How to compile a GWT project using maven ONLY

I have a GWT project that I currently compile using Eclipse GWT plugin, but now I would like to make my project compilable independently from the IDE, and the approach is to use Maven only.

From my research I found out that you need to add the GWT Compiler plugin to the pom.xml in order to compile the code from Java to Javascript files (the JS files can be later packaged inside a war), but I can't seem to find the compiler dependency in maven repository nor a good documentation of the compiler. Can you post a "basic" working pom.xml file that can be used to compile a Hello world GWT project, that would be very appreciated, Thank you.

EDIT:

I'm using GWT 2.7.0

Solution

You can use the gwt-maven-plugin. You have mentioned you have the Eclipse GWT plugin already, so you can create a new GWT project (e.g. right click on the Project Explorer -> New -> Other... -> GWT Web Application Project). Fill in the project name and package and make sure to enable the checkbox "Generate a Maven Project". Then you have a working sample of a pom.xml:

<?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">
   <!-- POM file generated with GWT webAppCreator -->
   <modelVersion>4.0.0</modelVersion>
   <groupId>com.world.hello</groupId>
   <artifactId>HelloWorld</artifactId>
   <packaging>war</packaging>
   <version>1.0-SNAPSHOT</version>
   <name>com.world.hello.HelloWorld</name>
   <properties>
      <!-- Setting maven.compiler.source to something different to 1.8
         needs that you configure the sourceLevel in gwt-maven-plugin since
         GWT compiler 2.8 requires 1.8 (see gwt-maven-plugin block below) -->
      <maven.compiler.source>1.8</maven.compiler.source>
      <maven.compiler.target>1.8</maven.compiler.target>
      <!-- Don't let your Mac use a crazy non-standard encoding -->
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
   </properties>
   <dependencyManagement>
      <dependencies>
         <!-- ensure all GWT deps use the same version (unless overridden) -->
         <dependency>
            <groupId>com.google.gwt</groupId>
            <artifactId>gwt</artifactId>
            <version>2.9.0</version>
            <type>pom</type>
            <scope>import</scope>
         </dependency>
      </dependencies>
   </dependencyManagement>
   <dependencies>
      <dependency>
         <groupId>com.google.gwt</groupId>
         <artifactId>gwt-servlet</artifactId>
         <scope>runtime</scope>
      </dependency>
      <dependency>
         <groupId>com.google.gwt</groupId>
         <artifactId>gwt-user</artifactId>
         <scope>provided</scope>
      </dependency>
      <dependency>
         <groupId>com.google.gwt</groupId>
         <artifactId>gwt-dev</artifactId>
         <scope>provided</scope>
      </dependency>
      <dependency>
         <groupId>junit</groupId>
         <artifactId>junit</artifactId>
         <version>4.11</version>
         <scope>test</scope>
      </dependency>
   </dependencies>
   <build>
      <!-- Output classes directly into the webapp, so that IDEs and "mvn process-classes" update them in DevMode -->
      <outputDirectory>${project.build.directory}/${project.build.finalName}/WEB-INF/classes</outputDirectory>
      <plugins>
         <!-- GWT Maven Plugin-->
         <plugin>
            <groupId>net.ltgt.gwt.maven</groupId>
            <artifactId>gwt-maven-plugin</artifactId>
            <version>1.0-rc-8</version>
            <executions>
               <execution>
                  <goals>
                     <goal>compile</goal>
                     <goal>test</goal>
                  </goals>
               </execution>
            </executions>
            <configuration>
               <moduleName>com.world.hello.HelloWorld</moduleName>
               <moduleShortName>HelloWorld</moduleShortName>
               <failOnError>true</failOnError>
               <!-- GWT compiler 2.8 requires 1.8, hence define sourceLevel here if you use
               a different source language for java compilation -->
               <sourceLevel>1.8</sourceLevel>
               <!-- Compiler configuration -->
               <compilerArgs>
                  <!-- Ask GWT to create the Story of Your Compile (SOYC) (gwt:compile) -->
                  <arg>-compileReport</arg>
                  <arg>-XcompilerMetrics</arg>
               </compilerArgs>
               <!-- DevMode configuration -->
               <warDir>${project.build.directory}/${project.build.finalName}</warDir>
               <classpathScope>compile+runtime</classpathScope>
               <!-- URL(s) that should be opened by DevMode (gwt:devmode). -->
               <startupUrls>
                  <startupUrl>HelloWorld.html</startupUrl>
               </startupUrls>
            </configuration>
         </plugin>
         <!-- Skip normal test execution, we use gwt:test instead -->
         <plugin>
            <artifactId>maven-surefire-plugin</artifactId>
            <version>2.17</version>
            <configuration>
               <skip>true</skip>
            </configuration>
         </plugin>
      </plugins>
   </build>
</project>

Running mvn clean install on the console will compile your project using Maven. Or you right click your project on the Project Explorer and select Maven -> Update Project...

Sometimes, after creating the GWT Maven Project, Eclipse doesn't automatically recognize it as a Maven Project. If that is the case, right click your project on the Project Explorer and select Configure -> Convert to Maven Project.