Re: java.lang.NullPointerException at com.google.gwt.dev.util.DiskCache.transferToStream(DiskCache.java:187)

On Monday, March 25, 2013 1:25:29 AM UTC+1, Kris wrote:

GWT 2.5.1

Maven 3.0.4

Hi, suddenly I get this error, and I google it for a while now, and can see others had the problem.

But no solution... 

 java.lang.NullPointerException

[ERROR]  at com.google.gwt.dev.util.DiskCache.transferToStream(DiskCache.java:187)

[ERROR]  at com.google.gwt.dev.util.DiskCacheToken.writeObject(DiskCacheToken.java:91)

[ERROR]  at sun.reflect.GeneratedMethodAccessor24.invoke(Unknown Source)

[ERROR]  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

The only reason this can happen is if the JVM is shutting down while threads are trying to write to the DiskCache, which would be abnormal.

And indeed it is: your problem is not this NPE, it's an internal compiler error:

[INFO] [ERROR] Unexpected internal compiler error

[INFO] java.lang.NoSuchFieldError: warningThreshold

[INFO]  at com.google.gwt.dev.javac.JdtCompiler.getCompilerOptions(JdtCompiler.java:413)

And this NoSuchFieldError can only happen if you have JDT/ECJ in your classpath (from a version incompatible with the one bundled within GWT).

You're best option is to use separate client and server code in distinct artifacts (see https://github.com/tbroyer/gwt-maven-archetypes for examples, https://groups.google.com/d/topic/codehaus-mojo-gwt-maven-plugin-users/vrLAcqp5oAg/discussion for the rationale; see also https://plus.google.com/113945685385052458154/posts/RDrK7ukVFqJ if you're OK to try alpha software) but a short-term solution is to use gwtSdkFirstInClasspath: http://mojo.codehaus.org/gwt-maven-plugin/compile-mojo.html#gwtSdkFirstInClasspath

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