Gives 5 hands on tips on how to improve a specific aspect of Quality on Java projects

1. Implementing Quality
on Java projects
Vincent Massol
Committer XWiki
XWiki SAS
@vmassol
27 au 29 mars 2013
Sunday, March 31, 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
• 3 books: JUnit in Action, Maven: A Developer’s Notebook, BBWM
Sunday, March 31, 13

3. What is Quality?
Sunday, March 31, 13

4. The XWiki project in summary
• 9 years old
• 28 active
committers
• 7 committers
do 80% of
work
• 700K NCLOC
• 11 commits/
day
• 16 mails/day
Sunday, March 31, 13

5. Examples of Quality actions
• Coding rules (Checkstyle, ...) • Ensure API stability
• Test coverage • Code reviews
• Track bugs • License header checks
• Don’t use Commons Lang 2.x • Release with Java 6
• Use SLF4J and don’t draw Log4J/ • Ensure javadoc exist
JCL in dependencies
• Prevent JAR hell
• Automated build
• Release often (every 2 weeks)
• Automated unit tests
• Collaborative design
• Stable automated
• Test on supported
functional tests environments (DB & Browsers)
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6. Quality Tip #1
API Stability
27 au 29 mars 2013
Sunday, March 31, 13

7. The Problem
Class Not Found or Method Not
Found
Sunday, March 31, 13

8. API Stability - Deprecations
/**
* ...
* @deprecated since 2.4M1 use {@link #transform(
* Block, TransformationContext)}
*/
@Deprecated
void transform(XDOM dom, Syntax syntax)
throws TransformationException;
Sunday, March 31, 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, March 31, 13

10. API Stability - CLIRR (2/2)
Example from XWiki 5.0M1 Release notes
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11. API Stability - Internal Package
Javadoc
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin
<configuration>
<excludePackageNames>*.internal.*
</excludePackageNames>
CLIRR
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>clirr-maven-plugin</artifactId>
<excludes>
<exclude>**/internal/**</exclude>
<exclude>**/test/**</exclude>
Sunday, March 31, 13

12. API Stability - Legacy Module
Aspect Weaving
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>aspectj-maven-plugin</...>
...
<configuration>
<weaveDependencies>
<weaveDependency>
<groupId>org.xwiki.rendering</...>
<artifactId>xwiki-rendering-api</...>
...
+ “Legacy” Profile
Sunday, March 31, 13

13. API Stability - Young APIs
/**
* ...
* @since 5.0M1
*/
@Unstable(<optional explanation>)
public EntityReference createEntityReference(String name,...)
{
...
}
+ max duration for keeping the annotation!
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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
• Java 8 and Virtual Extension/Defender methods
interface TestInterface {
public void testMe();
public void newMethod() default {
System.out.println("Default from interface");
}
}
Sunday, March 31, 13

15. Quality Tip #2
JAR Hell
27 au 29 mars 2013
Sunday, March 31, 13

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, March 31, 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!
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19. Maven: dependency version issue
<dependencies>
<dependency> Will run logback 0.9.9
<groupId>org.slf4j</groupId> with slf4J-api 1.4.0
<artifactId>slf4j-api</artifactId> instead of 1.5.0!
<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>
Sunday, March 31, 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, March 31, 13

21. Quality Tip #3
Test Coverage
27 au 29 mars 2013
Sunday, March 31, 13

22. The Problem
More bugs reported, overall quality
goes down and harder to debug
software
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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>}
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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
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25. Quizz Time!
Step 1: Building on my local machine gives the following:
[INFO] --- jacoco-maven-plugin:0.6.2.201302030002:check (jacoco-check)
[INFO] All coverage checks have been met.
Step 2: Building on the CI machine gave:
[INFO] --- jacoco-maven-plugin:0.6.2.201302030002:check (jacoco-check)
[WARNING] Insufficient code coverage for INSTRUCTION: 75.52% < 75.53%
Non determinism! Why?
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26. Quizz Answer
... because the JVM is non deterministic!
private Map componentEntries = new ConcurrentHashMap();
...
for (Map.Entry entry : componentEntries.entrySet())
{
if (entry.getValue().instance == component) {
key = entry.getKey();
oldDescriptor = entry.getValue().descriptor;
break;
}
}
Sunday, March 31, 13

27. Quality Tip #4
Functional Testing Stability
(with Jenkins)
27 au 29 mars 2013
Sunday, March 31, 13

28. The Problem
Too many false positives leading to
developers not paying attention to CI
emails anymore... leading to failing
software
Sunday, March 31, 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)
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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, March 31, 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, March 31, 13

32. Step 2: Mail Ext Plugin
Pre-send Script
import hudson.model.*
build.actions.each { action ->
if (action instanceof ParametersAction) {
if (action.getParameter("noEmail")) {
cancel = true
}
}
}
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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
27 au 29 mars 2013
Sunday, March 31, 13

35. The Problem
Bugs increasing, even simple to fix
ones, devs focusing too much on new
features (i.e. scope creep) vs fixing Bugs created vs closed
what exists
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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 40 bugs!)
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37. Results
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38. Conclusion
27 au 29 mars 2013
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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)
• Project seen as “less fun”
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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, March 31, 13