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  • How to map different UI views in a RESTful web application?

    - by MicE
    Hello, I'm designing a web application, which will support both standard UIs (accessed via browsers) and a RESTful API (an XML/JSON-based web service). User agents will be able to differentiate between these by using different values in the Accept HTTP header. The RESTful API will use the following URI structure (example for an "article" resource): GET /article/ - gets a list of articles POST /article/ - adds a new article PUT /article/{id} - updates an existing article based on {id} DELETE /article/{id} - deletes an existing article based on {id} The UI part of the application will however need to support multiple views, for example: a standard resource view a view for submitting a new resource a view for editing an existing resource a view for deleting an existing resource (i.e. display delete confirmation) Note that the latter three views are still accessed via GET, even though they are processed via overloaded POST. Possible solution: Introduce additional parameters (keywords) into URIs which would identify individual views - i.e. on top of the above, the application would support the following URIs (but only for Content-Type: text/html): GET /article/add - displays a form for adding a new article (fetched via GET, processed via POST) GET /article/123 - displays article 123 in "view" mode (fetched via GET) GET /article/123/edit - displays article 123 in "edit" mode (fetched via GET, processed via PUT overloaded as POST) GET /article/123/delete - displays "delete" confirmation for article 123 (fetched via GET, processed via DELETE overloaded as POST) A better implementation of the above might be to put the add/edit/delete keywords into a GET parameter - since they do not change the resource we're working with, it might be better to keep the base URI same for all of them. My question is: How would you map the above URI structure to UIs served to the regular user, considering that there can be several views per each resource, please? Do you agree with the possible solution detailed above, or would you recommend a different approach based on your experience? NB: we've already implemented an application which consists of a standalone RESTful API and a standalone web application. I'm currently looking into options for future projects where these two would be merged together (i.e. in order to reduce overhead). Thank you, M.

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  • Data Access Layer, Best Practices

    - by labratmatt
    I'm looking for input on the best way to refactor the data access layer (DAL) in my PHP based web app. I follow an MVC pattern: PHP/HTML/CSS/etc. views on the front end, PHP controllers/services in the middle, and a PHP DAL sitting on top of a relational database in the model. Pretty standard stuff. Things are working fine, but my DAL is getting large (codesmell?) and becoming a bit unwieldy. My DAL contains almost all of the logic to interface with my database and is full of functions that look like this: function getUser($user_id) { $statement = "select id, name from users where user_id=:user_id"; PDO builds statement and fetchs results as an array return $array_of_results_generated_by_PDO_fetch_method; } Notes: The logic in my controller only interacts with the model using functions like the above in the DAL I am not using a framework (I'm of the opinion that PHP is a templating language and there's no need to inject complexity via a framework) I generally use PHP as a procedural language and tend to shy away from its OOP approach (I enjoy OOP development but prefer to keep that complexity out of PHP) What approaches have you taken when your DAL has reached this point? Do I have a fundamental design problem? Do I simply need to chop my DAL into a number of smaller files (logically divide it)? Thanks.

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  • Architectural conundrum

    - by Dejan
    The worst thing when working on a one man project is the lack of input that you usually get from your coworkers. And because of the lack of that you tend to make obvious mistakes. After going down that road for some time I would need some help from the community. I started a little home-brew project that should turn into a portal of some sorts. And the main thing that is bothering me is the persistence layer that i have concocted. It should be completely separated from the presentation layer for starters and a OR mapper is also somewhere. This is because I have multiple data stores that have to be used. So the base idea was that the individual "repositories" operate each on their individual database and that the business layer then aggregates the business objects which are then transformed in the presentation layer into view objects. The main problem I face is the following: Multiple classes for the same concept - There is a DAL representation of a user and BL representation of user and a view representation of a user. I can handle the transformation with a tool but is this really the right way. I mean they are all nicely separated, but the overhead is quite something. What do you think? Am I going too deep into the separation of concern rabbit hole or is this still normal?

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  • Verbose Listing of All Application Layers/Tiers?

    - by leeand00
    I've looked at a few sites now, and I'm still struggling to find a complete listing of all the possible layers/tiers you can have in an application. From back in college (1999) I remember the following: Presentation Layer (Views) Application Layer (Controllers) Business Logic Layer (API/Rules) Persistence Layer (Database/Object Persistence/Model) I'm not advocating that they all be used...especially when you consider that too many layers/tiers could lead to an increase in complexity...I just wondered what the complete list might look like... Based on a couple of blogs I've found several different answers...and Javascript and client side technologies seem to have leaked in adding more client-side layers according to one blog the client side tier might even consist of Behavior Layer (Javascript, Flash) Presentation Layer (CSS/Images) Note: I though the entire client side layer was the presentation layer Structure Layer (XHTML, HTML) I'm just trying to get an abstract idea of what all the possible layers might be, (even though some people call them different things)

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  • Erlang OTP application design

    - by Toby Hede
    I am struggling a little coming to grips with the OTP development model as I convert some code into an OTP app. I am essentially making a web crawler and I just don't quite know where to put the code that does the actual work. I have a supervisor which starts my worker: -behaviour(supervisor). -define(CHILD(I, Type), {I, {I, start_link, []}, permanent, 5000, Type, [I]}). init(_Args) -> Children = [ ?CHILD(crawler, worker) ], RestartStrategy = {one_for_one, 0, 1}, {ok, {RestartStrategy, Children}}. In this design, the Crawler Worker is then responsible for doing the actual work: -behaviour(gen_server). start_link() -> gen_server:start_link(?MODULE, [], []). init([]) -> inets:start(), httpc:set_options([{verbose_mode,true}]), % gen_server:cast(?MODULE, crawl), % ok = do_crawl(), {ok, #state{}}. do_crawl() -> % crawl! ok. handle_cast(crawl}, State) -> ok = do_crawl(), {noreply, State}; do_crawl spawns a fairly large number of processes and requests that handle the work of crawling via http. Question, ultimately is: where should the actual crawl happen? As can be seen above I have been experimenting with different ways of triggering the actual work, but still missing some concept essential for grokering the way things fit together. Note: some of the OTP plumbing is left out for brevity - the plumbing is all there and the system all hangs together

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  • Alternatives to NServiceBus that doesn't use MSMQ

    - by G33kKahuna
    I think the title sums it all .... We have a .NET 2.0 system trying to implement a distributed pub/ sub model. I came across NServiceBus, RhinoBus and MassTransit. Unfortunately, these are MSMQ based. I am tasked to figure out pub/ sub alternatives that uses a different messaging alternatives ... the only reason for seeking MSMQ alternatives is to overcome the message size restriction. Since our enterprise app messages can potentially get truncated due to per message restriction... any guidance is much appreciated

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  • How to choose programming language for projects?

    - by bdhar
    This is a question I constantly encounter when I attend any technical forums / discussions / interviews. There is a similar article but it focuses on business merits as well. What I am looking for is a guide (not a checklist like this one which is abstract and not so accurate) which helps an architect to choose the programming language to implement a requirement. Is there a book or article available for the same purpose?

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  • C#: Inheritance, Overriding, and Hiding

    - by Rosarch
    I'm having difficulty with an architectural decision for my C# XNA game. The basic entity in the world, such as a tree, zombie, or the player, is represented as a GameObject. Each GameObject is composed of at least a GameObjectController, GameObjectModel, and GameObjectView. These three are enough for simple entities, like inanimate trees or rocks. However, as I try to keep the functionality as factored out as possible, the inheritance begins to feel unwieldy. Syntactically, I'm not even sure how best to accomplish my goals. Here is the GameObjectController: public class GameObjectController { protected GameObjectModel model; protected GameObjectView view; public GameObjectController(GameObjectManager gameObjectManager) { this.gameObjectManager = gameObjectManager; model = new GameObjectModel(this); view = new GameObjectView(this); } public GameObjectManager GameObjectManager { get { return gameObjectManager; } } public virtual GameObjectView View { get { return view; } } public virtual GameObjectModel Model { get { return model; } } public virtual void Update(long tick) { } } I want to specify that each subclass of GameObjectController will have accessible at least a GameObjectView and GameObjectModel. If subclasses are fine using those classes, but perhaps are overriding for a more sophisticated Update() method, I don't want them to have to duplicate the code to produce those dependencies. So, the GameObjectController constructor sets those objects up. However, some objects do want to override the model and view. This is where the trouble comes in. Some objects need to fight, so they are CombatantGameObjects: public class CombatantGameObject : GameObjectController { protected new readonly CombatantGameModel model; public new virtual CombatantGameModel Model { get { return model; } } protected readonly CombatEngine combatEngine; public CombatantGameObject(GameObjectManager gameObjectManager, CombatEngine combatEngine) : base(gameObjectManager) { model = new CombatantGameModel(this); this.combatEngine = combatEngine; } public override void Update(long tick) { if (model.Health <= 0) { gameObjectManager.RemoveFromWorld(this); } base.Update(tick); } } Still pretty simple. Is my use of new to hide instance variables correct? Note that I'm assigning CombatantObjectController.model here, even though GameObjectController.Model was already set. And, combatants don't need any special view functionality, so they leave GameObjectController.View alone. Then I get down to the PlayerController, at which a bug is found. public class PlayerController : CombatantGameObject { private readonly IInputReader inputReader; private new readonly PlayerModel model; public new PlayerModel Model { get { return model; } } private float lastInventoryIndexAt; private float lastThrowAt; public PlayerController(GameObjectManager gameObjectManager, IInputReader inputReader, CombatEngine combatEngine) : base(gameObjectManager, combatEngine) { this.inputReader = inputReader; model = new PlayerModel(this); Model.Health = Constants.PLAYER_HEALTH; } public override void Update(long tick) { if (Model.Health <= 0) { gameObjectManager.RemoveFromWorld(this); for (int i = 0; i < 10; i++) { Debug.WriteLine("YOU DEAD SON!!!"); } return; } UpdateFromInput(tick); // .... } } The first time that this line is executed, I get a null reference exception: model.Body.ApplyImpulse(movementImpulse, model.Position); model.Position looks at model.Body, which is null. This is a function that initializes GameObjects before they are deployed into the world: public void Initialize(GameObjectController controller, IDictionary<string, string> data, WorldState worldState) { controller.View.read(data); controller.View.createSpriteAnimations(data, _assets); controller.Model.read(data); SetUpPhysics(controller, worldState, controller.Model.BoundingCircleRadius, Single.Parse(data["x"]), Single.Parse(data["y"]), bool.Parse(data["isBullet"])); } Every object is passed as a GameObjectController. Does that mean that if the object is really a PlayerController, controller.Model will refer to the base's GameObjectModel and not the PlayerController's overriden PlayerObjectModel? In response to rh: This means that now for a PlayerModel p, p.Model is not equivalent to ((CombatantGameObject)p).Model, and also not equivalent to ((GameObjectController)p).Model. That is exactly what I do not want. I want: PlayerController p; p.Model == ((CombatantGameObject)p).Model p.Model == ((GameObjectController)p).Model How can I do this? override?

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  • Squid handling of concurrent cache misses

    - by Oliver H-H
    We're using a Squid cache to off-load traffic from our web servers, ie. it's setup as a reverse-proxy responding to inbound requests before they hit our web servers. When we get blitzed with concurrent requests for the same request that's not in the cache, Squid proxies all the requests through to our web ("origin") servers. For us, this behavior isn't ideal: our origin servers gets bogged down trying to fulfill N identical requests concurrently. Instead, we'd like the first request to proxy through to the origin server, the rest of the requests to queue at the Squid layer, and then all be fulfilled by Squid when the origin server has responded to that first request. Does anyone know how to configure Squid to do this? We've read through the documentation multiple times and thoroughly web-searched the topic, but can't figure out how to do it. We use Akamai too and, interestingly, this is its default behavior. (However, Akamai has so many nodes that we still see lots of concurrent requests in certain traffic spike scenarios, even with Akamai's super-node feature enabled.) This behavior is clearly configurable for some other caches, eg. the Ehcache documentation offers the option "Concurrent Cache Misses: A cache miss will cause the filter chain, upstream of the caching filter to be processed. To avoid threads requesting the same key to do useless duplicate work, these threads block behind the first thread." Some folks call this behavior a "blocking cache," since the subsequent concurrent requests block behind the first request until it's fulfilled or timed-out. Thx for looking over my noob question! Oliver

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  • VS 2010 Layer Diagram Validation Error is Showing A Dependency That Doesn't Even Exist (AV0001)

    - by Dan
    I'm getting the following validation error on my layer diagram Error 65 AV0001 : Invalid Dependency : Weld.Interface.Core(Assembly) -- Weld.Interface(Namespace) Layers: Application Framework Core, Application Framework | Dependencies: Namespace Reference D:\Projects\Windows Projects\Weld\Weld\ModelingProject1\Weld.layerdiagram 0 0 ModelingProject1 Weld.Interface.Core: This assembly and namespace does not have a reference to Weld.Interface and only references .NET Framework classes Weld.Interface: This assembly and namespace does not have a reference to Weld.Interface There is no dependancy between these two layers in the dependency diagram. I am confused why I am getting this error. No dependency in the project or code, and no dependency is even setup in the layer diagram. Somehow the Validation logic in the layer diagram is seeing a non existant dependency and saying it is an error. Any ideas what either I might have missed or what is causing this problem?

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  • Images in database vs file system

    - by Jesse
    We have a project coming up where we will be building a whole backend CMS system that will power our entire extranet and intranet with one package. The question I have been trying to find an answer to is which is better: storing images in the database (SQL Server 2005) so we may have integrity, single replication plan, etc OR storing on the file system? One issue we have is that we have multiple servers load balanced that require to have the same data at all times. As of now we have SQL replication taking care of that but file replication seems to be a little tougher. Another concern we have is that we would like to have multiple resolutions of the same image, we are not sure if creating and storing each version on the file system would be best or maybe dynamically pulling and creating the resolution image we would like upon request. Our concerns are the with the following: Data integrity Data replication Multiple resolutions Speed of database vs file system Overhead load of database vs file system Data management and backup Does anyone have a similar situation or have any input on what would be recommended? Thanks in advance for the help!

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  • How to structure an enterprise MVC app, and where does Business Logic go?

    - by James
    I am an MVC newbie. As far as I can tell: Controller: deals with routing requests View: deals with presentation of data Model: looks a whole lot like a Data Access layer Where does the Business Logic go? Take a large enterprise application with: Several different sources of data (WCF, WebServices and ADO) tied together in a data access layer (useing multiple different DTOs). A lot business logic segmented over several dlls. What is an appropriate way for an MVC web application to sit on top of this (in terms of code and project structure)? The example I have seen where everything just goes in the Model folder don't seem like they are appropriate for very large applications. Thanks for any advice!

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  • What kind of data processing problems would CUDA help with?

    - by Chris McCauley
    Hi, I've worked on many data matching problems and very often they boil down to quickly and in parallel running many implementations of CPU intensive algorithms such as Hamming / Edit distance. Is this the kind of thing that CUDA would be useful for? What kinds of data processing problems have you solved with it? Is there really an uplift over the standard quad-core intel desktop? Chris

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  • How to avoid injecting dependencies into an object so that it can pass them on?

    - by Pheter
    I am interested in applying dependency injection to my current project, which makes use of the MVC pattern. My controllers will call the models and therefore will need to inject the dependencies into the models. To do this, the controller must have the dependencies (such as a database object) in the first place. The controller doesn't need to make use of some of these dependencies (such as the database object), so I feel that it shouldn't be given this dependency. However, it has to have these dependencies if it is to inject them into the model objects. How can I avoid having dependencies injected into an object just so that it can pass them on? Doing so feels wrong and can result in many dependencies being injected into an object. Edit: I am using PHP.

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  • Calling sp and Performance strategy.

    - by Costa
    Hi I find my self in a situation where I have to choose between either creating a new sp in database and create the middle layer code. so loose some precious development time. also the procedure is likely to contain some joins. Or use two existing sp(s), the problem of this approach is that I am doing two round trips to database. which can be poor performance especially if I have database in another server. Which approach you will go?, and why? thanks

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  • Business entity: private instance VS single instance

    - by taoufik
    Suppose my WinForms application has a business entity Order, the entity is used in multiple views, each view handles a different domain or use-case in the application. As an example, one managing orders, the other one digging into one order and displaying additional data. If I'd use nHibernate (or any other ORM) and use one session/dataContext per view (or per db action), I'd end up getting two different instances for the same Order (let's say orderId = 1). Although functionally the same entity, they are technically two different instances. Yes, I could implement Equals/GetHashcode to make them "seem" the same. Why would you go for a single instance per entity vs private instances per view or per use-case? Having single instances has the advantage of sharing INotifyPropertyChanged events, and sharing additional (non-persistent) data. Having a private instance in each view would give you the flexibility of the undo functionality on a view level. In the example above, I'd allow the user to change order details, and give them the flexibility to not save the change. Here, synchronisation between the view/use-case happens on a data persistence level. What would your argument be?

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  • When should I use Dependency Injection and when utility methods?

    - by Roman
    I have a Java EE project with Spring IoC container. I've just found in Utils class static method sendMail(long list of params). I don't know why but I feel that it would look better if we had separate class (Spring bean with singleton scope) which will be responsible for sending email. But I can't find any arguments which can prove my position. So, are there any pros (or cons) in using DI in this (rather general) situation?

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  • Considerations when architecting an application using Dependency Injection

    - by Dan Bryant
    I've begun experimenting with dependency injection (in particular, MEF) for one of my projects, which has a number of different extensibility points. I'm starting to get a feel for what I can do with MEF, but I'd like to hear from others who have more experience with the technology. A few specific cases: My main use case at the moment is exposing various singleton-like services that my extensions make use of. My Framework assembly exposes service interfaces and my Engine assembly contains concrete implementations. This works well, but I may not want to allow all of my extensions to have access to all of my services. Is there a good way within MEF to limit which particular imports I allow a newly instantiated extension to resolve? This particular application has extension objects that I repeatedly instantiate. I can import multiple types of Controllers and Machines, which are instantiated in different combinations for a Project. I couldn't find a good way to do this with MEF, so I'm doing my own type discovery and instantiation. Is there a good way to do this within MEF or other DI frameworks? I welcome input on any other things to watch out for or surprising capabilities you've discovered that have changed the way you architect.

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  • Why put a DAO layer over a persistence layer (like JDO or Hibernate)

    - by Todd Owen
    Data Access Objects (DAOs) are a common design pattern, and recommended by Sun. But the earliest examples of Java DAOs interacted directly with relational databases -- they were, in essence, doing object-relational mapping (ORM). Nowadays, I see DAOs on top of mature ORM frameworks like JDO and Hibernate, and I wonder if that is really a good idea. I am developing a web service using JDO as the persistence layer, and am considering whether or not to introduce DAOs. I foresee a problem when dealing with a particular class which contains a map of other objects: public class Book { // Book description in various languages, indexed by ISO language codes private Map<String,BookDescription> descriptions; } JDO is clever enough to map this to a foreign key constraint between the "BOOKS" and "BOOKDESCRIPTIONS" tables. It transparently loads the BookDescription objects (using lazy loading, I believe), and persists them when the Book object is persisted. If I was to introduce a "data access layer" and write a class like BookDao, and encapsulate all the JDO code within this, then wouldn't this JDO's transparent loading of the child objects be circumventing the data access layer? For consistency, shouldn't all the BookDescription objects be loaded and persisted via some BookDescriptionDao object (or BookDao.loadDescription method)? Yet refactoring in that way would make manipulating the model needlessly complicated. So my question is, what's wrong with calling JDO (or Hibernate, or whatever ORM you fancy) directly in the business layer? Its syntax is already quite concise, and it is datastore-agnostic. What is the advantage, if any, of encapsulating it in Data Access Objects?

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  • Advantage of creating a generic repository vs. specific repository for each object?

    - by LuckyLindy
    We are developing an ASP.NET MVC application, and are now building the repository/service classes. I'm wondering if there are any major advantages to creating a generic IRepository interface that all repositories implement, vs. each Repository having its own unique interface and set of methods. For example: a generic IRepository interface might look like (taken from this answer): public interface IRepository : IDisposable { T[] GetAll<T>(); T[] GetAll<T>(Expression<Func<T, bool>> filter); T GetSingle<T>(Expression<Func<T, bool>> filter); T GetSingle<T>(Expression<Func<T, bool>> filter, List<Expression<Func<T, object>>> subSelectors); void Delete<T>(T entity); void Add<T>(T entity); int SaveChanges(); DbTransaction BeginTransaction(); } Each Repository would implement this interface (e.g. CustomerRepository:IRepository, ProductRepository:IRepository, etc). The alternate that we've followed in prior projects would be: public interface IInvoiceRepository : IDisposable { EntityCollection<InvoiceEntity> GetAllInvoices(int accountId); EntityCollection<InvoiceEntity> GetAllInvoices(DateTime theDate); InvoiceEntity GetSingleInvoice(int id, bool doFetchRelated); InvoiceEntity GetSingleInvoice(DateTime invoiceDate, int accountId); //unique InvoiceEntity CreateInvoice(); InvoiceLineEntity CreateInvoiceLine(); void SaveChanges(InvoiceEntity); //handles inserts or updates void DeleteInvoice(InvoiceEntity); void DeleteInvoiceLine(InvoiceLineEntity); } In the second case, the expressions (LINQ or otherwise) would be entirely contained in the Repository implementation, whoever is implementing the service just needs to know which repository function to call. I guess I don't see the advantage of writing all the expression syntax in the service class and passing to the repository. Wouldn't this mean easy-to-messup LINQ code is being duplicated in many cases? For example, in our old invoicing system, we call InvoiceRepository.GetSingleInvoice(DateTime invoiceDate, int accountId) from a few different services (Customer, Invoice, Account, etc). That seems much cleaner than writing the following in multiple places: rep.GetSingle(x => x.AccountId = someId && x.InvoiceDate = someDate.Date); The only disadvantage I see to using the specific approach is that we could end up with many permutations of Get* functions, but this still seems preferable to pushing the expression logic up into the Service classes. What am I missing?

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  • How can I avoid properties being reset at design-time in tightly bound user controls?

    - by David Anderson
    I have UserControl 'A' with a label, and this property: /// <summary> /// Gets or Sets the text of the control /// </summary> [ Browsable(true), EditorBrowsable(EditorBrowsableState.Always), Category("Appearance") ] public override string Text { get { return uxLabel.Text; } set { uxLabel.Text = value; } } I then have UserControl 'B' which has UserControl 'A' on it, and I set the Text Property to "My Example Label" in the designer. Then, I have my MainForm, which has UserControl 'B' on it. Each time I do a build or run, the Text property of UserControl 'A' is reset to its default value. I suppose this is because since I am doing a rebuild, it rebuilds both UserControl 'A' and 'B', thus causing the problem. How can I go about a better approach to design pattern to avoid this type of behavior when working with tightly bound controls and forms in a application?

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  • Store html form on client or server while building?

    - by Brett
    Hi, I have a fairly complex html form enhanced via jquery. It has multiple tabs, within each one things like a html form builder, uploads, descriptions. There is lots of data, and as the user flicks around the various tabs I'm thinking of posting the data to the server. For example, the form builder, has about 10 properties for each field, as the user flicks between the various fields, an ajax request saves the current values, then loads a new set from the new field clicked on. When the user hits save, the idea is then on the server all these bits and pieces come together and become the live version (i may store them as a temp version while the user is working away). So I guess my question is, for complex forms where the same fields are re-used within the one form, does anyone attempt to save all this data locally and upload it in one hit or do most of you do little ajax post's and compile it all when the final save button is hit? b

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