6 The Command Line

However, Grails takes it further through the use of convention and the grails command. When you type:

grails [command name]

Grails searches in the following directories for Gant scripts to execute:

• USER_HOME/.grails/scripts
• PROJECT_HOME/scripts
• PROJECT_HOME/plugins/*/scripts
• GRAILS_HOME/scripts

Grails will also convert command names that are in lower case form such as run-app into camel case. So typing

grails run-app

Results in a search for the following files:

• USER_HOME/.grails/scripts/RunApp.groovy
• PROJECT_HOME/scripts/RunApp.groovy
• PLUGINS_HOME/*/scripts/RunApp.groovy
• GLOBAL_PLUGINS_HOME/*/scripts/RunApp.groovy
• GRAILS_HOME/scripts/RunApp.groovy

If multiple matches are found Grails will give you a choice of which one to execute.

When Grails executes a Gant script, it invokes the "default" target defined in that script. If there is no default, Grails will quit with an error.

To get a list of all commands and some help about the available commands type:

grails help

which outputs usage instructions and the list of commands Grails is aware of:

Usage (optionals marked with *):
grails [environment]* [target] [arguments]*
Examples:
grails dev run-app
grails create-app books
Available Targets (type grails help 'target-name' for more info):
grails bootstrap
grails bug-report
grails clean
grails compile
...

Refer to the Command Line reference in the Quick Reference menu of the reference guide for more information about individual commands

It's often useful to provide custom arguments to the JVM when running Grails commands, in particular with run-app where you may for example want to set a higher maximum heap size. The Grails command will use any JVM options provided in the general JAVA_OPTS environment variable, but you can also specify a Grails-specific environment variable too:

export GRAILS_OPTS="-Xmx1G -Xms256m -XX:MaxPermSize=256m"
grails run-app

non-interactive mode

When you run a script manually and it prompts you for information, you can answer the questions and continue running the script. But when you run a script as part of an automated process, for example a continuous integration build server, there's no way to "answer" the questions. So you can pass the --non-interactive switch to the script command to tell Grails to accept the default answer for any questions, for example whether to install a missing plugin.

For example:

grails war --non-interactive

6.1 Interactive Mode

If you need to open a file whilst within interactive mode you can use the open command which will TAB complete file paths:

Even better, the open command understands the logical aliases 'test-report' and 'dep-report', which will open the most recent test and dependency reports respectively. In other words, to open the test report in a browser simply execute open test-report. You can even open multiple files at once: open test-report test/unit/MyTests.groovy will open the HTML test report in your browser and the MyTests.groovy source file in your text editor.

TAB completion also works for class names after the create-* commands:

If you need to run an external process whilst interactive mode is running you can do so by starting the command with a !:

Note that with ! (bang) commands, you get file path auto completion - ideal for external commands that operate on the file system such as 'ls', 'cat', 'git', etc.

The stop-app command will stop an application that has been run with the run-app command.

To exit interactive mode enter the exit command. Note that if the Grails application has been run with run-app normally it will terminate when the interactive mode console exits because the JVM will be terminated. An exception to this would be if the application were running in forked mode which means the application is running in a different JVM. In that case the application will be left running after the interactive mode console terminates. If you want to exit interactive mode and stop an application that is running in forked mode, use the quit command. The quit command will stop the running application and then close interactive mode.

6.2 Forked Execution

Forked Execution

Since Grails 2.3, the run-app, run-war, test-app and console commands are now executed in a forked JVM in order to isolate the build classpath from the runtime classpath.

Forked execution is configured via the grails-app/conf/BuildConfig.groovy file. The following is the default configuration:

grails.project.fork = [
   test: [maxMemory: 768, minMemory: 64, debug: false, maxPerm: 256, daemon:true], // configure settings for the test-app JVM
   run: [maxMemory: 768, minMemory: 64, debug: false, maxPerm: 256], // configure settings for the run-app JVM
   war: [maxMemory: 768, minMemory: 64, debug: false, maxPerm: 256], // configure settings for the run-war JVM
   console: [maxMemory: 768, minMemory: 64, debug: false, maxPerm: 256]// configure settings for the Console UI JVM
]

The memory requirements of the forked JVM can be tweaked as per the requirements of the application.

Forked Test Execution

When running the test-app command, a separate JVM is launched to execute this tests. This will have a notable impact on the speed of execution of the tests when running the command directly:

grails test-app

To mitigate this, Grails 2.3 and above include a feature that launches a background JVM on standby to run tests when using interactive mode. In other words, running test-app from interactive mode will result in faster test execution times:

$ grails
$ grails> test-app

It is recommended that forked execution is used for tests, however it does require modern hardware due to the use of multiple JVMs. You can therefore disable forked execution by setting the grails.project.fork.test setting to false:

forkConfig = [maxMemory: 1024, minMemory: 64, debug: false, maxPerm: 256]
grails.project.fork = [
   test: false,
   …
]

Using the Test Runner Daemon to Speed-up Test Execution

The default configuration for the testing is to activate a daemon to run tests using the daemon argument:

grails.project.fork = [
   test: [maxMemory: 768, minMemory: 64, debug: false, maxPerm: 256, daemon:true], // configure settings for the test-app JVM
   ...

This only works in interactive mode, so if you start Grails with the 'grails' command and then using test-app the daemon will be used:

$ grails
$ grails> test-app

This has the effect of speeding-up test executions times. You can disable the daemon by setting daemon to false. If the daemon becomes unresponsive you can restart it with restart-daemon:

$ grails> restart-daemon

Debugging and Forked Execution (--debug vs --debug-fork)

An important consideration when using forked execution is that the debug argument will allow a remote debugger to be attached to the build JVM but not the JVM that your application is running in. To debug your application you should use the debug-fork argument:

grails test-app --debug-fork

Or for run-app:

grails run-app --debug-fork

Forked Tomcat Execution

Grails 2.2 and above support forked JVM execution of the Tomcat container in development mode. This has several benefits including:

• Reduced memory consumption, since the Grails build system can exit
• Isolation of the build classpath from the runtime classpath
• The ability to deploy other Grails/Spring applications in parallels without conflicting dependencies

To enable forked execution you can set the grails.project.fork.run property to true:

grails.project.fork.run=true

Then just us the regular run-app command as per normal. Note that in forked mode the grails process will exit and leave the container running in the background. To stop the server there is a new stop-app command:

grails stop-app

To customize the JVM arguments passed to the forked JVM you can specify a map instead:

grails.project.fork.run= [maxMemory:1024, minMemory:64, debug:false, maxPerm:256, jvmArgs: '..arbitrary JVM arguments..']

Auto-deploying additional WAR files in Forked Mode

Since forked execution isolates classpaths more effectively than embedded execution you can deploy additional WAR files (such as other Grails or Spring applications) to the container.

The easiest way to do so is to drop the WAR files into the src/autodeploy directory (if it doesn't exist you can create it).

You can customize the location of the autodeploy directory by specifying an alternative location in BuildConfig.groovy:

grails.project.autodeploy.dir="/path/to/my/war/files"

Customizing the Forked Tomcat instance

If you want to programmatically customize the forked Tomcat instance you can do so by implementing a class named org.grails.plugins.tomcat.ForkedTomcatCustomizer which provides a method with the following signature:

void customize(Tomcat tomcat) {
 // your code here
}

6.3 Creating Gant Scripts

grails create-script compile-sources

Will create a script called scripts/CompileSources.groovy. A Gant script itself is similar to a regular Groovy script except that it supports the concept of "targets" and dependencies between them:

target(default:"The default target is the one that gets executed by Grails") {
    depends(clean, compile)
}
target(clean:"Clean out things") {
    ant.delete(dir:"output")
}
target(compile:"Compile some sources") {
    ant.mkdir(dir:"mkdir")
    ant.javac(srcdir:"src/java", destdir:"output")
}

As demonstrated in the script above, there is an implicit ant variable (an instance of groovy.util.AntBuilder) that allows access to the Apache Ant API.

In previous versions of Grails (1.0.3 and below), the variable was Ant, i.e. with a capital first letter.

You can also "depend" on other targets using the depends method demonstrated in the default target above.

The default target

In the example above, we specified a target with the explicit name "default". This is one way of defining the default target for a script. An alternative approach is to use the setDefaultTarget() method:

target("clean-compile": "Performs a clean compilation on the app source") {
    depends(clean, compile)
}
target(clean:"Clean out things") {
    ant.delete(dir:"output")
}
target(compile:"Compile some sources") {
    ant.mkdir(dir:"mkdir")
    ant.javac(srcdir:"src/java", destdir:"output")
}
setDefaultTarget("clean-compile")

This lets you call the default target directly from other scripts if you wish. Also, although we have put the call to setDefaultTarget() at the end of the script in this example, it can go anywhere as long as it comes after the target it refers to ("clean-compile" in this case).

Which approach is better? To be honest, you can use whichever you prefer - there don't seem to be any major advantages in either case. One thing we would say is that if you want to allow other scripts to call your "default" target, you should move it into a shared script that doesn't have a default target at all. We'll talk some more about this in the next section.

6.4 Re-using Grails scripts

The bootstrap script for example lets you bootstrap a Spring ApplicationContext instance to get access to the data source and so on (the integration tests use this):

includeTargets << grailsScript("_GrailsBootstrap")
target ('default': "Database stuff") {
    depends(configureProxy, packageApp, classpath, loadApp, configureApp)
    Connection c
    try {
        c = appCtx.getBean('dataSource').getConnection()
        // do something with connection
    }
    finally {
        c?.close()
    }
}

Pulling in targets from other scripts

Gant lets you pull in all targets (except "default") from another Gant script. You can then depend upon or invoke those targets as if they had been defined in the current script. The mechanism for doing this is the includeTargets property. Simply "append" a file or class to it using the left-shift operator:

includeTargets << new File("/path/to/my/script.groovy")
includeTargets << gant.tools.Ivy

Core Grails targets

As you saw in the example at the beginning of this section, you use neither the File- nor the class-based syntax for includeTargets when including core Grails targets. Instead, you should use the special grailsScript() method that is provided by the Grails command launcher (note that this is not available in normal Gant scripts, just Grails ones).

The syntax for the grailsScript() method is pretty straightforward: simply pass it the name of the Grails script to include, without any path information. Here is a list of Grails scripts that you could reuse:

There are many more scripts provided by Grails, so it is worth digging into the scripts themselves to find out what kind of targets are available. Anything that starts with an "_" is designed for reuse.

Script architecture

You maybe wondering what those underscores are doing in the names of the Grails scripts. That is Grails' way of determining that a script is internal , or in other words that it has not corresponding "command". So you can't run "grails _grails-settings" for example. That is also why they don't have a default target.

Internal scripts are all about code sharing and reuse. In fact, we recommend you take a similar approach in your own scripts: put all your targets into an internal script that can be easily shared, and provide simple command scripts that parse any command line arguments and delegate to the targets in the internal script. For example if you have a script that runs some functional tests, you can split it like this:

./scripts/FunctionalTests.groovy:
includeTargets << new File("${basedir}/scripts/_FunctionalTests.groovy")
target(default: "Runs the functional tests for this project.") {
    depends(runFunctionalTests)
}
./scripts/_FunctionalTests.groovy:
includeTargets << grailsScript("_GrailsTest")
target(runFunctionalTests: "Run functional tests.") {
    depends(...)
    …
}

Here are a few general guidelines on writing scripts:

• Split scripts into a "command" script and an internal one.
• Put the bulk of the implementation in the internal script.
• Put argument parsing into the "command" script.
• To pass arguments to a target, create some script variables and initialise them before calling the target.
• Avoid name clashes by using closures assigned to script variables instead of targets. You can then pass arguments direct to the closures.

6.5 Hooking into Events

The mechanism is deliberately simple and loosely specified. The list of possible events is not fixed in any way, so it is possible to hook into events triggered by plugin scripts, for which there is no equivalent event in the core target scripts.

Defining event handlers

Event handlers are defined in scripts called _Events.groovy. Grails searches for these scripts in the following locations:

• USER_HOME/.grails/scripts - user-specific event handlers
• PROJECT_HOME/scripts - applicaton-specific event handlers
• PLUGINS_HOME/*/scripts - plugin-specific event handlers
• GLOBAL_PLUGINS_HOME/*/scripts - event handlers provided by global plugins

Whenever an event is fired, all the registered handlers for that event are executed. Note that the registration of handlers is performed automatically by Grails, so you just need to declare them in the relevant _Events.groovy file.

Event handlers are blocks defined in _Events.groovy, with a name beginning with "event". The following example can be put in your /scripts directory to demonstrate the feature:

eventCreatedArtefact = { type, name ->
   println "Created $type $name"
}
eventStatusUpdate = { msg ->
   println msg
}
eventStatusFinal = { msg ->
   println msg
}

You can see here the three handlers eventCreatedArtefact, eventStatusUpdate, eventStatusFinal. Grails provides some standard events, which are documented in the command line reference guide. For example the compile command fires the following events:

• CompileStart - Called when compilation starts, passing the kind of compile - source or tests
• CompileEnd - Called when compilation is finished, passing the kind of compile - source or tests

Triggering events

To trigger an event simply include the Init.groovy script and call the event() closure:

includeTargets << grailsScript("_GrailsEvents")
event("StatusFinal", ["Super duper plugin action complete!"])

Common Events

Below is a table of some of the common events that can be leveraged:

6.6 Customising the build

The defaults

The core of the Grails build configuration is the grails.util.BuildSettings class, which contains quite a bit of useful information. It controls where classes are compiled to, what dependencies the application has, and other such settings.

Here is a selection of the configuration options and their default values:

The BuildSettings class has some other properties too, but they should be treated as read-only:

Of course, these properties aren't much good if you can't get hold of them. Fortunately that's easy to do: an instance of BuildSettings is available to your scripts as the grailsSettings script variable. You can also access it from your code by using the grails.util.BuildSettingsHolder class, but this isn't recommended.

Overriding the defaults

All of the properties in the first table can be overridden by a system property or a configuration option - simply use the "config option" name. For example, to change the project working directory, you could either run this command:

grails -Dgrails.project.work.dir=work compile

grails.project.work.dir = "work"

What happens if you use both a system property and a configuration option? Then the system property wins because it takes precedence over the BuildConfig.groovy file, which in turn takes precedence over the default values.

The BuildConfig.groovy file is a sibling of grails-app/conf/Config.groovy - the former contains options that only affect the build, whereas the latter contains those that affect the application at runtime. It's not limited to the options in the first table either: you will find build configuration options dotted around the documentation, such as ones for specifying the port that the embedded servlet container runs on or for determining what files get packaged in the WAR file.

Available build settings

Reloading Agent Cache Directory

Grails uses an agent based reloading system in the development environment that allows source code changes to be picked up while the application is running. This reloading agent caches information needed to carry out the reloading efficiently. By default this information is stored under <USER_HOME_DIR>/.grails/.slcache/. The GRAILS_AGENT_CACHE_DIR environment variable may be assigned a value to cause this cache information to be stored somewhere else. Note that this is an operating system environment variable, not a JVM system property or a property which may be defined in BuildConfig.groovy. This setting must be defined as an environment variable because the agent cache directory must be configured very early in the JVM startup process, before any Grails code is executed.

6.7 Ant and Maven

Maven Integration

Grails provides integration with Maven 3 with a Maven plugin.

Preparation

In order to use the Maven plugin, all you need is Maven 3 installed and set up. This is because you no longer need to install Grails separately to use it with Maven!

The Maven 3 integration for Grails has been designed and tested for Maven 3.1.0 and above. It will not work with earlier versions.

Creating a Grails Maven Project

Using the create-pom command you can generate a valid Maven pom.xml file for any existing Grails project. The below presents an example:

$ grails create-app myapp
$ cd myapp
$ grails create-pom com.mycompany

The create-pom command expects a group id as an argument. The name and the version are taken from the application.properties of the application. The Maven plugin will keep the version in the pom.xml in sync with the version in application.properties.

The following standard Maven commands are then possible:

• compile - Compiles a Grails project
• package - Builds a WAR file from the Grails project.
• install - Builds a WAR file (or plugin zip/jar if a plugin) and installs it into your local Maven cache
• test - Runs the tests of a Grails project
• clean - Cleans the Grails project

Other standard Maven commands will likely work too.

You can also use some of the Grails commands that have been wrapped as Maven goals:

• grails:create-controller - Calls the create-controller command
• grails:create-domain-class - Calls the create-domain-class command
• grails:create-integration-test - Calls the create-integration-test command
• grails:create-pom - Creates a new Maven POM for an existing Grails project
• grails:create-script - Calls the create-script command
• grails:create-service - Calls the create-service command
• grails:create-taglib - Calls the create-tag-lib command
• grails:create-unit-test - Calls the create-unit-test command
• grails:exec - Executes an arbitrary Grails command line script
• grails:generate-all - Calls the generate-all command
• grails:generate-controller - Calls the generate-controller command
• grails:generate-views - Calls the generate-views command
• grails:install-templates - Calls the install-templates command
• grails:list-plugins - Calls the list-plugins command
• grails:package - Calls the package command
• grails:run-app - Calls the run-app command

For a complete, up to date list, run mvn grails:help

Defining Plugin Dependencies

All Grails plugins are published to a standard Maven repository located at . When using the Maven plugin for Grails you must ensure that this repository is declared in your list of remote repositories:

<repository>
    <id>grails-plugins</id>
    <name>grails-plugins</name>
    <url>http://repo.grails.org/grails/plugins</url>
</repository>

With this done you can declare plugin dependencies within your pom.xml file:

<dependency>
    <groupId>org.grails.plugins</groupId>
    <artifactId>database-migration</artifactId>
    <version>1.1</version>
    <scope>runtime</scope>
    <type>zip</type>
</dependency>

Note that the type element must be set to zip.

Specifying the Grails Version to Use

The 2.4.0 version of the Maven plugin works with different versions of Grails. By default it tries to auto-detect the version of Grails to use from the grails-dependencies dependency definition found in the pom.xml:

<dependency>
    <groupId>org.grails</groupId>
    <artifactId>grails-dependencies</artifactId>
    <version>2.4.0</version>
</dependency>

If you change the version of grails-dependencies then a different version of Grails will be used. However, you can also explicitly define the Grails version to be used in the plugin configuration:

<plugin>
    <groupId>org.grails</groupId>
    <artifactId>grails-maven-plugin</artifactId>
    <version>2.4.0</version>
    <configuration>
        <grailsVersion>2.4.0</grailsVersion>
    </configuration>
    <extensions>true</extensions>
</plugin>

Debugging Grails Execution

The Maven plugin will run Grails commands in a separate process, meaning that the Grails process occupies a separate JVM as the Maven process.

To debug the Grails process you need to configure the forkDebug option in the plugin's configuration tag:

<plugin>
    <groupId>org.grails</groupId>
    <artifactId>grails-maven-plugin</artifactId>
    <version>2.4.0</version>
    <configuration>
        <forkDebug>true</forkDebug>
    </configuration>
    <extensions>true</extensions>
</plugin>

With this configuration in place the JVM executed in Maven will load in debug mode.

If you need to customize the memory of the forked process the following elements are available:

• forkMaxMemory - The maximum amount of heap (default 1024)
• forkMinMemory - The minimum amount of heap (default 512)
• forkPermGen - The amount of permgen (default 256)

Multi Module Maven Builds

The Maven plugin can be used to power multi-module Grails builds. The easiest way to set this is up is with the create-multi-project-build command:

$ grails create-app myapp
$ grails create-plugin plugin1
$ grails create-plugin plugin2
$ grails create-multi-project-build org.mycompany:parent:1.0

Running mvn install will build all projects together. To enable the 'grails' command to read the POMs you can modify BuildConfig.groovy to use the POM and resolve dependencies from your Maven local cache:

grails.project.dependency.resolution = {
    …
    pom true
    repositories {
        …
        mavenLocal()    
    }
}

By reading the pom.xml file you can do an initial mvn install from the parent project to build all plugins and install them into your local maven cache and then cd into your project and use the regular grails run-app command to run your application. All previously built plugins will be resolved from the local Maven cache.

Adding Grails commands to phases

The standard POM created for you by Grails already attaches the appropriate core Grails commands to their corresponding build phases, so "compile" goes in the "compile" phase and "war" goes in the "package" phase. That doesn't help though when you want to attach a plugin's command to a particular phase. The classic example is functional tests. How do you make sure that your functional tests (using which ever plugin you have decided on) are run during the "integration-test" phase?

Fear not: all things are possible. In this case, you can associate the command to a phase using an extra "execution" block:

<plugin>
    <groupId>org.grails</groupId>
    <artifactId>grails-maven-plugin</artifactId>
    <version>2.4.0</version>
    <extensions>true</extensions>
    <executions>
        <execution>
            <goals>
            …
            </goals>
        </execution>
        <!-- Add the "functional-tests" command to the "integration-test" phase -->
        <execution>
            <id>functional-tests</id>
            <phase>integration-test</phase>
            <goals>
                <goal>exec</goal>
            </goals>
            <configuration>
                <command>functional-tests</command>
            </configuration>
        </execution>
    </executions>
</plugin>

This also demonstrates the grails:exec goal, which can be used to run any Grails command. Simply pass the name of the command as the command system property, and optionally specify the arguments with the args property:

mvn grails:exec -Dcommand=create-webtest -Dargs=Book

Raising issues

If you come across any problems with the Maven integration, please raise a JIRA issue.

Ant Integration

When you create a Grails application with the create-app command, Grails doesn't automatically create an Ant build.xml file but you can generate one with the integrate-with command:

grails integrate-with --ant

This creates a build.xml file containing the following targets:

• clean - Cleans the Grails application
• compile - Compiles your application's source code
• test - Runs the unit tests
• run - Equivalent to "grails run-app"
• war - Creates a WAR file
• deploy - Empty by default, but can be used to implement automatic deployment

Each of these can be run by Ant, for example:

ant war

The build file is configured to use Apache Ivy for dependency management, which means that it will automatically download all the requisite Grails JAR files and other dependencies on demand. You don't even have to install Grails locally to use it! That makes it particularly useful for continuous integration systems such as CruiseControl or Jenkins.

It uses the Grails Ant task to hook into the existing Grails build system. The task lets you run any Grails script that's available, not just the ones used by the generated build file. To use the task, you must first declare it:

<taskdef name="grailsTask"
         classname="grails.ant.GrailsTask"
         classpathref="grails.classpath"/>

This raises the question: what should be in "grails.classpath"? The task itself is in the "grails-bootstrap" JAR artifact, so that needs to be on the classpath at least. You should also include the "groovy-all" JAR. With the task defined, you just need to use it! The following table shows you what attributes are available:

The task also supports the following nested elements, all of which are standard Ant path structures:

• classpath - The build classpath (used to load Gant and the Grails scripts).
• compileClasspath - Classpath used to compile the application's classes.
• runtimeClasspath - Classpath used to run the application and package the WAR. Typically includes everything in @compileClasspath.
• testClasspath - Classpath used to compile and run the tests. Typically includes everything in runtimeClasspath.

How you populate these paths is up to you. If you use the home attribute and put your own dependencies in the lib directory, then you don't even need to use any of them. For an example of their use, take a look at the generated Ant build file for new apps.

6.8 Grails Wrapper

Generating The Wrapper

The wrapper command can be used to generate the wrapper shell scripts and supporting jar files. Execute the wrapper command at the top of an existing Grails project.

grails wrapper

In order to do this of course Grails must be installed and configured. This is only a requirement for bootstrapping the wrapper. Once the wrapper is generated there is no need to have a Grails installation configured in order to use the wrapper.

See the wrapper command documentation for details about command line arguments.

By default the wrapper command will generate a grailsw shell script and grailsw.bat batch file at the top of the project. In addition to those, a wrapper/ directory (the name of the directory is configurable via command line options) is generated which contains some support files which are necessary to run the wrapper. All of these files should be checked into the source code control system along with the rest of the project. This allows developers to check the project out of source code control and immediately start using the wrapper to execute Grails commands without having to install and configure Grails.

Using The Wrapper

The wrapper script accepts all of the same arguments as the normal grails command.

./grailsw create-domain-class com.demo.Person
./grailsw run-app
./grailsw test-app unit:
etc...