I hope you already figured out the "why" question. Let me help you with the "how". We all have this PO/PM/CFO/boss (delete where inapplicable) that will ask us about the business impact: - Will it let us deliver the business features faster? - Will we gain a competitive edge? - Is it a kind of one-off task? - How much does it cost? We might hate to answer these "trivial" questions, but they are all valid. After all, we pick the tools to serve the purpose, not the other way around… In this session, I would like to present the approach IDEMIA took to upgrade any critical dependencies in our platforms. There is always some risk involved, but we have tools and practices that help us mitigate the issues, measure the impact and foresee potential consequences before they happen.

1. So, you wanna
migrate to Java9?
by Tomek Adamczewski
13/11/2017

2. Where are we?
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3. Cool features of Java 9
• Project Jigsaw
• JShell
• Enhanced Collections framework
• Enhanced @Deprecated
• Project Coin improvements
• Support for cgroup limits (think: docker)
• G1GC improvements
• Changes to JDK Release Model
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4. “Think trains, not limousines”
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5. 5
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13/11/2017 Definition of Done
• Code compiles
• New features merged to the master branch
• All tests pass
• The task is documented and closed

6. 1
6
Code
Compiles
jig·saw [jig-saw] n.
a complicated problem consisting of many
different parts
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7. There are no silver bullets
A lot of libraries or plugins are not compatible with Java 9 yet
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8. Useful tools
$ jdeps --jdk-internals -R --class-path ‘lib/*’ guava-HEAD-jre-SNAPSHOT.jar
split package: javax.annotation [jrt:/java.xml.ws.annotation, lib/jsr305-1.3.9.jar]
guava-HEAD-jre-SNAPSHOT.jar -> jdk.unsupported
com.google.common.cache.Striped64 -> sun.misc.Unsafe
JDK internal API (jdk.unsupported)
com.google.common.cache.Striped64$1 -> sun.misc.Unsafe
JDK internal API (jdk.unsupported)
(…)
JDK Internal API Suggested Replacement
---------------- ---------------------
sun.misc.Unsafe See http://openjdk.java.net/jeps/260
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9. …and hacks
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
<configuration>
- <source>1.8</source>
- <target>1.8</target>
+ <source>9</source>
+ <target>9</target>
+ <compilerArgs>
+ <arg>--add-exports</arg>
+ <arg>java.base/sun.security.jca=ALL-UNNAMED</arg>
+ </compilerArgs>
</configuration>
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10. …and hacks
java
① --add-opens java.base/java.lang=ALL-UNNAMED
② --add-modules java.xml.ws.annotation
③ --patch-module java.xml.ws.annotation=jsr305-3.0.2.jar
--class-path $dependencies
-jar $appjar
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11. 2
11
Code Compiles
New keyword
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12. JEP 302: Lambda Leftovers
Treatment of underscores
In many languages, it is common to use an underscore (_) to denote an unnamed
lambda parameter (and similarly for method and exception parameters):
(…)
Phase 2 came in Java 9, when this warning became an error.
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BiFunction<Integer, String, String> biss = (i, _) -> String.valueOf(i);

13. Sonar to the rescue!™
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14. Yet another tool to cope with?
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15. …not really!
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16. 3
16
New feature merged
to the master branch
Things might fail or
they might not fail
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17. Enhanced Collections framework
static <K,V> Map<K,V> of()
static <K,V> Map<K,V> of(K k1, V v1)
static <K,V> Map<K,V> of(K k1, V v1, K k2, V v2)
static <K,V> Map<K,V> of(K k1, V v1, K k2, V v2, K k3, V v3)
static <K,V> Map<K,V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5,
K k6, V v6, K k7, V v7, K k8, V v8, K k9, V v9, K k10, V v10)
static <K,V> Map<K,V> ofEntries(Map.Entry<? extends K,? extends V>... entries)
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Map<String, Integer> fooBar = Map.ofEntries(
entry("foo", 1),
entry("bar", 2),
// (...)
entry("baz", 42));

18. We’ve all done it before, didn’t we?
@SafeVarargs
public static <K, V> Map<K, V> map(Entry<K, ? extends V>... entries) {
return stream(entries)
.filter(Objects::nonNull)
.collect(toMap(Entry::getKey, Entry::getValue));
}
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19. private static final Map<String, ErrorReason> ERROR_REASON_MAPPER =
map(
entry("1001", Format_Incorrect),
entry("1002", Format_Expiry_Date_Incorrect),
// 95 more entries
entry(”6027", Entity_Already_Active));
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----------------------------------
BUILD SUCCESS
----------------------------------
Total time: 01:08 min (Wall Clock)

20. 20
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private static final Map<String, ErrorReason> ERROR_REASON_MAPPER =
MapUtils.<String, ErrorReason>map( //explicit generics improve compile time by ~50s
entry("1001", Format_Incorrect),
entry("1002", Format_Expiry_Date_Incorrect),
// 95 more entries
entry(”6027", Entity_Already_Active));
----------------------------------
BUILD SUCCESS
----------------------------------
Total time: 10.556 s (Wall Clock)

21. Jenkins build-timeout plugin
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Possible strategies
• Absolute
• Deadline
• Elastic
• Likely stuck
• No Activity
Possible actions
• Abort
• Fail
• Abort and restart
• Write build description

22. 4
22
All tests pass
Things might fail…
but they also might not fail
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23. OptUtils
/** @return ofNullable(t).map(provider).orElseGet(supplier) */
public static <T, R> R optGet(
T t,
Function<T, R> provider,
Supplier<R> supplier) {
return ofNullable(t).map(provider).orElseGet(supplier);
}
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24. You can “unit” test your performance
@Test
public void testPerf() throws Exception {
Result result = benchmark(4, 1000,
(thread, pass) -> singlePass(thread, pass));
LOG.info(Table.print(result));
assertExecTimes(result);
}
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25. Ugly? But it’s up to 10x faster…
/** @return ofNullable(t).map(provider).orElseGet(supplier) */
public static <T, R> R optGet(
T t,
Function<T, R> provider,
Supplier<R> supplier) {
return t == null ?
supplier.get() :
optGet(provider.apply(t), supplier);
}
/** @return ofNullable(t).orElseGet(supplier) */
public static <T> T optGet(T t, Supplier<T> supplier) {
return t == null ? supplier.get() : t;
}
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26. 5
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The task is documented
and closed
In case you just woke up…
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27. Brace yourself
Java WILL be updated every 6 months. Make sure you’re armed and ready
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28. CONTACT
tomasz.adamczewski@idemia.com