Avatar At A Glance
|Project Avatar (Source: avatar.java.net)|
Thin Server Architecture
What is really in Avatar?
All that is left on the Server – Services
An service extends either a REST, WebSocket or Push (SSE) abstraction and it’s life-cycle is completely handled by the framework. Service implementations can leverage built-in Node modules as well as most third-party modules. Thanks to Nashorn’s support for direct invocation of Java code you can also use most Java libraries directly.
The Client Side – Views
Putting it all together. A Simple Example.
Oracle provides a decent set of examples and documentation for Avatar which basically is enough to get you started. First thing to try it out yourself is a JDK 8 Early Access Build for your OS. At the time of writing I tried it with the latest Developer Preview b118. After installing you need to get the latest GlassFish Open Source Edition 4.0 server and unzip it into a suitable location. Make sure it runs with the installed JDK 8 by either putting <jdk8>/bin to your PATH environment variable or adding the following entry to the <gf4>/glassfish/config asenv.bat/conf
No go ahead to download latest avatar-1.0-ea.zip and expand it to the <gf4>/glassfish/ directory. After that you need to set a AVATAR_HOME environment variable and point it to the <gf4> install directory. And make sure to add %AVATAR_HOME%glassfishbin to your PATH environment variable.
If all of that is done you can switch to your workspace folder and issue the following command to have Avatar creating a simple example app for you:
avatar new --example=hello
It creates a basic “hello” application which only consists of a view. It is a good place to start exploring and you can directly start your Glassfish instance afterwards and deploy the application as you would with every typical Java EE application:
asadmin deploy hello
|The “hello-example” app.|
Pointing your browser to http://localhost:8080/hello will display the application. You can start editing the view located at <workspace>/hello/view/src/hello.html directly. While the server is running Avatar takes care of re-compiling it directly for the next request. This ensures a rapid development. This behavior is controlled by the “debug=true” property in the avatar.properties file and can be altered for productive systems. Further on, setting it to false causes all .js and .css files to be minimized before delivery.
At least if you first download and add the required YUI Compressor (jar download) to Avatar first. Due to license restrictions it hasn’t been bundled. Simply put it into <gf4>/glassfish/modules/avatar-ext/lib. You might need to create that directory first.
Beside this very simple example without any service at all there are more complex ones available with the distribution at %AVATAR_HOME%/Project-Avatar-examples/. For convenience reasons there is a complete examples.ear available which can be directly deployed and tested. To access the samples simply prefix the example name with “demo-“. So the “rest” example can be accessed via http://localhost:8080/demo-rest/.
|TodoMVC – Example App with Avatar|
You have to look out for different features to be showcased in the different examples. If you want to know how Avatar handles persistence you can exactly look into the rest example which uses a FileDataProvider to save the items. Another interesting example is the TodoMVC based app (http://localhost:8080/demo-todo/). It showcases a more complex view which also has been styled.
What is next?
I wish you a happy holiday season and a new year filled with peace and prosperity.
Author: Markus Eisele
Markus Eisele leads the developer adoption team for EMEA at Red Hat. He has been working with Java EE servers from different vendors for more than 14 years, and gives presentations on his favorite topics at leading international Java conferences. He is a Java Champion, former Java EE Expert Group member, and founder of JavaLand. He is excited to educate developers about how microservices architectures can integrate and complement existing platforms.
He is also the author of “Modern Java EE Design Patterns” and “Developing Reactive Microservices” by O’Reilly. You can follow more frequent updates on Twitter @myfear.