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  • Configuring JPA Primary key sequence generators

    - by pachunoori.vinay.kumar(at)oracle.com
    This article describes the JPA feature of generating and assigning the unique sequence numbers to JPA entity .This article provides information on jpa sequence generator annotations and its usage. UseCase Description Adding a new Employee to the organization using Employee form should assign unique employee Id. Following description provides the detailed steps to implement the generation of unique employee numbers using JPA generators feature Steps to configure JPA Generators 1.Generate Employee Entity using "Entities from Table Wizard". View image2.Create a Database Connection and select the table "Employee" for which entity will be generated and Finish the wizards with default selections. View image 3.Select the offline database sources-Schema-create a Sequence object or you can copy to offline db from online database connection. View image 4.Open the persistence.xml in application navigator and select the Entity "Employee" in structure view and select the tab "Generators" in flat editor. 5.In the Sequence Generator section,enter name of sequence "InvSeq" and select the sequence from drop down list created in step3. View image 6.Expand the Employees in structure view and select EmployeeId and select the "Primary Key Generation" tab.7.In the Generated value section,select the "Use Generated value" check box ,select the strategy as "Sequence" and select the Generator as "InvSeq" defined step 4. View image   Following annotations gets added for the JPA generator configured in JDeveloper for an entity To use a specific named sequence object (whether it is generated by schema generation or already exists in the database) you must define a sequence generator using a @SequenceGenerator annotation. Provide a unique label as the name for the sequence generator and refer the name in the @GeneratedValue annotation along with generation strategy  For  example,see the below Employee Entity sample code configured for sequence generation. EMPLOYEE_ID is the primary key and is configured for auto generation of sequence numbers. EMPLOYEE_SEQ is the sequence object exist in database.This sequence is configured for generating the sequence numbers and assign the value as primary key to Employee_id column in Employee table. @SequenceGenerator(name="InvSeq", sequenceName = "EMPLOYEE_SEQ")   @Entity public class Employee implements Serializable {    @Id    @Column(name="EMPLOYEE_ID", nullable = false)    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator="InvSeq")   private Long employeeId; }   @SequenceGenerator @GeneratedValue @SequenceGenerator - will define the sequence generator based on a  database sequence object Usage: @SequenceGenerator(name="SequenceGenerator", sequenceName = "EMPLOYEE_SEQ") @GeneratedValue - Will define the generation strategy and refers the sequence generator  Usage:     @GeneratedValue(strategy = GenerationType.SEQUENCE, generator="name of the Sequence generator defined in @SequenceGenerator")

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  • Reading All Users Session

    - by imran_ku07
      Introduction :            InProc Session is the widely used state management. Storing the session state Inproc is also the fastest method and is well-suited to small amounts of volatile data. Reading and writing current user Session is very easy. But some times we need to read all users session before taking a decision or sometimes we may need to check which users are currently active with the help of Session. But unfortunately there is no class in .Net Framework (i don't found myself) to read all user InProc Session Data. In this article i will use reflection to read all user Inproc Session.   Description :              This code will work equally in both MVC and webform, but for demonstration i will use a simple webform example. So let's create a simple Website and Add two aspx pages, Default.aspx and Default2.aspx. In Default.aspx just add a link to navigate to Default2.aspx and in Default.aspx.cs just add a Session. Default.aspx: <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="Default" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html ><head runat="server">    <title>Untitled Page</title></head><body>    <form id="form1" runat="server">    <div>        <a href="Default2.aspx">Click to navigate to next page</a>    </div>    </form></body></html>  Default.aspx.cs:  using System;using System.Data;using System.Configuration;using System.Collections;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Web.UI.HtmlControls;public partial class Default : System.Web.UI.Page{    protected void Page_Load(object sender, EventArgs e)    {        Session["User"] = "User" + DateTime.Now;    }} Now when every user click this link will navigate to Default2.aspx where all the magic appears.Default2.aspx.cs: using System;using System.Data;using System.Configuration;using System.Collections;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Web.UI.HtmlControls;using System.Reflection;using System.Web.SessionState;public partial class Default2 : System.Web.UI.Page{    protected void Page_Load(object sender, EventArgs e)    {        object obj = typeof(HttpRuntime).GetProperty("CacheInternal", BindingFlags.NonPublic | BindingFlags.Static).GetValue(null, null);        Hashtable c2 = (Hashtable)obj.GetType().GetField("_entries", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(obj);        foreach (DictionaryEntry entry in c2)        {            object o1 = entry.Value.GetType().GetProperty("Value", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(entry.Value, null);            if (o1.GetType().ToString() == "System.Web.SessionState.InProcSessionState")            {                SessionStateItemCollection sess = (SessionStateItemCollection)o1.GetType().GetField("_sessionItems", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(o1);                if (sess != null)                {                    if (sess["User"] != null)                    {                        Label1.Text += sess["User"] + " is Active.<br>";                    }                }            }        }    }}            Now just open more than one browsers or more than one browser instance and then navigate to Default.aspx and click the link, you will see all the user's Session data.    How this works :        InProc session data is stored in the HttpRuntime’s internal cache in an implementation of ISessionStateItemCollection that implements ICollection. In this code, first of all i got CacheInternal Static Property of HttpRuntime class and then with the help of this object i got _entries private member which is of type ICollection. Then simply enumerate this dictionary and only take object of type System.Web.SessionState.InProcSessionState and finaly got SessionStateItemCollection for each user.Summary :        In this article, I shows you how you can get all current user Sessions. However one thing you will find when executing this code is that it will not show the current user Session which is set in the current request context because Session will be saved after all the Page Events.

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  • A simple Dynamic Proxy

    - by Abhijeet Patel
    Frameworks such as EF4 and MOQ do what most developers consider "dark magic". For instance in EF4, when you use a POCO for an entity you can opt-in to get behaviors such as "lazy-loading" and "change tracking" at runtime merely by ensuring that your type has the following characteristics: The class must be public and not sealed. The class must have a public or protected parameter-less constructor. The class must have public or protected properties Adhere to this and your type is magically endowed with these behaviors without any additional programming on your part. Behind the scenes the framework subclasses your type at runtime and creates a "dynamic proxy" which has these additional behaviors and when you navigate properties of your POCO, the framework replaces the POCO type with derived type instances. The MOQ framework does simlar magic. Let's say you have a simple interface:   public interface IFoo      {          int GetNum();      }   We can verify that the GetNum() was invoked on a mock like so:   var mock = new Mock<IFoo>(MockBehavior.Default);   mock.Setup(f => f.GetNum());   var num = mock.Object.GetNum();   mock.Verify(f => f.GetNum());   Beind the scenes the MOQ framework is generating a dynamic proxy by implementing IFoo at runtime. the call to moq.Object returns the dynamic proxy on which we then call "GetNum" and then verify that this method was invoked. No dark magic at all, just clever programming is what's going on here, just not visible and hence appears magical! Let's create a simple dynamic proxy generator which accepts an interface type and dynamically creates a proxy implementing the interface type specified at runtime.     public static class DynamicProxyGenerator   {       public static T GetInstanceFor<T>()       {           Type typeOfT = typeof(T);           var methodInfos = typeOfT.GetMethods();           AssemblyName assName = new AssemblyName("testAssembly");           var assBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(assName, AssemblyBuilderAccess.RunAndSave);           var moduleBuilder = assBuilder.DefineDynamicModule("testModule", "test.dll");           var typeBuilder = moduleBuilder.DefineType(typeOfT.Name + "Proxy", TypeAttributes.Public);              typeBuilder.AddInterfaceImplementation(typeOfT);           var ctorBuilder = typeBuilder.DefineConstructor(                     MethodAttributes.Public,                     CallingConventions.Standard,                     new Type[] { });           var ilGenerator = ctorBuilder.GetILGenerator();           ilGenerator.EmitWriteLine("Creating Proxy instance");           ilGenerator.Emit(OpCodes.Ret);           foreach (var methodInfo in methodInfos)           {               var methodBuilder = typeBuilder.DefineMethod(                   methodInfo.Name,                   MethodAttributes.Public | MethodAttributes.Virtual,                   methodInfo.ReturnType,                   methodInfo.GetParameters().Select(p => p.GetType()).ToArray()                   );               var methodILGen = methodBuilder.GetILGenerator();               methodILGen.EmitWriteLine("I'm a proxy");               if (methodInfo.ReturnType == typeof(void))               {                   methodILGen.Emit(OpCodes.Ret);               }               else               {                   if (methodInfo.ReturnType.IsValueType || methodInfo.ReturnType.IsEnum)                   {                       MethodInfo getMethod = typeof(Activator).GetMethod(/span>"CreateInstance",new Type[]{typeof((Type)});                                               LocalBuilder lb = methodILGen.DeclareLocal(methodInfo.ReturnType);                       methodILGen.Emit(OpCodes.Ldtoken, lb.LocalType);                       methodILGen.Emit(OpCodes.Call, typeofype).GetMethod("GetTypeFromHandle"));  ));                       methodILGen.Emit(OpCodes.Callvirt, getMethod);                       methodILGen.Emit(OpCodes.Unbox_Any, lb.LocalType);                                                              }                 else                   {                       methodILGen.Emit(OpCodes.Ldnull);                   }                   methodILGen.Emit(OpCodes.Ret);               }               typeBuilder.DefineMethodOverride(methodBuilder, methodInfo);           }                     Type constructedType = typeBuilder.CreateType();           var instance = Activator.CreateInstance(constructedType);           return (T)instance;       }   }   Dynamic proxies are created by calling into the following main types: AssemblyBuilder, TypeBuilder, Modulebuilder and ILGenerator. These types enable dynamically creating an assembly and emitting .NET modules and types in that assembly, all using IL instructions. Let's break down the code above a bit and examine it piece by piece                Type typeOfT = typeof(T);              var methodInfos = typeOfT.GetMethods();              AssemblyName assName = new AssemblyName("testAssembly");              var assBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(assName, AssemblyBuilderAccess.RunAndSave);              var moduleBuilder = assBuilder.DefineDynamicModule("testModule", "test.dll");              var typeBuilder = moduleBuilder.DefineType(typeOfT.Name + "Proxy", TypeAttributes.Public);   We are instructing the runtime to create an assembly caled "test.dll"and in this assembly we then emit a new module called "testModule". We then emit a new type definition of name "typeName"Proxy into this new module. This is the definition for the "dynamic proxy" for type T                 typeBuilder.AddInterfaceImplementation(typeOfT);               var ctorBuilder = typeBuilder.DefineConstructor(                         MethodAttributes.Public,                         CallingConventions.Standard,                         new Type[] { });               var ilGenerator = ctorBuilder.GetILGenerator();               ilGenerator.EmitWriteLine("Creating Proxy instance");               ilGenerator.Emit(OpCodes.Ret);   The newly created type implements type T and defines a default parameterless constructor in which we emit a call to Console.WriteLine. This call is not necessary but we do this so that we can see first hand that when the proxy is constructed, when our default constructor is invoked.   var methodBuilder = typeBuilder.DefineMethod(                      methodInfo.Name,                      MethodAttributes.Public | MethodAttributes.Virtual,                      methodInfo.ReturnType,                      methodInfo.GetParameters().Select(p => p.GetType()).ToArray()                      );   We then iterate over each method declared on type T and add a method definition of the same name into our "dynamic proxy" definition     if (methodInfo.ReturnType == typeof(void))   {       methodILGen.Emit(OpCodes.Ret);   }   If the return type specified in the method declaration of T is void we simply return.     if (methodInfo.ReturnType.IsValueType || methodInfo.ReturnType.IsEnum)   {                               MethodInfo getMethod = typeof(Activator).GetMethod("CreateInstance",                                                         new Type[]{typeof(Type)});                               LocalBuilder lb = methodILGen.DeclareLocal(methodInfo.ReturnType);                                                     methodILGen.Emit(OpCodes.Ldtoken, lb.LocalType);       methodILGen.Emit(OpCodes.Call, typeof(Type).GetMethod("GetTypeFromHandle"));       methodILGen.Emit(OpCodes.Callvirt, getMethod);       methodILGen.Emit(OpCodes.Unbox_Any, lb.LocalType);   }   If the return type in the method declaration of T is either a value type or an enum, then we need to create an instance of the value type and return that instance the caller. In order to accomplish that we need to do the following: 1) Get a handle to the Activator.CreateInstance method 2) Declare a local variable which represents the Type of the return type(i.e the type object of the return type) specified on the method declaration of T(obtained from the MethodInfo) and push this Type object onto the evaluation stack. In reality a RuntimeTypeHandle is what is pushed onto the stack. 3) Invoke the "GetTypeFromHandle" method(a static method in the Type class) passing in the RuntimeTypeHandle pushed onto the stack previously as an argument, the result of this invocation is a Type object (representing the method's return type) which is pushed onto the top of the evaluation stack. 4) Invoke Activator.CreateInstance passing in the Type object from step 3, the result of this invocation is an instance of the value type boxed as a reference type and pushed onto the top of the evaluation stack. 5) Unbox the result and place it into the local variable of the return type defined in step 2   methodILGen.Emit(OpCodes.Ldnull);   If the return type is a reference type then we just load a null onto the evaluation stack   methodILGen.Emit(OpCodes.Ret);   Emit a a return statement to return whatever is on top of the evaluation stack(null or an instance of a value type) back to the caller     Type constructedType = typeBuilder.CreateType();   var instance = Activator.CreateInstance(constructedType);   return (T)instance;   Now that we have a definition of the "dynamic proxy" implementing all the methods declared on T, we can now create an instance of the proxy type and return that out typed as T. The caller can now invoke the generator and request a dynamic proxy for any type T. In our example when the client invokes GetNum() we get back "0". Lets add a new method on the interface called DayOfWeek GetDay()   public interface IFoo      {          int GetNum();          DayOfWeek GetDay();      }   When GetDay() is invoked, the "dynamic proxy" returns "Sunday" since that is the default value for the DayOfWeek enum This is a very trivial example of dynammic proxies, frameworks like MOQ have a way more sophisticated implementation of this paradigm where in you can instruct the framework to create proxies which return specified values for a method implementation.

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  • Using Lightbox with _Screen

    Although, I have to admit that I discovered Bernard Bout's ideas and concepts about implementing a lightbox in Visual FoxPro quite a while ago, there was no "spare" time in active projects that allowed me to have a closer look into his solution(s). Luckily, these days I received a demand to focus a little bit more on this. This article describes the steps about how to integrate and make use of Bernard's lightbox class in combination with _Screen in Visual FoxPro. The requirement in this project was to be able to visually lock the whole application (_Screen area) and guide the user to an information that should not be ignored easily. Depending on the importance any current user activity should be interrupted and focus put onto the notification. Getting the "meat", eh, source code Please check out Bernard's blog on Foxite directly in order to get the latest and greatest version. As time of writing this article I use version 6.0 as described in this blog entry: The Fastest Lightbox Ever The Lightbox class is sub-classed from the imgCanvas class from the GdiPlusX project on VFPx and therefore you need to have the source code of GdiPlusX as well, and integrate it into your development environment. The version I use is available here: Release GDIPlusX 1.20 As soon as you open the bbGdiLightbox class the first it, VFP might ask you to update the reference to the gdiplusx.vcx. As we have the sources, no problem and you have access to Bernard's code. The class itself is pretty easy to understand, some properties that you do not need to change and three methods: Setup(), ShowLightbox() and BeforeDraw() The challenge - _Screen or not? Reading Bernard's article about the fastest lightbox ever, he states the following: "The class will only work on a form. It will not support any other containers" Really? And what about _Screen? Isn't that a form class, too? Yes, of course it is but nonetheless trying to use _Screen directly will fail. Well, let's have look at the code to see why: WITH This .Left = 0 .Top = 0 .Height = ThisForm.Height .Width = ThisForm.Width .ZOrder(0) .Visible = .F.ENDWITH During the setup of the lightbox as well as while capturing the image as replacement for your forms and controls, the object reference Thisform is used. Which is a little bit restrictive to my opinion but let's continue. The second issue lies in the method ShowLightbox() and introduced by the call of .Bitmap.FromScreen(): Lparameters tlVisiblilty* tlVisiblilty - show or hide (T/F)* grab a screen dump with controlsIF tlVisiblilty Local loCaptureBmp As xfcBitmap Local lnTitleHeight, lnLeftBorder, lnTopBorder, lcImage, loImage lnTitleHeight = IIF(ThisForm.TitleBar = 1,Sysmetric(9),0) lnLeftBorder = IIF(ThisForm.BorderStyle < 2,0,Sysmetric(3)) lnTopBorder = IIF(ThisForm.BorderStyle < 2,0,Sysmetric(4)) With _Screen.System.Drawing loCaptureBmp = .Bitmap.FromScreen(ThisForm.HWnd,; lnLeftBorder,; lnTopBorder+lnTitleHeight,; ThisForm.Width ,; ThisForm.Height) ENDWITH * save it to a property This.capturebmp = loCaptureBmp ThisForm.SetAll("Visible",.F.) This.DraW() This.Visible = .T.ELSE ThisForm.SetAll("Visible",.T.) This.Visible = .F.ENDIF My first trials in using the class ended in an exception - GdiPlusError:OutOfMemory - thrown by the Bitmap object. Frankly speaking, this happened mainly because of my lack of knowledge about GdiPlusX. After reading some documentation, especially about the FromScreen() method I experimented a little bit. Capturing the visible area of _Screen actually was not the real problem but the dimensions I specified for the bitmap. The modifications - step by step First of all, it is to get rid of restrictive object references on Thisform and to change them into either This.Parent or more generic into This.oForm (even better: This.oControl). The Lightbox.Setup() method now sets the necessary object reference like so: *====================================================================* Initial setup* Default value: This.oControl = "This.Parent"* Alternative: This.oControl = "_Screen"*====================================================================With This .oControl = Evaluate(.oControl) If Vartype(.oControl) == T_OBJECT .Anchor = 0 .Left = 0 .Top = 0 .Width = .oControl.Width .Height = .oControl.Height .Anchor = 15 .ZOrder(0) .Visible = .F. EndIfEndwith Also, based on other developers' comments in Bernard articles on his lightbox concept and evolution I found the source code to handle the differences between a form and _Screen and goes into Lightbox.ShowLightbox() like this: *====================================================================* tlVisibility - show or hide (T/F)* grab a screen dump with controls*====================================================================Lparameters tlVisibility Local loControl m.loControl = This.oControl If m.tlVisibility Local loCaptureBmp As xfcBitmap Local lnTitleHeight, lnLeftBorder, lnTopBorder, lcImage, loImage lnTitleHeight = Iif(m.loControl.TitleBar = 1,Sysmetric(9),0) lnLeftBorder = Iif(m.loControl.BorderStyle < 2,0,Sysmetric(3)) lnTopBorder = Iif(m.loControl.BorderStyle < 2,0,Sysmetric(4)) With _Screen.System.Drawing If Upper(m.loControl.Name) == Upper("Screen") loCaptureBmp = .Bitmap.FromScreen(m.loControl.HWnd) Else loCaptureBmp = .Bitmap.FromScreen(m.loControl.HWnd,; lnLeftBorder,; lnTopBorder+lnTitleHeight,; m.loControl.Width ,; m.loControl.Height) EndIf Endwith * save it to a property This.CaptureBmp = loCaptureBmp m.loControl.SetAll("Visible",.F.) This.Draw() This.Visible = .T. Else This.CaptureBmp = .Null. m.loControl.SetAll("Visible",.T.) This.Visible = .F. Endif {loadposition content_adsense} Are we done? Almost... Although, Bernard says it clearly in his article: "Just drop the class on a form and call it as shown." It did not come clear to my mind in the first place with _Screen, but, yeah, he is right. Dropping the class on a form provides a permanent link between those two classes, it creates a valid This.Parent object reference. Bearing in mind that the lightbox class can not be "dropped" on the _Screen, we have to create the same type of binding during runtime execution like so: *====================================================================* Create global lightbox component*==================================================================== Local llOk, loException As Exception m.llOk = .F. m.loException = .Null. If Not Vartype(_Screen.Lightbox) == "O" Try _Screen.AddObject("Lightbox", "bbGdiLightbox") Catch To m.loException Assert .F. Message m.loException.Message EndTry EndIf m.llOk = (Vartype(_Screen.Lightbox) == "O")Return m.llOk Through runtime instantiation we create a valid binding to This.Parent in the lightbox object and the code works as expected with _Screen. Ease your life: Use properties instead of constants Having a closer look at the BeforeDraw() method might wet your appetite to simplify the code a little bit. Looking at the sample screenshots in Bernard's article you see several forms in different colors. This got me to modify the code like so: *====================================================================* Apply the actual lightbox effect on the captured bitmap.*====================================================================If Vartype(This.CaptureBmp) == T_OBJECT Local loGfx As xfcGraphics loGfx = This.oGfx With _Screen.System.Drawing loGfx.DrawImage(This.CaptureBmp,This.Rectangle,This.Rectangle,.GraphicsUnit.Pixel) * change the colours as needed here * possible colours are (220,128,0,0),(220,0,0,128) etc. loBrush = .SolidBrush.New(.Color.FromArgb( ; This.Opacity, .Color.FromRGB(This.BorderColor))) loGfx.FillRectangle(loBrush,This.Rectangle) EndwithEndif Create an additional property Opacity to specify the grade of translucency you would like to have without the need to change the code in each instance of the class. This way you only need to change the values of Opacity and BorderColor to tweak the appearance of your lightbox. This could be quite helpful to signalize different levels of importance (ie. green, yellow, orange, red, etc...) of notifications to the users of the application. Final thoughts Using the lightbox concept in combination with _Screen instead of forms is possible. Already Jim Wiggins comments in Bernard's article to loop through the _Screen.Forms collection in order to cascade the lightbox visibility to all active forms. Good idea. But honestly, I believe that instead of looping all forms one could use _Screen.SetAll("ShowLightbox", .T./.F., "Form") with Form.ShowLightbox_Access method to gain more speed. The modifications described above might provide even more features to your applications while consuming less resources and performance. Additionally, the restrictions to capture only forms does not exist anymore. Using _Screen you are able to capture and cover anything. The captured area of _Screen does not include any toolbars, docked windows, or menus. Therefore, it is advised to take this concept on a higher level and to combine it with additional classes that handle the state of toolbars, docked windows and menus. Which I did for the customer's project.

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  • How do I set up MVP for a Winforms solution?

    - by JonWillis
    Question moved from Stackoverflow - http://stackoverflow.com/questions/4971048/how-do-i-set-up-mvp-for-a-winforms-solution I have used MVP and MVC in the past, and I prefer MVP as it controls the flow of execution so much better in my opinion. I have created my infrastructure (datastore/repository classes) and use them without issue when hard coding sample data, so now I am moving onto the GUI and preparing my MVP. Section A I have seen MVP using the view as the entry point, that is in the views constructor method it creates the presenter, which in turn creates the model, wiring up events as needed. I have also seen the presenter as the entry point, where a view, model and presenter are created, this presenter is then given a view and model object in its constructor to wire up the events. As in 2, but the model is not passed to the presenter. Instead the model is a static class where methods are called and responses returned directly. Section B In terms of keeping the view and model in sync I have seen. Whenever a value in the view in changed, i.e. TextChanged event in .Net/C#. This fires a DataChangedEvent which is passed through into the model, to keep it in sync at all times. And where the model changes, i.e. a background event it listens to, then the view is updated via the same idea of raising a DataChangedEvent. When a user wants to commit changes a SaveEvent it fires, passing through into the model to make the save. In this case the model mimics the view's data and processes actions. Similar to #b1, however the view does not sync with the model all the time. Instead when the user wants to commit changes, SaveEvent is fired and the presenter grabs the latest details and passes them into the model. in this case the model does not know about the views data until it is required to act upon it, in which case it is passed all the needed details. Section C Displaying of business objects in the view, i.e. a object (MyClass) not primitive data (int, double) The view has property fields for all its data that it will display as domain/business objects. Such as view.Animals exposes a IEnumerable<IAnimal> property, even though the view processes these into Nodes in a TreeView. Then for the selected animal it would expose SelectedAnimal as IAnimal property. The view has no knowledge of domain objects, it exposes property for primitive/framework (.Net/Java) included objects types only. In this instance the presenter will pass an adapter object the domain object, the adapter will then translate a given business object into the controls visible on the view. In this instance the adapter must have access to the actual controls on the view, not just any view so becomes more tightly coupled. Section D Multiple views used to create a single control. i.e. You have a complex view with a simple model like saving objects of different types. You could have a menu system at the side with each click on an item the appropriate controls are shown. You create one huge view, that contains all of the individual controls which are exposed via the views interface. You have several views. You have one view for the menu and a blank panel. This view creates the other views required but does not display them (visible = false), this view also implements the interface for each view it contains (i.e. child views) so it can expose to one presenter. The blank panel is filled with other views (Controls.Add(myview)) and ((myview.visible = true). The events raised in these "child"-views are handled by the parent view which in turn pass the event to the presenter, and visa versa for supplying events back down to child elements. Each view, be it the main parent or smaller child views are each wired into there own presenter and model. You can literately just drop a view control into an existing form and it will have the functionality ready, just needs wiring into a presenter behind the scenes. Section E Should everything have an interface, now based on how the MVP is done in the above examples will affect this answer as they might not be cross-compatible. Everything has an interface, the View, Presenter and Model. Each of these then obviously has a concrete implementation. Even if you only have one concrete view, model and presenter. The View and Model have an interface. This allows the views and models to differ. The presenter creates/is given view and model objects and it just serves to pass messages between them. Only the View has an interface. The Model has static methods and is not created, thus no need for an interface. If you want a different model, the presenter calls a different set of static class methods. Being static the Model has no link to the presenter. Personal thoughts From all the different variations I have presented (most I have probably used in some form) of which I am sure there are more. I prefer A3 as keeping business logic reusable outside just MVP, B2 for less data duplication and less events being fired. C1 for not adding in another class, sure it puts a small amount of non unit testable logic into a view (how a domain object is visualised) but this could be code reviewed, or simply viewed in the application. If the logic was complex I would agree to an adapter class but not in all cases. For section D, i feel D1 creates a view that is too big atleast for a menu example. I have used D2 and D3 before. Problem with D2 is you end up having to write lots of code to route events to and from the presenter to the correct child view, and its not drag/drop compatible, each new control needs more wiring in to support the single presenter. D3 is my prefered choice but adds in yet more classes as presenters and models to deal with the view, even if the view happens to be very simple or has no need to be reused. i think a mixture of D2 and D3 is best based on circumstances. As to section E, I think everything having an interface could be overkill I already do it for domain/business objects and often see no advantage in the "design" by doing so, but it does help in mocking objects in tests. Personally I would see E2 as a classic solution, although have seen E3 used in 2 projects I have worked on previously. Question Am I implementing MVP correctly? Is there a right way of going about it? I've read Martin Fowler's work that has variations, and I remember when I first started doing MVC, I understood the concept, but could not originally work out where is the entry point, everything has its own function but what controls and creates the original set of MVC objects.

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  • Read & Write app.config

    - by Rodney Vinyard
    Imports System.Configuration   Public Class Form1       Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load           Dim config As System.Configuration.Configuration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None)         Me.txtFromFolder.Text = ConfigurationManager.AppSettings("fromFolder")         Me.txtToFolder.Text = ConfigurationManager.AppSettings("toFolder")         End Sub       Private Sub Form1_FormClosing(ByVal sender As System.Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles MyBase.FormClosing             'to write         Dim config As System.Configuration.Configuration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None)           config.AppSettings.Settings.Remove("fromFolder")         config.AppSettings.Settings.Add("fromFolder", txtFromFolder.Text.Trim)           config.AppSettings.Settings.Remove("toFolder")         config.AppSettings.Settings.Add("toFolder", txtToFolder.Text.Trim)           config.Save(ConfigurationSaveMode.Modified)           ConfigurationManager.RefreshSection("appSettings")       End Sub

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  • JRockit Virtual Edition Debug Key

    - by changjae.lee
    There are a few keys that can help the debugging of the JRVE env in console. you can type in each keys in JRVE console to see what's happening under the hood. key '0' : System information key '5' : Enable shutdown key '7' : Start JRockit Management Server (port 7091) key '8' : Statistics Counters key '9' : Full Thread Dump key '0' : Status of Debug-key Below is the sample out from each keys. Debug-key '1' pressed ============ JRockitVE System Information ============ JRockitVE version : 11.1.1.3.0-67-131044 Kernel version : 6.1.0.0-97-131024 JVM version : R27.6.6-28_o-125824-1.6.0_17-20091214-2104-linux-ia32 Hypervisor version : Xen 3.4.0 Boot state : 0x007effff Uptime : 0 days 02:04:31 CPU : uniprocessor @2327 Mhz CPU usage : 0% ctx/s: 285 preempt/s: 0 migrations/s: 0 Physical pages : 82379/261121 (321/1020 MB) Network info : 10.179.97.64 (10.179.97.64/255.255.254.0) GateWay : 10.179.96.1 MAC address : 00:16:3e:7e:dc:78 Boot options : vfsCwd : /application/user_projects/domains/wlsve_domain mainArgs : java -javaagent:/jrockitve/services/sshd/sshd.jar -cp /jrockitve/jrockit/lib/tools.jar:/jrockitve/lib/common.jar:/application/patch_wls1032/profiles/default/sys_manifest_classpath/weblogic_patch.jar:/application/wlserver_10.3/server/lib/weblogic.jar -Dweblogic.Name=WlsveAdmin -Dweblogic.Domain=wlsve_domain -Dweblogic.management.username=weblogic -Dweblogic.management.password=welcome1 -Dweblogic.management.GenerateDefaultConfig=true weblogic.Server consLog : /jrockitve/log/jrockitve.log mounts : ext2 / dev0; posixLocale : en_US posixTimezone : Asia/Seoul posixEncoding : ISO-8859-1 Local disk : Size: 1024M, Used: 728M, Free: 295M ======================================================== Debug-key '5' pressed Shutdown enabled. Debug-key '7' pressed [JRockit] Management server already started. Ignoring request. Debug-key '8' pressed Starting stat recording Debug-key '8' pressed ========= Statistics Counters for the last second ========= dev.eth0_rx.cnt : 22 packets dev.eth0_rx_bytes.cnt : 2704 bytes dev.net_interrupts.cnt : 22 interrupts evt.timer_ticks.cnt : 123 ticks hyper.priv_entries.cnt : 144 entries schedule.context_switches.cnt : 271 switches schedule.idle_cpu_time.cnt : 997318849 nanoseconds schedule.idle_cpu_time_0.cnt : 997318849 nanoseconds schedule.total_cpu_time.cnt : 1000031757 nanoseconds time.system_time.cnt : 1000 ns time.timer_updates.cnt : 123 updates time.wallclock_time.cnt : 1000 ns ======================================= Debug-key '9' pressed ===== FULL THREAD DUMP =============== Fri Jun 4 08:22:12 2010 BEA JRockit(R) R27.6.6-28_o-125824-1.6.0_17-20091214-2104-linux-ia32 "Main Thread" id=1 idx=0x4 tid=1 prio=5 alive, in native, waiting -- Waiting for notification on: weblogic/t3/srvr/T3Srvr@0x646ede8[fat lock] at jrockit/vm/Threads.waitForNotifySignal(JLjava/lang/Object;)Z(Native Method) at java/lang/Object.wait(J)V(Native Method) at java/lang/Object.wait(Object.java:485) at weblogic/t3/srvr/T3Srvr.waitForDeath(T3Srvr.java:919) ^-- Lock released while waiting: weblogic/t3/srvr/T3Srvr@0x646ede8[fat lock] at weblogic/t3/srvr/T3Srvr.run(T3Srvr.java:479) at weblogic/Server.main(Server.java:67) at jrockit/vm/RNI.c2java(IIIII)V(Native Method) -- end of trace "(Signal Handler)" id=2 idx=0x8 tid=2 prio=5 alive, in native, daemon Open lock chains ================ Chain 1: "ExecuteThread: '0' for queue: 'weblogic.socket.Muxer'" id=23 idx=0x50 tid=20 waiting for java/lang/String@0x630c588 held by: "ExecuteThread: '1' for queue: 'weblogic.socket.Muxer'" id=24 idx=0x54 tid=21 (active) ===== END OF THREAD DUMP =============== Debug-key '0' pressed Debug-keys enabled Happy Cloud Walking :)

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  • Problems with Level Architect, Citrus Engine, Flash

    - by Idan
    I am using the Citrus Engine to make a Flash game, and the Level Architect doesn't work well for me. Firstly, when I first launch it and open my project and my level, nothing is shown, no assets and not anything I have previously done with my level. To fix it, I open another project. The other project works fine, meaning I can see the assets and the level. Then I go back to the actual project I am working on, and the problem is fixed, only it does not fix the second problem: I can't add my own assests. I follow the manual and add tags like this: [Property(value="0")] But it doesn't change a thing in the level architect window (even after I close and reopen it). Any ideas? Thanks! Here's the code of the class I want to be shown in the Level Architect: package { import com.citrusengine.objects.PhysicsObject; import com.citrusengine.objects.platformer.Sensor; import flash.utils.clearTimeout; import flash.utils.setTimeout; /** * @author Aymeric */ public class Teleporter extends Sensor { [Property(value="0")] public var endX:Number=0; [Property(value="0")] public var endY:Number=0; public var object:PhysicsObject; [Property(value="0")] public var time:Number = 0; public var needToTeleport:Boolean = false; protected var _teleporting:Boolean = false; private var _teleportTimeoutID:uint; public function Teleporter(name:String, params:Object = null) { super(name, params); } override public function destroy():void { clearTimeout(_teleportTimeoutID); super.destroy(); } override public function update(timeDelta:Number):void { super.update(timeDelta); if (needToTeleport) { _teleporting = true; _teleportTimeoutID = setTimeout(_teleport, time); needToTeleport = false; } _updateAnimation(); } protected function _teleport():void { _teleporting = false; object.x = endX; object.y = endY; clearTimeout(_teleportTimeoutID); } protected function _updateAnimation():void { if (_teleporting) { _animation = "teleport"; } else { _animation = "normal"; } } } }

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  • Using Entity Framework Entity splitting customisations in an ASP.Net application

    - by nikolaosk
    I have been teaching in the past few weeks many people on how to use Entity Framework. I have decided to provide some of the samples I am using in my classes. First let’s try to define what EF is and why it is going to help us to create easily data-centric applications.Entity Framework is an object-relational mapping (ORM) framework for the .NET Framework.EF addresses the problem of Object-relational impedance mismatch . I will not be talking about that mismatch because it is well documented in many...(read more)

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  • Parsing "true" and "false" using Boost.Spirit.Lex and Boost.Spirit.Qi

    - by Andrew Ross
    As the first stage of a larger grammar using Boost.Spirit I'm trying to parse "true" and "false" to produce the corresponding bool values, true and false. I'm using Spirit.Lex to tokenize the input and have a working implementation for integer and floating point literals (including those expressed in a relaxed scientific notation), exposing int and float attributes. Token definitions #include <boost/spirit/include/lex_lexertl.hpp> namespace lex = boost::spirit::lex; typedef boost::mpl::vector<int, float, bool> token_value_type; template <typename Lexer> struct basic_literal_tokens : lex::lexer<Lexer> { basic_literal_tokens() { this->self.add_pattern("INT", "[-+]?[0-9]+"); int_literal = "{INT}"; // To be lexed as a float a numeric literal must have a decimal point // or include an exponent, otherwise it will be considered an integer. float_literal = "{INT}(((\\.[0-9]+)([eE]{INT})?)|([eE]{INT}))"; literal_true = "true"; literal_false = "false"; this->self = literal_true | literal_false | float_literal | int_literal; } lex::token_def<int> int_literal; lex::token_def<float> float_literal; lex::token_def<bool> literal_true, literal_false; }; Testing parsing of float literals My real implementation uses Boost.Test, but this is a self-contained example. #include <string> #include <iostream> #include <cmath> #include <cstdlib> #include <limits> bool parse_and_check_float(std::string const & input, float expected) { typedef std::string::const_iterator base_iterator_type; typedef lex::lexertl::token<base_iterator_type, token_value_type > token_type; typedef lex::lexertl::lexer<token_type> lexer_type; basic_literal_tokens<lexer_type> basic_literal_lexer; base_iterator_type input_iter(input.begin()); float actual; bool result = lex::tokenize_and_parse(input_iter, input.end(), basic_literal_lexer, basic_literal_lexer.float_literal, actual); return result && std::abs(expected - actual) < std::numeric_limits<float>::epsilon(); } int main(int argc, char *argv[]) { if (parse_and_check_float("+31.4e-1", 3.14)) { return EXIT_SUCCESS; } else { return EXIT_FAILURE; } } Parsing "true" and "false" My problem is when trying to parse "true" and "false". This is the test code I'm using (after removing the Boost.Test parts): bool parse_and_check_bool(std::string const & input, bool expected) { typedef std::string::const_iterator base_iterator_type; typedef lex::lexertl::token<base_iterator_type, token_value_type > token_type; typedef lex::lexertl::lexer<token_type> lexer_type; basic_literal_tokens<lexer_type> basic_literal_lexer; base_iterator_type input_iter(input.begin()); bool actual; lex::token_def<bool> parser = expected ? basic_literal_lexer.literal_true : basic_literal_lexer.literal_false; bool result = lex::tokenize_and_parse(input_iter, input.end(), basic_literal_lexer, parser, actual); return result && actual == expected; } but compilation fails with: boost/spirit/home/qi/detail/assign_to.hpp: In function ‘void boost::spirit::traits::assign_to(const Iterator&, const Iterator&, Attribute&) [with Iterator = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, Attribute = bool]’: boost/spirit/home/lex/lexer/lexertl/token.hpp:434: instantiated from ‘static void boost::spirit::traits::assign_to_attribute_from_value<Attribute, boost::spirit::lex::lexertl::token<Iterator, AttributeTypes, HasState>, void>::call(const boost::spirit::lex::lexertl::token<Iterator, AttributeTypes, HasState>&, Attribute&) [with Attribute = bool, Iterator = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, AttributeTypes = boost::mpl::vector<int, float, bool, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, HasState = mpl_::bool_<true>]’ ... backtrace of instantiation points .... boost/spirit/home/qi/detail/assign_to.hpp:79: error: no matching function for call to ‘boost::spirit::traits::assign_to_attribute_from_iterators<bool, __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, void>::call(const __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >&, const __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >&, bool&)’ boost/spirit/home/qi/detail/construct.hpp:64: note: candidates are: static void boost::spirit::traits::assign_to_attribute_from_iterators<bool, Iterator, void>::call(const Iterator&, const Iterator&, char&) [with Iterator = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >] My interpretation of this is that Spirit.Qi doesn't know how to convert a string to a bool - surely that's not the case? Has anyone else done this before? If so, how?

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  • Python class representation under the hood

    - by decentralised
    OK, here is a simple Python class: class AddSomething(object): __metaclass__ = MyMetaClass x = 10 def __init__(self, a): self.a = a def add(self, a, b): return a + b We have specified a metaclass, and that means we could write something like this: class MyMetaClass(type): def __init__(cls, name, bases, cdict): # do something with the class Now, the cdict holds a representation of AddSomething: AddSomething = type('AddSomething', (object,), {'x' : 10, '__init__': __init__, 'add': add}) So my question is simple, are all Python classes represented in this second format internally? If not, how are they represented? EDIT - Python 2.7

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  • SQL SERVER – SSIS Look Up Component – Cache Mode – Notes from the Field #028

    - by Pinal Dave
    [Notes from Pinal]: Lots of people think that SSIS is all about arranging various operations together in one logical flow. Well, the understanding is absolutely correct, but the implementation of the same is not as easy as it seems. Similarly most of the people think lookup component is just component which does look up for additional information and does not pay much attention to it. Due to the same reason they do not pay attention to the same and eventually get very bad performance. Linchpin People are database coaches and wellness experts for a data driven world. In this 28th episode of the Notes from the Fields series database expert Tim Mitchell (partner at Linchpin People) shares very interesting conversation related to how to write a good lookup component with Cache Mode. In SQL Server Integration Services, the lookup component is one of the most frequently used tools for data validation and completion.  The lookup component is provided as a means to virtually join one set of data to another to validate and/or retrieve missing values.  Properly configured, it is reliable and reasonably fast. Among the many settings available on the lookup component, one of the most critical is the cache mode.  This selection will determine whether and how the distinct lookup values are cached during package execution.  It is critical to know how cache modes affect the result of the lookup and the performance of the package, as choosing the wrong setting can lead to poorly performing packages, and in some cases, incorrect results. Full Cache The full cache mode setting is the default cache mode selection in the SSIS lookup transformation.  Like the name implies, full cache mode will cause the lookup transformation to retrieve and store in SSIS cache the entire set of data from the specified lookup location.  As a result, the data flow in which the lookup transformation resides will not start processing any data buffers until all of the rows from the lookup query have been cached in SSIS. The most commonly used cache mode is the full cache setting, and for good reason.  The full cache setting has the most practical applications, and should be considered the go-to cache setting when dealing with an untested set of data. With a moderately sized set of reference data, a lookup transformation using full cache mode usually performs well.  Full cache mode does not require multiple round trips to the database, since the entire reference result set is cached prior to data flow execution. There are a few potential gotchas to be aware of when using full cache mode.  First, you can see some performance issues – memory pressure in particular – when using full cache mode against large sets of reference data.  If the table you use for the lookup is very large (either deep or wide, or perhaps both), there’s going to be a performance cost associated with retrieving and caching all of that data.  Also, keep in mind that when doing a lookup on character data, full cache mode will always do a case-sensitive (and in some cases, space-sensitive) string comparison even if your database is set to a case-insensitive collation.  This is because the in-memory lookup uses a .NET string comparison (which is case- and space-sensitive) as opposed to a database string comparison (which may be case sensitive, depending on collation).  There’s a relatively easy workaround in which you can use the UPPER() or LOWER() function in the pipeline data and the reference data to ensure that case differences do not impact the success of your lookup operation.  Again, neither of these present a reason to avoid full cache mode, but should be used to determine whether full cache mode should be used in a given situation. Full cache mode is ideally useful when one or all of the following conditions exist: The size of the reference data set is small to moderately sized The size of the pipeline data set (the data you are comparing to the lookup table) is large, is unknown at design time, or is unpredictable Each distinct key value(s) in the pipeline data set is expected to be found multiple times in that set of data Partial Cache When using the partial cache setting, lookup values will still be cached, but only as each distinct value is encountered in the data flow.  Initially, each distinct value will be retrieved individually from the specified source, and then cached.  To be clear, this is a row-by-row lookup for each distinct key value(s). This is a less frequently used cache setting because it addresses a narrower set of scenarios.  Because each distinct key value(s) combination requires a relational round trip to the lookup source, performance can be an issue, especially with a large pipeline data set to be compared to the lookup data set.  If you have, for example, a million records from your pipeline data source, you have the potential for doing a million lookup queries against your lookup data source (depending on the number of distinct values in the key column(s)).  Therefore, one has to be keenly aware of the expected row count and value distribution of the pipeline data to safely use partial cache mode. Using partial cache mode is ideally suited for the conditions below: The size of the data in the pipeline (more specifically, the number of distinct key column) is relatively small The size of the lookup data is too large to effectively store in cache The lookup source is well indexed to allow for fast retrieval of row-by-row values No Cache As you might guess, selecting no cache mode will not add any values to the lookup cache in SSIS.  As a result, every single row in the pipeline data set will require a query against the lookup source.  Since no data is cached, it is possible to save a small amount of overhead in SSIS memory in cases where key values are not reused.  In the real world, I don’t see a lot of use of the no cache setting, but I can imagine some edge cases where it might be useful. As such, it’s critical to know your data before choosing this option.  Obviously, performance will be an issue with anything other than small sets of data, as the no cache setting requires row-by-row processing of all of the data in the pipeline. I would recommend considering the no cache mode only when all of the below conditions are true: The reference data set is too large to reasonably be loaded into SSIS memory The pipeline data set is small and is not expected to grow There are expected to be very few or no duplicates of the key values(s) in the pipeline data set (i.e., there would be no benefit from caching these values) Conclusion The cache mode, an often-overlooked setting on the SSIS lookup component, represents an important design decision in your SSIS data flow.  Choosing the right lookup cache mode directly impacts the fidelity of your results and the performance of package execution.  Know how this selection impacts your ETL loads, and you’ll end up with more reliable, faster packages. If you want me to take a look at your server and its settings, or if your server is facing any issue we can Fix Your SQL Server. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: Notes from the Field, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL Tagged: SSIS

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  • Nautilus doesn't work

    - by bruce
    Whenever I open nautilus it crashes and I get this error in terminal. i am running saucy. does anybody know of a different file manger that i can install? sys:1: Warning: g_object_set: assertion 'G_IS_OBJECT (object)' failed totem-video-thumbnailer couldn't open file 'file:///home/bruce/New%20Project.ogv' sys:1: Warning: g_object_unref: assertion 'G_IS_OBJECT (object)' failed Segmentation fault (core dumped)

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  • Using Entity Framework Table splitting customisations in an ASP.Net application

    - by nikolaosk
    I have been teaching in the past few weeks many people on how to use Entity Framework. I have decided to provide some of the samples I am using in my classes. First let’s try to define what EF is and why it is going to help us to create easily data-centric applications.Entity Framework is an object-relational mapping (ORM) framework for the .NET Framework.EF addresses the problem of Object-relational impedance mismatch . I will not be talking about that mismatch because it is well documented in many...(read more)

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  • Physics/Graphics Components

    - by Brett Powell
    I have spent the last 48 hours reading up on Object Component systems, and feel I am ready enough to start implementing it. I got the base Object and Component classes created, but now that I need to start creating the actual components I am a bit confused. When I think of them in terms of HealthComponent or something that would basically just be a property, it makes perfect sense. When it is something more general as a Physics/Graphics component, I get a bit confused. My Object class looks like this so far (If you notice any changes I should make please let me know, still new to this)... typedef unsigned int ID; class GameObject { public: GameObject(ID id, Ogre::String name = ""); ~GameObject(); ID &getID(); Ogre::String &getName(); virtual void update() = 0; // Component Functions void addComponent(Component *component); void removeComponent(Ogre::String familyName); template<typename T> T* getComponent(Ogre::String familyName) { return dynamic_cast<T*>(m_components[familyName]); } protected: // Properties ID m_ID; Ogre::String m_Name; float m_flVelocity; Ogre::Vector3 m_vecPosition; // Components std::map<std::string,Component*> m_components; std::map<std::string,Component*>::iterator m_componentItr; }; Now the problem I am running into is what would the general population put into Components such as Physics/Graphics? For Ogre (my rendering engine) the visible Objects will consist of multiple Ogre::SceneNode (possibly multiple) to attach it to the scene, Ogre::Entity (possibly multiple) to show the visible meshes, and so on. Would it be best to just add multiple GraphicComponent's to the Object and let each GraphicComponent handle one SceneNode/Entity or is the idea to have one of each Component needed? For Physics I am even more confused. I suppose maybe creating a RigidBody and keeping track of mass/interia/etc. would make sense. But I am having trouble thinking of how to actually putting specifics into a Component. Once I get a couple of these "Required" components done, I think it will make a lot more sense. As of right now though I am still a bit stumped.

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  • Allocating Entities within an Entity System

    - by miguel.martin
    I'm quite unsure how I should allocate/resemble my entities within my entity system. I have various options, but most of them seem to have cons associated with them. In all cases entities are resembled by an ID (integer), and possibly has a wrapper class associated with it. This wrapper class has methods to add/remove components to/from the entity. Before I mention the options, here is the basic structure of my entity system: Entity An object that describes an object within the game Component Used to store data for the entity System Contains entities with specific components Used to update entities with specific components World Contains entities and systems for the entity system Can create/destroy entites and have systems added/removed from/to it Here are my options, that I have thought of: Option 1: Do not store the Entity wrapper classes, and just store the next ID/deleted IDs. In other words, entities will be returned by value, like so: Entity entity = world.createEntity(); This is much like entityx, except I see some flaws in this design. Cons There can be duplicate entity wrapper classes (as the copy-ctor has to be implemented, and systems need to contain entities) If an Entity is destroyed, the duplicate entity wrapper classes will not have an updated value Option 2: Store the entity wrapper classes within an object pool. i.e. Entities will be return by pointer/reference, like so: Entity& e = world.createEntity(); Cons If there is duplicate entities, then when an entity is destroyed, the same entity object may be re-used to allocate another entity. Option 3: Use raw IDs, and forget about the wrapper entity classes. The downfall to this, I think, is the syntax that will be required for it. I'm thinking about doing thisas it seems the most simple & easy to implement it. I'm quite unsure about it, because of the syntax. i.e. To add a component with this design, it would look like: Entity e = world.createEntity(); world.addComponent<Position>(e, 0, 3); As apposed to this: Entity e = world.createEntity(); e.addComponent<Position>(0, 3); Cons Syntax Duplicate IDs

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  • What are the software design essentials? [closed]

    - by Craig Schwarze
    I've decided to create a 1 page "cheat sheet" of essential software design principles for my programmers. It doesn't explain the principles in any great depth, but is simply there as a reference and a reminder. Here's what I've come up with - I would welcome your comments. What have I left out? What have I explained poorly? What is there that shouldn't be? Basic Design Principles The Principle of Least Surprise – your solution should be obvious, predictable and consistent. Keep It Simple Stupid (KISS) - the simplest solution is usually the best one. You Ain’t Gonna Need It (YAGNI) - create a solution for the current problem rather than what might happen in the future. Don’t Repeat Yourself (DRY) - rigorously remove duplication from your design and code. Advanced Design Principles Program to an interface, not an implementation – Don’t declare variables to be of a particular concrete class. Rather, declare them to an interface, and instantiate them using a creational pattern. Favour composition over inheritance – Don’t overuse inheritance. In most cases, rich behaviour is best added by instantiating objects, rather than inheriting from classes. Strive for loosely coupled designs – Minimise the interdependencies between objects. They should be able to interact with minimal knowledge of each other via small, tightly defined interfaces. Principle of Least Knowledge – Also called the “Law of Demeter”, and is colloquially summarised as “Only talk to your friends”. Specifically, a method in an object should only invoke methods on the object itself, objects passed as a parameter to the method, any object the method creates, any components of the object. SOLID Design Principles Single Responsibility Principle – Each class should have one well defined purpose, and only one reason to change. This reduces the fragility of your code, and makes it much more maintainable. Open/Close Principle – A class should be open to extension, but closed to modification. In practice, this means extracting the code that is most likely to change to another class, and then injecting it as required via an appropriate pattern. Liskov Substitution Principle – Subtypes must be substitutable for their base types. Essentially, get your inheritance right. In the classic example, type square should not inherit from type rectangle, as they have different properties (you can independently set the sides of a rectangle). Instead, both should inherit from type shape. Interface Segregation Principle – Clients should not be forced to depend upon methods they do not use. Don’t have fat interfaces, rather split them up into smaller, behaviour centric interfaces. Dependency Inversion Principle – There are two parts to this principle: High-level modules should not depend on low-level modules. Both should depend on abstractions. Abstractions should not depend on details. Details should depend on abstractions. In modern development, this is often handled by an IoC (Inversion of Control) container.

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  • Low coupling and tight cohesion

    - by hidayat
    Of course it depends on the situation. But when a lower lever object or system communicate with an higher level system, should callbacks or events be preferred to keeping a pointer to higher level object? For example, we have a world class that has a member variable vector<monster> monsters. When the monster class is going to communicate with the world class, should I prefer using a callback function then or should I have a pointer to the world class inside the monster class?

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  • Use a Fake Http Channel to Unit Test with HttpClient

    - by Steve Michelotti
    Applications get data from lots of different sources. The most common is to get data from a database or a web service. Typically, we encapsulate calls to a database in a Repository object and we create some sort of IRepository interface as an abstraction to decouple between layers and enable easier unit testing by leveraging faking and mocking. This works great for database interaction. However, when consuming a RESTful web service, this is is not always the best approach. The WCF Web APIs that are available on CodePlex (current drop is Preview 3) provide a variety of features to make building HTTP REST services more robust. When you download the latest bits, you’ll also find a new HttpClient which has been updated for .NET 4.0 as compared to the one that shipped for 3.5 in the original REST Starter Kit. The HttpClient currently provides the best API for consuming REST services on the .NET platform and the WCF Web APIs provide a number of extension methods which extend HttpClient and make it even easier to use. Let’s say you have a client application that is consuming an HTTP service – this could be Silverlight, WPF, or any UI technology but for my example I’ll use an MVC application: 1: using System; 2: using System.Net.Http; 3: using System.Web.Mvc; 4: using FakeChannelExample.Models; 5: using Microsoft.Runtime.Serialization; 6:   7: namespace FakeChannelExample.Controllers 8: { 9: public class HomeController : Controller 10: { 11: private readonly HttpClient httpClient; 12:   13: public HomeController(HttpClient httpClient) 14: { 15: this.httpClient = httpClient; 16: } 17:   18: public ActionResult Index() 19: { 20: var response = httpClient.Get("Person(1)"); 21: var person = response.Content.ReadAsDataContract<Person>(); 22:   23: this.ViewBag.Message = person.FirstName + " " + person.LastName; 24: 25: return View(); 26: } 27: } 28: } On line #20 of the code above you can see I’m performing an HTTP GET request to a Person resource exposed by an HTTP service. On line #21, I use the ReadAsDataContract() extension method provided by the WCF Web APIs to serialize to a Person object. In this example, the HttpClient is being passed into the constructor by MVC’s dependency resolver – in this case, I’m using StructureMap as an IoC and my StructureMap initialization code looks like this: 1: using StructureMap; 2: using System.Net.Http; 3:   4: namespace FakeChannelExample 5: { 6: public static class IoC 7: { 8: public static IContainer Initialize() 9: { 10: ObjectFactory.Initialize(x => 11: { 12: x.For<HttpClient>().Use(() => new HttpClient("http://localhost:31614/")); 13: }); 14: return ObjectFactory.Container; 15: } 16: } 17: } My controller code currently depends on a concrete instance of the HttpClient. Now I *could* create some sort of interface and wrap the HttpClient in this interface and use that object inside my controller instead – however, there are a few why reasons that is not desirable: For one thing, the API provided by the HttpClient provides nice features for dealing with HTTP services. I don’t really *want* these to look like C# RPC method calls – when HTTP services have REST features, I may want to inspect HTTP response headers and hypermedia contained within the message so that I can make intelligent decisions as to what to do next in my workflow (although I don’t happen to be doing these things in my example above) – this type of workflow is common in hypermedia REST scenarios. If I just encapsulate HttpClient behind some IRepository interface and make it look like a C# RPC method call, it will become difficult to take advantage of these types of things. Second, it could get pretty mind-numbing to have to create interfaces all over the place just to wrap the HttpClient. Then you’re probably going to have to hard-code HTTP knowledge into your code to formulate requests rather than just “following the links” that the hypermedia in a message might provide. Third, at first glance it might appear that we need to create an interface to facilitate unit testing, but actually it’s unnecessary. Even though the code above is dependent on a concrete type, it’s actually very easy to fake the data in a unit test. The HttpClient provides a Channel property (of type HttpMessageChannel) which allows you to create a fake message channel which can be leveraged in unit testing. In this case, what I want is to be able to write a unit test that just returns fake data. I also want this to be as re-usable as possible for my unit testing. I want to be able to write a unit test that looks like this: 1: [TestClass] 2: public class HomeControllerTest 3: { 4: [TestMethod] 5: public void Index() 6: { 7: // Arrange 8: var httpClient = new HttpClient("http://foo.com"); 9: httpClient.Channel = new FakeHttpChannel<Person>(new Person { FirstName = "Joe", LastName = "Blow" }); 10:   11: HomeController controller = new HomeController(httpClient); 12:   13: // Act 14: ViewResult result = controller.Index() as ViewResult; 15:   16: // Assert 17: Assert.AreEqual("Joe Blow", result.ViewBag.Message); 18: } 19: } Notice on line #9, I’m setting the Channel property of the HttpClient to be a fake channel. I’m also specifying the fake object that I want to be in the response on my “fake” Http request. I don’t need to rely on any mocking frameworks to do this. All I need is my FakeHttpChannel. The code to do this is not complex: 1: using System; 2: using System.IO; 3: using System.Net.Http; 4: using System.Runtime.Serialization; 5: using System.Threading; 6: using FakeChannelExample.Models; 7:   8: namespace FakeChannelExample.Tests 9: { 10: public class FakeHttpChannel<T> : HttpClientChannel 11: { 12: private T responseObject; 13:   14: public FakeHttpChannel(T responseObject) 15: { 16: this.responseObject = responseObject; 17: } 18:   19: protected override HttpResponseMessage Send(HttpRequestMessage request, CancellationToken cancellationToken) 20: { 21: return new HttpResponseMessage() 22: { 23: RequestMessage = request, 24: Content = new StreamContent(this.GetContentStream()) 25: }; 26: } 27:   28: private Stream GetContentStream() 29: { 30: var serializer = new DataContractSerializer(typeof(T)); 31: Stream stream = new MemoryStream(); 32: serializer.WriteObject(stream, this.responseObject); 33: stream.Position = 0; 34: return stream; 35: } 36: } 37: } The HttpClientChannel provides a Send() method which you can override to return any HttpResponseMessage that you want. You can see I’m using the DataContractSerializer to serialize the object and write it to a stream. That’s all you need to do. In the example above, the only thing I’ve chosen to do is to provide a way to return different response objects. But there are many more features you could add to your own re-usable FakeHttpChannel. For example, you might want to provide the ability to add HTTP headers to the message. You might want to use a different serializer other than the DataContractSerializer. You might want to provide custom hypermedia in the response as well as just an object or set HTTP response codes. This list goes on. This is the just one example of the really cool features being added to the next version of WCF to enable various HTTP scenarios. The code sample for this post can be downloaded here.

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  • Retrieving Custom Attributes Using Reflection

    - by Scott Dorman
    The .NET Framework allows you to easily add metadata to your classes by using attributes. These attributes can be ones that the .NET Framework already provides, of which there are over 300, or you can create your own. Using reflection, the ways to retrieve the custom attributes of a type are: System.Reflection.MemberInfo public abstract object[] GetCustomAttributes(bool inherit); public abstract object[] GetCustomAttributes(Type attributeType, bool inherit); public abstract bool IsDefined(Type attributeType, bool inherit); System.Attribute public static Attribute[] GetCustomAttributes(MemberInfo member, bool inherit); public static bool IsDefined(MemberInfo element, Type attributeType, bool inherit); If you take the following simple class hierarchy: public abstract class BaseClass { private bool result;   [DefaultValue(false)] public virtual bool SimpleProperty { get { return this.result; } set { this.result = value; } } }   public class DerivedClass : BaseClass { public override bool SimpleProperty { get { return true; } set { base.SimpleProperty = value; } } } Given a PropertyInfo object (which is derived from MemberInfo, and represents a propery in reflection), you might expect that these methods would return the same result. Unfortunately, that isn’t the case. The MemberInfo methods strictly reflect the metadata definitions, ignoring the inherit parameter and not searching the inheritance chain when used with a PropertyInfo, EventInfo, or ParameterInfo object. It also returns all custom attribute instances, including those that don’t inherit from System.Attribute. The Attribute methods are closer to the implied behavior of the language (and probably closer to what you would naturally expect). They do respect the inherit parameter for PropertyInfo, EventInfo, and ParameterInfo objects and search the implied inheritance chain defined by the associated methods (in this case, the property accessors). These methods also only return custom attributes that inherit from System.Attribute. This is a fairly subtle difference that can produce very unexpected results if you aren’t careful. For example, to retrieve the custom  attributes defined on SimpleProperty, you could use code similar to this: PropertyInfo info = typeof(DerivedClass).GetProperty("SimpleProperty"); var attributeList1 = info.GetCustomAttributes(typeof(DefaultValueAttribute), true)); var attributeList2 = Attribute.GetCustomAttributes(info, typeof(DefaultValueAttribute), true));   The attributeList1 array will be empty while the attributeList2 array will contain the attribute instance, as expected. Technorati Tags: Reflection,Custom Attributes,PropertyInfo

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  • Engine Rendering pipeline : Making shaders generic

    - by fakhir
    I am trying to make a 2D game engine using OpenGL ES 2.0 (iOS for now). I've written Application layer in Objective C and a separate self contained RendererGLES20 in C++. No GL specific call is made outside the renderer. It is working perfectly. But I have some design issues when using shaders. Each shader has its own unique attributes and uniforms that need to be set just before the main draw call (glDrawArrays in this case). For instance, in order to draw some geometry I would do: void RendererGLES20::render(Model * model) { // Set a bunch of uniforms glUniformMatrix4fv(.......); // Enable specific attributes, can be many glEnableVertexAttribArray(......); // Set a bunch of vertex attribute pointers: glVertexAttribPointer(positionSlot, 2, GL_FLOAT, GL_FALSE, stride, m->pCoords); // Now actually Draw the geometry glDrawArrays(GL_TRIANGLES, 0, m->vertexCount); // After drawing, disable any vertex attributes: glDisableVertexAttribArray(.......); } As you can see this code is extremely rigid. If I were to use another shader, say ripple effect, i would be needing to pass extra uniforms, vertex attribs etc. In other words I would have to change the RendererGLES20 render source code just to incorporate the new shader. Is there any way to make the shader object totally generic? Like What if I just want to change the shader object and not worry about game source re-compiling? Any way to make the renderer agnostic of uniforms and attributes etc?. Even though we need to pass data to uniforms, what is the best place to do that? Model class? Is the model class aware of shader specific uniforms and attributes? Following shows Actor class: class Actor : public ISceneNode { ModelController * model; AIController * AI; }; Model controller class: class ModelController { class IShader * shader; int textureId; vec4 tint; float alpha; struct Vertex * vertexArray; }; Shader class just contains the shader object, compiling and linking sub-routines etc. In Game Logic class I am actually rendering the object: void GameLogic::update(float dt) { IRenderer * renderer = g_application->GetRenderer(); Actor * a = GetActor(id); renderer->render(a->model); } Please note that even though Actor extends ISceneNode, I haven't started implementing SceneGraph yet. I will do that as soon as I resolve this issue. Any ideas how to improve this? Related design patterns etc? Thank you for reading the question.

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  • What permissions are required for SET IDENTITY_INSERT ON?

    - by AaronBertrand
    SQL Server 2000's SET IDENTITY_INSERT ON topic says: Execute permissions default to the sysadmin fixed server role, and the db_owner and db_ddladmin fixed database roles, and the object owner. While the SET IDENTITY_INSERT topic for SQL Server 2005 (and up) says: User must own the object, or be a member of the sysadmin fixed server role, or the db_owner and db_ddladmin fixed database roles. This was clearly adapted from the 2000 books online and re-written by someone who misinterpreted "db_owner...(read more)

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  • Create Auto Customization Criteria OAF Search Page

    - by PRajkumar
    1. Create a New Workspace and Project Right click Workspaces and click create new OAworkspace and name it as PRajkumarCustSearch. Automatically a new OA Project will also be created. Name the project as CustSearchDemo and package as prajkumar.oracle.apps.fnd.custsearchdemo   2. Create a New Application Module (AM) Right Click on CustSearchDemo > New > ADF Business Components > Application Module Name -- CustSearchAM Package -- prajkumar.oracle.apps.fnd.custsearchdemo.server   3. Enable Passivation for the Root UI Application Module (AM) Right Click on CustSearchAM > Edit SearchAM > Custom Properties > Name – RETENTION_LEVEL Value – MANAGE_STATE Click add > Apply > OK   4. Create Test Table and insert data some data in it (For Testing Purpose)   CREATE TABLE xx_custsearch_demo (   -- ---------------------     -- Data Columns     -- ---------------------     column1                  VARCHAR2(100),     column2                  VARCHAR2(100),     column3                  VARCHAR2(100),     column4                  VARCHAR2(100),     -- ---------------------     -- Who Columns     -- ---------------------     last_update_date    DATE         NOT NULL,     last_updated_by     NUMBER   NOT NULL,     creation_date          DATE         NOT NULL,     created_by               NUMBER   NOT NULL,     last_update_login   NUMBER  );   INSERT INTO xx_custsearch_demo VALUES('v1','v2','v3','v4',SYSDATE,0,SYSDATE,0,0); INSERT INTO xx_custsearch_demo VALUES('v1','v3','v4','v5',SYSDATE,0,SYSDATE,0,0); INSERT INTO xx_custsearch_demo VALUES('v2','v3','v4','v5',SYSDATE,0,SYSDATE,0,0); INSERT INTO xx_custsearch_demo VALUES('v3','v4','v5','v6',SYSDATE,0,SYSDATE,0,0); Now we have 4 records in our custom table   5. Create a New Entity Object (EO) Right click on SearchDemo > New > ADF Business Components > Entity Object Name – CustSearchEO Package -- prajkumar.oracle.apps.fnd.custsearchdemo.schema.server Database Objects -- XX_CUSTSEARCH_DEMO   Note – By default ROWID will be the primary key if we will not make any column to be primary key   Check the Accessors, Create Method, Validation Method and Remove Method   6. Create a New View Object (VO) Right click on CustSearchDemo > New > ADF Business Components > View Object Name -- CustSearchVO Package -- prajkumar.oracle.apps.fnd.custsearchdemo.server   In Step2 in Entity Page select CustSearchEO and shuttle them to selected list   In Step3 in Attributes Window select columns Column1, Column2, Column3, Column4, and shuttle them to selected list   In Java page deselect Generate Java file for View Object Class: CustSearchVOImpl and Select Generate Java File for View Row Class: CustSearchVORowImpl   7. Add Your View Object to Root UI Application Module Select Right click on CustSearchAM > Application Modules > Data Model Select CustSearchVO and shuttle to Data Model list   8. Create a New Page Right click on CustSearchDemo > New > Web Tier > OA Components > Page Name -- CustSearchPG Package -- prajkumar.oracle.apps.fnd.custsearchdemo.webui   9. Select the CustSearchPG and go to the strcuture pane where a default region has been created   10. Select region1 and set the following properties: ID -- PageLayoutRN Region Style -- PageLayout AM Definition -- prajkumar.oracle.apps.fnd.custsearchdemo.server.CustSearchAM Window Title – AutoCustomize Search Page Window Title – AutoCustomization Search Page Auto Footer -- True   11. Add a Query Bean to Your Page Right click on PageLayoutRN > New > Region Select new region region1 and set following properties ID – QueryRN Region Style – query Construction Mode – autoCustomizationCriteria Include Simple Panel – False Include Views Panel – False Include Advanced Panel – False   12. Create a New Region of style table Right Click on QueryRN > New > Region Using Wizard Application Module – prajkumar.oracle.apps.fnd.custsearchdemo.server.CustSearchAM Available View Usages – CustSearchVO1   In Step2 in Region Properties set following properties Region ID – CustSearchTable Region Style – Table   In Step3 in View Attributes shuttle all the items (Column1, Column2, Column3, Column4) available in “Available View Attributes” to Selected View Attributes: In Step4 in Region Items page set style to “messageStyledText” for all items   13. Select CustSearchTable in Structure Panel and set property Width to 100%   14. Include Simple Search Panel Right Click on QueryRN > New > simpleSearchPanel Automatically region2 (header Region) and region1 (MessageComponentLayout Region) created Set Following Properties for region2 Id – SimpleSearchHeader Text -- Simple Search   15. Now right click on message Component Layout Region (SimpleSearchMappings) and create two message text input beans and set the below properties to each   Message TextInputBean1 Id – SearchColumn1 Search Allowed – True Data Type – VARCHAR2 Maximum Length – CSS Class – OraFieldText Prompt – Column1   Message TextInputBean2 Id – SearchColumn2 Search Allowed -- True Data Type – VARCHAR2 Maximum Length – 100 CSS Class – OraFieldText Prompt – Column2   16. Now Right Click on query Components and create simple Search Mappings. Then automatically SimpleSearchMappings and QueryCriteriaMap1 created   17.  Now select the QueryCriteriaMap1 and set the below properties Id – SearchColumn1Map Search Item – SearchColumn1 Result Item – Column1   18. Now again right click on simpleSearchMappings -> New -> queryCriteriaMap, and then set the below properties Id – SearchColumn2Map Search Item – SearchColumn2 Result Item – Column2   19. Congratulation you have successfully finished Auto Customization Search page. Run Your CustSearchPG page and Test Your Work            

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  • box2d resize bodies arround point

    - by philipp
    I have a compound object, consisting of a b2Body, vector-graphics and a list polygons which describe the b2body's shapes. This object has its own transformation matrix to centralize the storage of transformations. So far everything is working quiet fine, even scaling works, but not if i scale around a point. In the initialization phase of the object it is scaled around a point. This happens in this order: transform the main matrix transform the vector graphics and the polygons recreate the b2Body After this function ran, the shapes and all the graphics are exactly where they should be, BUT: after the first steps of the b2World the graphical stuff moves away from the body. When I ran the debugger I found out that the position of the body is 0/0 the red dot shows the center of scaling. the first image shows the basic setup and the second the final position of the graphics. This distance stays constant for the rest of the simulation. If I set the position via myBody.SetPosition( sx, sy ); the whole scenario just plays a bit more distant for the origin. Any Idea how to fix this? EDIT:: I came deeper down to the problem and it lies in the fact that i must not scale the transform matrix for the b2body shapes around the center, but set the b2body's position back to the point after scaling. But how can I calculate that point? EDIT 2 :: I came ever deeper down to it, even solved it, but this is a slow solution and i hope that there is somebody who understands what formula I need. assuming to have a set polygons relative to an origin as basis shapes for a b2body: scaling the whole object around a certain point is done in the following steps: i scale everything around the center except the polygons i create a clone of the polygons matrix i scale this clone around the point i calculate dx, dy as difference of clone.tx - original.tx and clone.ty - original.ty i scale the original polygon matrix NOT around the point i recreate the body i create the fixture i set the position of the body to dx and dy done! So what i an interested in is a formula for dx and dy without cloning matrices, scaling the clone around a point, getting dx and dy and finally scale the vertex matrix.

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