Why am I getting a ClassCastException when generating javadocs?

Question

I'm using ant to generate javadocs, but get this exception over and over - why?

I'm using JDK version 1.6.0_06.

[javadoc] java.lang.ClassCastException: com.sun.tools.javadoc.ClassDocImpl cannot be cast to com.sun.javadoc.AnnotationTypeDoc
  [javadoc]     at com.sun.tools.javadoc.AnnotationDescImpl.annotationType(AnnotationDescImpl.java:46)
  [javadoc]     at com.sun.tools.doclets.formats.html.HtmlDocletWriter.getAnnotations(HtmlDocletWriter.java:1739)
  [javadoc]     at com.sun.tools.doclets.formats.html.HtmlDocletWriter.writeAnnotationInfo(HtmlDocletWriter.java:1713)
  [javadoc]     at com.sun.tools.doclets.formats.html.HtmlDocletWriter.writeAnnotationInfo(HtmlDocletWriter.java:1702)
  [javadoc]     at com.sun.tools.doclets.formats.html.HtmlDocletWriter.writeAnnotationInfo(HtmlDocletWriter.java:1681)
  [javadoc]     at com.sun.tools.doclets.formats.html.FieldWriterImpl.writeSignature(FieldWriterImpl.java:130)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.builders.FieldBuilder.buildSignature(FieldBuilder.java:184)
  [javadoc]     at sun.reflect.GeneratedMethodAccessor8.invoke(Unknown Source)
  [javadoc]     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  [javadoc]     at java.lang.reflect.Method.invoke(Method.java:597)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.builders.FieldBuilder.invokeMethod(FieldBuilder.java:114)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.builders.AbstractBuilder.build(AbstractBuilder.java:90)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.builders.AbstractMemberBuilder.build(AbstractMemberBuilder.java:56)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.builders.FieldBuilder.buildFieldDoc(FieldBuilder.java:158)
  [javadoc]     at sun.reflect.GeneratedMethodAccessor51.invoke(Unknown Source)
  [javadoc]     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  [javadoc]     at java.lang.reflect.Method.invoke(Method.java:597)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.builders.FieldBuilder.invokeMethod(FieldBuilder.java:114)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.builders.AbstractBuilder.build(AbstractBuilder.java:90)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.builders.AbstractMemberBuilder.build(AbstractMemberBuilder.java:56)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.builders.ClassBuilder.buildFieldDetails(ClassBuilder.java:301)
  [javadoc]     at sun.reflect.GeneratedMethodAccessor43.invoke(Unknown Source)
  [javadoc]     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  [javadoc]     at java.lang.reflect.Method.invoke(Method.java:597)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.builders.ClassBuilder.invokeMethod(ClassBuilder.java:101)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.builders.AbstractBuilder.build(AbstractBuilder.java:90)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.builders.ClassBuilder.buildClassDoc(ClassBuilder.java:124)
  [javadoc]     at sun.reflect.GeneratedMethodAccessor19.invoke(Unknown Source)
  [javadoc]     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  [javadoc]     at java.lang.reflect.Method.invoke(Method.java:597)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.builders.ClassBuilder.invokeMethod(ClassBuilder.java:101)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.builders.AbstractBuilder.build(AbstractBuilder.java:90)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.builders.ClassBuilder.build(ClassBuilder.java:108)
  [javadoc]     at com.sun.tools.doclets.formats.html.HtmlDoclet.generateClassFiles(HtmlDoclet.java:155)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.AbstractDoclet.generateClassFiles(AbstractDoclet.java:164)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.AbstractDoclet.startGeneration(AbstractDoclet.java:106)
  [javadoc]     at com.sun.tools.doclets.internal.toolkit.AbstractDoclet.start(AbstractDoclet.java:64)
  [javadoc]     at com.sun.tools.doclets.formats.html.HtmlDoclet.start(HtmlDoclet.java:42)
  [javadoc]     at com.sun.tools.doclets.standard.Standard.start(Standard.java:23)
  [javadoc]     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  [javadoc]     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
  [javadoc]     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  [javadoc]     at java.lang.reflect.Method.invoke(Method.java:597)
  [javadoc]     at com.sun.tools.javadoc.DocletInvoker.invoke(DocletInvoker.java:215)
  [javadoc]     at com.sun.tools.javadoc.DocletInvoker.start(DocletInvoker.java:91)
  [javadoc]     at com.sun.tools.javadoc.Start.parseAndExecute(Start.java:340)
  [javadoc]     at com.sun.tools.javadoc.Start.begin(Start.java:128)
  [javadoc]     at com.sun.tools.javadoc.Main.execute(Main.java:41)
  [javadoc]     at com.sun.tools.javadoc.Main.main(Main.java:31)

Answer 1

It looks like this has been reported as a Java bug. It appears to be caused by using annotations from a 3rd party library (like JUnit) and not including the jar with that annotation in the javadoc invocation.

If that is the case, just use the -classpath option on javadoc and include the extra jar files.