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  • Implementing separation of concerns via MVC

    - by user2368481
    I'm creating a question to see if my understanding of MVC separation is correct, I haven't been able to find a clear answer anywhere online. So is this the right way to implement it (in Java): I would have 3 .java files, one each for Model, Controller, View. I would put all the classes related to Model in the Model.java like so: //Model.java { public class Model //class fields public Model(); public ModelClassA(); public ModelClassB(); public ModelClassC(); } With the ModelClasses being any class that I consider belonging to the Model. Is it correct to have the classes within the Model Class, as I have read that nested classes should be avoided where possible.

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  • Is the separation of program logic and presentation layer going too far?

    - by Timwi
    In a Drupal programming guide, I noticed this sentence: The theme hook receives the total number of votes and the number of votes for just that item, but the template wants to display a percentage. That kind of work shouldn't be done in a template; instead, the math is performed here. The math necessary to calculate a percentage from a total and a number is (number/total)*100. Is this application of two basic arithmetic operators within a presentation layer already too much? Is the maintenance of the entire system severely compromised by this amount of mathematics? The WPF (Windows Presentation Framework) and its UI mark-up language, XAML, seem to go to similar extremes. If you try to so much as add two numbers in the View (the presentation layer), you have committed a cardinal sin. Consequently, XAML has no operators for any arithmetic whatsoever. Is this ultra-strict separation really the holy grail of programming? What are the significant gains to be had from taking the separation to such extremes?

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  • Separation of concerns and authentication

    - by Tom Gilder
    I'm trying to be a Good Developer and separate my concerns out. I've got an ASP.NET MVC project with all my web code, and a DAL project with all the model code. Sometimes code in the DAL needs to check if the current user is authorized to perform some actions, by checking something like CurrentUser.IsAdmin. For the web site, the current is derived from the Windows username (from HttpContext.Current.User.Identity), but this is clearly a web concern and shouldn't be coupled to the DAL. What's the best pattern to loosely couple the authentication? Should the DAL be asking the MVC code for a username, or the MVC be telling the DAL? Are there advantages or disadvantages to one or the other? Thank you!

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  • Rhino Mocks, Dependency Injection, and Separation of Concerns

    - by whatispunk
    I am new to mocking and dependency injection and need some guidance. My application is using a typical N-Tier architecture where the BLL references the DAL, and the UI references the BLL but not the DAL. Pretty straight forward. Lets say, for example, I have the following classes: class MyDataAccess : IMyDataAccess {} class MyBusinessLogic {} Each exists in a separate assembly. I want to mock MyDataAccess in the tests for MyBusinessLogic. So I added a constructor to the MyBusinessLogic class to take an IMyDataAccess parameter for the dependency injection. But now when I try to create an instance of MyBusinessLogic on the UI layer it requires a reference to the DAL. I thought I could define a default constructor on MyBusinessLogic to set a default IMyDataAccess implementation, but not only does this seem like a codesmell it didn't actually solve the problem. I'd still have a public constructor with IMyDataAccess in the signature. So the UI layer still requires a reference to the DAL in order to compile. One possible solution I am toying with is to create an internal constructor for MyBusinessLogic with the IMyDataAccess parameter. Then I can use an Accessor from the test project to call the constructor. But there's still that smell. What is the common solution here. I must just be doing something wrong. How could I improve the architecture?

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  • Example: Cross Cutting Concerns of an Application

    A little while ago I was given an opportunity to design and implement a new system that sent data via an HTTP Post method and then processed the results that were returned so that they could be inserted in to a database. My system had eight core concerns that it needed to fulfill. Eight Core Concerns Database Access Data Entities Worker Result Processing Process Flow Manager Email/Notification Error Handling Logging Of these eight, five were actually cross cutting concerns. 5 Cross Cutting Concerns Database Access Data Entities Email/Notification Error Handling Logging These five cross cutting concerns were determined after I created an aspect oriented model to help identity the system components that could be factored out into separate components.  These separated components would then be included in the system so that they could be used by various other components.  These five components allow all of the other components to access the database, store data, send notifications, handle errors, and log all system events.  Thus, these components are used to share unique aspects to the system via their implementation. The use of Aspect oriented architecture greatly helped me define what components I needed to create and what each of those components could do.  It also showed how all of the other aspects depended on each other so that each component did not have to re-implement code that was already created in the existing system.

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  • Command-Query-Separation and multithreading safe interfaces

    - by Tobias Langner
    I like the command query separation pattern (from OOSC / Eiffel - basically you either return a value or you change the state of the class - but not both). This makes reasoning about the class easier and it is easier to write exception safe classes. Now, with multi threading, I run into a major problem: the separation of the query and the command basically invalidates the result from the query as anything can happen between those 2. So my question is: how do you handle command query separation in an multi-threaded environment? Clarification example: A stack with command query separation would have the following methods: push (command) pop (command - but does not return a value) top (query - returns the value) empty (query) The problem here is - I can get empty as status, but then I can not rely on top really retrieving an element since between the call of empty and the call of top, the stack might have been emptied. Same goes for pop & top. If I get an item using top, I can not be sure that the item that I pop is the same. This can be solved using external locks - but that's not exactly what I call threadsafe design.

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  • ASP.Net MVC - What replaces events to support loose coupling?

    - by James
    What feature(s) of ASP.Net MVC can replace the way events can be used in Webforms to support loosely coupled components. For example, take a simple pager control: A page number is clicked Pager fires off a "PageChange" event with the new page number This subscribing page/control received the event and handles initiating a call to fetch and bind new data. What tools are available in ASP.Net MVC to support Loose coupling Component re-usability Separation of logic for a single page/view (such a very complex "portal" type page).

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  • Sortie des spécifications d'OpenCL 1.2 : séparation compilation/linkage, partitionnement et support de nouveaux types de périphériques

    Sortie des spécifications d'OpenCL 1.2 Séparation compilation/linkage, partitionnement et support de nouveaux types de périphérique Le groupe Khronos vient de ratifier et publier les spécifications d'OpenCL 1.2 (Open Computing Language), l'API et extension standardisée du langage C pour supporter le développement sur GPU et la programmation parallèle distribuée sur plusieurs types de processeurs compatibles. Parmi les nouveautés de cette version, citons : Le partitionnement des périphériques permet de diviser un périphérique en plusieurs sous-périphériques pour contrôler directement les tâches assignées à chaque unité de calcul ; Séparation de la compilation et ...

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  • Visual Studio Talk Show #118 is now online - Command-Query Responsibility Separation (French)

    - by guybarrette
    http://www.visualstudiotalkshow.com Erik Renaud: La séparation des responsabilités entre les commandes et les requêtes Nous discutons avec Erik Renaud de la séparation des responsabilités entre les commandes et les requêtes (Command-Query Responsibility Separation - CQRS). La plupart des applications lisent les données beaucoup plus fréquemment qu'ils font des écritures. Sur la base de cette déclaration, une bonne idée consiste à séparer le code qui est responsable de l’écriture des données du code qui est responsable des requêtes (lecture). Erik Renaud est un coach .NET et co-fondateur de nVentive, une société conseil qui aide les équipes de développement logiciel au moyen de « coaching » et de « guidance ». Ses mandats courants se concentrent dans les grandes institutions financières en créant de nouvelles équipes qui supportent directement leurs activités primaires. Erik cumule plus de 10 ans d’expérience en développement logiciel, en faisant du coaching pour des équipes pour des besoins en architecture, modélisation et analyse. Pour la seconde année, il a reçu de Microsoft la reconnaissance MVP. Il est un ScrumMaster certifié, ce qui l’aide à guider les équipes vers le succès, et offre souvent des formations pour les technologies orientées objet. Il peut être rejoint au [email protected], ou vu tout partout où le kendo est pratiqué. var addthis_pub="guybarrette";

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  • Command Query Separation

    - by Liam McLennan
    Command query separation is a strategy, proposed by Bertrand Meyer, that each of an object’s methods should be either a command or a query. A command is an operation that changes the state of a system, and a query is an operation that returns a value. This is not the same thing as CQRS, hence why I think that CQRS is poorly named. An Example of Command Query Separation Consider a system that models books and shelves. There is a rule that a shelf may not be removed if it holds any books. One way to implement the removal is to write a method Shelf.Remove() that internally checks to make sure that the shelf is empty before removing it. If the shelf is not empty then it is not removed and an error is returned. To implement this feature following the principle of command query separation would require two methods, one to query the shelf and determine if it is empty and a second method to remove the shelf. Separating the query from the command makes the shelf class simpler to use because the state change is clear and explicit.

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  • Why is CSS3 doing animations?

    - by Joseph the Dreamer
    Like what the title says, why are there animations in CSS3? With basis from the "rule" of separation of concerns, HTML is the content, CSS is the style, and JavaScript is the interactive component. And by interactivity, one can conclude that anything moving due to any interaction, user or non-user triggered should be covered by JavaScript, not CSS. So why did they make CSS3 capable of doing animations? Doesn't it breach the rule, which is separation of concerns? Is there anything I missed that makes animations qualified to be classified as styles rather than interaction?

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  • Visual Studio Talk Show #118 is now online - Command-Query Responsibility Separation (French)

    http://www.visualstudiotalkshow.com Erik Renaud: La sparation des responsabilits entre les commandes et les requtes Nous discutons avec Erik Renaud de la sparation des responsabilits entre les commandes et les requtes (Command-Query Responsibility Separation - CQRS). La plupart des applications lisent les donnes beaucoup plus frquemment qu'ils font des critures. Sur la base de cette dclaration, une bonne ide consiste sparer le code qui est responsable de lcriture des donnes du code qui est...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Valid concerns over shared developer team

    - by alphadogg
    Say your company is committed (and don't want to consider not doing this) to sharing/pooling a development team across a handful of business units. What would you setup as concerns/expectations that must be cleared before doing this? For example: Need agreement between units on how much actual time (FTE) is allocated to each unit Need agreement on scheduling of staff need agreement on request procedure if extra time is required by one party etc... Have you been in a situation like this as a manager of one unit destined to use this? If so, what were problems you experienced? What would you have or did implement? Same if you were the manager of the shared team. Please assume, for discussion, that the people concerned know that you can swap devs in and out on a whim. I don't want to know the disadvantages of this approach; I know them. I want to anticipate issues and know how to mitigate the fallout.

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  • Entity Framework and layer separation

    - by Thomas
    I'm trying to work a bit with Entity Framework and I got a question regarding the separation of layers. I usually use the UI - BLL - DAL approach and I'm wondering how to use EF here. My DAL would usually be something like GetPerson(id) { // some sql return new Person(...) } BLL: GetPerson(id) { Return personDL.GetPerson(id) } UI: Person p = personBL.GetPerson(id) My question now is: since EF creates my model and DAL, is it a good idea to wrap EF inside my own DAL or is it just a waste of time? If I don't need to wrap EF would I still place my Model.esmx inside its own class library or would it be fine to just place it inside my BLL and work some there? I can't really see the reason to wrap EF inside my own DAL but I want to know what other people are doing. So instead of having the above, I would leave out the DAL and just do: BLL: GetPerson(id) { using (TestEntities context = new TestEntities()) { var result = from p in context.Persons.Where(p => p.Id = id) select p; } } What to do?

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  • CQRS – Questions and Concerns

    - by Dylan Smith
    I’ve been doing a lot of learning on CQRS and Event Sourcing over the last little while and I have a number of questions that I haven’t been able to answer. 1. What is the benefit of CQRS when compared to a typical DDD architecture that uses Event Sourcing and properly captures intent and behavior via verb-based commands? (other than Scalability) 2. When using CQRS what do you do with complex query-based logic? I’m going to elaborate on #1 in this blog post and I’ll do a follow-up post on #2. I watched through Greg Young’s video on the business benefits of CQRS + Event Sourcing and first let me say that I thought it was an excellent presentation that really drives home a lot of the benefits to this approach to architecture (I watched it twice in a row I enjoyed it so much!). But it didn’t answer some of my questions fully (I wish I had been there to ask these of Greg in person!). So let me pick apart some of the points he makes and how they relate to my first question above. I’m completely sold on the idea of event sourcing and have a clear understanding of the benefits that it brings to the table, so I’m not going to question that. But you can use event sourcing without going to a CQRS architecture, so my main question is around the benefits of CQRS + Event Sourcing vs Event Sourcing + Typical DDD architecture Architecture with Event Sourcing + Commands on Left, CQRS on Right Greg talks about how the stereotypical architecture doesn’t support DDD, but is that only because his diagram shows DTO’s coming up from the client. If we use the same diagram but allow the client to send commands doesn’t that remove a lot of the arguments that Greg makes against the stereotypical architecture? We can now introduce verbs into the system. We can capture intent now (storing it still requires event sourcing, but you can implement event sourcing without doing CQRS) We can create a rich domain model (as opposed to an anemic domain model) Scalability is obviously a benefit that CQRS brings to the table, but like Greg says, very few of the systems we create truly need significant scalability Greg talks about the ability to scale your development efforts. He says CQRS allows you to split the system into 3 parts (Client, Domain/Commands, Reads) and assign 3 teams of developers to work on them in parallel; letting you scale your development efforts by 3x with nearly linear gains. But in the stereotypical architecture don’t you already have 2 separate modules that you can split your dev efforts between: The client that sends commands/queries and receives DTO’s, and the Domain which accepts commands/queries, and generates events/DTO’s. If this is true it’s not really a 3x scaling you achieve with CQRS but merely a 1.5x scaling which while great doesn’t sound nearly as dramatic (“I can do it with 10 devs in 12 months – let me hire 5 more and we can have it done in 8 months”). Making the Query side “stupid simple” such that you can assign junior developers (or even outsource it) sounds like a valid benefit, but I have some concerns over what you do with complex query-based logic/behavior. I’m going to go into more detail on this in a follow-up blog post shortly. He also seemed to focus on how “stupid-simple” it is doing queries against the de-normalized data store, but I imagine there is still significant complexity in the event handlers that interpret the events and apply them to the de-normalized tables. It sounds like Greg suggests that because we’re doing CQRS that allows us to apply Event Sourcing when we otherwise wouldn’t be able to (~33:30 in the video). I don’t believe this is true. I don’t see why you wouldn’t be able to apply Event Sourcing without separating out the Commands and Queries. The queries would just operate against the domain model instead of the database. But you’d still get the benefits of Event Sourcing. Without CQRS the queries would only be able to operate against the current state rather than the event history, but even in CQRS the domain behaviors can only operate against the current state and I don’t see that being a big limiting factor. If some query needs to operate against something that is not captured by the current state you would just have to update the domain model to capture that information (no different than if that statement were made about a Command under CQRS). Some of the benefits I do see being applicable are that your domain model might end up being simpler/smaller since it only needs to represent the state needed to process commands and not worry about the reads (like the Deactivate Inventory Item and associated comment example that Greg provides). And also commands that can be handled in a Transaction Script style manner by the command handler simply generating events and not touching the domain model. It also makes it easier for your senior developers to focus on the command behavior and ignore the queries, which is usually going to be a better use of their time. And of course scalability. If anybody out there has any thoughts on this and can help educate me further, please either leave a comment or feel free to get in touch with me via email:

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  • PCI DSS requirement 6.4.2 separation of duties between development/test environments

    - by Aleksandar Ivanisevic
    6.4.2 Is there separation of duties between personnel assigned to the development/test environments and those assigned to the production environment? What does the separation of duties here mean? Is it in the sense of http://www.sans.edu/research/security-laboratory/article/it-separation-duties or something else? The formulation "between test and production environment" is really confusing me, it looks like they mean that one should have different sysadmins for test and production? Or do they just mean that developers shouldn't have access to production? thanks.

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  • Survey Probes the Project Management Concerns of Financial Services Executives

    - by Melissa Centurio Lopes
    Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Do you wonder what are the top reasons why large projects in the financial industry fail to meet budgets, schedules, and other key performance criteria? Being able to answer this question can provide important insight and value of good project management practices for your organization. According to 400 senior executives who participated in a new survey conducted by the Economist Intelligence Unit and sponsored by Oracle, unrealistic project goals is the main reason for roadblocks to success Other common stumbling blocks are poor alignment between project and organizational goals, inadequate human resources, lack of strong leadership, and unwillingness among team members to point out problems. This survey sample also had a lot to say about the impact of regulatory compliance on the overall portfolio management process. Thirty-nine percent acknowledged that regulations enabled efficient functioning of their businesses. But a similar number said that regulations often require more financial resources than were originally allocated to bring projects in on time. Regulations were seen by 35 percent of the executives as roadblocks to their ability to invest in the organization’s growth and success. These revelations among others are discussed in depth in a new on-demand Webcast titled “Too Good to Fail: Developing Project Management Expertise in Financial Services” now available from Oracle. The Webcast features Brian Gardner, editor of the Economist Intelligence Unit, who presents these findings from this survey along with Guy Barlow, director of industry strategy for Oracle Primavera. Together, they analyze what the numbers mean for project and program managers and the financial services industry. Register today to watch the on-demand Webcast and get a full rundown and analysis of the survey results. Take the Economist Intelligence Unit benchmarking survey and see how your views compare with those of other financial services industry executives in ensuring project success.  Read more in the October Edition of the quarterly Information InDepth EPPM Newsletter

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  • Entity/Component based engine rendering separation from logic

    - by Denis Narushevich
    I noticed in Unity3D that each gameObject(entity) have its own renderer component, as far I understand, such component handle rendering logic. I wonder if it is a common practice in entity/component based engines, when single entity have renderer components and logic components such as position, behavior altogether in one box? Such approach sound odd to me, in my understanding entity itself belongs to logic part and shouldn't contain any render specific things inside. With such approach it is impossible to swap renderers, it would require to rewrite all that customized renderers. The way I would do it is, that entity would contain only logic specific components, like AI,transform,scripts plus reference to mesh, or sprite. Then some entity with Camera component would store all references to object that is visible to the camera. And in order to render all that stuff I would have to pass Camera reference to Renderer class and render all sprites,meshes of visible entities. Is such approach somehow wrong?

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  • rsync problems and security concerns

    - by MB.
    Hi I am attempting to use rsync to copy files between two linux servers. both on 10.04.4 I have set up the ssh and a script running under a cron job. this is the message i get back from the cron job. To: mark@ubuntu Subject: Cron ~/rsync.sh Content-Type: text/plain; charset=ANSI_X3.4-1968 X-Cron-Env: X-Cron-Env: X-Cron-Env: X-Cron-Env: Message-Id: <20120708183802.E0D54FC2C0@ubuntu Date: Sun, 8 Jul 2012 14:38:01 -0400 (EDT) rsync: link_stat "/home/mark/#342#200#223rsh=ssh" failed: No such file or directory (2) rsync: opendir "/Library/WebServer/Documents/.cache" failed: Permission denied (13) rsync: recv_generator: mkdir "/Library/Library" failed: Permission denied (13) * Skipping any contents from this failed directory * rsync error: some files/attrs were not transferred (see previous errors) (code 23) at main.c(1060) [sender=3.0.7] Q.1 can anyone tell me why I get this message -- rsync: link_stat "/home/mark/#342#200#223rsh=ssh" failed: No such file or directory (2) the script is: #!/bin/bash SOURCEPATH='/Library' DESTPATH='/Library' DESTHOST='192.168.1.15' DESTUSER='mark' LOGFILE='rsync.log' echo $'\n\n' >> $LOGFILE rsync -av –rsh=ssh $SOURCEPATH $DESTUSER@$DESTHOST:$DESTPATH 2>&1 >> $LOGFILE echo “Completed at: `/bin/date`” >> $LOGFILE Q2. I know I have several problems with the permissions all of the files I am copying usually require me to use sudo to manipulate them. My question is then is there a way i can run this job without giving my user root access or using root in the login ?? Thanks for the help .

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  • Separation of development responsibilities in a new project

    - by dreza
    We have very recently started a new project (MVC 3.0) and some of our early discussion has been around how the work and development will be split amongst the team members to ensure we get the least amount of overlap of work and so help make it a bit easier for each developer to get on and do their work. The project is expected to take about 6 months - 1 year (although not all developers are likely to be on and might filter off towards the end), Our team is going to be small so this will help out a bit I believe. The team will essentially consist of: 3 x developers (All different levels i.e. more senior, intermediate and junior) 1 x project manager / product owner / tester An external company responsbile for doing our design work General project/development decisions so far have included: Develop in an Agile way using SCRUM techniques (We are still very much learning this approach as a company) Use MVVM archectecture Use Ninject and DI where possible Attempt to use as TDD as much as possible to drive development. Keep our controllers as skinny as possible Keep our views as simple as possible During our discussions two approaches have been broached as too how to seperate the workload given our objectives outlined above. OPTION 1: A framework seperation where each person is responsible for conceptual areas with overlap and discussion primarily in the integration areas. The integration areas would the responsibily of both developers as required. View prototypes (**Graphic designer**) | - Mockups | Views (Razor and view helpers etc) & Javascript (**Developer 1**) | - View models (Integration point) | Controllers and Application logic (**Developer 2**) | - Models (Integration point) | Domain model and persistence (**Developer 3**) OPTION 2: A more task orientated approach where each person is responsible for the completion of the entire task (story) from view - controller - model. QUESTION: For those who have worked in small teams developing MVC projects how have you managed the workload distribution in this situation. I can't imagine the junior would be responsible for building parts of the underlying architecture so would given them responsibility for the view make sense considering we are trying to keep it simple?

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