Getting started with grails

Remarks#

Grails is a very powerful rapid application development (RAD) framework, for the Java platform aimed at multiplying developers’ productivity thanks to a Convention-over-Configuration, sensible defaults and opinionated APIs. It integrates smoothly with the JVM and the Groovy language allowing you to be immediately productive whilst providing powerful features, including integrated object-relational-mapping (ORM), Domain-Specific Languages (DSL), runtime and compile-time meta-programming and asynchronous programming.

The Grails homepage is found here

Versions#

Grails Installation

Note: GRAILS requires a Java JDK installed (a runtime environment JRE is not sufficient) on your system, before setting up Grails. Please refer to, how to install JDK. As of this writing, it is recommended to install the latest JDK.

For Mac OSX, Linux, Cygwin, Solaris and FreeBSD:

The simplest way to manage Grails versions is using sdkman. If sdkman is installed, you can then install any version of Grails using

sdk install grails [version]

This will take care of all steps to get this right. If you skip the version, the latest version of grails will be installed. For more about using sdkman, refer to sdkman usage page.

For Linux:

    GRAILS_HOME=$HOME/bin/grails/current
    # abbreviating it using "..." for brevity
    PATH=$GRAILS_HOME/bin:$JAVA_HOME/bin: ... :$PATH

For Windows:

1. Download a Java JDK from Oracle and install on your Windows machine. Take note of the installation folder.
2. Download a version of Grails manually from the Downloads page.
3. Extract the Grails file, anywhere you like.
4. Important: You must set up 2 new environment variables JAVA_HOME and GRAILS_HOME (for Windows 10 found under *Control Panel \ System and Security \ System \ Advanced System settings \ Advanced tab \ Environment Variables) *, pointing to the extracted directories, e.g.

Name: JAVA_HOME

Value: C:\Programs\Java\jdk1.8.0_31

Name: GRAILS_HOME

Value: c:\grails\grails-3.2.4

5. Important: You must extend the Windows PATH variable to include both JAVA_HOME and GRAILS_HOME. The path variable is also found in then control panel (see 4), e.g. add the following at the end:

;C:\Programs\Java\jdk1.8.0_31\bin;c:\grails\grails-3.2.4;c:\grails\grails-3.2.4\bin

5. To verify your installation is correct, open a Command Prompt and type GRAILS -VERSION. You should get something like:

| Grails Version: 3.2.4
| Groovy Version: 2.4.6
| JVM Version: 1.8.0_65

Creating an application

To create a Grails application, use the grails create-app command. The following command creates a Grails application, named myapp in the current directory:

grails create-app fancy-app

Running it, is as simple as visiting the, newly created, application directory:

cd fancy-app

and then

grails run-app 
// in order to run the app on a different port, e.g. 8888, use this instead
grails run-app -port 8888
// in order to run the app with a secure communication
grails run-app -https

Testing an Application

The create-* commands in Grails automatically create unit or integration tests for you within the src/test/groovy directory. It is of course up to you to populate these tests with valid test logic, information on which can be found in the section on Unit and integration tests.

To execute tests you run the test-app command as follows:

grails test-app

Creating a Model

A model (see: Model-View-Controller pattern) in Grails is represented by a so-called Domain Class. Domain classes can define both the persistence and presentation of information in grails. Domain classes can also contain validations.

To manage a fleet of cars in your Grails application you could define a domain class to describe, store and represent various cars in your fleet.

To create a stub for a domain class execute the following command inside your application folder:

grails create-domain-class org.fleetmanager.Car

Next, open the generated car.groovy file and edit your domain class as follows:

package org.fleetmanager

class Car {
   String      manufacturer
   String      model
   String      color
   Integer     year
   Date        acquisitionDate
   Boolean     isElectric
}

Finally, generate a controller for your car domain and a view using the following Grails command:

grails generate-all org.fleetmanager.Car

Now, you can run your applications, select the car controller and manage your fleet.