New GWT maven plugin - maven

Question

I'm getting the error below when when I try to compile.
The goal is gwt:compile
I do set the moduleName as a variable.
The module name is com.example.app.App
Same thing command line ~/work/projects/gwt/app$ mvn gwt:compile "-DmoduleName=com.example.app.App"
Failed to execute goal
net.ltgt.gwt.maven:gwt-maven-plugin:1.0-rc-6:compile (default-cli) on
project mysandbox: The parameters 'moduleName' for goal
net.ltgt.gwt.maven:gwt-maven-plugin:1.0-rc-6:compile are missing or
invalid -> [Help 1]
On the other hand mvn package worked.
Here's my pom:
<?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/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>app</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>pom</packaging>
<prerequisites>
<maven>${mavenVersion}</maven>
</prerequisites>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<mavenVersion>3.0</mavenVersion>
</properties>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>com.google.gwt</groupId>
<artifactId>gwt</artifactId>
<version>2.8.0</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
</dependency>
</dependencies>
</dependencyManagement>
<build>
<plugins>
<plugin>
<groupId>net.ltgt.gwt.maven</groupId>
<artifactId>gwt-maven-plugin</artifactId>
<inherited>false</inherited>
<configuration>
<launcherDir>${project.build.directory}/gwt/launcherDir</launcherDir>
</configuration>
</plugin>
</plugins>
<pluginManagement>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<!-- Do not upgrade past 3.1 to avoid triggering https://issues.apache.org/jira/browse/MSOURCES-95 -->
<version>3.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
<plugin>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-maven-plugin</artifactId>
<version>9.3.14.v20161028</version>
<configuration>
<skip>true</skip>
</configuration>
</plugin>
<plugin>
<groupId>net.ltgt.gwt.maven</groupId>
<artifactId>gwt-maven-plugin</artifactId>
<version>1.0-rc-6</version>
<extensions>true</extensions>
<configuration>
<sourceLevel>1.8</sourceLevel>
<failOnError>true</failOnError>
</configuration>
</plugin>
<plugin>
<artifactId>maven-source-plugin</artifactId>
<version>3.0.1</version>
<executions>
<execution>
<id>attach-sources</id>
<phase>package</phase>
<goals>
<goal>jar-no-fork</goal>
</goals>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.tomcat.maven</groupId>
<artifactId>tomcat6-maven-plugin</artifactId>
<version>2.2</version>
</plugin>
<plugin>
<groupId>org.apache.tomcat.maven</groupId>
<artifactId>tomcat7-maven-plugin</artifactId>
<version>2.2</version>
</plugin>
</plugins>
</pluginManagement>
</build>
<modules>
<module>app-client</module>
<module>app-shared</module>
<module>app-server</module>
</modules>
</project>

Answer 1

So, you have a multi-module Maven project. Invoking mvn gwt:compile will try to execute that "goal" on each of the 4 modules (root module and 3 submodules). Because your moduleName property (used to configure the moduleName property of the gwt:compile goal) likely only exists in the app-client submodule, gwt:compile fails when applied to the root module or the app-shared submodule.
If you want to build your project, run mvn package (and if you don't want to run tests, pass -DskipTests).
Technically, you could also run mvn gwt:compile, but directly inside the submodule. For that to work, you'd first have to mvn install the app-shared submodule; otherwise Maven won't be able to resolve the dependency (as you would no longer be executing the full "reactor build".
For many reasons (see http://blog.lexspoon.org/2012/12/recursive-maven-considered-harmful.html and http://blog.ltgt.net/maven-is-broken-by-design/ as starting points), I highly discourage this practice (mvn install is an anti-pattern; most of the time what you want is actually mvn verify); and I also discourage using any phase before package with multi-module builds (which boils down to only ever using mvn package, possibly with -DskipTests, and mvn verify)