Github user pwendell commented on the pull request:
https://github.com/apache/spark/pull/17#issuecomment-36436518
Hey @ScrapCodes - this is really cool! It's great that we will get this
into Spark 1.0 so that we can support Java 8 lambdas moving forward. I have
some high level suggestions focused on the build and documentation:
1. Would you mind writing a "Upgrading from pre 1.0 versions of Spark"
section in the Java programming guide. It should go over the backwards
incompatible stuff and explain what users will need to change.
2. Would you mind adding breif README file in the java8-tests directory
that explains what it is? From what I can tell these need to be isolated in a
separate directory since we don't require JDK 8 to build Spark. It would be
good to explain that, because it looks pretty ugly having that top-level
directory sitting there and people might get confused.
3. When running the tests in Maven, I noticed this puts all of the output
to the console, and actually it didn't show the test summaries as they were
running. This will blow up the output on Jenkins and makes it hard to see
what's going on. I think we've configured the other Maven tests to output to a
file and show summaries, it would be good if this matched how those work.
4. I found it hard to get SBT to use the correct Java version without
setting Java 8 as my system default. I was able to fix that with the following
changes - mind adding these?
A. Change the sbt/sbt script so it respects JAVA_HOME similar to
./spark-class. Right now it just uses the "java" which is not easy to switch
around between versions.
B. In SparkBuild I pass through JAVA_HOME.
```
javacOptions := Seq("-target", JAVAC_JVM_VERSION, "-source",
JAVAC_JVM_VERSION),
+ // Pass through user defined JAVA_HOME if set
+ javaHome := Option(System.getenv("JAVA_HOME")).map(h => new File(h)),
```
5. Would you mind adding a warning to `dev/run-tests` script if the Java
version is less than 1.8? Unfortunately I think this will mean again checking
for JAVA_HOME. We should print a warning at the top saying that Java 8 tests
will not run if the JDK version is < 1.8.
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