Just ran into some trouble when upgrading gradle from 0.5.2 to 0.6.

I'm getting the following stack trace...

Caused by: org.gradle.api.GradleException: An error occurred starting the Jetty server.
at org.gradle.api.plugins.jetty.AbstractJettyRunTask.startJettyInternal(AbstractJettyRunTask.java:299)
at org.gradle.api.plugins.jetty.AbstractJettyRunTask.startJetty(AbstractJettyRunTask.java:232)
at org.gradle.api.plugins.jetty.AbstractJettyRunTask$1.execute(AbstractJettyRunTask.java:60)
at org.gradle.api.plugins.jetty.AbstractJettyRunTask$1.execute(AbstractJettyRunTask.java:47)
at org.gradle.api.internal.AbstractTask.doExecute(AbstractTask.java:219)
at org.gradle.api.internal.AbstractTask.execute(AbstractTask.java:174)
... 9 common frames omitted
Caused by: java.lang.NullPointerException
at org.gradle.api.plugins.jetty.AbstractJettyRunTask.startJettyInternal(AbstractJettyRunTask.java:281)
... 14 common frames omitted

I had a quick look at the code and my guess is that the following code is the culprit:

if (getStopPort() > 0 && getStopKey() != null) {
Monitor monitor = new Monitor(getStopPort(), getStopKey(), new Server[]

, !daemon);
monitor.start();
}

This code will attempt to autobox the stop port to an int value but because the stop port is null by default (according to chapter 18.4 of the user guide) it can throw a NPE during autoboxing.

As I expected, adding the following line to my build.gradle stopped this NPE from occuring...

stopPort = 8081