Slides for presentation / demo for a basic introduction to writing custom detectors for FindBugs. Talk was given at the London Java Community Unconference 2, 26th June 2010. The example code that goes with the slides is here: http://bit.ly/fb_demo.

1. A basic introduction to Writing Custom Detectors for FindBugs

5. Ant task / maven plugin – part of CI build

7. Dependent libraries (binaries)

8. Other JVM languages, compiled to ByteCode? FindBugs What's FindBugs?

10. Flag common API misuses

11. Environment/platform-specific constraints

13. A sequence of operations that is doomed to fail Custom Detectors Why create a custom detector?

15. messages.xml

17. One detector class can report multiple bug types. Custom Detectors FindBugs Plugins

22. Usually pronounced eb-sih-dic.

23. It is not ASCII-compatible.

24. … but it becomes relevant when your code runs in an IBM mainframe! The EBCDIC Issue What's EBCDIC? “ EBCDIC is not relevant to your life.” -Joel Spolsky

30. Imagine you're sending bytes over the network and the client is expecting ISO8859-1 text:

31. On ASCII-compatible platforms , the code above sends the correct ISO8859-1 bytes for HELLO .

32. On z/OS , it sends data that ISO88591-decodes to: ÈÅÓÓÖ

33. The code should look something like: The EBCDIC Issue If you �Unicode, you’ll �����EBCDIC connection.getOutputStream().write( "HELLO" .getBytes()); connection.getOutputStream().write( "HELLO" .getBytes( " ISO8859-1 " ));

35. Not a suitable solution if different libraries make different assumptions about the default.

37. The EBCDIC Issue Affected Java Class Library Methods java.lang.String.getBytes() java.lang.String(byte[] bytes) java.io.ByteArrayOutputStream.toString() java.io.FileReader(String filename) java.io.FileReader(File file) java.io.FileReader(FileDescriptor fileDescriptor) java.io.FileWriter(String filename) java.io.FileWriter(File file) java.io.FileWriter(FileDescriptor fileDescriptor) java.io.InputStreamReader(InputStream input) java.io.OutputStreamWriter(OutputStream output) java.io.PrintStream(File file) java.io.PrintStream(OutputStream output) java.io.PrintStream(String string) java.io.PrintWriter(File file) java.io.PrintWriter(OutputStream output) java.io.PrintWriter(String string) java.util.Scanner(InputStream input) java.util.Formatter(String filename) java.util.Formatter(File file) java.util.Formatter(OutputStream output)

38. -> See code. Default Encoding Detector Implementation of the default encoding detector

41. XMethod, MethodDescriptor, Method (BCEL)

43. StatelessDetector: Marker interface – detector is cloned on each class so any state that is not cloned can be GC'd

44. DataflowAnalysis: Provides access to a control flow graph More FindBugs Classes

48. Presentation on custom detectors by FindBugs authors: http://bit.ly/fb_4r

49. Daniel Schneller's blog posts about custom detectors: http://bit.ly/fb_dsblog

50. Josh Cummings' blog post about testing detectors: http://bit.ly/fb_jcblog

51. ByteCode Outline plugin for Eclipse: http://asm.ow2.org/eclipse/index.html

52. FindBugs Mailing List Links