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  • Simple but good pattern for EJB

    - by Sara
    What would you suggest as a good and practical but simple pattern for a soloution with: HTML + JSP (as a view/presentation) SERVLETS (controller, request, session-handling) EJB (persistence, businesslogic) MySQL DB And is it necessary to use an own layer of DAO for persistence? I use JPA to persist objects to my DB. Should I withdraw business logic from my EJB? Sources online all tell me different things and confuses me...

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  • strategy for observer pattern?

    - by fayer
    I want to use observer pattern for a logging system. We have got logObservers and logObservables. The class that will have to log something will implement iLogObservable and include these methods: private $logObservers = array(); public function addLogObserver($logObserver) { $this->logObservers[] = $logObserver; } public function removeLogObserver($logObserver) { $this->logObservers[] = $logObserver; } public function write($type, $message) { foreach($this->logObservers as $logObserver) { $logObserver->log($level, $message); ; } } Then I noticed, that a lot of classes that will use logging will have these methods and I have to copy paste. So isn't it better to have these methods in a class I call LogObservable or just Log and then use strategy (instantiate this class inside all classes that will have to log). When I change the methods in Log, all logObservables will be affected. However, I have not seen anyone use observer pattern with strategy pattern yet, but it seems to be very efficient and remove the duplications. What do you think?

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  • In a PHP project, how do you organize and access your helper objects?

    - by Pekka
    How do you organize and manage your helper objects like the database engine, user notification, error handling and so on in a PHP based, object oriented project? Say I have a large PHP CMS. The CMS is organized in various classes. A few examples: the database object user management an API to create/modify/delete items a messaging object to display messages to the end user a context handler that takes you to the right page a navigation bar class that shows buttons a logging object possibly, custom error handling etc. I am dealing with the eternal question, how to best make these objects accessible to each part of the system that needs it. my first apporach, many years ago was to have a $application global that contained initialized instances of these classes. global $application; $application->messageHandler->addMessage("Item successfully inserted"); I then changed over to the Singleton pattern and a factory function: $mh =&factory("messageHandler"); $mh->addMessage("Item successfully inserted"); but I'm not happy with that either. Unit tests and encapsulation become more and more important to me, and in my understanding the logic behind globals/singletons destroys the basic idea of OOP. Then there is of course the possibility of giving each object a number of pointers to the helper objects it needs, probably the very cleanest, resource-saving and testing-friendly way but I have doubts about the maintainability of this in the long run. Most PHP frameworks I have looked into use either the singleton pattern, or functions that access the initialized objects. Both fine approaches, but as I said I'm happy with neither. I would like to broaden my horizon on what is possible here and what others have done. I am looking for examples, additional ideas and pointers towards resources that discuss this from a long-term, real-world perspective. Also, I'm interested to hear about specialized, niche or plain weird approaches to the issue. Bounty I am following the popular vote in awarding the bounty, the answer which is probably also going to give me the most. Thank you for all your answers!

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  • Service Layer Pattern - Could we avoid the service layer on a specific case?

    - by lidermin
    Hi, we are trying to implement an application using the Service Layer Pattern cause our application needs to connect to other multiple applications too, and googling on the web, we found this link of a demonstrative graphic for the "right" way of apply the pattern: martinfowler.com - Service Layer Pattern But now we have a question: what if our system needs to implement some business logic, only for our application (like some maintenance data for the system itself) that we don't need to share with other systems. Based on this graphic: As it seems, it will be unnecesary to implement a service layer just for that; it will be more practical to avoid the service layer, and just go from User Interface to the Business Layer (for example). What should be the right way in this case to implement the Service Layer Pattern? What do you suggest us for a scenario like the one I told you? Thanks in advance.

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  • Calling DI Container directly in method code (MVC Actions)

    - by fearofawhackplanet
    I'm playing with DI (using Unity). I've learned how to do Constructor and Property injection. I have a static container exposed through a property in my Global.asax file (MvcApplication class). I have a need for a number of different objects in my Controller. It doesn't seem right to inject these throught the constructor, partly because of the high quantity of them, and partly because they are only needed in some Actions methods. The question is, is there anything wrong with just calling my container directly from within the Action methods? public ActionResult Foo() { IBar bar = (Bar)MvcApplication.Container.Resolve(IBar); // ... Bar uses a default constructor, I'm not actually doing any // injection here, I'm just telling my conatiner to give me Bar // when I ask for IBar so I can hide the existence of the concrete // Bar from my Controller. } This seems the simplest and most efficient way of doing things, but I've never seen an example used in this way. Is there anything wrong with this? Am I missing the concept in some way?

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  • Modular enterprise architecture using MVC and Orchard CMS

    - by MrJD
    I'm making a large scale MVC application using Orchard. And I'm going to be separating my logic into modules. I'm also trying to heavily decouple the application for maximum extensibility and testability. I have a rudimentary understanding of IoC, Repository Pattern, Unit of Work pattern and Service Layer pattern. I've made myself a diagram. I'm wondering if it is correct and if there is anything I have missed regarding an extensible application. Note that each module is a separate project.

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  • What is there so useful in the Decorator Pattern? My example doesn't work

    - by Green
    The book says: The decorator pattern can be used to extend (decorate) the functionality of a certain object I have a rabbit animal. And I want my rabbit to have, for example, reptile skin. Just want to decorate a common rabbit with reptile skin. I have the code. First I have abstract class Animal with everythig that is common to any animal: abstract class Animal { abstract public function setSleep($hours); abstract public function setEat($food); abstract public function getSkinType(); /* and more methods which for sure will be implemented in any concrete animal */ } I create class for my rabbit: class Rabbit extends Animal { private $rest; private $stomach; private $skinType = "hair"; public function setSleep($hours) { $this->rest = $hours; } public function setFood($food) { $this->stomach = $food; } public function getSkinType() { return $this->$skinType; } } Up to now everything is OK. Then I create abstract AnimalDecorator class which extends Animal: abstract class AnimalDecorator extends Animal { protected $animal; public function __construct(Animal $animal) { $this->animal = $animal; } } And here the problem comes. Pay attention that AnimalDecorator also gets all the abstract methods from the Animal class (in this example just two but in real can have many more). Then I create concrete ReptileSkinDecorator class which extends AnimalDecorator. It also has those the same two abstract methods from Animal: class ReptileSkinDecorator extends AnimalDecorator { public function getSkinColor() { $skin = $this->animal->getSkinType(); $skin = "reptile"; return $skin; } } And finaly I want to decorate my rabbit with reptile skin: $reptileSkinRabbit = ReptileSkinDecorator(new Rabbit()); But I can't do this because I have two abstract methods in ReptileSkinDecorator class. They are: abstract public function setSleep($hours); abstract public function setEat($food); So, instead of just re-decorating only skin I also have to re-decorate setSleep() and setEat(); methods. But I don't need to. In all the book examples there is always ONLY ONE abstract method in Animal class. And of course it works then. But here I just made very simple real life example and tried to use the Decorator pattern and it doesn't work without implementing those abstract methods in ReptileSkinDecorator class. It means that if I want to use my example I have to create a brand new rabbit and implement for it its own setSleep() and setEat() methods. OK, let it be. But then this brand new rabbit has the instance of commont Rabbit I passed to ReptileSkinDecorator: $reptileSkinRabbit = ReptileSkinDecorator(new Rabbit()); I have one common rabbit instance with its own methods in the reptileSkinRabbit instance which in its turn has its own reptileSkinRabbit methods. I have rabbit in rabbit. But I think I don't have to have such possibility. I don't understand the Decarator pattern right way. Kindly ask you to point on any mistakes in my example, in my understanding of this pattern. Thank you.

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  • Find First Specific Byte in a Byte[] Array c#

    - by divinci
    Hi there, I have a byte array and wish to find the first occurance (if any) of a specific byte. Can you guys help me with a nice, elegant and efficient way to do it? /// Summary /// Finds the first occurance of a specific byte in a byte array. /// If not found, returns -1. public int GetFirstOccurance(byte byteToFind, byte[] byteArray) { }

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  • what happens to running/blocked runnables when executorservice is shutdown()

    - by prmatta
    I posted a question about a thread pattern today, and almost everyone suggested that I look into the ExecutorService. While I was looking into the ExecutorService, I think I am missing something. What happens if the service has a running or blocked threads, and someone calls ExecutorService.shutdown(). What happens to threads that are running or blocked? Does the ExecutorService wait for those threads to complete before it terminates? The reason I ask this is because a long time ago when I used to dabble in Java, they deprecated Thread.stop(), and I remember the right way of stopping a thread was to use sempahores and extend Thread when necessary: public void run () { while (!this.exit) { try { block(); //do something } catch (InterruptedException ie) { } } } public void stop () { this.exit = true; if (this.thread != null) { this.thread.interrupt(); this.thread = null; } } How does ExecutorService handle running threads?

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  • C# event or delegate or other solution?

    - by user295734
    Looking for some help or programmng ideas or mayeb there is some pattern that would help. Have an application that needs to fire alot of events sequentially, it could up to 100 or more unique events, it will be dynamic depeneding on the situation. Trying to find the best practice for doing this. My main idea right now is to create a list of objects iterate thru them, and fire each event. This seems wrong, or bad practice. Or maybe have one object and pass a list or params into one event? Or am I missing some feature in .NET that i could be using or implementing?

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  • Are there any MVP Frameworks projects out there?

    - by Greg Malcolm
    MVC is used a number of popular frameworks. To name just a few, Ruby on Rails, ASP.NET MVC, Monorail, Spring MVC. Are there any equivalent frameworks using any variant of MVP? Most of the examples I've found online seem to be custom implementations of the pattern rather than reusable frameworks. Suggestions need not be specific to any particular programming language, my interest is mostly academic.

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  • Passing data between objects in Chain of Responsibility pattern

    - by AbrahamJP
    While implementing the Chain of Responsibility pattern, i came across a dilemma om how to pass data between objects in the chain. The datatypes passed between object in the chain can differ for each object. As a temporary fix I had created a Static class containing a stack where each object in the chain can push the results to the stack while the next object in the chain could pop the results from the stack. Here is a sample code on what I had implemented. public interface IHandler { void Process(); } public static class StackManager { public static Stack DataStack = new Stack(); } //This class doesn't require any input to operate public class OpsA : IHandler { public IHandler Successor {get; set; } public void Process() { //Do some processing, store the result into Stack var ProcessedData = DoSomeOperation(); StackManager.DataStack.Push(ProcessedData); if(Successor != null) Successor(); } } //This class require input data to operate upon public class OpsB : IHandler { public IHandler Successor {get; set; } public void Process() { //Retrieve the results from the previous Operation var InputData = StackManager.DataStack.Pop(); //Do some processing, store the result into Stack var NewProcessedData = DoMoreProcessing(InputData); StackManager.DataStack.Push(NewProcessedData); if(Successor != null) Successor(); } } public class ChainOfResponsibilityPattern { public void Process() { IHandler ProcessA = new OpsA(); IHandler ProcessB = new OpsB(); ProcessA.Successor = ProcessB; ProcessA.Process(); } } Please help me to find a better approach to pass data between handlers objects in the chain.

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  • Implementing the procducer-consumer with .NET 4.0 new

    - by bitbonk
    With alle the new paralell programming features in .NET 4.0, what would be a a simple and fast way to implement the producer-consumer pattern (where at least one thread is producing and enqueuing task items and one other thread executes (dequeues) these tasks). Can we benfit from all these new APIs? What is your preferred implementation of this pattern?

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  • "Circuit breaker" for net.msmq?

    - by Alex
    Hi, The Circuit Breaker pattern, from the book Release It!, protects a service from requests while it is failing (or recovering). The net.msmq binding used with transactions give us nice retry and poison message capabilities. But I am missing the implementation of such a "Circuit breaker" pattern. A service is put under even heavier load by retries while it is already in a failure condition (like DB connectivity issues causing loads of blocked threads etc.). Anyone knows about a behavior extension or similar that explicitly closes the service host when defined failure thresholds have been exceeded? Cheers, Alex

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  • [Delphi] How would you refactor this code?

    - by Al C
    This hypothetical example illustrates several problems I can't seem to get past, even though I keep trying!! ... Suppose the original code is a long event handler, coded in the UI, triggered when a user clicks a cell in a grid. Expressed as pseudocode it's: if Condition1=true then begin //loop through every cell in row, //if aCell/headerCellValue>1 then //color aCell red end else if Condition2=true then begin //do some other calculation adding cell and headerCell values, and //if some other product>2 then //color the whole row green end else show an error message I look at this and say "Ah, refactor to the strategy pattern! The code will be easier to understand, easier to debug, and easier to later extend!" I get that. And I can easily break the code into multiple procedures. The problem is ultimately scope related. Assume the pseudocode makes extensive use of grid properties, values displayed in cells, maybe even built-in grid methods. How do you move all that to another unit, without referencing the grid component in the UI--which would break all the "rules" about loose coupling that make OOP valuable? ... I'm really looking forward to responses. Thanks, as always -- Al C.

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  • Is extending a singleton class wrong?

    - by Anwar Shaikh
    I am creating a logger for an application. I am using a third party logger library. In which logger is implemented as singleton. I extended that logger class because I want to add some more static functions. In these static functions I internally use the instance (which is single) of Logger(which i inherited). I neither creates instance of MyLogger nor re-implemented the getInstance() method of super class. But I am still getting warnings like destructor of MyLogger can not be created as parent class (Loggger) destructor is not accessible. I want to know, I am I doing something wrong? Inheriting the singleton is wrong or should be avoided??

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  • Immutable classes in C++

    - by ereOn
    Hi, In one of my projects, I have some classes that represent entities that cannot change once created, aka. immutable classes. Example : A class RSAKey that represent a RSA key which only has const methods. There is no point changing the existing instance: if you need another one, you just create one. My objects sometimes are heavy and I enforced the use of smart pointers to avoid copy. So far, I have the following pattern for my classes: class RSAKey : public boost::noncopyable, public boost::enable_shared_from_this<RSAKey> { public: /** * \brief Some factory. * \param member A member value. * \return An instance. */ static boost::shared_ptr<const RSAKey> createFromMember(int member); /** * \brief Get a member. * \return The member. */ int getMember() const; private: /** * \brief Constructor. * \param member A member. */ RSAKey(int member); /** * \brief Member. */ const int m_member; }; So you can only get a pointer (well, a smart pointer) to a const RSAKey. To me, it makes sense, because having a non-const reference to the instance is useless (it only has const methods). Do you guys see any issue regarding this pattern ? Are immutable classes something common in C++ or did I just created a monster ? Thank you for your advices !

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  • MyController class must produce class according to the enum type.

    - by programmerist
    GenoTipController must produce class according to the enum type. i have 3 class: _Company,_Muayene,_Radyoloji. Also i have CompanyView Class GetPersonel method. if you look GenoTipController my codes need refactoring. Can you understand me? i need a class according to ewnum type must me produce class. For example; case DataModelType.Radyoloji it must return radyoloji= new Radyoloji . Everything must be one switch case? public class GenoTipController { public _Company GenerateCompany(DataModelType modeltype) { _Company company = null; switch (modeltype) { case DataModelType.Radyoloji: break; case DataModelType.Satis: break; case DataModelType.Muayene: break; case DataModelType.Company: company = new Company(); break; default: break; } return company; } public _Muayene GenerateMuayene(DataModelType modeltype) { _Muayene muayene = null; switch (modeltype) { case DataModelType.Radyoloji: break; case DataModelType.Satis: break; case DataModelType.Muayene: muayene = new Muayene(); break; case DataModelType.Company: break; default: break; } return muayene; } public _Radyoloji GenerateRadyoloji(DataModelType modeltype) { _Radyoloji radyoloji = null; switch (modeltype) { case DataModelType.Radyoloji: radyoloji = new Radyoloji(); break; case DataModelType.Satis: break; case DataModelType.Muayene: break; case DataModelType.Company: break; default: break; } return radyoloji; } } public class CompanyView { public static List GetPersonel() { GenoTipController controller = new GenoTipController(); _Company company = controller.GenerateCompany(DataModelType.Company); return company.GetPersonel(); } } public enum DataModelType { Radyoloji, Satis, Muayene, Company } }

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  • how can i use switch statement on type-safe enum pattern

    - by Fer
    I found a goodlooking example about implementation enums in a different way. That is called type-safe enum pattern i think. I started using it but i realized that i can not use it in a switch statement. My implementation looks like the following: public sealed class MyState { private readonly string m_Name; private readonly int m_Value; public static readonly MyState PASSED= new MyState(1, "OK"); public static readonly MyState FAILED= new MyState(2, "ERROR"); private MyState(int value, string name) { m_Name = name; m_Value = value; } public override string ToString() { return m_Name; } public int GetIntValue() { return m_Value; } } What can i add to my class in order to be able to use this pattern in switch statements in C#? Thanks.

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