public: void SeekForWhiskas(...) { // Implementation could be here or moved // to a source file (depends on me wanting // to inline it or not) } virtual void Render(...) { // Here comes the rendering routine, that // is specific for cats SomehowDrawAppropriateCat(...); } }; class Dog : public IRenderable { public: void Bark(...) { // Same as for 'SeekForWhiskas(...)' } virtual void Render(...) { // Here comes the rendering routine, that // is specific for dogs DrawMadDog(...); } }; And then somewhere else I can do drawing the way that an appropriate rendering routine is called: IRenderable* dog = new Dog(); dog->Render(...); My question is about logical wrapping of such kind of code. I want to break apart the code, that corresponds to rendering of the current object and it's own methods (Render and Bark in this example), so that my class implementation doesn't turn into a mess (imagine that I have 10 methods like Bark and of course my Render method doesn't fit in their company and would be hard to find). Two ways of making what I want to (as far as I know) are: Making appropriate routines that look like RenderCat(Cat& cat, RenderInterface* ri), joining them to render namespace and then the functions inside a class would look like virtual void Render(...) { RenderCat(*this, ...); }, but this is plain stupid, because I'll lose access to Cat's private members and friending these functions looks like a total design disaster. Using visitor pattern, but this would also mean I have to rebuild my app's design and looks like an inadequate way to make my code complicated from the very beginning. Any brilliant ideas? :)

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  • Creating a "permanent" Cocoa object

    - by quixoto
    I have an object factory that hands out instances of certain "constant" objects. I'd like these objects to be protected against bad memory management by clients. This is how I've overridden the class's key methods. Am I missing anything (code or other considerations)? - (id)retain { return self; } - (NSUInteger)retainCount { return UINT_MAX; } - (void)release { // nothing. }

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  • NHibernate requires events to be virtual?

    - by Jimit
    I'm attempting to map an entity hierarchy using NHibernate almost all of which have events. When attempting to build a session factory however, I get error messages similar to the following: Core.Domain.Entities.Delivery: method remove_Scheduled should be virtual Delivery is an entity in my domain model with an event called Scheduled. Since events cannot be declared virtual I'm at a loss as to how to proceed here. Why would NHibernate need events to be virtual?

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  • FluentNHibernate: mapping a Version property

    - by Brian
    How do I map a Version property using conventions (e.g. IClassConvention, AutomapperConfiguration)? public abstract class Entity { ... public virtual int? Version { get; protected set; } ... } <class ...> <version name="Version" column="version" generated="never" type="Int32" unsaved-value="0" /> </class>

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  • Error "Create a concrete instance!"

    - by dododedodonl
    Hey All, I've got another problem in the same code... I'm getting this error: *** initialization method -initWithFormat:locale:arguments: cannot be sent to an abstract object of class NSString_RegEx: Create a concrete instance! But I don't understand the error or what I should do...

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  • C++ game designing & polymorphism question

    - by Kotti
    Hi! I'm trying to implement some sort of 'just-for-me' game engine and the problem's plot goes the following way: Suppose I have some abstract interface for a renderable entity, e.g. IRenderable. And it's declared the following way: interface IRenderable { // (...) // Suppose that Backend is some abstract backend used // for rendering, and it's implementation is not important virtual void Render(Backend& backend) = 0; }; What I'm doing right now is something like declaring different classes like class Ball : public IRenderable { virtual void Render(Backend& backend) { // Rendering implementation, that is specific for // the Ball object // (...) } }; And then everything looks fine. I can easily do something like std::vector<IRenderable*> items, push some items like new Ball() in this vector and then make a call similiar to foreach (IRenderable* in items) { item->Render(backend); } Ok, I guess it is the 'polymorphic' way, but what if I want to have different types of objects in my game and an ability to manipulate their state, where every object can be manipulated via it's own interface? I could do something like struct GameState { Ball ball; Bonus bonus; // (...) }; and then easily change objects state via their own methods, like ball.Move(...) or bonus.Activate(...), where Move(...) is specific for only Ball and Activate(...) - for only Bonus instances. But in this case I lose the opportunity to write foreach IRenderable* simply because I store these balls and bonuses as instances of their derived, not base classes. And in this case the rendering procedure turns into a mess like ball.Render(backend); bonus.Render(backend); // (...) and it is bad because we actually lose our polymorphism this way (no actual need for making Render function virtual, etc. The other approach means invoking downcasting via dynamic_cast or something with typeid to determine the type of object you want to manipulate and this looks even worse to me and this also breaks this 'polymorphic' idea. So, my question is - is there some kind of (probably) alternative approach to what I want to do or can my current pattern be somehow modified so that I would actually store IRenderable* for my game objects (so that I can invoke virtual Render method on each of them) while preserving the ability to easily change the state of these objects? Maybe I'm doing something absolutely wrong from the beginning, if so, please point it out :) Thanks in advance!

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  • C#/.NET Project - Am I setting things up correctly?

    - by JustLooking
    1st solution located: \Common\Controls\Controls.sln and its project: \Common\Controls\Common.Controls\Common.Controls.csproj Description: This is a library that contains this class: public abstract class OurUserControl : UserControl { // Variables and other getters/setters common to our UserControls } 2nd solution located: \AControl\AControl.sln and its project: \AControl\AControl\AControl.csproj Description: Of the many forms/classes, it will contain this class: using Common.Controls; namespace AControl { public partial class AControl : OurUserControl { // The implementation } } A note about adding references (not sure if this is relevant): When I add references (for projects I create), using the names above: 1. I add Common.Controls.csproj to AControl.sln 2. In AControl.sln I turn off the build of Common.Controls.csproj 3. I add the reference to Common.Controls (by project) to AControl.csproj. This is the (easiest) way I know how to get Debug versions to match Debug References, and Release versions to match Release References. Now, here is where the issue lies (the 3rd solution/project that actually utilizes the UserControl): 3rd solution located: \MainProj\MainProj.sln and its project: \MainProj\MainProj\MainProj.csproj Description: Here's a sample function in one of the classes: private void TestMethod<T>() where T : Common.Controls.OurUserControl, new() { T TheObject = new T(); TheObject.OneOfTheSetters = something; TheObject.AnotherOfTheSetters = something_else; // Do stuff with the object } We might call this function like so: private void AnotherMethod() { TestMethod<AControl.AControl>(); } This builds, runs, and works. No problem. The odd thing is after I close the project/solution and re-open it, I have red squigglies everywhere. I bring up my error list and I see tons of errors (anything that deals with AControl will be noted as an error). I'll see errors such as: The type 'AControl.AControl' cannot be used as type parameter 'T' in the generic type or method 'MainProj.MainClass.TestMethod()'. There is no implicit reference conversion from 'AControl.AControl' to 'Common.Controls.OurUserControl'. or inside the actual method (the properties located in the abstract class): 'AControl.AControl' does not contain a definition for 'OneOfTheSetters' and no extension method 'OneOfTheSetters' accepting a first argument of type 'AControl.AControl' could be found (are you missing a using directive or an assembly reference?) Meanwhile, I can still build and run the project (then the red squigglies go away until I re-open the project, or close/re-open the file). It seems to me that I might be setting up the projects incorrectly. Thoughts?

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  • GA Framework for Virtual Machines

    - by PeanutPower
    Does anyone know of any .NET genetic algorithm frameworks for evolving instructions sets in virtual machines to solve abstract problems? I would be particularly interested in a framework which allows virtual machines to self propagate within a pool and evolve against a fitness function determined by a data set with "good" outputs given expected inputs.

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  • Any Free Alternative to the ASP.net Calendar Control?

    - by Ronnie Overby
    Here are the problems I am having with the control from the factory: no easy way to get the first visible date (yeah I could use day render, but at that point in the page cycle, I can't do what I need to, which is manipulate a collection in viewstate) changing the visibledate property in my code does not raise the visiblemonthchanged event. That just doesn't make any sense to me. Can someone suggest a free, improved calendar control?

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  • How best can I extract a logical model from a physical DB model

    - by Dean
    We have made substantial changes to our physical DB, now as it is the ne dof the project I would like to abstract a logical model from this, to allow me to generate schemas for both Oracle and SQL Server. Can anyone guide me as to the best way to achieve this. I was hoping TOAD data modeller would help but I can't seem to see any options to do what I require?

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  • Trying to setup externalizing properties in spring

    - by Gandalf StormCrow
    Hi all, I'm building my project with maven so according to maven way, config should be in src/main/conf , how can I say to my spring application context that that is where jdbc.properties is found? Here is example bean : <bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="location" value="jdbc.properties" /> </bean> Spring assumens that this configuration is inside src/main/webapp/WEB-INF, I hope I've been clear if not I'll rephrase my question thank you

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  • Determine if an element is a jQueryUI Widget

    - by Boycs
    I have written a jquery-ui widget using the Widget Factory... I need to be able to determine in code whether the element is already a widget or not... My investmentGrid widget is created on #container with $('#container').investmentGrid() I need to be able to determine elsewhere in the code if $('#container') is already an investmentGrid

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  • Ninject: Controller Constructor with int argument

    - by Fleents
    How can you instantiate a Controller that has an int argument? Using Ninject.. My HomeController has a constructor like this: private int _masterId; Public HomeController(int masterId){ _masterId = masterId; } I created a controller factory like this: public class NinjectControllerFactory : DefaultControllerFactory { IKernel kernel = new StandardKernel(new ExampleConfigModule()); protected override IController GetControllerInstance(Type controllerType) { return controllerType == null ? null : (IController)kernel.Get(controllerType, 1); } }

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  • Problem when subClassing NSDate

    - by iFloh
    Hi, I first time tried to subClassed an NSDate to give it 2 methods that I need. Compiles fine, but in runtime I try to access it I get an error. Lets say I just want the current date which is unmodified in the subClass: [myNSDate date]; I get the error -[NSDate initWithTimeIntervalSinceReferenceDate:]: method only defined for abstract class. Define -[myNSDate initWithTimeIntervalSinceReferenceDate:]! what is different?

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  • How i change the Enabled= attribute via a preloaded field

    - by user1904656
    I want to modify the PXUIField Enabled=false/true using an existing boolean field #region LastBatNbr public abstract class lastBatNbr : PX.Data.IBqlField { } protected String _LastBatNbr; [PXDBString(10, IsFixed = true)] [PXUIField(DisplayName = "Last Batch Nbr")] public virtual String LastBatNbr { get { return this._LastBatNbr; } set { this._LastBatNbr = value; } } #endregion

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  • Improving MVP in Scala

    - by Alexey Romanov
    The classical strongly typed MVP pattern looks like this in Scala: trait IView { } trait Presenter[View <: IView] { // or have it as an abstract type member val view : View } case class View1(...) extends IView { ... } case object Presenter1 extends Presenter[View1] { val view = View1(...) } Now, I wonder if there is any nice way to improve on it which I am missing...

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  • Mapping One-to-One subclass in Fluent NHibernate

    - by Mike C.
    I have the following database structure: Event table Id - Guid (PK) Name - NVarChar Description - NVarChar SpecialEvent table Id - Guid (PK) StartDate - DateTime EndDate - DateTime I have an abstract Event class, and a SpecialEvent class that inherits from it. Eventually I will have a RecurringEvent class which will inherit from the Event class also. I'd like to map the SpecialEvent class while preserving a one-to-one relationship mapped with the Ids, if possible. Can anybody point me in the correct direction? Thanks!

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  • NHibernate unable to create SessionFactory

    - by Tyler
    I'm having a bit of trouble setting up NHibernate, and I'm not too sure what the problem is exactly. I'm attempting to save a domain object to the database (Oracle 10g XE). However, I'm getting a TypeInitializationException while trying to create the ISessionFactory. Here is what my hibernate.cfg.xml looks like: <?xml version="1.0" encoding="utf-8"?> <hibernate-configuration xmlns="urn:nhibernate-configuration-2.2" > <session-factory name="MyProject.DataAccess"> <property name="connection.driver_class">NHibernate.Driver.OracleClientDriver</property> <property name="connection.connection_string"> User ID=myid;Password=mypassword;Data Source=localhost </property> <property name="show_sql">true</property> <property name="dialect">NHibernate.Dialect.OracleDialect</property> <property name="proxyfactory.factory_class">NHibernate.ByteCode.LinFu.ProxyFactoryFactory, NHibernate.ByteCode.LinFu</property> <mapping resource="MyProject/Domain/User.hbm.xml"/> </session-factory> </hibernate-configuration> I created a DAO which I will use to persist domain objects to the database. The DAO uses a HibernateUtil class that creates the SessionFactory. Both classes are in the DataAccess namespace along with the Hibernate configuration. This is where the exception is occuring. Here's that class: public class HibernateUtil { private static ISessionFactory SessionFactory = BuildSessionFactory(); private static ISessionFactory BuildSessionFactory() { try { // This seems to be where the problem occurs return new Configuration().Configure().BuildSessionFactory(); } catch (TypeInitializationException ex) { Console.WriteLine("Initial SessionFactory creation failed." + ex); throw new Exception("Unable to create SessionFactory."); } } public static ISessionFactory GetSessionFactory() { return SessionFactory; } } The DataAccess namespace references the NHibernate DLLs. This is virtually the same setup I've used with Hibernate in Java, so I'm not entirely sure what I'm doing wrong here. Any ideas? Edit The innermost exception is the following: "Could not find file 'C:\Users\Tyler\Documents\Visual Studio 2010\Projects\MyProject\MyProject\ConsoleApplication\bin\Debug\hibernate.cfg.xml'." ConsoleApplication contains the entry point where I've created a User object and am trying to persist it with my DAO. Why is it looking for the configuration file there? The actual persisting takes place in the DAO, which is in DataAccess. Also, when I add the configuration file to ConsoleApplication, it still does not find it.

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  • Binding Jar Library

    - by Juliano
    I'm trying to bind a jar library (jCIFS) on MFA, but i'm stuck on some errors, like this one: 'Jcifs.Util.MD4' does not implement inherited abstract member 'Java.Security.MessageDigestSpi.EngineDigest() After some research, i found some topics about this, telling to edit the metadata to change the permissions of the classes, like this: <attr path="/api/package[@name='java.security']/class[@name='MessageDigestSpi']/method[@name='engineDigest']" name="visibility">public</attr> But the error didn't change, and a still won't get what this error means. Anyone ? Thanks.

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  • How to create factories with attr_accesible?

    - by regedarek
    How to deal with factories and attr_accessible? My example: # model class SomeModel attr_accessible :name, full_name, other_name end #spec require 'spec_helper' describe "test" do it do create(:some_model, name: "test name", user: User.first) #factory end end #error ruby(17122,0x12a055000) malloc: *** error for object 0x8: pointer being freed was not allocated *** set a breakpoint in malloc_error_break to debug I think the error is because user_id is not in attr_accesible atributes

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  • populate CoreData data model from JSON files prior to app start

    - by johannes_d
    I am creating an iPad App that displays data I got from an API in JSON format. My Core Data model has several entities(Countries, Events, Talks, ...). For each entity I have one .json file that contains all instances of the entity and its attributes as well as its relationships. I would like to populate my Core Data data model with these entities before the start of the App (otherwise it takes about 15 minutes for the iPad to create all the instances of the entities from the several JSON files using factory methods). I am currently importing the data into CoreData like this: -(void)fetchDataIntoDocument:(UIManagedDocument *)document { dispatch_queue_t dataQ = dispatch_queue_create("Data import", NULL); dispatch_async(dataQ, ^{ //Fetching data from application bundle NSURL *tedxgroupsurl = [[NSBundle mainBundle] URLForResource:@"contries" withExtension:@"json"]; NSURL *tedxeventsurl = [[NSBundle mainBundle] URLForResource:@"events" withExtension:@"json"]; //converting the JSON files to NSDictionaries NSError *error = nil; NSDictionary *countries = [NSJSONSerialization JSONObjectWithData:[NSData dataWithContentsOfURL:countriesurl] options:kNilOptions error:&error]; countries = [countries objectForKey:@"countries"]; NSDictionary *events = [NSJSONSerialization JSONObjectWithData:[NSData dataWithContentsOfURL:eventsurl] options:kNilOptions error:&error]; events = [events objectForKey:@"events"]; //creating entities using factory methods in NSManagedObject Subclasses (Country / Event) [document.managedObjectContext performBlock:^{ NSLog(@"creating countries"); for (NSDictionary *country in countries) { [Country countryWithCountryInfo:country inManagedObjectContext:document.managedObjectContext]; //creating Country entities } NSLog(@"creating events"); for (NSDictionary *event in events) { [Event eventWithEventInfo:event inManagedObjectContext:document.managedObjectContext]; // creating Event entities } NSLog(@"done creating, saving document"); [document saveToURL:document.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:NULL]; }]; }); dispatch_release(dataQ); } This combines the different JSON files into one UIManagedDocument which i can then perform fetchRequests on to populate tableViews, mapView, etc. I'm looking for a way to create this document outside my application & add it to the mainBundle. Then I could copy it once to the apps DocumentsDirectory and be able I use it (instead of creating the Document within the app from the original JSON files). Any help is appreciated!

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  • Ldap invalid credentials not loading authentication failure url

    - by Murari
    Able to do the custom ldap authentication for external db authorities. But when i am trying to test wrong password the authentication failure url is not showing instead my browser prints the exception details.Below is my securitycontext.xml and exption given <http auto-config="false" access-decision-manager-ref="accessDecisionManager" access-denied-page="/accessDenied.jsp"> <!-- Restrict access to ALL other pages --> <intercept-url pattern="/index.jsp" filters="none" /> <!-- Don't set any role restrictions on login.jsp --> <intercept-url pattern="/**" access="IS_AUTHENTICATED_ANONYMOUSLY" /> <intercept-url pattern="/service/**" access="PRIV_Report User, PRIV_305" /> <logout logout-success-url="/index.jsp" /> <form-login authentication-failure-url="/index.jsp?error=1" default-target-url="/home.jsp" /> <anonymous/> </http> <b:bean id="accessDecisionManager" class="org.springframework.security.vote.AffirmativeBased"> <b:property name="decisionVoters"> <b:list> <b:ref bean="roleVoter" /> <b:ref bean="authenticatedVoter" /> </b:list> </b:property> </b:bean> <b:bean id="roleVoter" class="org.springframework.security.vote.RoleVoter"> <b:property name="rolePrefix" value="PRIV_" /> </b:bean> <b:bean id="authenticatedVoter" class="org.springframework.security.vote.AuthenticatedVoter"> </b:bean> <b:bean id="contextSource" class="org.springframework.security.ldap.DefaultSpringSecurityContextSource"> <b:constructor-arg value="ldap://mydomain:389" /> </b:bean> <b:bean id="ldapTemplate" class="org.springframework.ldap.core.LdapTemplate"> <b:constructor-arg ref="contextSource" /> </b:bean> <b:bean id="ldapAuthenticationProvider" class="com.zo.sas.gwt.security.login.server.SASLdapAuthenticationProvider"> <b:property name="authenticator" ref="ldapAuthenticator" /> <custom-authentication-provider /> </b:bean> <b:bean id="ldapAuthenticator" class="com.zo.sas.gwt.security.login.server.SASAuthenticator"> <b:property name="contextSource" ref="contextSource" /> <b:property name="userDnPatterns"> <b:value>uid={0},OU=People</b:value> </b:property> </b:bean> and my exception logs..... org.springframework.ldap.AuthenticationException: [LDAP: error code 49 - Invalid Credentials]; nested exception is javax.naming.AuthenticationException: [LDAP: error code 49 - Invalid Credentials] org.springframework.ldap.support.LdapUtils.convertLdapException(LdapUtils.java:180) org.springframework.ldap.core.support.AbstractContextSource.createContext(AbstractContextSource.java:266) org.springframework.ldap.core.support.AbstractContextSource.getContext(AbstractContextSource.java:106) com.zo.sas.gwt.security.login.server.SASAuthenticator.authenticate(SASAuthenticator.java:55) com.zo.sas.gwt.security.login.server.SASLdapAuthenticationProvider.authenticate(SASLdapAuthenticationProvider.java:45) org.springframework.security.providers.ProviderManager.doAuthentication(ProviderManager.java:188) org.springframework.security.AbstractAuthenticationManager.authenticate(AbstractAuthenticationManager.java:46) org.springframework.security.ui.webapp.AuthenticationProcessingFilter.attemptAuthentication(AuthenticationProcessingFilter.java:82) org.springframework.security.ui.AbstractProcessingFilter.doFilterHttp(AbstractProcessingFilter.java:258) org.springframework.security.ui.SpringSecurityFilter.doFilter(SpringSecurityFilter.java:53) org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:390) org.springframework.security.ui.logout.LogoutFilter.doFilterHttp(LogoutFilter.java:89) org.springframework.security.ui.SpringSecurityFilter.doFilter(SpringSecurityFilter.java:53) org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:390) org.springframework.security.context.HttpSessionContextIntegrationFilter.doFilterHttp(HttpSessionContextIntegrationFilter.java:235) org.springframework.security.ui.SpringSecurityFilter.doFilter(SpringSecurityFilter.java:53) org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:390) org.springframework.security.util.FilterChainProxy.doFilter(FilterChainProxy.java:175) org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:183) org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:138) This is my index.jsp <html> <script type="text/javascript" language="javascript"> var dictionary = { loginErr: "${SPRING_SECURITY_LAST_EXCEPTION.message}", error: "${param.error}" }; </script> <head> </head> <body > <iframe src="javascript:''" id="__gwt_historyFrame" style="width:0;height:0;border:0"></iframe> <script type="text/javascript" language="javascript" src="com.zo.sas.gwt.sasworkflow.home.Home.nocache.js"></script> </body> </html>

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