SpringMVC - Change view when accessed by Mobile - java

I was wondering if someone has already solved this. I have a SpringMVC app and we are adding support to WebKit type mobiles (iPhone and Android basically) so I was wondering someone has found an elegant way of defining specific views depending on the client that sent the request.
I know that a simple if in a Controller implementation can do the trick, but I'm looking for something more flexible/elegant (a specific ViewResolver implementation, or an interceptor maybe).
Help will be greatly appreciated... as always =)
This is a pretty old question. What you need to do is use Spring-Mobile to achieve this in a standard elegant manner

Update: look at spring-mobile
Original answer:
It would be pretty simple to create a custom ViewResolver that resolves views based on the User-Agent header.
here is a list of mobile user agents (page removed from wikipedia). Check the header against it, and resolve a mobile view.
if the user-agent is not a mobile, then return null, thus letting other resolvers resolve a view.
make sure your resolvers are defined (in the spring xml) in the proper order, so that the mobile resolver is consulted first.

Like #Bohzo and yourself already said spring-mobile is the way to go.
As of version 1.1 you can use the LiteDeviceDelegatingViewResolver to configure the type of behavior you're describing.
Device Aware View Management
http://static.springsource.org/spring-mobile/docs/current/reference/html/device.html#device-aware-view-management
Spring Mobile includes AbstractDeviceDelegatingViewResolver, an abstract ViewResolver wrapper that delegates to another view resolver implementation, allowing for resolution of device specific view names without the need for a dedicated mapping to be defined for each view. A lightweight implementation is provided, which supports adjusting view names based on whether the calling device is normal, mobile, or tablet based.
Within your application, you can then create alternate views for normal, mobile or tablet devices, and given the proper configuration, Spring Mobile will adjust the view name to resolve to the correct one. This happens internally, without the need to add conditional logic through your controllers.

Ok I found a more specific answer. There is a problem with the solution that Bozho proposed. the fact that the ViewResolvers no longer have access to the HttpServletRequest. There is a way to access the request but its kind of dirty IMHO.
So that said, this is a very elegant and easy to implement solution. Basicly it involves a custom ViewResolver (as Bozho proposed) but it adds an handlerInterceptor that adds the User-Agent to the model so you no longer have to add it manually.

To access current Request inside ViewResolvers.
HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.currentRequestAttributes())
.getRequest();

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Pretty Faces (or Rewrite). http://www.ocpsoft.org/prettyfaces/
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This will be far more secure and easy than handling the uri changes per request.
HTH

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Updates
Some nice guys tell us to use observable pattern to do this. The following snippets is my code. But it does not work as expected. The ui cannot be refreshed.
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http://en.wikipedia.org/wiki/Observer_pattern
In case you parse the received data, have a look at the Eclipse Databinding framework.
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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?
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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.

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