What is the advantage of using Direct Web Remoting over a REST web services design?

Question

I have an enterprise Java web application deployed in tomcat. I am looking for ways to integrate a HTML & JS UI with the mid tier java code. So far, from looking around I have read that there are two ways to do this which fit my requirements :

1) DWR - Direct web remoting

2) Use REST web services.

I am not sure which approach to use.

Edit: What is the advantage of using DWR over a rest WS design?

Is there a better approach available? Some people asked me to have a look at GWT, but I am not sure if these are scalable.

Edit 2: I will most likely be using dojo for the UI development(Works well with REST/DWR??), and I want to keep the java code chages minimal. I understand that by using web services, I would have to write an additional WS client layer on top of the existing java code.

Also, the usual enterprise needs, performance, scalability, etc.

Answer 1

Ok so you're building a web client frontend to your java backend, there are a few ways to go about this:

• You want to use java standards as much as possible, preferably living in the java EE world: JSF . You will need some knowledge of HTML, XML and perhaps even javascript (though limited). Personally I have had a pretty buggy experience with JSF+richfaces to the extent that I don't use it anymore.

• You are very well acquainted with java desktop application development but don't know much about javascript: vaadin : it allows you to write plain java using desktop application terminology which will be compiled to javascript. Currently I am working on a big vaadin project and it is very nice to be working with pure java in eclipse, the downside is however that you are far removed from the actual frontend, so tweaking can be tricky. Additionally everything is stored in sessions (afaik) and scales poorly.

• You are primarily a frontend person with unrivaled javascript skills: use a REST interface in java and a pure js/html/css frontend. Personally I think this is the cleanest design and I have designed a few of my own applications like this. The downside is that managing large javascript projects tends to be hard because...well...javascript sucks. The upside is that this will always be the fastest most lightweight option available to you.

Ideologically I would definitely suggest the last approach but this can be hard for large projects. If you have the hardware to throw at it, vaadin is a nice option. My JSF 2 experience was a bit disappointing due to the bugs in (necessary) third party libraries like richfaces.

PS: I have never heard of DWR but the last stable release seems 2 years old and all it seems to do is expose java code as javascript methods which can be better handled with a REST interface.

Answer 2

Open interface standards like REST and SOAP make it easy to build code to consume these services if you are using frameworks to build a REST Client and a SOAP client code respectively. But the point is that you need to have this client code to make calls to these services.

DWR on the other hand, generates this client code. Your java classes are ready to be called (like you would do in Java).