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This means that generating the javadocs can suddenly fail only by upgrading the JDK
The -Xdoclint option allows you to disable some or all of the new checks provided by javadoc. You can disable the reference checks with -Xdoclint:all,-reference
See https://jira.codehaus.org/browse/MSITE-701 for the details.
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With jdk <1.8, when jarsigner can not verify a jar then exit code is 1 (this is normal); while with jdk 1.8, result code is 0.
This issue has been registered as https://bugs.openjdk.java.net/browse/JDK-8031572