Tools for automatic detection of static errors. While common tools work with source-code, this approach analyses Java byte-code. It discovers possible Java Linkage Errors such as NoSuchMethodError.

1. STATIC PROBLEMS
DETECTION
Overview and Tool Demonstration
Kamil Ježek kjezek@kiv.zcu.cz
Přemek Brada brada@kiv.zcu.cz
Západočeská univerzita v Plzni
Katedra informatiky a výpočetní techniky

2. What We Detect
LinkageError
ClassCastException
NoSuchMethodError
IncompatibleClassChangeError
…
and more
Recompilable problems
Duplicated and redundant libraries

3. Brief Example
LineIterator it = ...
String line = it.next();
class LineIterator {
Object next();
}

4. Where We Detect Problems
• Binaries (modules, libraries)
Source
code

5. Is This Real Problem?
75% of programs
riddled with static errors

6. Probable Cause
51% developers
unfamiliar with problem

7. Compatibility May Be Tricky
public class Main {
public static void main(String[] args) {
Object n = new LineIterator().next();
}
}
public class LineIterator {
public String next() {
return …;
}
}

8. JVM and Compiler Differences
public class Main {
public static void main(String[] args) {
LineIterator it = …
Object n = it.next();
}
}
public class LineIterator {
public Object next() {
return …;
}
}
public interface LineIterator {
public Object next();
}
v1 v2

9. Evidence in Real Life Software
Popular projects
• Apache Roller
• Commons-IO
Even Maven is not answer

10. Example 1: Apache Roller
Apache Roller links to two httpcore versions

11. Impact on Apache Roller
Method releaseConnection() invoked by
Spring-web missing in httpcore 4.1
• Reported and acknowledged

12. Example 2: Apache Commons-io
Commons-io is distributed in two packages

13. Impact of Apache Commons-IO
Maven Central Repository
org.apache.commons used by 542 projects
commons-io used by 293 projects

14. We Propose Solution
JAR files
Reverse
Engineering
Verification Report

15. Architecture
Another
integration
Eclipse
Plugin
Maven Plugin
Backward
Compatibility
Composition
Verification
Reverse
Engineering

16. Detected Problems
● Missing dependencies (1)
● Inconsistent dependencies (2)
● Redundant dependencies (3)
● Duplicated dependencies (4)
Source
code
(1)
(2)
(4)
(3)

17. Reverse Engineering
class LineIterator {
Object next(...) { … }
}
class Client {
private iterate(...) {
LineIterator it = IOUtils.lineIterator(…);
while (it.hasNext()) {
String data = it.next();
}
ConsumerChanged in 2.xProvider
<<Class>>
LineIterator
<<Method>>
next
<<Return>>
Object
<<Class>>
LineIterator
<<Method>>
next
<<Return>>
String

18. Verification
>
≥
<
≤
=
≠
?
ConsumerProvider
<<Class>>
LineIterator
<<Method>>
next
<<Return>>
Object
<<Class>>
LineIterator
<<Method>>
next
<<Return>>
String

19. Impact Demonstration
• Problem with duplicated Commons-IO
• Based on semi-real Booking web application

20. Web Page With Bug

21. Standard Debug I

22. Standard Debug II
• Log analysis (when enabled)
2015-04-15 17:17:58.538 WARN [org.eclipse.jetty.util.thread.QueuedThreadPool:run:577] -
java.lang.NoSuchMethodError: org.apache.commons.io.LineIterator.next()Ljava/lang/String;
at cz.zcu.kiv.examples.booking.preferences.RatingLoader.load(RatingLoader.java:29)
at cz.zcu.kiv.examples.booking.server.RunServer$2.handle(RunServer.java:53)
at spark.webserver.MatcherFilter.doFilter(MatcherFilter.java:139)
at spark.webserver.JettyHandler.doHandle(JettyHandler.java:54)

23. Our Way: Maven plugin
• > mvn install
cz.zcu.kiv.examples.booking.preferences.RatingLoader
#4 <>-- org.apache.commons.io.LineIterator
Method: next
Generalised Return type: java.lang.String x java.lang.Object
=============================================================
Duplicated <>-- org.apache.commons.io.LineIterator
#5 /../.m2/repository/../commons-io-1.3.2.jar
-> #4
#6 /../.m2/repository/../commons-io-2.1.jar
---------------------------------------------------------------------------------
Must remove /../.m2/repository/../commons-io-1.3.2.jar
-> #5
---------------------------------------------------------------------------------
Redundant /../.m2/repository/../jetty-security-9.0.2.v20130417.jar

24. Eclipse Plugin

25. Easy to Fix Now
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>1.3.2 2.1</version>
<type>jar</type>
<scope>compile</scope>
</dependency>

26. Result is Working System

27. We Offer
• Presented tools
• Customization
• Development of new features

28. Conclusion
• Automatic tools
• Problems detected early in development
• Solve current problems
• Cheaper and more robust software

29. Discussion
Questions now
or
Kamil Ježek kjezek@kiv.zcu.cz
Přemek Brada brada@kiv.zcu.cz
Západočeská univerzita v Plzni
Katedra informatiky a výpočetní techniky