Google App Engine and Maven

Google has announced support for building Java applications on the App Engine platform. This is great news for new App Engine developers and especially for those Java developers who had to learn Python to use App Engine.

I created a project for App Engine using Maven for builds. These were the steps I needed to follow:

1. Publish the App Engine libraries to the local Maven repository. Goto the app-engine-java-sdk directory (where app-engine sdk is installed) and execute the following commands:

mvn install:install-file -Dfile=lib/appengine-tools-api.jar -DgroupId=com.google -DartifactId=appengine-tools -Dversion=1.2.0 -Dpackaging=jar -DgeneratePom=true

mvn install:install-file -Dfile=lib/shared/appengine-local-runtime-shared.jar -DgroupId=com.google -DartifactId=appengine-local-runtime-shared -Dversion=1.2.0 -Dpackaging=jar -DgeneratePom=true

mvn install:install-file -Dfile=lib/user/appengine-api-1.0-sdk-1.2.0.jar -DgroupId=com.google -DartifactId=appengine-sdk-1.2.0-api -Dversion=1.2.0 -Dpackaging=jar -DgeneratePom=true

mvn install:install-file -Dfile=lib/user/orm/datanucleus-appengine-1.0.0.final.jar -DgroupId=org.datanucleus -DartifactId=datanucleus-appengine -Dversion=1.0.0.final -Dpackaging=jar -DgeneratePom=true

2. Create a maven pom file. This is the one that I used:

<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-4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.shalin</groupId>
    <artifactId>test</artifactId>
    <packaging>war</packaging>
    <version>1.0</version>
    <name>Test</name>
    <url>http://shalinsays.blogspot.com</url>
    
    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>com.google</groupId>
            <artifactId>appengine-tools</artifactId>
            <version>1.2.0</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>com.google</groupId>
            <artifactId>appengine-local-runtime-shared</artifactId>
            <version>1.2.0</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>com.google</groupId>
            <artifactId>appengine-sdk-1.2.0-api</artifactId>
            <version>1.2.0</version>
            <scope>compile</scope>
        </dependency>

        <dependency>
            <artifactId>standard</artifactId>
            <groupId>taglibs</groupId>
            <version>1.1.2</version>
            <type>jar</type>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <artifactId>jstl</artifactId>
            <groupId>javax.servlet</groupId>
            <version>1.1.2</version>
            <type>jar</type>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.geronimo.specs</groupId>
            <artifactId>geronimo-el_1.0_spec</artifactId>
            <version>1.0.1</version>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.geronimo.specs</groupId>
            <artifactId>geronimo-jsp_2.1_spec</artifactId>
            <version>1.0.1</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.geronimo.specs</groupId>
            <artifactId>geronimo-servlet_2.5_spec</artifactId>
            <version>1.2</version>
            <scope>provided</scope>
        </dependency>
        
        <dependency>
            <groupId>org.apache.geronimo.specs</groupId>
            <artifactId>geronimo-jpa_3.0_spec</artifactId>
            <version>1.1.1</version>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.geronimo.specs</groupId>
            <artifactId>geronimo-jta_1.1_spec</artifactId>
            <version>1.1.1</version>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>org.datanucleus</groupId>
            <artifactId>datanucleus-appengine</artifactId>
            <version>1.0.0.final</version>
            <scope>compile</scope>
        </dependency>

    </dependencies>
    <build>
        <finalName>test</finalName>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.5</source>
                    <target>1.5</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

3. Create the standard maven directory structure and add the pom.xml in the same directory as the src directory.

You're done!

I tested this with a simple servlet based application and it worked fine. I did not test the JPA/JDO integration so it might be a little rough around the edges. But it should work for the most part. Note, App Engine supports Java 6. If you want to use Java 6, you can change the "source" and "target" in the build section to 1.6 instead of 1.5