Maven exec plugin main class missing
It should be mainClass
not mainclass
.
-Dexec.mainClass="org.hsqldb.Server"
Read more on this here and here.
And hsqldb should be in your maven dependencies:
<dependency>
<groupId>org.hsqldb</groupId>
<artifactId>hsqldb</artifactId>
<version>2.0.0</version>
</dependency>
Please be aware, that the "configuration" section must be out of the execution section (see example below). Otherwise you get the "missing or invalid mainClass" error.
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.2</version>
<dependencies>
<dependency>
<groupId>org.versly</groupId>
<artifactId>versly-wsdoc</artifactId>
<version>1.0-SNAPSHOT</version>
<scope>compile</scope>
</dependency>
</dependencies>
<executions>
<execution>
<phase>prepare-package</phase>
<goals>
<goal>java</goal>
</goals>
</execution>
</executions>
<configuration>
<mainClass>org.versly.rest.wsdoc.RestDocAssembler</mainClass>
<arguments>
<argument>${project.build.directory}/classes</argument>
</arguments>
</configuration>
</plugin>