Heroku Java Webapp War Deployment

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">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.example</groupId>
    <version>1.0-SNAPSHOT</version>
    <artifactId>artifact</artifactId>
    <dependencies>
        <dependency>
            <groupId>org.eclipse.jetty</groupId>
            <artifactId>jetty-server</artifactId>
            <version>7.4.5.v20110725</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.jetty</groupId>
            <artifactId>jetty-deploy</artifactId>
            <version>7.4.5.v20110725</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.jetty</groupId>
            <artifactId>jetty-servlet</artifactId>
            <version>7.4.5.v20110725</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>2.5</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.3.2</version>
                <configuration>
                    <source>1.6</source>
                    <target>1.6</target>
                </configuration>
            </plugin>

            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>appassembler-maven-plugin</artifactId>
                <version>1.1.1</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>assemble</goal>
                        </goals>
                        <configuration>
                            <assembleDirectory>target</assembleDirectory>
                            <generateRepository>true</generateRepository>
                            <programs>
                                <program>
                                    <mainClass>root.StartWebApp</mainClass>
                                    <name>webapp</name>
                                </program>
                            </programs>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
</project>

Procfile

web: sh target/bin/webapp

StartWebApp.java

package root;

import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.webapp.WebAppContext;

public class StartWebApp {
    public static void main(String[] args) throws Exception {
        String portStr = System.getenv("PORT");
        int port = (portStr == null) ? 8085 : Integer.parseInt(portStr);
        Server server = new Server(port);
        WebAppContext webapp = new WebAppContext();
        webapp.setContextPath("/");
        // change the name of the war as needed.
        webapp.setWar("target/classes/mywebapp.war");
        server.setHandler(webapp);

        server.start();
        server.join();
    }


}