Не удалось выполнить цель org.codehaus.mojo: exec-maven-plugin: 1.5.0: java (default-cli) в проекте nextrtc-signaling-serverrror

Я протестировал nextrtc-signaling-server, который является открытым исходным кодом для Java. Но я столкнулся с проблемой сборки Maven. Я надеюсь, что это решено.

Мой журнал консоли.

 [INFO] Building jar: D:\signallinServer\nextrtc-signaling-server\target\nextrtc-signaling-server-0.0.4-SNAPSHOT-javadoc.jar
 [INFO] 
 [INFO] --- exec-maven-plugin:1.5.0:java (default-cli) @ nextrtc-signaling-server ---
 [INFO] ------------------------------------------------------------------------
 [INFO] BUILD FAILURE
 [INFO] ------------------------------------------------------------------------
 [INFO] Total time: 12.430 s
 [INFO] Finished at: 2016-08-29T11:12:34+09:00
 [INFO] Final Memory: 26M/223M
 [INFO] ------------------------------------------------------------------------
 [ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.5.0:java (default-cli) on project nextrtc-signaling-server: The parameters 'mainClass' for goal org.codehaus.mojo:exec-maven-plugin:1.5.0:java are missing or invalid -> [Help 1]
 [ERROR] 
 [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
 [ERROR] Re-run Maven using the -X switch to enable full debug logging.
 [ERROR] 
 [ERROR] For more information about the errors and possible solutions, please read the following articles:
 [ERROR] [Help 1]  http://cwiki.apache.org/confluence/display/MAVEN/PluginParameterException

POM.xml

http://maven.apache.org/xsd/maven-4.0.0.xsd "> 4.0.0

<groupId>org.nextrtc.signalingserver</groupId>
<artifactId>nextrtc-signaling-server</artifactId>
<version>0.0.4-SNAPSHOT</version>
<packaging>jar</packaging>

<name>nextrtc-signaling-server</name>
<url>http://nextrtc.org</url>
<description>Library providing signaling protocol for WebRTC</description>

<licenses>
    <license>
        <name>MIT License</name>
        <url>http://www.opensource.org/licenses/mit-license.php</url>
    </license>
</licenses>

<developers>
    <developer>
        <name>Marcin Ślósarz</name>
        <email>[email protected]</email>
        <organization>NextRTC</organization>
        <organizationUrl>http://nextrtc.org</organizationUrl>
    </developer>
</developers>

<issueManagement>
    <url>https://github.com/mslosarz/nextrtc-signaling-server/issues</url>
    <system>GitHub Issues</system>
</issueManagement>

<scm>
    <connection>scm:git:https://github.com/mslosarz/nextrtc-signaling-server.git</connection>
    <developerConnection>scm:git:[email protected]:mslosarz/nextrtc-signaling-server.git</developerConnection>
    <url>https://github.com/mslosarz/nextrtc-signaling-server</url>
</scm>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
    <spring-version>4.2.4.RELEASE</spring-version>
</properties>

<distributionManagement>
    <snapshotRepository>
        <id>ossrh</id>
        <url>https://oss.sonatype.org/content/repositories/snapshots</url>
    </snapshotRepository>
    <repository>
        <id>ossrh</id>
        <url>https://oss.sonatype.org/service/local/staging/deploy/maven2/</url>
    </repository>
</distributionManagement>

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.1</version>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-source-plugin</artifactId>
            <version>2.2.1</version>
            <executions>
                <execution>
                    <id>attach-sources</id>
                    <goals>
                        <goal>jar</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-gpg-plugin</artifactId>
            <version>1.5</version>
            <executions>
                <execution>
                    <id>sign-artifacts</id>
                    <phase>verify</phase>
                    <goals>
                        <goal>sign</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-javadoc-plugin</artifactId>
            <version>2.9.1</version>
            <executions>
                <execution>
                    <id>attach-javadocs</id>
                    <goals>
                        <goal>jar</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>${spring-version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-websocket</artifactId>
        <version>${spring-version}</version>
    </dependency>
    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>1.2.17</version>
    </dependency>
    <dependency>
        <groupId>joda-time</groupId>
        <artifactId>joda-time</artifactId>
        <version>2.9.2</version>
    </dependency>
    <dependency>
        <groupId>javax.websocket</groupId>
        <artifactId>javax.websocket-api</artifactId>
        <version>1.1</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.1.0</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>1.16.6</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>com.google.guava</groupId>
        <artifactId>guava</artifactId>
        <version>19.0</version>
    </dependency>
    <dependency>
        <groupId>com.google.code.gson</groupId>
        <artifactId>gson</artifactId>
        <version>2.5</version>
    </dependency>
    <dependency>
        <groupId>org.apache.commons</groupId>
        <artifactId>commons-lang3</artifactId>
        <version>3.4</version>
    </dependency>
    <dependency>
        <groupId>com.googlecode.zohhak</groupId>
        <artifactId>zohhak</artifactId>
        <version>1.1.1</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.mockito</groupId>
        <artifactId>mockito-core</artifactId>
        <version>1.10.19</version>
        <scope>test</scope>
        <exclusions>
            <exclusion>
                <artifactId>hamcrest-core</artifactId>
                <groupId>org.hamcrest</groupId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-test</artifactId>
        <version>${spring-version}</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
        <exclusions>
            <exclusion>
                <groupId>org.hamcrest</groupId>
                <artifactId>hamcrest-core</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.hamcrest</groupId>
        <artifactId>hamcrest-all</artifactId>
        <version>1.3</version>
        <scope>test</scope>
    </dependency>
</dependencies>

I've built this source at "clean package exec: Java" (Maven Goals)

Что мне нужно сделать? Я очень хочу это исправить.