When comparing Play Framework vs Grails, the Slant community recommends Play Framework for most people. In the question“What are the best web frameworks to create a web REST API?” Play Framework is ranked 15th while Grails is ranked 25th.
Ranked in these QuestionsQuestion Ranking
Pro Asynchronous Core
Pro Interoperable with Java
It's like Java, but more Haskell-y.
Pro Good documentation and a great community
Play has quite a large community which provides numerous tutorials and videos related to developing with Play.
The Play official documentation covers many things, such as the framework itself but also specific stuff such as Akka, SBT and Netty.
There are also many big companies that base their main sites around Play, one of them is LinkedIn which provides third-party documentation on a regular basis.
Pro Play is an extensive ecosystem
Play uses Akka for concurrency, Scala for a templating engine, Netty as a client-server framework and SBT (Simple Build Tool) for building. And they all come out of the box.
Play also comes with the option to scaffold your applications. Play is an all-embracing ecosystem designed to increase developer productivity and shorten development times.
Pro Simple for beginners
Play is very simple to get started. The documentation is very helpful for beginners and advanced users alike and the official website has a great "Getting Started" tutorial to begin developing with Play.
Pro Readable code
Play framework's convention over configuration methodology makes most Play projects have a very similar structure. This means that the code written for the framework is very readable. This enables a developer to switch between applications without having to relearn the ecosystem for every project. The built-in templating system also helps with code and makes it possible to have a very low count of lines of code.
Pro Can use Java, one of the most widely known languages
Java is one of the most widely known languages, so people coming from that background can jump right in and not have to learn a new language syntax.
Pro Good Websocket Support
Pro Grails is highly scalable
Grails is an abstraction over Spring and Hibernate. This makes Grails applications fast and scalable. This is because both Spring and Hibernate are themselves scalable.
Pro More than 900 plugins
Grails is a full-stack web framework, not just MVC. It contains a lot of stuff out of the box, but it doesn’t enforce it. It contains over 900 plugins which provide a Groovy API for a lot of useful and well-known Java libraries. And what is more important is that they are super easy to install!
Pro Very fast setup and scaffolding
Setting up a new project is quite fast and code generation (scaffolding) saves you a lot of time. It also uses a convention over configuration principle which helps you bypass all the configuration trouble.
Grails also comes with a reloading mechanism out of the box.
Pro Easy to use
Grails is designed to be a rapid development framework with a straight learning curve. It advocates convention over configuration. Extensibility is very simple when using plugins (there is a lot of them). One command in the console – and all the dependencies and configurations are managed for you.
Pro Great UI design alternatives
Pro Great documentation and community
The Documentation section is actually a wiki, which can be modified by any logged in user. It has an official manual, tutorials, screencasts, a sample app and much more. If that does not do it for you, then there are countless third-party tutorials, more than 12k questions on SO and much much more
Con Backward incompatibility
The jump from Play 1 to Play 2.x caused a lot of confusion. While it is important to have some kind of evolution, sometimes it causes backward incompatibility which can create some problems. It makes tutorials or modules made for the old version obsolete. This can make it hard for beginners to find useful resources. The template engine which used Groovy now uses Scala.
Con Not as many resources to learn
Other languages and frameworks have countless tutorials, books, moocs, etc. Java and Play does not have nearly as much.
Con Grails is a fairly complex framework
Grails is a pretty heavy piece of software. It's functionality is covered by GORM (Grails' Object Relational Mapping) which is a facade for hybernate and by Spring MVC.
Everything is glued by core Spring and furthermore, Grails adds another level of abstraction on top of all this. These things may create some trouble down the road when debugging.
Con Too obtuse and JVM centric
If you're a big fan of the JVM and have mastered all its goofy quirks, Grails might be a good choice, but there are other frameworks out there that are more straightforward and easier to use.