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(Quick Reference) # 6.7 Ant and Maven - Reference Documentation Authors: Graeme Rocher, Peter Ledbrook, Marc Palmer, Jeff Brown, Luke Daley, Burt Beckwith, Lari Hotari Version: 2.4.3 ## 6.7 Ant and Maven If all the other projects in your team or company are built using a standard build tool such as Ant or Maven, you become the black sheep of the family when you use the Grails command line to build your application. Fortunately, you can easily integrate the Grails build system into the main build tools in use today (well, the ones in use in Java projects at least). ### 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:
Attribute | Description | Required
--- | --- | ---
home | The location of the Grails installation directory to use for the build. | Yes, unless classpath is specified.
classpathref | Classpath to load Grails from. Must include the "grails-bootstrap" artifact and should include "grails-scripts". | Yes, unless `home` is set or you use a `classpath` element.
script | The name of the Grails script to run, e.g. "TestApp". | Yes.
args | The arguments to pass to the script, e.g. "-unit -xml". | No. Defaults to "".
environment | The Grails environment to run the script in. | No. Defaults to the script default.
includeRuntimeClasspath | Advanced setting: adds the application's runtime classpath to the build classpath if true. | No. Defaults to `true`.
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. | Quick Reference (hide)