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• Spring bean initialization in a web app

  - by EugeneP

  We work with a web application and autowire beans using WebApplicationContextUtils in the init method. Could you clarify some details about bean initialization? The question rises from the static factory method. Suppose there's a bean that is created in a static factory method. As we can see, when the web app is deployed, the ContextLoaderListener initializes all the beans present in Spring xml config file. Now happens such a thing. In the static factory method we run a timer that starts ticking. But in reality we wouldn't want it to start ticking unless the bean is injected into a property of the object ! That is question number one - all the beans are automatically initialized on deploy - correct? And after that when we need an injection, it simply feels the link with the address of the object created during initialization, though OBJECT WAS CREATED ON WEB APP DEPLOY, immediately ! (I assume the default singleton-creation Spring behavior) Second question: are all copies of a web app use the same beans, so all beans are WEB-APP wide, every Spring bean is shared between all the copies of this web app running?

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• Validate HAML from ActiveRecord: scope/controller/helpers for link_to etc?

  - by Chris Boyle

  I like HAML. So much, in fact, that in my first Rails app, which is the usual blog/CMS thing, I want to render the body of my Page model using HAML. So here is app/views/pages/_body.html.haml: .entry-content= Haml::Engine.new(body, :format => :html5).render ...and it works (yay, recursion). What I'd like to do is validate the HAML in the body when creating or updating a Page. I can almost do that, but I'm stuck on the scope argument to render. I have this in app/models/page.rb: validates_each :body do |record, attr, value| begin Haml::Engine.new(value, :format => :html5).render(record) rescue Exception => e record.errors.add attr, "line #{(e.respond_to? :line) && e.line || 'unknown'}: #{e.message}" end end You can see I'm passing record, which is a Page, but even that doesn't have a controller, and in particular doesn't have any helpers like link_to, so as soon as a Page uses any of that it's going to fail to validate even when it would actually render just fine. So I guess I need a controller as scope for this, but accessing that from here in the model (where the validator is) is a big MVC no-no, and as such I don't think Rails gives me a way to do it. (I mean, I suppose I could stash a controller in some singleton somewhere or something, but... excuse me while I throw up.) What's the least ugly way to properly validate HAML in an ActiveRecord validator?

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• What exactly is a reentrant function?

  - by eSKay

  Most of the times, the definition of reentrance is quoted from Wikipedia: A computer program or routine is described as reentrant if it can be safely called again before its previous invocation has been completed (i.e it can be safely executed concurrently). To be reentrant, a computer program or routine: Must hold no static (or global) non-constant data. Must not return the address to static (or global) non-constant data. Must work only on the data provided to it by the caller. Must not rely on locks to singleton resources. Must not modify its own code (unless executing in its own unique thread storage) Must not call non-reentrant computer programs or routines. How is safely defined? If a program can be safely executed concurrently, does it always mean that it is reentrant? What exactly is the common thread between the six points mentioned that I should keep in mind while checking my code for reentrant capabilities? Also, Are all recursive functions reentrant? Are all thread-safe functions reentrant? Are all recursive and thread-safe functions reentrant? While writing this question, one thing comes to mind: Are the terms like reentrance and thread safety absolute at all i.e. do they have fixed concrete definations? For, if they are not, this question is not very meaningful. Thanks!

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• Using Everyauth/Express and Multiple Configurations?

  - by Zane Claes

  I'm successfully using Node.js + Express + Everyauth ( https://github.com/abelmartin/Express-And-Everyauth/blob/master/app.js ) to login to Facebook, Twitter, etc. from my application. The problem I'm trying to wrap my head around is that Everyauth seems to be "configure and forget." I set up a single everyauth object and configure it to act as middleware for express, and then forget about it. For example, if I want to create a mobile Facebook login I do: var app = express.createServer(); everyauth.facebook .appId('AAAA') .appSecret('BBBB') .entryPath('/login/facebook') .callbackPath('/callback/facebook') .mobile(true); // mobile! app.use(everyauth.middleware()); everyauth.helpExpress(app); app.listen(8000); Here's the problem: Both mobile and non-mobile clients will connect to my server, and I don't know which is connecting until the connection is made. Even worse, I need to support multiple Facebook app IDs (and, again, I don't know which one I will want to use until the client connects and I partially parse the input). Because everyauth is a singleton which in configured once, I cannot see how to make these changes to the configuration based upon the request that is made. What it seems like is that I need to create some sort of middleware which acts before the everyauth middleware to configure the everyauth object, such that everyauth subsequently uses the correct appId/appSecret/mobile parameters. I have no clue how to go about this... Suggestions? Here's the best idea I have so far, though it seems terrible: Create an everyauth object for every possible configuration using a different entryPath for each...

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• wpf command pattern

  - by evan

  I have a wpf gui which displays a list of information in separate window and in a separate thread from the main application. As the user performs actions in the main window the side window is updated. (For example if you clicked page down in the main window a listbox in the side window would page down). Right now the architecture for this application feels very messy and I'm sure there is a cleaner way to do it. It looks like this: Main Window contains a singleton SideWindowControl which communicates with an instance of the SideWindowDisplay using events - so, for example, the pagedown button would work like: 1) the event handler of the button on the main window calls SideWindowControl.PageDown() 2) in the PageDown() function a event is created and thrown. 3) finally the gui, ShowSideWindowDisplay is subscribing to the SideWindowControl.Actions event handles the event and actually scrolls the listbox down - note because it is in a different thread it has to do that by running the command via Dispatcher.Invoke() This just seems like a very messy way to this and there must be a clearer way (The only part that can't change is that the main window and the side window must be on different threads). Perhaps using WPF commands? I'd really appreciate any suggestions!! Thanks

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• NetBeans Platform - how to refresh the property sheet view of a node?

  - by I82Much

  Hi all, I am using the PropertySheetView component to visualize and edit the properties of a node. This view should always reflect the most recent properties of the object; if there is a change to the object in another process, I want to somehow refresh the view and see the updated properties. The best way I was able to do this is something like the following (making use of EventBus library to publish and subscribe to changes in objects): public DomainObjectWrapperNode(DomainObject obj) { super (Children.LEAF, Lookups.singleton(obj)); EventBus.subscribe(DomainObject.class, this); } public void onEvent(DomainObject event) { // Do a check to determine if the updated object is the one wrapped by this node; // if so fire a property sets change firePropertySetsChange(null, this.getPropertySets()); } This works, but my place in the scrollpane is lost when the sheet refreshes; it resets the view to the top of the list and I have to scroll back down to where I was before the refresh action. So my question is, is there a better way to refresh the property sheet view of a node, specifically so my place in the property list is not lost upon refresh?

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• How do you pass a generic delegate argument to a method in .NET 2.0 - UPDATED

  - by Seth Spearman

  Hello, I have a class with a delegate declaration as follows... Public Class MyClass Public Delegate Function Getter(Of TResult)() As TResult ''#the following code works. Public Shared Sub MyMethod(ByVal g As Getter(Of Boolean)) ''#do stuff End Sub End Class However, I do not want to explicitly type the Getter delegate in the Method call. Why can I not declare the parameter as follows... ... (ByVal g As Getter(Of TResult)) Is there a way to do it? My end goal was to be able to set a delegate for property setters and getters in the called class. But my reading indicates you can't do that. So I put setter and getter methods in that class and then I want the calling class to set the delegate argument and then invoke. Is there a best practice for doing this. I realize in the above example that I can set set the delegate variable from the calling class...but I am trying to create a singleton with tight encapsulation. For the record, I can't use any of the new delegate types declared in .net35. Answers in C# are welcome. Any thoughts? Seth

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• Avoiding mass propagation of properties and events for exposure to ViewModels.

  - by firoso

  I have an MVVM application I am developing that is to the point where I'm ready to start putting together a user interface (my client code is largely functional) I'm now running into the issue that I'm trying to get my application data to where I need it so that it can be consumed by the view model and then bound to the view. Unfortunately, it seems that I've either got a few structural oversights, or I'm just going to have to face the reality that I need to be propogating events and raising excessive amounts of errors to notify view models that thier properties have changed. Let me go into some examples of my issue: I have a class "Unit" contained in a class "Test", contained in a class "Session" contained in a class "TestManager" which is contained in "TestDataModel" which is utilized by "TestViewModel" which is databound to by my "TestView" .... WHOA. Now, consider that Unit (the bottom of the heiarchy) has a property called "Results" that is updated periodically, I want to expose that to my viewmodel and then databind it to my view, trouble is, the only way I can really think to do this is to perpetuate events WAY up a chain that say "I've been updated!" and then request the new value... This seems like an aweful way to do this. Alternatively, I could register a static event and raise it, and have the appropriate "Unit view model" grab the event and request the update. This SEEMS better... but... static events? Is that a taboo idea? Also, having an expression like: TestDataModel.TestManager.Session.Test.Unit.Results[i] Seems REALLY gross to have on a View Model. I know this all reeks of a bad design issue, but I can't figure out what I did wrong? Should I be using more singleton/container controlled lifetimes type objects? Register object instances with static helper containers? Obviously these are hard questions to answer without being intimate with the existing structure, but if you've run into situations like this, what did you do to refactor? Should I just live with this, add mass events, and propogate them?

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• Database cache that I'm not aware of?

  - by Martin

  I'm using asp.net mvc, linq2sql, iis7 and sqlserver express 2008. I get these intermittent server errors, primary key conflicts on insertion. I'm using a different setup on my development computer so I can't debug. After a while they go away. Restarting iis helps. I'm getting the feeling there is cache somewhere that I'm not aware of. Can somebody help me sort out these errors? Cannot insert duplicate key row in object 'dbo.EnquiryType' with unique index 'IX_EnquiryType'. Edits regarding Venemos answer Is it possible that another application is also accessing the same database simultaneously? Yes there is, but not this particular table and no inserts or updates. There is one other table with which I experience the same problem but it has to do with a different part of the model. How often an in what context do you create a new DataContext instance? Only once, using the singleton pattern. Are the primary keys generated by the database or by the application? Database. Which version of ASP.NET MVC and which version of .NET are you using? RC2 and 3.5.

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• MVVM and avoiding Monolithic God object

  - by bufferz

  I am in the completion stage of a large project that has several large components: image acquisition, image processing, data storage, factory I/O (automation project) and several others. Each of these components is reasonably independent, but for the project to run as a whole I need at least one instance of each component. Each component also has a ViewModel and View (WPF) for monitoring status and changing things. My question is the safest, most efficient, and most maintainable method of instantiating all of these objects, subscribing one class to an Event in another, and having a common ViewModel and View for all of this. Would it best if I have a class called God that has a private instance of all of these objects? I've done this in the past and regretted it. Or would it be better if God relied on Singleton instances of these objects to get the ball rolling. Alternatively, should Program.cs (or wherever Main(...) is) instantiate all of these components, and pass them to God as parameters and then let Him (snicker) and His ViewModel deal with the particulars of running this projects. Any other suggestions I would love to hear. Thank you!

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• How to collect and inject all beans of a given type in Spring XML configuration

  - by GrzegorzOledzki

  One of the strongest accents of the Spring framework is the Dependency Injection concept. I understand one of the advices behind that is to separate general high-level mechanism from low-level details (as announced by Dependency Inversion Principle). Technically, that boils down to having a bean implementation to know as little as possible about a bean being injected as a dependency, e.g. public class PrintOutBean { private LogicBean logicBean; public void action() { System.out.println(logicBean.humanReadableDetails()); } //... } <bean class="PrintOutBean"> <property name="loginBean" ref="ShoppingCartBean"/> </bean> But what if I wanted to a have a high-level mechanism operating on multiple dependent beans? public class MenuManagementBean { private Collection<Option> options; public void printOut() { for (Option option:options) { // do something for option } //... } } I know one solution would be to use @Autowired annotation in the singleton bean, that is... @Autowired private Collection<Option> options; But doesn't it violate the separation principle? Why do I have to specify what dependents to take in the very same place I use them (i.e. MenuManagementBean class in my example)? Is there a way to inject collections of beans in the XML configuration like this (without any annotation in the MMB class)? <bean class="MenuManagementBean"> <property name="options"> <xxx:autowire by-type="MyOptionImpl"/> </property> </bean>

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• Silverlight Binding - Binds when item is added but doesn't get updates.

  - by dw

  Hello, I'm sorta at a loss to why this doesn't work considering I got it from working code, just added a new level of code, but here's what I have. Basically, when I bind the ViewModel to a list, the binding picks up when Items are added to a collection. However, if an update occurs to the item that is bound, it doesn't get updated. Basically, I have an ObservableCollection that contains a custom class with a string value. When that string value gets updated I need it to update the List. Right now, when I debug, the list item does get updated correctly, but the UI doesn't reflect the change. If I set the bound item to a member variable and null it out then reset it to the right collection it will work, but not desired behavior. Here is a mockup of the code, hopefully someone can tell me where I am wrong. Also, I've tried implementing INofityPropertyChanged at every level in the code below. public class Class1 { public string ItemName; } public class Class2 { private Class2 _items; private Class2() //Singleton { _items = new ObservableCollection<Class1>(); } public ObservableCollection<Class1> Items { get { return _items; } internal set { _items = value; } } } public class Class3 { private Class2 _Class2Instnace; private Class3() { _Class2Instnace = Class2.Instance; } public ObservableCollection<Class1> Items2 { get {return _Class2Instnace.Items; } } } public class MyViewModel : INofityPropertyChanged { private Class3 _myClass3; private MyViewModel() { _myClass3 = new Class3(); } private BindingItems { get { return _myClass3.Items2; } // Binds when adding items but not when a Class1.ItemName gets updated. } }

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• EventAggregator, is it thread-safe?

  - by pfaz

  Is this thread-safe? The EventAggregator in Prism is a very simple class with only one method. I was surprised when I noticed that there was no lock around the null check and creation of a new type to add to the private _events collection. If two threads called GetEvent simultaneously for the same type (before it exists in _events) it looks like this would result in two entries in the collection. /// <summary> /// Gets the single instance of the event managed by this EventAggregator. Multiple calls to this method with the same <typeparamref name="TEventType"/> returns the same event instance. /// </summary> /// <typeparam name="TEventType">The type of event to get. This must inherit from <see cref="EventBase"/>.</typeparam> /// <returns>A singleton instance of an event object of type <typeparamref name="TEventType"/>.</returns> public TEventType GetEvent<TEventType>() where TEventType : EventBase { TEventType eventInstance = _events.FirstOrDefault(evt => evt.GetType() == typeof(TEventType)) as TEventType; if (eventInstance == null) { eventInstance = Activator.CreateInstance<TEventType>(); _events.Add(eventInstance); } return eventInstance; }

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• CompositionHost.Initialize() can not execute twice.

  - by Khoa

  I am currently try to integrate MEF and PRISM to work with each other. Everything is working fine so far. Now i would like to use MEF runtime module discovery (DeploymentCatalog) which will be used to download XAPs from server directory and then plug it into one of the Region inside my MAIN UI. I am using UnityBootStrapper and inside this class i also integrated MEF container. This sample application is based on Glenn Block (http://codebetter.com/glennblock/2010/01/03/mef-and-prism-exploration-mef-module-loading/). The following code is used to initialize CompositionContainer inside my Bootstrapper: // This is the host catalog which contains all parts of running assembly. var catalog = GetHostCatalog(); // Create MEF container which initial catalog var container = new CompositionContainer(catalog); // here we explicitly map a part to make it available on imports elsewhere, using // Unity to resolve the export so dependencies are resolved // We do this because region manager is third-party ... therefore, we need to // export explicitly because the implementation doesn't have its own [export] tag container.ComposeExportedValue<IRegionManager>(Container.Resolve<IRegionManager>()); container.ComposeExportedValue<IEventAggregator>(Container.Resolve<IEventAggregator>()); // Obtain CatalogService as a singleton // All dynamic modules will use this service to add its parts. Container.RegisterInstance<ICatalogService>(new CatalogService(catalog)); // Initialize the container CompositionHost.Initialize(container); Now i have another class called DeploymentCatalogService which is used to download the XAP from server. The current problem i am facing is that inside DeploymentCatalogService Initialize method, CompositionHost container is try to initialize its container with aggregateCatalog again. _aggregateCatalog = new AggregateCatalog(); _aggregateCatalog.Catalogs.Add(new DeploymentCatalog()); CompositionHost.Initialize(_aggregateCatalog); This causes an Exception which stated that The container has already been initialized. Is there a way to use the existing container and update it with the new aggregateCatalog? Hope this is not too confusing. Please be nice i am still new to MEF. Cheers,

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• Structure map and generics (in XML config)

  - by James D

  Hi I'm using the latest StructureMap (2.5.4.264), and I need to define some instances in the xml configuration for StructureMap using generics. However I get the following 103 error: Unhandled Exception: StructureMap.Exceptions.StructureMapConfigurationException: StructureMap configuration failures: Error: 103 Source: Requested PluginType MyTest.ITest`1[[MyTest.Test,MyTest]] configured in Xml cannot be found Could not create a Type for 'MyTest.ITest`1[[MyTest.Test,MyTest]]' System.ApplicationException: Could not create a Type for 'MyTest.ITest`1[[MyTest.Test,MyTest]]' ---> System.TypeLoadException: Could not loa d type 'MyTest.ITest`1' from assembly 'StructureMap, Version=2.5.4.264, Culture=neutral, PublicKeyToken=e60ad81abae3c223'. at System.RuntimeTypeHandle._GetTypeByName(String name, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMark& stackMark, Boolean loadTypeFromPartialName) at System.RuntimeTypeHandle.GetTypeByName(String name, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMark& stackMark) at System.RuntimeType.PrivateGetType(String typeName, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMark& s tackMark) at System.Type.GetType(String typeName, Boolean throwOnError) at StructureMap.Graph.TypePath.FindType() --- End of inner exception stack trace --- at StructureMap.Graph.TypePath.FindType() at StructureMap.Configuration.GraphBuilder.ConfigureFamily(TypePath pluginTypePath, Action`1 action) A simply replication of the code is as follows: public interface ITest<T> { } public class Test { } public class Concrete : ITest<Test> { } Which I then wish to define in the XML configuration something as follows: <DefaultInstance PluginType="MyTest.ITest`1[[MyTest.Test,MyTest]],MyTest" PluggedType="MyTest.Concrete,MyTest" Scope="Singleton" /> I've been racking my brain, however I can't see what I'm doing wrong - I've used Type.GetType to verify the type actually is valid which it is. Anyone have any ideas? Thanks !

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• "Detecting" and loading of "plugins" in GAE

  - by Patrick Cornelissen

  Hi! I have a "plugin like" architecture and I want to create one instance of each class that implements a dedicated interface and put these in a cache. (To have a singleton-ish effect). The plugins will be provided as jars and put into the app engine war file before the app is uploaded. I have tried to use the ClassPathScanningCandidateComponentProvider as I'm using spring anyway, but this didn't work. The provider complained that it was not able to find the HttpServletResponse class file while scanning the classpath. I can't get around this, when I add the servlet jar, then I'll get of course problems, because the same jar is also provided by the GAE. If I don't, I'm getting the error above... So I tried to add a static initialization code, but of course this doesn't work, because the class is initialized when it's instantiated for the first time. (Well I knew that but it was worth a try) The last chance I currently see is that I create a properties file with all plugin classes when the package is created, but this requires writing of a maven plugin etc. and I'd like to avoid that. Is there something that I am missing?

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• How do you pass a generic delegate argument to a method in .NET 2.0

  - by Seth Spearman

  Hello, I have a class with a delegate declaration as follows... Public Class MyClass Public Delegate Function Getter(Of TResult)() As TResult 'the following code works. Public Shared Sub MyMethod(ByVal g As Getter(Of Boolean)) 'do stuff End Sub End Class However, I do not want to explicitly type the Getter delegate in the Method call. Why can I not declare the parameter as follows... ... (ByVal g As Getter(Of TResult)) Is there a way to do it? My end goal was to be able to set a delegate for property setters and getters in the called class. But my reading indicates you can't do that. So I put setter and getter methods in that class and then I want the calling class to set the delegate argument and then invoke. Is there a best practice for doing this. I realize in the above example that I can set set the delegate variable from the calling class...but I am trying to create a singleton with tight encapsulation. For the record, I can't use any of the new delegate types declared in .net35. Answers in C# are welcome. Any thoughts? Seth

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• c# wpf command pattern

  - by evan

  I have a wpf gui which displays a list of information in separate window and in a separate thread from the main application. As the user performs actions in the main window the side window is updated. (For example if you clicked page down in the main window a listbox in the side window would page down). Right now the architecture for this application feels very messy and I'm sure there is a cleaner way to do it. It looks like this: Main Window contains a singleton SideWindowControl which communicates with an instance of the SideWindowDisplay using events - so, for example, the pagedown button would work like: 1) the event handler of the button on the main window calls SideWindowControl.PageDown() 2) in the PageDown() function a event is created and thrown. 3) finally the gui, ShowSideWindowDisplay is subscribing to the SideWindowControl.Actions event handles the event and actually scrolls the listbox down - note because it is in a different thread it has to do that by running the command via Dispatcher.Invoke() This just seems like a very messy way to this and there must be a clearer way (The only part that can't change is that the main window and the side window must be on different threads). Perhaps using WPF commands? I'd really appreciate any suggestions!! Thanks

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• No operations allowed after statement closed issue

  - by Washu

  I have the next methods in my singleton to execute the JDBC connections public void openDB() throws ClassNotFoundException, IllegalAccessException, InstantiationException, SQLException { Class.forName("com.mysql.jdbc.Driver").newInstance(); String url = "jdbc:mysql://localhost/mbpe_peru";//mydb conn = DriverManager.getConnection(url, "root", "admin"); st = conn.createStatement(); } public void sendQuery(String query) throws SQLException { st.executeUpdate(query); } public void closeDB() throws SQLException { st.close(); conn.close(); } And I'm having a problem in a void where i have to call this twice. private void jButton1ActionPerformed(ActionEvent evt) { Main.getInstance().openDB(); Main.getInstance().sendQuery("call insertEntry('"+EntryID()+"','"+SupplierID()+"');"); Main.getInstance().closeDB(); Main.getInstance().openDB(); for(int i=0;i<dataBox.length;i++){ Main.getInstance().sendQuery("call insertCount('"+EntryID()+"','"+SupplierID()+"','"+BoxID()+"'); Main.getInstance().closeDB(); } } I have already tried to keep the connection open and send the 2 querys and after that closed and it didnt work... The only way it worked was to not use the methods, declare the commands for the connection and use different variables for the connection and the statement. I thought that if i close the Connecion and the Statement I could use the variable once again since is a method but I'm not able to. Is there any way to solve this using my methods for the JDBC connection?

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• Which pattern to use for logging? Dependency Injection or Service Locator?

  - by andlju

  Consider this scenario. I have some business logic that now and then will be required to write to a log. interface ILogger { void Log(string stuff); } interface IDependency { string GetInfo(); } class MyBusinessObject { private IDependency _dependency; public MyBusinessObject(IDependency dependency) { _dependency = dependency; } public string DoSomething(string input) { // Process input var info = _dependency.GetInfo(); var intermediateResult = PerformInterestingStuff(input, info); if (intermediateResult== "SomethingWeNeedToLog") { // How do I get to the ILogger-interface? } var result = PerformSomethingElse(intermediateResult); return result; } } How would you get the ILogger interface? I see two main possibilities; Pass it using Dependency Injection on the constructor. Get it via a singleton Service Locator. Which method would you prefer, and why? Or is there an even better pattern? Update: Note that I don't need to log ALL method calls. I only want to log a few (rare) events that may or may not occur within my method.

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• Java : Inner class of an interface (from google guice)

  - by bsreekanth

  Hello, I was going through the source of google guice, and found an unfamiliar piece of code. It would be great learning if someone can clarify it. I have very basic understanding of inner classes, as they keep the implementation details close to the public interface. Otherwise the inner class may pollute the namespace. Now, I see the below lines at public static final Scope SINGLETON = new Scope() { public <T> Provider<T> scope(final Key<T> key, final Provider<T> creator) { return new Provider<T>() { ......... } It assign an inner class instance to the static variable, but Scope is an interface defined as (at) public interface Scope Is it possible to instantiate the interface?? or is it a succinct syntax for an anonymous implementation of an interface?? If anyone can explain what the author is intended by multiple nested classes above (Scope and Provider), and why it make sense to implement this way, it would help me to understand. thanks.

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• SpringMvc java.lang.NullPointerException When Posting Form To Server

  - by dev_darin

  I have a form with a user name field on it when i tab out of the field i use a RESTFUL Web Service that makes a call to a handler method in the controller. The method makes a call to a DAO class that checks the database if the user name exists. This works fine, however when the form is posted to the server i call the same exact function i would call in the handler method however i get a java.lang.NullPointerException when it accesses the class that makes a call to the DAO object. So it does not even access the DAO object the second time. I have exception handlers around the calls in all my classes that makes calls. Any ideas as to whats happening here why i would get the java.lang.NullPointerException the second time the function is called.Does this have anything to do with Spring instantiating DAO classes using a Singleton method or something to that effect? What can be done to resolve this? This is what happens the First Time The Method is called using the Web Service(this is suppose to happen): 13011 [http-8084-2] INFO com.crimetrack.jdbc.JdbcOfficersDAO - Inside jdbcOfficersDAO 13031 [http-8084-2] DEBUG org.springframework.jdbc.core.JdbcTemplate - Executing prepared SQL query 13034 [http-8084-2] DEBUG org.springframework.jdbc.core.JdbcTemplate - Executing prepared SQL statement [SELECT userName FROM crimetrack.tblofficers WHERE userName = ?] 13071 [http-8084-2] DEBUG org.springframework.jdbc.datasource.DataSourceUtils - Fetching JDBC Connection from DataSource 13496 [http-8084-2] DEBUG org.springframework.jdbc.core.StatementCreatorUtils - Setting SQL statement parameter value: column index 1, parameter value [adminz], value class [java.lang.String], SQL type unknown 13534 [http-8084-2] DEBUG org.springframework.jdbc.datasource.DataSourceUtils - Returning JDBC Connection to DataSource 13537 [http-8084-2] INFO com.crimetrack.jdbc.JdbcOfficersDAO - No username was found in exception 13537 [http-8084-2] INFO com.crimetrack.service.ValidateUserNameManager - UserName :adminz does NOT exist The Second time When The Form Is 'Post' and a validation method handles the form and calls the same method the web service would call: 17199 [http-8084-2] INFO com.crimetrack.service.OfficerRegistrationValidation - UserName is not null so going to check if its valid for :adminz 17199 [http-8084-2] INFO com.crimetrack.service.OfficerRegistrationValidation - User Name in try.....catch block is adminz 17199 [http-8084-2] INFO com.crimetrack.service.ValidateUserNameManager - Inside Do UserNameExist about to validate with username : adminz 17199 [http-8084-2] INFO com.crimetrack.service.ValidateUserNameManager - UserName :adminz EXCEPTION OCCURED java.lang.NullPointerException

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• Where should I put validation code?

  - by D Lawson

  I'm creating interfaces and abstract classes that represent a messaging framework for short text-based messages like SMS, email, twitter, xml, etc.. and I was wondering where I should put the message validation code. The thing is that I am only writing the superclasses and interfaces, so I'm not putting the actual implementation in, I'll just put the hooks in that allow others to validate the content of the messages. The way I see it, I could do it several ways: in the abstract superclass "Message", have an abstract method 'isValid'. A variation on this would be to have isValid be called when the Message constructor is called, throwing a MalformedMessageException if the message is formatted incorrectly. in the transport layer, immediately before sending, validate the message. I would have a send(Message) method that calls an isValid(Message) method immediately before it sends. have a singleton message validator with a static method isValid(Message) that is called at some point. I'm sure there are other options that I'm missing. Currently, I'm leaning towards the first one, but it doesn't feel right to me to have validation code in what should be a domain object.

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• Can't add or remove object from NSMutableSet

  - by Dan Ray

  Check it: - (IBAction)toggleFavorite { DataManager *data = [DataManager sharedDataManager]; NSMutableSet *favorites = data.favorites; if (thisEvent.isFavorite == YES) { NSLog(@"Toggling off"); thisEvent.isFavorite = NO; [favorites removeObject:thisEvent.guid]; [favoriteIcon setImage:[UIImage imageNamed:@"notFavorite.png"] forState:UIControlStateNormal]; } else { NSLog(@"Toggling on, adding %@", thisEvent.guid); thisEvent.isFavorite = YES; [favorites addObject:thisEvent.guid]; [favoriteIcon setImage:[UIImage imageNamed:@"isFavorite.png"] forState:UIControlStateNormal]; } NSLog(@"favorites array now contains %d members", [favorites count]); } This is fired from a custom UIButton. The UI part works great--toggles the image used for the button, and I can see from other stuff that the thisEvent.isFavorite BOOL is toggling happily. I can also see in the debugger that I'm getting my DataManager singleton. But here's my NSLog: 2010-05-13 08:24:32.946 MyApp[924:207] Toggling on, adding 05db685f65e2 2010-05-13 08:24:32.947 MyApp[924:207] favorites array now contains 0 members 2010-05-13 08:24:33.666 MyApp[924:207] Toggling off 2010-05-13 08:24:33.666 MyApp[924:207] favorites array now contains 0 members 2010-05-13 08:24:34.060 MyApp[924:207] Toggling on, adding 05db685f65e2 2010-05-13 08:24:34.061 MyApp[924:207] favorites array now contains 0 members 2010-05-13 08:24:34.296 MyApp[924:207] Toggling off 2010-05-13 08:24:34.297 MyApp[924:207] favorites array now contains 0 members Worst part is, this USED to work, and I don't know what I did to break it.

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• Automating Excel through the PIA makes VBA go squiffy.

  - by Jon Artus

  I have absolutely no idea how to start diagnosing this, and just wondered if anyone had any suggestions. I'm generating an Excel spreadsheet by calling some Macros from a C# application, and during the generation process it somehow breaks. I've got a VBA class containing all of my logging/error-handling logic, which I instantiate using a singleton-esque accessor, shown here: Private mcAppFramework As csys_ApplicationFramework Public Function AppFramework() As csys_ApplicationFramework If mcAppFramework Is Nothing Then Set mcAppFramework = New csys_ApplicationFramework Call mcAppFramework.bInitialise End If Set AppFramework = mcAppFramework End Function The above code works fine before I've generated the spreadsheet, but afterwards fails. The problem seems to be the following line; Set mcAppFramework = New csys_ApplicationFramework which I've never seen fail before. If I add a watch to the variable being assigned here, the type shows as csys_ApplicationFramework/wksFoo, where wksFoo is a random worksheet in the same workbook. What seems to be happening is that while the variable is of the right type, rather than filling that slot with a new instance of my framework class, it's making it point to an existing worksheet instead, the equivalent of Set mcAppFramework = wksFoo which is a compiler error, as one might expect. Even more bizarrely, if I put a breakpoint on the offending line, edit the line, and then resume execution, it works. For example, I delete the word 'New' move off the line, move back, re-type 'New' and resume execution. This somehow 'fixes' the workbook and it works happily ever after, with the type of the variable in my watch window showing as csys_ApplicationFramework/csys_ApplicationFramework as I'd expect. This implies that manipulating the workbook through the PIA is somehow breaking it temporarily. All I'm doing in the PIA is opening the workbook, calling several macros using Excel.Application.Run(), and saving it again. I can post a few more details if anyone thinks that it's relevant. I don't know how VBA creates objects behind the scenes or how to debug this. I also don't know how the way the code executes can change without the code itself changing. As previously mentioned, VBA has frankly gone a bit squiffy on me... Any thoughts?

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