When comparing Vaadin vs ActFramework, the Slant community recommends ActFramework for most people. In the question“What are the best Java web frameworks?” ActFramework is ranked 5th while Vaadin is ranked 7th. The most important reason people chose ActFramework is:
There are two aspects of performance: how quick a developer can deliver a feature and how fast the app is running on the product server. Act is designed to deliver excellent results in both aspects. With unbeatable developing experience, Act makes it very easy to release a feature; on the other side Act is very fast in runtime. Check out this 3rd party benchmark [result](https://github.com/networknt/microservices-framework-benchmark).
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Pros

Pro Compiles Java to JavaScript
Vaadin uses GWT to compile Java code into JavaScript. This means that developers using Vaadin can write both frontend and backend code in Java.
Pro Easy to use
Vaadin has a 'design mode' which allows developers to drag and drop components into a canvas and then provide the logic for every component. There are also a lot of third party tutorials and guides which help with the initial learning curve.
Pro Top notch documentation
The book of Vaadin is a must have for every developer that uses Vaadin to make web apps. It is an excellent reference manual and all around a great tool for every Vaadin related need. You can find and download the pdf online or get it for free in almost any Vaadin sponsored conference.
The online documentation is also very good. It has some tutorials and video guides.
There is also a vibrant community which sorround Vaadin, for any problem you may have there is a big chance that someone has already asked and answered that question on StackOverflow or in the Vaadin forums. If not, it will probably be answered quickly if you ask it.
Pro Modern, configurable theming
Vaadin comes with the Valo Theme, a Sass-based theme and engine that calculates styles based on configurable variables and making it easy to define a completely new theme with a few lines of SCSS.
Pro Easy to develop prototypes quickly
Vaadin has what is called the Vaadin Directory which is a repository of downloadable Vaadin components which can be easily used for development. To use something from the repository, you need to download the JAR file and add it to the project.
Pro Performance
There are two aspects of performance: how quick a developer can deliver a feature and how fast the app is running on the product server. Act is designed to deliver excellent results in both aspects. With unbeatable developing experience, Act makes it very easy to release a feature; on the other side Act is very fast in runtime. Check out this 3rd party benchmark result.
Pro Hot reload
You never restart while you're working on your Act application. Act's hot reload feature is fast and stable, it makes you feel like dealing with scripting language frameworks like Django or NodeJs. Watch this video and feel it.
Pro Scalability
Act is built as a stateless framework. It supports horizontal scale.
Pro Secure
Act is built as a secure product. It provides built-in CSRF/XSS prevention mechanism. And act-aaa makes it very easy to implement Authentication/Authorization/Auditing in your app.
Pro Superb RESTful support
Act makes creating RESTful service a kids game. It features AdaptiveRecord (allows front end to drive the data structure), JSON response control (just declare the fields you want to present or hide) and RESTful URL routing with path variables.
Pro Easy to deploy
ActFramework is not a servlet framework and there are no requirements on containers/app servers. It has a small package size (a helloworld distribution package size is less than 20 MB), a small memory feet print (a helloworld app heap usage is less than 20MB) and a fast boot up speed (a helloworld app starts in less than 3s).
Pro Templating
Act's view architecture is very flexible and support using multiple view engines in your app. The default template engine is Rythm, a very developer friendly and powerful template engine. Act also support other templating solutions including freemarker, velocity, thymeleaf, and mustache via plugins.
Pro Configuration for multiple environments
Act supports load configuration from a common dir and then overwriting it from a profile dir. Makes it very easy to manage configurations in different environments (e.g., dev, uat, sit, prod) Watch this video to see the innovative way Act delivers its configuration support.
Pro Concise and expressive
Act does not require you to put Annotation when it is able to infer the intention from other parts of the code, i.e., you don't use @PathVariable
or @RequestParam
to tell Act the binding parameter name. And you don't need a ModelMap
to bind variables to render argument names. Act has sophisticated byte class scanner to detect the variable names to do bindings automatically.
Pro Comply to standards
Act's IoC is built on top of Genie, a fast dependency injection library that fully supports JSR330, and Act's validation solution is built on top of JSR303. Act is NOT an odd framework to most Java developers. Unlike Play1.x, ACT applications follow the standard maven project structure and it is very easy to integrate other Java libraries.
Pro Database access
Act's DB layer is extremely easy to use. It supports SQL databases (through ebean orm) and MongoDB (through morphia). Using multiple datasource can never be that easy with Act's DB layer. Go here for more information on this.
Pro Fast and flexible routing
You can configure your routing in either Spring MVC/Jersey style with annotation or Play style with route table or a combination of both. Act's routing supports RESTful URL path variables, optionally validated with regular expressions.
Cons
Con Weak scalability
Since Vaadin stores the UI state and logic in the server, this means that for every user interaction a request needs to be sent to the server and the client needs to wait so it can know how to react. This leads to higher traffic and load times.
Con Incomplete microservice support
Although Act is built to be a great framework that supports microservice development, it lacks some of the key features at the moment, like sending requests to other microservices from within the app, service governance, and messaging handling.
Con Very small community
As of February 2017, Act is a brand new framework (even though the project started at the end of 2014). Community is still forming.
Con Functional testing support still under development
Developers are still working on innovative functional testing support for Act.
Con Documentation is still being written
Act's documentation is still under development.
