I'm trying to wrap my head around navigation rules in JSF2.0. If I have a button with an action method, is the purpose of the navigation rule to move me to a 'results' page? This seems too simple I guess, couldn't you just f:ajax and update a result area on the page? What is the real purpose of navigation rules and how can one effectively use them in JSF 2.0?
Bonus points for metaphors that use ponies.
The point of navigation rules is that they allow the server to decide, based on the data in a request, which view to show next - a results page, an error page, the next of several possible following pages in a workflow, whatever.
They're not always useful - most applications only have linear workflows and show errors in-page so that you never really need navigation rules. I've always considered it a bit weird that such an (in my experience) rarely-useful feature became a core concept in Struts and JSF. But it would certainly be useful for a workflow with lots of branching logic.
As for AJAX - that's a different use case. If you're switching to a completely different view, you should do a full update rather than use AJAX.
Why not let your pony jump you on this site and find out the basics from a good tutorial :)
Related
I have few gwt mvp design related questions:
Can we use event bus to switch views from one presenter to other via controller using custom event?
If above is true, can the custom event (say changeViewEvent) contain name of next view, on the basis of which controller can take a decision, which presenter to show?
Is it a good design to make views reusable(as a widget) in an application, though i don't agree with this, but will be happy if someone has any thing to mention in favor of this.
PS: all my views make use of custom widgets and there is no gwt specific widgets(buttons, checkbox etc...) in views.
You can do anything you want, but you have to consider the consequences. For example, if you switch views without creating a history event, a user may be thrown out of your app when a user hits a back button expecting to see the previous view.
I very much like the Activities and Places design pattern. It takes care of all of the issues (history handling, bookmarks, tokens, etc.) You can also extend it to add animation effects when switching views on mobile devices - mgwt does that.
I have few gwt mvp design related questions :
Can we use event bus to switch views from one prsenter to other via controller using custom event ?
This is a bad practice, unless you have real good reasons to do that. Since you're changing the view without having an impact on the url, you won't know what is a the state of a view at a choosen moment, you cannot get back to a previous view in an easy way, and finally, people will have difficulties reading the code, since you're out of the "standard".
The only reference for you should be the url, you cannot assume data is loaded neither the applicatio is in a given state: each and any view may be the start of the navigation story for your users, so if you get information from any other source than the Place, you're probably doing wrong, especially if your source is an event. the only special case here is you don't want users to enter your app in a certain view state, so you 'impose' that another url is called before, and restrict the access to the view through an event starting from a given application state
If above is true, can the custom event (say changeViewEvent) contain name of next view, on the basis of which controller can
take a decission, which prsenter to show ?
as said before, you're reinventing the wheel. It's far better to adapt to the existing mechanism that is well thought and covers the majority of cases. You can put a json formatter to tokenize your url while developing so it's not a nightmare to put variables in. And when you're done, create a nicer regular url format
Is it a good design to make views reusable(as a widget) in an application, though i don't agree with this, but will be happy if
someone has any thing to mention in favor of this.
depends on what you call a View. if it's the activitie's view then youm might need that in very few cases, it's better to inherit a basic view and fork its children for each activity (even if the view does nothing, time will show it will evolve differently): this is better since the base view contains what is common without the specifics of each child activity.
Finally if you mean a composition of widgets when you say, a view, then you should definitely reuse them, it will make you obliged to improove your widgets and compositions to be in a constant improvement, this will heop you for the rest of the project, and maybe for other projects
I'm building a page that has a search box that will populate a grid on the same page. There is also a button the user can select to bring up a "window" (JQuery UI "pop-up" in the same page) that lets the user configure said grid.
These are two separate forms but I don't want what was submitted as part of one to undo the other (so when the user submits to change the grid layout the search needs to re-run as well.
I'd rather not store things in session for this since that brings with it its own issues (search results may be large, shouldn't be saved when the page is re-entered later, etc.).
I've considered doing "one large form" (i.e. surrounding all the inputs) for the entire page that is backed by a form backing bean. I would then use which button is clicked to determine the action to take. There will eventually be other buttons on the page as well to add more functionality. This would be similar to how .NET (non-MVC) handles things.
I'm interested in how others may have solved similar challenges. Are there potential issues with my approach that I'm not seeing? Better ways that work with the framework?
What do you mean with:
but I don't want what was submitted as part of one to undo the other
. Are you referring to posting the form and loading the whole page, which in turn will "reset" the other form?
If that is the case I would still keep one page with two forms and make the posts using Ajax (as you may know jQuery makes this a breeze). Upon receiving a response for either call you will need to update the other form accordingly.
Note that you may still have your forms in two separate views if it helps keeping the code clean and then pull their html with Ajax calls into another view. But my point is that at the end I would still keep both in one page since it sounds like they depend on each other so updating one when the other changes may be easier this way,
Let me know if I misunderstood your question.
I have a web-app in Java, Spring, Struts 2 and Hibernate, that servers multiple clients. Each client with multiple users. To create a personal feel for each client, i would like to customize the header for each client.
I'm using sitemesh as decorator, and am looking for tips or examples or someone who can point me in the right direction as to how to acomplish this in the best practice.
What would you think? Should i just code it direct in the header.jsp? Extracting the info about the logged in user and from that create a custom header by code? Or is there a more clever solution out there?
Thanks!
Update:
To further clearify what i want:
Different properties-files for each client is not an option. We are looking at potentionally hundreds of clients. It needs to be database-driven. But thats the easy part. There is no problem storing the information in db and extracting it when needed.
What im trying to figure out is if there is some sort of standard way of doing this. Some sort of filter or Action that is run before the sitemesh decorator that will provide the decorator with the correct info?
Struts2 provides application scope, for variables which are global to the application.
Load all the customer specific strings into #application scope (I would use spring to do this when the application starts up). From there referencing the strings would be pretty obvious: #application.greeting I don't like the idea of using an interceptor because there is nothing to intercept. I would say for what you are doing application scope is the perfect place. If it is a single client system I can see no reason why anything would be stored in application scope.
Aside: Tiles uses a different template paradigm than site mesh, and they have slightly different purposes. As such the two can be complimentary. Tiles relying on XML definitions can have it's definitions stored in a DB and is definitely less computationally intensive, however where there is interplay between different UI components... or disparate elements appearing on the page you need to use sitemesh. So for basic template needs tiles does everything and is quite easy to understand but say you wanted to make add a certain widget in the middle of the page which relies on JS which needs to be added to the header it would be tricky to do this in Tiles (although the obvious solution is to just roll the JS functionality into one JS file for all possible uses in a particular part of the site).
Asside 2: By using a view technology such as velocity or freemarker in conjunction with tiles it is conceivable to move the entire view layer into a database. I just thought I would mention that as for some maintenance issues that could be extremely beneficial.
Sitemesh makes it's decisions about what decoration to use based upon the requested URL string, so unless you have a reference to the client in every url - either as part of the main url string or as a known parameter, then Sitemesh out of the box is not going to help.
This leaves a few possibilities to achieve what you want;
1) Write a filter that runs before Sitemesh that adds, for example, "&clientId="xx" to every incoming request.
2) Dive into the source code for Sitemesh & look for where Sitemesh finally makes it's decision about which decorators to use and override it. I've never tried this so I don't know how practical this might be.
3) Make the style sheet definition in your jsp pages an OGNL expression and provide that information in a base action class that all your actions extend. In this way you end up with (potentially) a different CSS file for each client and you provide your customisation via CSS.
Hope that this helps.
I have just read the description of MVC desing pattern and I havesome questions: I am Android developer (junior), and I want to make my code more clear. So, should I use MVC for it? And must every activity has own model? Is there any good tutorial for it? Thank you.
It's already implemented. MVC pattern on Android
you need not to do anything, As Android is prebuilt MVC
MVC is kind of an idea more than a specific way of doing things (like a 1-to-1 relation between activities and models). The idea is to separate the model, view, and controller, so that stuff makes sense.
In Android, more than one activity can refer to a single model (for example, an activity with a list of houses you can search on, an "edit house" activity, and a map that shows them as points in their coordinates). So, to answer your second question: no, they don't need to have their own model.
And yes, you should use MVC, if it makes sense. Just think about your models as a separate entity from the actual application, and your activities as "users" of the models.
On Android, I've found the MVP (Model, View, Presenter) pattern to be a more direct correlation with the overall system architecture. Your activities comprise the Views, which in the MVP setup are responsible for managing their own events and controlling their own appearance. The presenter serves as a facilitator between the model and the view, providing the data when the View requests it. Depending on your needs, the presenters may or may not be a service. As for the View/Model ratio, it really depends on what you're trying to show on your screen at any one point. When android was running on phones only, it made sense to have pretty much a one to one correlation between Activities and your model. Now, the normal case is to have a one to one correlation between your model and your fragments, which your activity then marshalls about by showing the appropriate fragments.
If you want to do MVC, though, again, now that fragments are a tool in the toolbox this is much easier than it once was, especially with well developed event system (such as the one included in RoboGuice) - Think of your fragments as your Views, and your activities as controllers - Ordering your views about, providing them data from the model, and handling transitions to other controllers.
The choice of pattern depends on your needs - if one's application is to be heeavily service driven, MVP is probably a better way to go. If, however, the app is just a thin client over a database, then MVC might be easier. It's all up to you :)
'get started' resource for MVP : http://www.jamespeckham.com/blog/10-11-21/MVP_on_Android.aspx
I am embarking on my first GWT app and I am using GWT Platform which is based on the talks Ray Ryan gave at Google IO about MVP. I am trying to structure my app the correct way. My understanding is that I have a presenter for every view in the app and every view is essentially a page in the app.
Where I get confused is how to handle non-dynamic pages. Like say you have just an 'About' page(like the one on Stack Overfliw) which has no interactivity at all. Would you still define a presenter and view for that?
The other part of this question is do you only ever have one html file in the app that all the compiled javascript is loaded into?
yes, for the second question. only one html page. all you do is switch panels inside that html.
when you do a RootPanel.get( ['id'] ).add() you're actually changing only a part of the page.
as for about page, not really needed to implement a presenter.
a presenter defines 'events' that will happen on your view, so your view can call those methods on your controller. if the view does not have any events happening, it doesnt need a controller. no point implementing nothing :)