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  • Factory Method Implementation

    - by cedar715
    I was going through the 'Factory method' pages in SO and had come across this link. And this comment. The example looked as a variant and thought to implement in its original way: to defer instantiation to subclasses... Here is my attempt. Does the following code implements the Factory pattern of the example specified in the link? Please validate and suggest if this has to undergo any re-factoring. public class ScheduleTypeFactoryImpl implements ScheduleTypeFactory { @Override public IScheduleItem createLinearScheduleItem() { return new LinearScheduleItem(); } @Override public IScheduleItem createVODScheduleItem() { return new VODScheduleItem(); } } public class UseScheduleTypeFactory { public enum ScheduleTypeEnum { CableOnDemandScheduleTypeID, BroadbandScheduleTypeID, LinearCableScheduleTypeID, MobileLinearScheduleTypeID } public static IScheduleItem getScheduleItem(ScheduleTypeEnum scheduleType) { IScheduleItem scheduleItem = null; ScheduleTypeFactory scheduleTypeFactory = new ScheduleTypeFactoryImpl(); switch (scheduleType) { case CableOnDemandScheduleTypeID: scheduleItem = scheduleTypeFactory.createVODScheduleItem(); break; case BroadbandScheduleTypeID: scheduleItem = scheduleTypeFactory.createVODScheduleItem(); break; case LinearCableScheduleTypeID: scheduleItem = scheduleTypeFactory.createLinearScheduleItem(); break; case MobileLinearScheduleTypeID: scheduleItem = scheduleTypeFactory.createLinearScheduleItem(); break; default: break; } return scheduleItem; } }

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  • Validation with State Pattern for Multi-Page Forms in ASP.NET

    - by philrabin
    I'm trying to implement the state pattern for a multi-page registration form. The data on each page will be accumulated and stored in a session object. Should validation (including service layer calls to the DB) occur on the page level or inside each state class? In other words, should the concrete implementation of IState be concerned with the validation or should it be given a fully populated and valid object? See "EmptyFormState" class below: namespace Example { public class Registrar { private readonly IState formEmptyState; private readonly IState baseInformationComplete; public RegistrarSessionData RegistrarSessionData { get; set;} public Registrar() { RegistrarSessionData = new RegistrarSessionData(); formEmptyState = new EmptyFormState(this); baseInformationComplete = new BasicInfoCompleteState(this); State = formEmptyState; } public IState State { get; set; } public void SubmitData(RegistrarSessionData data) { State.SubmitData(data); } public void ProceedToNextStep() { State.ProceedToNextStep(); } } //actual data stored in the session //to be populated by page public class RegistrarSessionData { public string FirstName { get; set; } public string LastName { get; set; } //will include values of all 4 forms } //State Interface public interface IState { void SubmitData(RegistrarSessionData data); void ProceedToNextStep(); } //Concrete implementation of IState //Beginning state - no data public class EmptyFormState : IState { private readonly Registrar registrar; public EmptyFormState(Registrar registrar) { this.registrar = registrar; } public void SubmitData(RegistrarSessionData data) { //Should Validation occur here? //Should each state object contain a validation class? (IValidator ?) //Should this throw an exception? } public void ProceedToNextStep() { registrar.State = new BasicInfoCompleteState(registrar); } } //Next step, will have 4 in total public class BasicInfoCompleteState : IState { private readonly Registrar registrar; public BasicInfoCompleteState(Registrar registrar) { this.registrar = registrar; } public void SubmitData(RegistrarSessionData data) { //etc } public void ProceedToNextStep() { //etc } } }

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  • Best practice for DAO pattern ?

    - by Tony
    I've seen a lot of codes use a service-dao pattern , I don't know the origin of this pattern . It force the front layer call service , then delegates some of the service task to dao. I want to ask : Does DAO layer do purely data access related task ? What about exception encapsulation ? Is there other pattern can be used to replace this ?

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  • Is ASP.NET MVC is really MVC? Or how to separate model from controller?

    - by Andrey
    Hi all, This question is a bit rhetorical. At some point i got a feeling that ASP.NET MVC is not that authentic implementation of MVC pattern. Or i didn't understood it. Consider following domain: electric bulb, switch and motion detector. They are connected together and when you enter the room motion detector switches on the bulb. If i want to represent them as MVC: switch is model, because it holds the state and contains logic bulb is view, because it presents the state of model to human motion detector is controller, because it converts user actions to generic model commands Switch has one private field (On/Off) as a State and two methods (PressOn, PressOff). If you call PressOn when it is Off it goes to On, if you call it again state doesn't change. Bulb can be replaced with buzzer, motion detector with timer or button, but the model still represent the same logic. Eventually system will have same behavior. This is how i understand classical MVC decomposition, please correct me if i am wrong. Now let's decompose it in ASP.Net MVC way. Bulb is still a view Controller will be switch + motion detector Model is some object that will just pass state to bulb. So the logic that defines behavior moves to controller. Question 1: Is my understanding of MVC and ASP.NET MVC correct? Question 2: If yes, do you agree that ASP.NET MVC is not 100% accurate implementation? And back to life. The final question is how to separate model from controller in case of ASP.NET MVC. There can be two extremes. Controller does basic stuff and call model to do all the logic. Another is controller does all the logic and model is just something like class with properties that is mapped to DB. Question 3: Where should i draw the line between this extremes? How to balance? Thanks, Andrey

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  • design for a wrapper around command-line utilities

    - by hatchetman82
    im trying to come up with a design for a wrapper for use when invoking command line utilities in java. the trouble with runtime.exec() is that you need to keep reading from the process' out and err streams or it hangs when it fills its buffers. this has led me to the following design: public class CommandLineInterface { private final Thread stdOutThread; private final Thread stdErrThread; private final OutputStreamWriter stdin; private final History history; public CommandLineInterface(String command) throws IOException { this.history = new History(); this.history.addEntry(new HistoryEntry(EntryTypeEnum.INPUT, command)); Process process = Runtime.getRuntime().exec(command); stdin = new OutputStreamWriter(process.getOutputStream()); stdOutThread = new Thread(new Leech(process.getInputStream(), history, EntryTypeEnum.OUTPUT)); stdOutThread.setDaemon(true); stdOutThread.start(); stdErrThread = new Thread(new Leech(process.getErrorStream(), history, EntryTypeEnum.ERROR)); stdErrThread.setDaemon(true); stdErrThread.start(); } public void write(String input) throws IOException { this.history.addEntry(new HistoryEntry(EntryTypeEnum.INPUT, input)); stdin.write(input); stdin.write("\n"); stdin.flush(); } } public class Leech implements Runnable{ private final InputStream stream; private final History history; private final EntryTypeEnum type; private volatile boolean alive = true; public Leech(InputStream stream, History history, EntryTypeEnum type) { this.stream = stream; this.history = history; this.type = type; } public void run() { BufferedReader reader = new BufferedReader(new InputStreamReader(stream)); String line; try { while(alive) { line = reader.readLine(); if (line==null) break; history.addEntry(new HistoryEntry(type, line)); } } catch (Exception e) { e.printStackTrace(); } } } my issue is with the Leech class (used to "leech" the process' out and err streams and feed them into history - which acts like a log file) - on the one hand reading whole lines is nice and easy (and what im currently doing), but it means i miss the last line (usually the prompt line). i only see the prompt line when executing the next command (because there's no line break until that point). on the other hand, if i read characters myself, how can i tell when the process is "done" ? (either complete or waiting for input) has anyone tried something like waiting 100 millis since the last output from the process and declaring it "done" ? any better ideas on how i can implement a nice wrapper around things like runtime.exec("cmd.exe") ?

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  • How to design tag database structure?

    - by liuxingruo
    I have a subjects database, and I want to create a new tag database to tag the subjects, but I have no idea how to design the new tag database structure. I'm assuming the new database looks like this: tag_id tag_name tagged_subject_ids 1 tag1 1, 2, 3, 5, 10 2 tag2 2, 4, 5, 6, 10, 12 so, if I want to select the tags belong to subject 1: SELECT tag_name FROM tag_database WHERE tagged_subject_ids LIKE '1'; I think the way that I select tag may be very slow, so please help me. Thanks!

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  • Blackberry User Interface Design - Customizable UI?

    - by John Stewart
    I am trying to design a Blackberry Application and I am wondering if there are any resources on how to create custom user interface elements, skin existing ones and what other possibilities are there? I have developed a few iPhone applications with custom UI and stuff, so not sure what BB world offers in terms of UI development. Any tips, suggestions or ideas would be great.

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  • IoC, Containers, and NServiceBus confusion

    - by andy
    Hey guys, here's my setup Castle Windsor is my container NServiceBus is itself using it's own container internally, Spring by default I'm implementing the PubSub config. Ok, if I have my Bus.Publish happening within my IWantToRunAtStartup class, then everything is fine. As a test for example on Run() we can start a timer and it'll go into a Service style loop. However, what if I want to abstract NServiceBus from my app, and have my app go: new CustomPulisherClass().Notify(ISomeMessage msg); In this situation, how do I implement CustomPublisherClass. My confusion is coming from the fact that NServiceBus is already running as a Service, it's already been "Started". How to I get at the correct instance of the Bus object? cheers andy

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  • Row level user permissions, help with design

    - by bambam
    Hi, Say I am creating a forums application, I understand how to design a forum level permission system with Groups. i.e. you create a forum to group mapping, and assign users to a group to give them access to a particular forum. How can I refine the permissions to allow for row level permissions (or in forum terms, post level).

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  • What's the best practice way to convert enum to string?

    - by dario
    Hi. I have enum like this: public enum ObectTypes { TypeOne, TypeTwo, TypeThree, ... TypeTwenty } then I need to convert this enum to string. Now Im doing this that way: public string ConvertToCustomTypeName(ObjectTypes typeObj) { string result = string.Empty; switch (typeObj) { case ObjectTypes.TypeOne: result = "This is type T123"; break; case ObjectTypes.TypeTwo: result = "This is type T234"; break; ... case ObjectTypes.TypeTwenty: result = "This is type last"; break; } return result; } Im quite sure that there is better way do do this, Im looking for some good practice solution. Thanks in advance.

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  • Tracking the user function that threw the exception

    - by makerofthings7
    I've been given a large application with only one try..catch at the outer most level. This application also throws exceptions all the time, and is poorly documented. Is there any pattern I can implement that will tell me what user method is being called, the exception being thrown, and also the count of exceptions? I'm thinking of using a dictionary with reflection to get the needed information, but I'm not sure if this will work. What do you think?

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  • Joomla Template Design

    - by John
    Hi, Can I create any design I want and then use it in a Joomla template or is there certain rules you have to stick to? I ask this as most of the Joomla templates I see pretty much have the same layout e.g. top bar content box, right hand menu and bottom bar. Thanks

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  • Which Code Should Go Where in MVC Structure

    - by Oguz
    My problem is in somewhere between model and controller.Everything works perfect for me when I use MVC just for crud (create, read, update, delete).I have separate models for each database table .I access these models from controller , to crud them . For example , in contacts application,I have actions (create, read, update, delete) in controller(contact) to use model's (contact) methods (create, read, update, delete). The problem starts when I try to do something more complicated. There are some complex processes which I do not know where should I put them. For example , in registering user process. I can not just finish this process in user model because , I have to use other models too (sending mails , creating other records for user via other models) and do lots of complex validations via other models. For example , in some complex searching processes , I have to access lots of models (articles, videos, images etc.) Or, sometimes , I have to use apis to decide what I will do next or which database model I will use to record data So where is the place to do this complicated processes. I do not want to do them in controllers , Because sometimes I should use these processes in other controllers too. And I do not want to put these process in models because , I use models as database access layers .May be I am wrong,I want to know . Thank you for your answer .

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  • Gmail-like labelling system

    - by Dimitris
    Hi I am looking into a number of ways to implement a labelling system similar to the one in Gmail. Basically I have a Resource at the lowest level and I would like to provide a number of organisational groupings for that resource in the form of labels. If anyone has implemented something like that I would like to hear your views. My idea is to have within the Resource instance a List<Label>. I need to have an efficient mechanism in order to do very fast searches based on the labels or based on the resources. Thanks Dimitris

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  • How does a WCF server inform a WCF client about changes? (Better solution then simple polling, e.g.

    - by Ian Ringrose
    see also "WCF push to client through firewall" I need to have a WCF client that connect to a WCF server, then when some of the data changes on the server the clients need to update its display. As there is likely to be a firewall between the clients and the server. All communications must be over HTTP The server can not make an (physical) outgoing call to the client. As I am writing both the client and the server I do not need to limit the solution to only using soap etc. I am looking for built in surport for "long polling" / "Comet" etc Thanks for the most informative answer from Drew Marsh on how to implement long polling in WCF. However I thought the main “selling point” of WCF was that you could do this sort of thing just by configuring the channels to be used in the config file. E.g I want a channel that logically two way but physically incoming only.

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  • Single Responsibility Principle usage how can i call sub method correctly?

    - by Phsika
    i try to learn SOLID prencibles. i writed two type of code style. which one is : 1)Single Responsibility Principle_2.cs : if you look main program all instance generated from interface 1)Single Responsibility Principle_3.cs : if you look main program all instance genareted from normal class My question: which one is correct usage? which one can i prefer? namespace Single_Responsibility_Principle_2 { class Program { static void Main(string[] args) { IReportManager raporcu = new ReportManager(); IReport wordraporu = new WordRaporu(); raporcu.RaporHazirla(wordraporu, "data"); Console.ReadKey(); } } interface IReportManager { void RaporHazirla(IReport rapor, string bilgi); } class ReportManager : IReportManager { public void RaporHazirla(IReport rapor, string bilgi) { rapor.RaporYarat(bilgi); } } interface IReport { void RaporYarat(string bilgi); } class WordRaporu : IReport { public void RaporYarat(string bilgi) { Console.WriteLine("Word Raporu yaratildi:{0}",bilgi); } } class ExcellRaporu : IReport { public void RaporYarat(string bilgi) { Console.WriteLine("Excell raporu yaratildi:{0}",bilgi); } } class PdfRaporu : IReport { public void RaporYarat(string bilgi) { Console.WriteLine("pdf raporu yaratildi:{0}",bilgi); } } } Second 0ne all instance genareted from normal class namespace Single_Responsibility_Principle_3 { class Program { static void Main(string[] args) { WordRaporu word = new WordRaporu(); ReportManager manager = new ReportManager(); manager.RaporHazirla(word,"test"); } } interface IReportManager { void RaporHazirla(IReport rapor, string bilgi); } class ReportManager : IReportManager { public void RaporHazirla(IReport rapor, string bilgi) { rapor.RaporYarat(bilgi); } } interface IReport { void RaporYarat(string bilgi); } class WordRaporu : IReport { public void RaporYarat(string bilgi) { Console.WriteLine("Word Raporu yaratildi:{0}",bilgi); } } class ExcellRaporu : IReport { public void RaporYarat(string bilgi) { Console.WriteLine("Excell raporu yaratildi:{0}",bilgi); } } class PdfRaporu : IReport { public void RaporYarat(string bilgi) { Console.WriteLine("pdf raporu yaratildi:{0}",bilgi); } } }

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  • Java Polymorphism - Selecting correct method based on subtype

    - by Marty Pitt
    Hi Given the following Class and Service layer signatures: public class PersonActionRequest { PersonVO person // ... other fields } public class MyServiceLayerClass { public void requestAction(PersonActionRequest request) { PersonVO abstractPerson = request.getPerson(); // call appropriate executeAction method based on subclass of PersonVO } private void executeAction(PersonVO person) {} private void executeAction(EmployeeVO employee) {} private void executeAction(ManagerVO manager) {} private void executeAction(UnicornWranglerVO unicornWrangler) {} } As discussed here, java will select the best method based on type info at compile time. (Ie., it will always select executeAction(PersonVO person) ). What's the most appropriate way to select the correct method? The internet tells me that using instanceof gets me slapped. However, I don't see the appropraite way to select the method without explictly casting abstractPerson to one of the other concrete types. Thanks Marty

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  • Sharing a connection string

    - by coure06
    hi, I am developing a class library (C#) that i will use it for my different projects (later). My class library dll will use the connection string /data context of the project which will reference my new dll. How can i do it? Lets say i have a class Library Project named "CLP", and a website project "WP". I can add reference to CLP.dll file but how i will pass a connection string/data context object to that dll? as CLP.dll will access db based on the connection string of the "WP". Not sure my problem is clear or not!

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  • Messaging pattern question

    - by Al Bundy
    Process A is calculating values for objects a1, a2, a3 etc. and is sending results to the middleware queue (RabbitMQ). Consumers read the queue and process these results further. Periodically process A has to send a snapshot of these values, so consumers could do some other calculations. Values for these objects might change independently. The queue might look like this a1, a1, a2, a1, a2, a2, a3... Consumers process each item in the queue. The snapshot has to contain all objects and consumers will process this message for all objects in one go. So the requirement is to have a queue like this: a1, a1, a3, a2, a2, [snapshot, a1, a2, a3], a3, a1 ... The problem is that these items are of different types: one type for objects like a1, a2 and other for a snapshot. This means that they should be processed in a diferent queues, but in that case there is a race condition: consumers might process objects before processing a snapshot. Is there any pattern to solve this (quite common) problem? We are using RabbitMQ for message queueing.

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  • Where UnityContainerElement in Unity 2?

    - by TheAbdalla
    I was in Unity 1.2, use the following code: UnityConfigurationSection UnitySection = (UnityConfigurationSection)ConfigurationManager.GetSection("Unity"); Dictionary<string, IUnityContainer> Containers = new Dictionary<string, IUnityContainer>(); foreach (UnityContainerElement element in UnitySection.Containers) { IUnityContainer container = new UnityContainer(); Containers.Add(element.Name, container); element.Configure(Containers[element.Name]); } but, I couldn't do so in the Unity 2.0 beta2, because The class 'UnityContainerElement' does not exist in Unity 2 beta2. How can I do this in the new version?

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  • What is the basic pattern for using (N)Hibernate?

    - by Vilx-
    I'm creating a simple Windows Forms application with NHibernate and I'm a bit confused about how I'm supposed to use it. To quote the manual: ISession (NHibernate.ISession) A single-threaded, short-lived object representing a conversation between the application and the persistent store. Wraps an ADO.NET connection. Factory for ITransaction. Holds a mandatory (first-level) cache of persistent objects, used when navigating the object graph or looking up objects by identifier. Now, suppose I have the following scenario: I have a simple classifier which is a MSSQL table with two columns - ID (auto_increment) and Name (nvarchar). To edit this classifier I create a form which contains a single gridview and two buttons - OK and Cancel. The user can nearly directly edit the table in the gridview, and when he hits OK the changes he made are persisted to the DB (or if he hits cancel, nothing happens). Now, I have several questions about how to organize this: What should the lifetime of my ISession be? Should I create a single ISession for my whole application; an ISession for each of my forms (the application is single-threaded MDI); or an ISession for every DB operation/transaction? Does NHibernate offer some kind of built-in dirty tracking or must I do this myself? The manual mentions something like it here and there but does not go into details. How is this done? Is there not a huge overhead? Is it somehow tied with the cache(s) that NHibernate has? What are these caches for? Are they not specific to a single ISession? That is, if I use a seperate ISession for every transaction, won't it break the dirty tracking? How does the built-in dirty tracking detect deleted objects?

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