Maven exec-maven-plugin错过了mainClass

Question

我试图在要构建微服务示例的目录中运行命令。

$ mvn exec:java

并发生错误。

Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.6.0:java (default-cli) on project hola-dropwizard: The parameters 'mainClass' for goal org.codehaus.mojo:exec-maven-plugin:1.6.0:java are missing or invalid -> [Help 1]