Using JRebel from pure Maven in a web application

Hi there folks!

I'm sure you've read every bit and piece about how to bend Maven to do your bidding. This time I'm most probably going to duplicate a lot of stuff found on other sites but I'm simply sick and tired of looking it up every single time I need it. We're going to configure a Maven web application project to run under Jetty (mvn jetty:run) with JRebel to do the reloading. So let's get started!

Installing Maven and JRebel

That one is a no brainer but for the sake of completeness I list this particular step here as well.

The pom.xml

The pom.xml file we're going to use looks like this:

<?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>org.example</groupId>
  <artifactId>war</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <name>Example Web application</name>

  <properties>
    <!-- stop stuppid Maven message about build being platform-dependant -->
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <build>
    <plugins>
      <!-- make sure we're using Java 1.6 and not some stone age version -->
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
          <source>1.6</source>
          <target>1.6</target>
        </configuration>
      </plugin>
      <!-- enable jetty:run mojo -->
      <plugin>
        <groupId>org.mortbay.jetty</groupId>
        <artifactId>jetty-maven-plugin</artifactId>
        <configuration>
          <scanIntervalSeconds>0</scanIntervalSeconds>
        </configuration>
      </plugin>
      <!-- enable generation of jrebel.xml - needed for the agent -->
      <plugin>
        <groupId>org.zeroturnaround</groupId>
        <artifactId>jrebel-maven-plugin</artifactId>
        <executions>
          <execution>
            <id>generate-rebel-xml</id>
            <phase>process-resources</phase>
            <goals>
              <goal>generate</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>

Running Maven with JRebel

You need to specify the javaagent as JRebel in order for the class-reloading to work. You do that by extending the environment variable MAVEN_OPTS with the following:

set MAVEN_OPTS=-javaagent:C:\progra~1\ZeroTurnaround\JRebel\jrebel.jar %MAVEN_OPTS%

With that in place run mvn jetty:run or mvn tomcat:run and you're all set!

Doing reloading

Please bare in mind that Maven is not Eclipse! When you save a file it doesn't automatically recompile it so in order for the modified class to be reloaded you need to recompile the project using mvn compile!

Well that pretty much summarizes it. It's not very difficult to setup as you see here but there are steps that are not described all in one place so here it is for your entertainment :)

Have fun!