NullPointerException when packaging BIRT 4.3.1 in maven jar-with-dependencies

<p>I'm trying to package BIRT <strong>4.3.1</strong> in an executable jar using <strong>maven</strong>.

Excerpt from <em>pom.xml</em>:</p><pre class="_prettyXprint"><project [...]>  [...]  <dependencies>  [...]    <dependency>      <groupId>org.eclipse.birt.runtime</groupId>      <artifactId>org.eclipse.birt.runtime</artifactId>      <version>4.3.1</version>    </dependency>  </dependencies>  <build>    <plugins>      <plugin>        <groupId>org.codehaus.mojo</groupId>        <artifactId>exec-maven-plugin</artifactId>        <version>1.2.1</version>        <executions>          <execution>            <goals>              <goal>java</goal>            </goals>          </execution>        </executions>        <configuration>          <mainClass>com.domain.App</mainClass>        </configuration>      </plugin>      <plugin>        <artifactId>maven-assembly-plugin</artifactId>        <configuration>          <archive>            <manifest>              <mainClass>com.domain.App</mainClass>            </manifest>          </archive>          <descriptorRefs>            <descriptorRef>jar-with-dependencies</descriptorRef>          </descriptorRefs>        </configuration>      </plugin>    </plugins>  </build></project></pre><p>The main class, <em>App.java</em>:</p><pre class="_prettyXprint">package com.domain;import org.eclipse.birt.core.exception.BirtException;import org.eclipse.birt.report.engine.api.EngineException;import org.eclipse.birt.report.engine.api.IReportEngine;import org.eclipse.birt.report.engine.api.IReportRunnable;public class App {  public static void main(String[] args) {    try {      IReportEngine birtEngine = BirtEngine.getBirtEngine();      IReportRunnable design = birtEngine          .openReportDesign("/path/to/file.rptdesign");          } catch (EngineException e) {      e.printStackTrace();    } catch (BirtException e) {      e.printStackTrace();    }  }}</pre><p><em>BirtEngine.java:</em>
 </p><pre class="_prettyXprint">package com.domain;import org.eclipse.birt.report.engine.api.EngineConfig;import org.eclipse.birt.report.engine.api.IReportEngine;import org.eclipse.birt.core.framework.Platform;import org.eclipse.birt.core.exception.BirtException;import org.eclipse.birt.report.engine.api.IReportEngineFactory;public class BirtEngine {  private static IReportEngine birtEngine = null;  public static synchronized IReportEngine getBirtEngine()      throws BirtException {    if (birtEngine == null) {      EngineConfig config = new EngineConfig();      Platform.startup(config);      IReportEngineFactory factory = (IReportEngineFactory) Platform          .createFactoryObject(IReportEngineFactory.EXTENSION_REPORT_ENGINE_FACTORY);      birtEngine = factory.createReportEngine(config);    }    return birtEngine;  }}</pre><p>When I run:</p><pre class="_prettyXprint">...$ exec:java</pre><p>I see:</p><pre class="_prettyXprint">[INFO] BUILD SUCCESSFUL</pre><p>But when I run:</p><pre class="_prettyXprint">...$ mvn compile assembly:single...$ java -jar ./target/Test-1.0-SNAPSHOT-jar-with-dependencies.jar</pre><p>I see:</p><pre class="_prettyXprint">[INFO] BUILD SUCCESSFUL</pre><p>followed by:</p><pre class="_prettyXprint">Exception in thread "main" java.lang.NullPointerException  at com.domain.BirtEngine.getBirtEngine(BirtEngine.java:23)  at com.domain.App.main(App.java:11)</pre><p>BirtEngine.java:23 is:
 birtEngine = factory.createReportEngine(config);
 
App.java:11 is:
 IReportEngine birtEngine = BirtEngine.getBirtEngine();

Why do I get an error when packaging BIRT in a <strong>maven jar-with-dependencies</strong>? What should I do differently?
 </p>