Add more Java versions to Travis CI build matrix

[joschi]

In order to cover the Java/JDK versions we want to support with Dropwizard with Travis CI, this pull request adds OpenJDK 8 through 11 (EA) to the Travis CI build matrix.

There were some minor changes in the Maven build, mostly adding build profiles for the respective Java/JDK versions.

The following issues are open until Java 11 is completely supported without hacks:

• JASSIST-271 Allow running on Java 11 by falling back to ClassLoader.defineClass for Java > 10 jboss-javassist/javassist#198
• https://liquibase.jira.com/browse/CORE-3262 (this also affects Java 10)

[jplock]

@nickbabcock @joschi is this an issue with the SelfValidatorTest or javassist? It only seems to be failing on jdk8 for some reason.

ERROR] complexExample(io.dropwizard.validation.SelfValidationTest)  Time elapsed: 0.253 s  <<< ERROR!
java.lang.NoClassDefFoundError: java/lang/StackWalker$Option
	at io.dropwizard.validation.SelfValidationTest.complexExample(SelfValidationTest.java:198)
Caused by: java.lang.ClassNotFoundException: java.lang.StackWalker$Option
	at io.dropwizard.validation.SelfValidationTest.complexExample(SelfValidationTest.java:198)
[ERROR] invalidExample(io.dropwizard.validation.SelfValidationTest)  Time elapsed: 0.005 s  <<< ERROR!
java.lang.NoClassDefFoundError: Could not initialize class javassist.util.proxy.DefineClassHelper
	at io.dropwizard.validation.SelfValidationTest.invalidExample(SelfValidationTest.java:210)
[ERROR] subClassExample(io.dropwizard.validation.SelfValidationTest)  Time elapsed: 0.006 s  <<< ERROR!
java.lang.NoClassDefFoundError: Could not initialize class javassist.util.proxy.DefineClassHelper
	at io.dropwizard.validation.SelfValidationTest.subClassExample(SelfValidationTest.java:142)
[ERROR] annotatedSubClassExample(io.dropwizard.validation.SelfValidationTest)  Time elapsed: 0.005 s  <<< ERROR!
java.lang.NoClassDefFoundError: Could not initialize class javassist.util.proxy.DefineClassHelper
	at io.dropwizard.validation.SelfValidationTest.annotatedSubClassExample(SelfValidationTest.java:153)
[ERROR] overridingSubClassExample(io.dropwizard.validation.SelfValidationTest)  Time elapsed: 0.005 s  <<< ERROR!
java.lang.NoClassDefFoundError: Could not initialize class javassist.util.proxy.DefineClassHelper
	at io.dropwizard.validation.SelfValidationTest.overridingSubClassExample(SelfValidationTest.java:164)
[ERROR] testDirectContextUsage(io.dropwizard.validation.SelfValidationTest)  Time elapsed: 0.004 s  <<< ERROR!
java.lang.NoClassDefFoundError: Could not initialize class javassist.util.proxy.DefineClassHelper
	at io.dropwizard.validation.SelfValidationTest.testDirectContextUsage(SelfValidationTest.java:190)
[ERROR] failingExample(io.dropwizard.validation.SelfValidationTest)  Time elapsed: 0.004 s  <<< ERROR!
java.lang.NoClassDefFoundError: Could not initialize class javassist.util.proxy.DefineClassHelper
	at io.dropwizard.validation.SelfValidationTest.failingExample(SelfValidationTest.java:134)
[ERROR] multipleTestingOfSameClass(io.dropwizard.validation.SelfValidationTest)  Time elapsed: 0.003 s  <<< ERROR!
java.lang.NoClassDefFoundError: Could not initialize class javassist.util.proxy.DefineClassHelper
	at io.dropwizard.validation.SelfValidationTest.multipleTestingOfSameClass(SelfValidationTest.java:180)
[ERROR] correctExample(io.dropwizard.validation.SelfValidationTest)  Time elapsed: 0.003 s  <<< ERROR!
java.lang.NoClassDefFoundError: Could not initialize class javassist.util.proxy.DefineClassHelper
	at io.dropwizard.validation.SelfValidationTest.correctExample(SelfValidationTest.java:172)

[joschi]

@jplock Javassist 3.23.0-GA doesn't support Java 8 anymore and Javassist 3.22.0-GA doesn't support Java 11.

We'll either have to stop supporting Java 8 (EOL soon), not support Java 11 (released soon), or rewrite the functionality with a different library (e. g. Byte Buddy).

I think I'll give Byte Buddy a try if I have a few minutes to spare.

[jplock]

@joschi maybe when the next release comes out containing jboss-javassist/javassist#204, the tests will work again on JDK8. That puts us in a tricky position. We should support the latest LTS release (JDK11), but I'm not sure we should lose JDK8 support in DW 2.0.0 or not yet.

[RohanNagar]

Does adding the two dependencies above mean that Dropwizard applications will no longer need --add-modules java.xml.bind on Java 9+? Right now I need to manually include that option when running on Java 9

(Or not since they are runtime dependencies?)

[joschi]

@RohanNagar Yes, the additional command line parameters for java.xml.bind can be removed.

[joschi]

The pull request is done and ready to merge from my perspective.

The AppVeyor build failed for unrelated reasons (address already in use in parallel tests).