1. Implementing Quality
on Java projects
Vincent Massol
Committer XWiki
CTO XWiki SAS
@vmassol
Sunday, April 21, 13

2. Vincent Massol
• Speaker Bio
•CTO XWiki SAS
• Your Projects
•XWiki (community-driven open source project)
•Past: Maven, Apache Cargo, Apache Cactus, Pattern
Testing
• Other Credentials:
•LesCastCodeurs podcast
•Creator of OSSGTP open source group in Paris
Sunday, April 21, 13

3. What is Quality?
Sunday, April 21, 13

4. The XWiki project in summary
• 9 years old
• 28 active
committers
• 7 committers
do 80% of
work
• 700K
NCLOC
• 11 commits/
day
Sunday, April 21, 13

5. Examples of Quality actions
• Coding rules (Checkstyle, ...)
• Test coverage
• Track bugs
• Don’t use Commons Lang 2.x
• Use SLF4J and don’t draw
Log4J/JCL in dependencies
• Automated build
• Automated unit tests
• Stable automated functional
tests
• Ensure API stability
• Code reviews
• License header checks
• Release with Java 6
• Ensure javadoc exist
• Prevent JAR hell
• Release often (every 2 weeks)
• Collaborative design
• Test on supported
environments (DB & Browsers)
Sunday, April 21, 13

6. Quality Tip #1
API Stability
Sunday, April 21, 13

7. The Problem
Class Not Found or Method Not
Found
Sunday, April 21, 13

8. API Stability - Deprecations
/**
* ...
* @deprecated since 2.4M1 use {@link #transform(
* Block, TransformationContext)}
*/
@Deprecated
void transform(XDOM dom, Syntax syntax)
throws TransformationException;
Sunday, April 21, 13

9. API Stability - CLIRR (1/2)
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>clirr-maven-plugin</artifactId>
<configuration>
<ignored>
<difference>
<differenceType>7006</differenceType>
<className>org/xwiki/.../MetaDataBlock</className>
<method>org.xwiki....block.Block clone()</method>
<to>org.xwiki.rendering.block.MetaDataBlock</to>
<justification>XDOM#clone() doesn't clone the meta
data</justification>
</difference>
...
Sunday, April 21, 13

10. API Stability - CLIRR (2/2)
Example from XWiki 5.0M1 Release notes
Sunday, April 21, 13

11. API Stability - Internal Package
Javadoc
CLIRR
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>clirr-maven-plugin</artifactId>
<excludes>
<exclude>**/internal/**</exclude>
<exclude>**/test/**</exclude>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin
<configuration>
<excludePackageNames>*.internal.*
</excludePackageNames>
Sunday, April 21, 13

12. API Stability - Legacy Module
Aspect Weaving
+ “Legacy” Profile
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>aspectj-maven-plugin</...>
...
<configuration>
<weaveDependencies>
<weaveDependency>
<groupId>org.xwiki.rendering</...>
<artifactId>xwiki-rendering-api</...>
...
Sunday, April 21, 13

13. API Stability - Young APIs
/**
* ...
* @since 5.0M1
*/
@Unstable(<optional explanation>)
public EntityReference createEntityReference(String name,...)
{
...
}
+ max duration for keeping the annotation!
Sunday, April 21, 13

14. API Stability - Next steps
• Annotation or package for SPI?
• Better define when to use the @Unstable
annotation
• Not possible to add a new method to an existing
Interface without breaking compatibility
•Java 8 and Virtual Extension/Defender methods
interface TestInterface {
public void testMe();
public void newMethod() default {
System.out.println("Default from interface"); }
Sunday, April 21, 13

15. Quality Tip #2
JAR Hell
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16. The Problem
Class Not Found or Method Not
Found or not working feature
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17. No duplicate classes @ runtime
<plugin>
<groupId>com.ning.maven.plugins</groupId>
<artifactId>maven-duplicate-finder-plugin</artifactId>
<executions>
<execution>
<phase>verify</phase>
<goals>
<goal>check</goal>
</goals>
<configuration>
<failBuildInCaseOfConflict>true</...>
<exceptions>
...
Sunday, April 21, 13

18. Surprising results...
• Commons Beanutils bundles some classes from Commons
Collections, apparently to avoid drawing a dependency to it...
• Xalan bundles a lot of other projects (org/apache/xml/**, org/
apache/bcel/**, JLex/**, java_cup/**, org/apache/regexp/**). In
addition, it even has these jars in its source tree without any
indication about their versions...
• stax-api, geronimo-stax-api_1.0_spec and xml-apis all draw
javax.xml.stream.* classes
• xmlbeans and xml-apis draw incompatible versions of
org.w3c.dom.* classes
14 exceptions in total!
Sunday, April 21, 13

19. Maven: dependency version issue
<dependencies>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.4.0</version>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>0.9.9</version>
<!-- Depends on org.slf4j:slf4j-api:1.5.0 -->
</dependency>
</dependencies>
Will run logback 0.9.9
with slf4J-api 1.4.0
instead of 1.5.0!
Sunday, April 21, 13

20. Maven: ensure correct version
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-enforcer-plugin</artifactId>
<executions>
<execution>
<id>enforce-version-compatibility</id>
<phase>verify</phase>
<goals>
<goal>enforce</goal>
</goals>
<configuration>
<rules>
<requireUpperBoundDeps/>
</rules>
Sunday, April 21, 13

21. Quality Tip #3
Test Coverage
Sunday, April 21, 13

22. The Problem
More bugs reported, overall
quality goes down and harder to
debug software
Sunday, April 21, 13

23. Use Jacoco to fail the build
<plugin>
<groupId>org.jacoco</groupId>
<artifactId>jacoco-maven-plugin</artifactId>
<executions>
<execution><id>jacoco-prepare</id>
<goals><goal>prepare-agent</goal></goals>
</execution>
<execution><id>jacoco-check</id>
<goals><goal>check</goal></goals>
</execution>
</executions>
<configuration>
<check>
<instructionRatio>${xwiki.jacoco.instructionRatio}</...>
</check>}
Sunday, April 21, 13

24. Strategy
• When devs add code (and thus
tests), increase the TPC percentage
• Put the Jacoco check in “Quality”
Maven Profile
• Have a CI job to execute that
profile regularly
•About 15% overhead compared to build
without checks
• “Cheat mode”: Add easier-to-write
test
Sunday, April 21, 13

25. Quizz Time!
[INFO] --- jacoco-maven-plugin:0.6.2.201302030002:check (jacoco-check)
[INFO] All coverage checks have been met.
[INFO] --- jacoco-maven-plugin:0.6.2.201302030002:check (jacoco-check)
[WARNING] Insufficient code coverage for INSTRUCTION: 75.52% < 75.53%
Step 1: Building on my local machine gives the following:
Step 2: Building on the CI machine gave:
Non determinism! Why?
Sunday, April 21, 13

26. Quizz Answer
private Map componentEntries = new ConcurrentHashMap();
...
for (Map.Entry entry : componentEntries.entrySet())
{
if (entry.getValue().instance == component) {
key = entry.getKey();
oldDescriptor = entry.getValue().descriptor;
break;
}
}
... because the JVM is non deterministic!
Sunday, April 21, 13

27. Quality Tip #4
Functional Testing
Stability
Sunday, April 21, 13

28. The Problem
Too many false positives
leading to developers not
paying attention to CI emails
anymore... leading to failing
software
Sunday, April 21, 13

29. False positives examples
• The JVM has crashed
• VNC is down (we run Selenium tests)
• Browser crash (we run Selenium tests)
• Git connection issue
• Machine slowness (if XWiki cannot start under 2 minutes
then it means the machine has some problems)
• Nexus is down (we deploy our artifacts to a Nexus
repository)
• Connection issue (Read time out)
Sunday, April 21, 13

30. Step 1: Groovy PostBuild Plugin (1/2)
def messages = [
[".*A fatal error has been detected by the Java Runtime Environment.*",
"JVM Crash", "A JVM crash happened!"],
[".*Error: cannot open display: :1.0.*",
"VNC not running", "VNC connection issue!"],
...
]
def shouldSendEmail = true
messages.each { message ->
if (manager.logContains(message.get(0))) {
manager.addWarningBadge(message.get(1))
manager.createSummary("warning.gif").appendText(...)
manager.buildUnstable()
shouldSendEmail = false
}
}
Sunday, April 21, 13

31. Step 1: Groovy PostBuild Plugin (2/2)
... continued from previous slide...
if (!shouldSendEmail) {
def pa = new ParametersAction([
new BooleanParameterValue("noEmail", true)
])
manager.build.addAction(pa)
}
Sunday, April 21, 13

32. Step 2: Mail Ext Plugin
import hudson.model.*
build.actions.each { action ->
if (action instanceof ParametersAction) {
if (action.getParameter("noEmail")) {
cancel = true
}
}
}
Pre-send Script
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33. Results
+ use the Scriptler plugin to automate configuration for all jobs
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34. Quality Tip #5
Bug Fixing Day
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35. The Problem
Bugs increasing, even
simple to fix
ones, devs focusing too much on
new features (i.e. scope creep)
vs fixing what exists
Bugs created vs closed
Sunday, April 21, 13

36. Bug Fixing Day
• Every Thursday
• Goal is to close the max number of bugs
• Triaging: Can be closed with Won’t fix,
Duplicate, Cannot Reproduce, etc
• Close low hanging fruits in priority
• Started with last 365 days then with last 547
days and currently with last 730 days (we
need to catch up with 6 bugs!)
Sunday, April 21, 13

37. Results
Sunday, April 21, 13

38. Conclusion
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39. Parting words
• Slowly add new quality check over time
• Everyone must be on board
• Favor Active Quality (i.e. make the build fail) over
Passive checks
• Be ready to adapt/remove checks if found not useful
enough
• Quality brings some risks:
•Potentially less committers for your project (especially open
source)
Sunday, April 21, 13

40. Be proud of your Quality!
“I have offended God and
mankind because my work
didn't reach the quality it should
have.”
Leonardo da Vinci, on his death bed
Sunday, April 21, 13