I'm currently working on a Struts2 application that integrates a wizard / workflow in order to produce the desired results. To make it more clear, there is a business object that is changed on three different pages (mostly with AJAX calls). At the moment I'm using a ModelDriven action (that's extended by all the actions working with the same business object) coupled with the Scope interceptor. While this works okay if the user is handling data for only one business object at a time, if the user opens the wizard for different objects in multiple tabs (and we all do this when we want to finish things faster) everything will get messy, mostly due to the fact that I have only one business object stored in the session.
I have read a few articles about using a Conversation Scope Interceptor (main article) and about using the Scope plug-in (here). However, both approaches seem to have problems:
the Conversation Scope Interceptor doesn't auto-expire the conversations, nor does it integrate properly with Struts2;
the Scope plug-in lacks proper documentation and the last build was made in 2007 (and actually includes some of the ideas written by Mark Menard when he defines his Conversation Scope Interceptor, though it doesn't use the same code).
Spring's WebFlow plug-in seems a bit too complex to be used at the moment. I'm currently looking for something that can be implemented in a few hours time, though I don't mind if you can suggest something that works as needed, even if it requires more time than I'd currently want to spend on this now.
So, seasoned Struts2 developers, what do you suggest? How should I implement this?
Okay this isn't a fully baked idea. But seeing as no else has provided anything, here is what I would start with.
1) See if you can move the whole flow into a single page. I'm a big believer in the less pages is better approach. It doesn't reduce complexity for the application at all, but the user generally finds the interface a lot more intuitive. One of the easiest ways to go about this is by using the json plugin and a lot of ajax calls to your json services.
2) If you must transition between pages (or simply think it is too much client side work to implement #1) then I'd look to the s:token tag. The very first page to kick off a flow will use this tag, which will create a unique value each invocation. You will store a map in your session of model objects. An action will need to be provided with a model by looking it up from the session.
There are a couple challenges with #2. One how do you keep the session from getting too many domain objects? a) Well it might not matter, if the session is set to say six hours you can be rather sure that over night they will get cleared up. b) provided a self management interface which can get/set/list objects in the session. It might be what you thought of at first but it would let a worker do a certain amount and then stop and work on another. If the unit of work has some meaningful name (an invoice number or whatever) it could be quite useful.
A little more sophistication would be to move the model objects out of the session and into the service layer. At which point when inserted you would set an insertion time. You would probably need a manager to hold each type of model object and each manager would have a daemon thread that would periodically scan the map of domain objects and clean out expired ones.
You can figure out more complicated system by kicking a flow off with a token and then using another token on each page. "flowId" and "currentPageId" respectively, then you can graph allowable transitions.
Mind you at this point spring web flow is starting to look pretty good.
There is now a conversation plugin for Struts2 that achieves all these goals with very little work required by the developer: http://code.google.com/p/struts2-conversation/
It has:
-nested conversations
-cleanup of dead conversations
-convention over configuration with annotations and naming conventions
-inherited conversations
-fully integrated with Struts2
-the conversation scope can also be used by Spring IoC container-managed beans
Hope it helps somebody.
Related
We are happy users of the ASP.NET MVC framework and SQL Server, currently using LINQ-to-SQL. It serves our needs well with a consumer-facing application with about 1.4 million users and 2+ million active uniques per month.
We are long overdue to start logging all user actions (views of articles, searches on our site, etc.) and we're trying to scope out the right architecture to do so.
We'd like the archiving system to be its own entity, and not part of the main SQL cluster that stores the production articles and search engine. We'd like it to be its own SQL cluster, starting out with just one box initially.
To simplify the problem, let's say we just want to log the search terms that these millions of users enter into our site for the month, and we want to do so in the least cycle-intensive-way possible.
My questions:
(1) Is there an asynchronous way to dump the search terms to a remote box? Does LINQ support async for this?
(2) Would you recommend building up a cache of say 1,000 (userId, searchTerm, date) logging items in a RAM cache, and then flushing those at intervals to the database? I assume this method would cut down on open/close connections.
Or am I thinking about this entirely wrong? We'd like to strike a balance between ease of implementation and robustness.
1)Sure you can, there are different solution to achieve it. Linq is not the instrument you need.
2)There should not be any major improvement by doing it, the "logging" will be triggered only when a search is performed. You will end up with two calls instead of one, not a big deal.
A suggestion is to use AOP
You can create a clean and separate layer for logging using Postsharp (there are other alternatives though). You will then decorate your actions with the required logging attribute only when you need to trace what is passed to the action.
Main advantages with this approch are :
Logging logic doesn't reside inside your code (you don't need to change your methods code) but is executed before/after your method.
Clean separation of the Aspect from the target method.
You can easily switch on/off the aspects
AOP is a common practice specially when it comes to behavior that can be added to more than one method, like logging, authentication and so on. And yes it can be used in an async way.
1)I would suggest you to create an HttpModule that "catch" all the search terms used by the users. How and where you will dump those information(you said you will use a SQL box) it's another matter which is outside the scope of the module which should just catch the Search tems.
Then you can create a component that contains the login to store those information using Async call(or even a third part component like Log4Net )
2) if you want create a kind of batch insert caching all the information you need to store and at some point dump them on SQL I would use MSMQ or any other technology that support the Reliability: I think you want loose all those information in the case of a system-crash,etc
I'm new to Grails and web development. I started doing a project on Schedule management website stuff. I came across the Service concept that is provided by Grails. I understood the concept, but still I have confusion on when to use services.
For example, I need to implement a search module, where the manager can search for a user to find his schedules. In this case it will be good to implement it as a controller or as a service?
So,
When and where should I use Service?
To add to Grooveek's answer;
It is also nice to use Services to keep your Controllers nice and clean.
So Views just render data to the screen, Domain objects store state, Controllers route the user around the application, and Services perform the work.
I don't have enough reputation to comment on an answer or vote up so I have to provide an answer that really should be a comment. Anyways...
+1 on #tim_yates answer. Gotta love thin controllers. 2 things that I would add to the description of a controller:
Would be to translate parameters from the browser before hitting a service (e.g. Date, number, etc.)
Would be to translate data returned from services into something consumable for the views.
For me, ideally, services would never deal with translating a String parameter to it's inherent type. Or deal with building a model to be displayed on a view.
What and where I should use Service?
When you want your controller do to something that may be reused by other controllers
In our application we're doing a functional separation of service. We have a CorePersistanceService, which provides method to create, delete, update and manipulate Core Domain Classes (core for us).
I think persistance services are a good way to reuse GORM code throughout Grails code. You can create method in domain classes, but I don't like that, it's way less maintanable I think
We have a PDFService class for our PDF creation, a SolrService which connect to Solr, a Statisticservice that gather all our methods which collects statictics on our datas
Services in Grails are a manner to gather methods around a particular functional theme, in order to give possibility to reuse them in controllers (I forgot to mention our SecurityService, which is a pretty good Cross-Applications Example)
What's the best way to handle a conversation-based web flow in Rails? I'm wondering if there is anything similar to http://grails.org/doc/1.0.x/guide/single.html#6.5%20Web%20Flow
A web flow is a conversation that spans multiple requests and retains state for the scope of the flow. A web flow also has a defined start and end state.
Web flows don't require an HTTP session, but instead store their state in a serialized form, which is then restored using a flow execution key that Grails passes around as a request parameter. This makes flows far more scalable than other forms of stateful application that use the HttpSession and its inherit memory and clustering concerns.
Web flow is essentially an advanced state machine that manages the "flow" of execution from one state to the next. Since the state is managed for you, you don't have to be concerned with ensuring that users enter an action in the middle of some multi step flow, as web flow manages that for you. This makes web flow perfect for use cases such as shopping carts, hotel booking and any application that has multi page work flows.
I just started looking into this question myself, but from the perspective of DRYing up view code. Not finding much, but there is:
https://github.com/jcoglan/action_flow which may take some rejigging for newer Rails
http://rubyforge.org/frs/?group_id=2769 which has no docs and looks alpha
The age and activity levels on each project lead me to believe they've been abandoned.
Wiring up flows as point-to-point links of imperative calls with routes/controllers/actions/views that make fixed assumptions about where they fall in the chain (or worse, entrain lots of conditionals to deal with different flows), is certainly one way I've seen it done. Still wondering if that is the preferred stock in trade in the Rails world, or if there are other idioms that supplant it that I just don't know about.
I want to decouple the MVC web pages, and the order in which they are displayed. Generally speaking, I think these are the scenarios I need to address, but I'm lot locked into a particular way of thinking. I just want to find a pattern or an object that will assist in controlling the flow.
Sample Page Sequencing:
Forward only: The user can only progress forward though the workflow, until finished.
-- Special case: If a user navigates to, or manually enters in an invalid URL, then the system should respond accordingly (redirect to current step)
Forward - Back (read only): The user may progress through the wizard, but the back button allows for read only view of previous data.
Forward - Back (read write): The user may go back and update data in previous entries. This may cause the workflow to reset to the prior state.
For those times when a user may enter into more than one "valid state", the forward concept above should accomodate that (such as in a State Machine)
Question:
How would I implement this page control flow in a MVC3 / WF4 application?
We're ourselves considering an architecture similar to your proposal.
The MVC part is mainly auto-generated code with Llblgen Pro + custom ASP.Net templates,
therefore, we want to control the business logic (and page workflow) from somewhere else.
We're still studing the final decision, and WF 4.0 is one candidate (as it's quite easy to create a reusable activities' library), but Stateless state-machine seems an really simpler approach and easier to maintain.
We already have an ORM-generated persistence layer, therefore, it's not a big deal to resume the state of a paused workflow any time in the future.
Have a look at Stateless and let us know if it fits.
An example explained: http://blogs.msdn.com/b/nblumhardt/archive/2009/04/16/state-machines-in-domain-models.aspx
Actualized VS 2010 code with examples: https://github.com/haf/Stateless
I explored this idea. In my opinion, Workflow Foundation would only be worth it if your process takes a long time (like days).
Otherwise, you'll find that writing some kind of custom code (like a State Machine) is a much easier solution than trying to incorporate Workflow Foundation.
However, if you're looking for examples, here's one:
http://code.msdn.microsoft.com/Windows-Workflow-233b5e3c/sourcecode?fileId=22211&pathId=1790082120
In my pet project I want to have a user system with the following requirements:
It needs to work with Db4o as a persistance model
I want to use DI (by means of Turbine) to deliver the needed dependencies to my user model
It needs to be easy to plug in to asp.net-mvc
It needs to be testable without much hassle
It needs to support anonymous users much like SO does
I want Authentication and Authorization separated (the first can live without the second)
It needs to be safe
I'm aware I'm putting a few technologies before functionalities here, but as it is a pet project and I want to learn some new stuff I think it is reasonable to include them as requirements.
Halfway in rolling my own I realized I am probably suffering some NIH syndrome.
As I don't really like how needlessly complex the existing user framework in asp.net is, it is actually mostly only all the more complicated stuff regarding security that's now giving me some doubts.
Would it be defendable to go on and roll my own? If not how would you go about fulfilling all the above requirements with the existing IPrinciple based framework?
It sounds to me like what you want to do is roll your own Custom .NET Membership Provider.
It will allow you to use the built-in ASP.NET Authentication/Authorization attributes on your Controller Actions while giving you complete control over the implementation inside the provider (which will allow you to code it to meet the requirements stated above).
Direct from MSDN...
Implementing a Membership Provider
I think you recognize where the thin parts in your consideration are: namely in that you've included how to do what you're doing as motive in why you're doing it and the NIH (funny: I'd never seen that before) issue.
Putting those aside, your provider is something that you could potentially reuse and it may simplify some of your future efforts. It should also serve to familiarize you further with the issue. As long as you understand the ASP.NET framework so you can work with it too if you need to (and aren't specialized such that you don't know what you're doing if you're not using your tool) then I believe you've already crafted your defense.
As DOK mentioned, be cautious that you're not rolling your own here to avoid a larger task at hand in whatever your other functionality is. Don't let this be a distraction: it should be something your application really needs. If it's not, then I'd lean towards focusing on your software's core mission instead.
If you go ahead and create your own custom solution, you will have a better idea of how difficult it is and what features you want. This will help you to evaluate off-the-shelf solutions for future projects.
OTOH, spending time developing functionality that is already readily available means you won't be spending that time working on the major functionality of your project. Unless authentication and authorization are a major component of your project, you might consider investing your time, and expanding your knowledge, in another area.
I too am working on a pet Project using ASP.net MVC and db4o and did the same thing, so you're at least not alone in going down that route :). One of the biggest reasons for me to start playing around with db4o as persistence layer is that especially authorization on field level (i.e I'm allowed to see Person A's first name but not Person B's first name) is though to achieve if you're forced into complex SQL statements and an anemic domain model.
Since I had complex authorization needs that needed to be persisted (and synchronized) in both db4o and Solr indexes I started working on rolling out my own, but only because I knew up front it was one of the key features of my pet project that I wanted 100% control over.
Now I might still use the .Net Membership provider for authentication but not (solely) for authorization of objects but only after i POC'd my authorization needs using my own.