See the light - agile, industrial strength, rapid web application development made easy

(Quick Reference) # 5.7 Ant and Maven - Reference Documentation Authors: Graeme Rocher, Peter Ledbrook, Marc Palmer, Jeff Brown, Luke Daley, Burt Beckwith, Lari Hotari Version: 2.3.8 ## 5.7 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). ### 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. ### Maven Integration Grails provides integration with Maven 2 with a Maven plugin. #### Preparation In order to use the Maven plugin, all you need is Maven 2 installed and set up. This is because you no longer need to install Grails separately to use it with Maven! The Maven 2 integration for Grails has been designed and tested for Maven 2.0.9 and above. It will not work with earlier versions. The default mvn setup DOES NOT supply sufficient memory to run the Grails environment. We recommend that you add the following environment variable setting to prevent poor performance: `export MAVEN_OPTS="-Xmx512m -XX:MaxPermSize=256"` #### 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` #### Creating a Grails Maven Project using the Archetype You can create a Maven Grails project without having Grails installed, simply run the following command:
    mvn archetype:generate -DarchetypeGroupId=org.grails \
        -DarchetypeArtifactId=grails-maven-archetype \
        -DarchetypeVersion=2.1.0.RC1 \
        -DgroupId=example -DartifactId=my-app
Choose whichever grails version, group ID and artifact ID you want for your application, but everything else must be as written. This will create a new Maven project with a POM and a couple of other files. What you won't see is anything that looks like a Grails application. So, the next step is to create the project structure that you're used to. But first, to set target JDK to Java 6, do that now. Open my-app/pom.xml and change
    <plugin>
      <artifactId>maven-compiler-plugin</artifactId>
      <configuration>
        <source>1.5</source>
        <target>1.5</target>
      </configuration>
    </plugin>
to
    <plugin>
      <artifactId>maven-compiler-plugin</artifactId>
      <configuration>
        <source>1.6</source>
        <target>1.6</target>
      </configuration>
    </plugin>
Then you're ready to create the project structure:
    cd my-app
    mvn initialize
#### 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`. #### Forked Grails Execution By default the Maven plugin will run Grails commands in-process, meaning that the Grails process occupies the same JVM as the Maven process. This can put strain on the Maven process for particularly large applications. In this case it is recommended to use forked execution. Forked execution can be configured in the `configuration` element of the plugin:
    <plugin>
        <groupId>org.grails</groupId>
        <artifactId>grails-maven-plugin</artifactId>
        <version>${grails.version}</version>
        <configuration>
            <!-- Whether for Fork a JVM to run Grails commands -->
            <fork>true</fork>
        </configuration>
        <extensions>true</extensions>
    </plugin>
With this configuration in place a separate JVM will be forked when running Grails commands. If you wish to debug the JVM that is forked you can add the `forkDebug` element:
    <!-- Whether for Fork a JVM to run Grails commands -->
        <fork>true</fork>
        <forkDebug>true</forkDebug>
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>2.1.0.RC2</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
#### Debugging a Grails Maven Project Maven can be launched in debug mode using the "mvnDebug" command. To launch your Grails application in debug, simply run:
    mvnDebug grails:run-app
The process will be suspended on startup and listening for a debugger on port 8000. If you need more control of the debugger, this can be specified using the MAVEN_OPTS environment variable, and launch Maven with the default "mvn" command:
    MAVEN_OPTS="-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=5005"
    mvn grails:run-app
#### Raising issues If you come across any problems with the Maven integration, please raise a JIRA issue. | Quick Reference (hide)