Maven does not resolve a local Grails plug-in

Question

My goal is to take a Grails web application and build it into a Web ARchive (WAR file) using Maven, and the key is that it must populate the "plugins" folder without live access to the internet. An "out of the box" Grails webapp will already have the plugins folder populated with JAR files, but the maven build script should take care of populating it, just like it does for any traditional WAR projects (such as WEB-INF/lib/ if it's empty)

This is an error when executing mvn grails:run-app with Grails 1.1 using Maven 2.0.10 and org.grails:grails-maven-plugin:1.0. (This "hibernate-1.1" plugin is needed to do GORM.)

[INFO] [grails:run-app]
Running pre-compiled script
Environment set to development
Plugin [hibernate-1.1] not installed, resolving..
Reading remote plugin list ...
Error reading remote plugin list [svn.codehaus.org], building locally...
Unable to list plugins, please check you have a valid internet connection: svn.codehaus.org
Reading remote plugin list ...
Error reading remote plugin list [plugins.grails.org], building locally...
Unable to list plugins, please check you have a valid internet connection: plugins.grails.org
Plugin 'hibernate' was not found in repository. If it is not stored in a configured repository you will need to install it manually. Type 'grails list-plugins' to find out what plugins are available.

The build machine does not have access to the internet and must use an internal/enterprise repository, so this error is just saying that maven can't find the required artifact anywhere. That dependency is already included with the stock Grails software that's installed locally, so I just need to figure out how to get my POM file to unpackage that ZIP file into my webapp's "plugins" folder.

I've tried installing the plugin manually to my local repository and making it an explicit dependency in POM.xml, but it's still not being recognized. Maybe you can't pull down grails plugins like you would a standard maven reference?
mvn install:install-file -DgroupId=org.grails -DartifactId=grails-hibernate -Dversion=1.1 -Dpackaging=zip -Dfile=%GRAILS_HOME%/plugins/grails-hibernate-1.1.zip

I can manually setup the Grails webapp from the command-line, which creates that local ./plugins folder properly. This is a step in the right direction, so maybe the question is: how can I incorporate this goal into my POM? mvn grails:install-plugin -DpluginUrl=%GRAILS_HOME%/plugins/grails-hibernate-1.1.zip

Here is a copy of my POM.xml file, which was generated using an archetype.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"&gt;
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.samples</groupId>
    <artifactId>sample-grails</artifactId>
    <packaging>war</packaging>
    <name>Sample Grails webapp</name>
    <properties>
        <sourceComplianceLevel>1.5</sourceComplianceLevel>
    </properties>
    <version>0.0.1-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>org.grails</groupId>
            <artifactId>grails-crud</artifactId>
            <version>1.1</version>
        </dependency>
        <dependency>
            <groupId>org.grails</groupId>
            <artifactId>grails-gorm</artifactId>
            <version>1.1</version>
        </dependency>
        <dependency>
            <groupId>opensymphony</groupId>
            <artifactId>oscache</artifactId>
            <version>2.4</version>
            <exclusions>
                <exclusion>
                    <groupId>commons-logging</groupId>
                    <artifactId>commons-logging</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>javax.jms</groupId>
                    <artifactId>jms</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>javax.servlet</groupId>
                    <artifactId>servlet-api</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>hsqldb</groupId>
            <artifactId>hsqldb</artifactId>
            <version>1.8.0.7</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.5.6</version>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>
        <!--
        <dependency>
            <groupId>org.grails</groupId>
            <artifactId>grails-hibernate</artifactId>
            <version>1.1</version>
            <type>zip</type>
        </dependency>
        -->
    </dependencies>
    <build>
        <pluginManagement />
        <plugins>
            <plugin>
                <groupId>org.grails</groupId>
                <artifactId>grails-maven-plugin</artifactId>
                <version>1.0</version>
                <extensions>true</extensions>
                <executions>
                    <execution>
                        <goals>
                            <goal>init</goal>
                            <goal>maven-clean</goal>
                            <goal>validate</goal>
                            <goal>config-directories</goal>
                            <goal>maven-compile</goal>
                            <goal>maven-test</goal>
                            <goal>maven-war</goal>
                            <goal>maven-functional-test</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>${sourceComplianceLevel}</source>
                    <target>${sourceComplianceLevel}</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Answer 1

This is a tricky problem. I was going to suggest using Grails 1.3, which allows you to pull Grails plugins from Maven-compatible repositories, but I don't think this helps with Maven (at the moment).

So, I'm going to suggest something I haven't tried myself, but may work. I have some confidence because I wrote the relevant code in the Grails Maven plugin ;) No guarantees though.

With that out of the way, let's get started. First, you need to grab the code for the relevant Grails plugins. For example, you can get Hibernate from here:

http://svn.codehaus.org/grails/trunk/grails-plugins/grails-hibernate/tags/RELEASE_1_1/

You just need a copy of the code, so a read-only checkout will be fine.

Once you have the code, run mvn grails:create-pom -DgroupId=org.grails.plugins from the root of the plugin project. This will generate a POM. Next, you will need to edit the POM and change the packaging to "grails-plugin". You should also be able to remove the <executions> block from the Grails Plugin configuration.

The POM will now allow you to build and package the Hibernate plugin, but you still have to deploy it. So add your local repository to the POM's distribution management and run mvn deploy. Once that's done, you should be able to add the plugin as a standard dependency in your application's POM.

It's hard work, but at least you should only have to do it once per version of the plugin!

Answer 2

I was able to come up with a workaround just to get up and running.

This requires Grails be installed locally and that GRAILS_HOME be set. It will clear out and then populate the project's "plugins" folder during the maven "validate" phase. (Insert this into the POM above.)

<plugins>
    <plugin>
        <artifactId>maven-antrun-plugin</artifactId>
        <executions>
            <execution>
                <phase>validate</phase>
                <goals>
                    <goal>run</goal>
                </goals>
                <configuration>
                    <tasks>
                        <!-- clear out this project's plugins folder if it exists, otherwise you will get prompted to upgrade it after re-building -->
                        <delete dir="${basedir}/plugins/" includeemptydirs="true"/>
                    </tasks>
                </configuration>
            </execution>
        </executions>
    </plugin>
    <plugin>
        <groupId>org.grails</groupId>
        <artifactId>grails-maven-plugin</artifactId>
        <version>1.0</version>
        <extensions>true</extensions>
        <executions>
            <execution>
                <id>create plugins folder</id>
                <phase>validate</phase>
                <goals>
                    <goal>install-plugin</goal>
                </goals>
                <configuration>
                <pluginUrl>${env.GRAILS_HOME}/plugins/grails-hibernate-1.1.zip</pluginUrl>
                </configuration>
            </execution>
        </executions>
    </plugin>
</plugins>