This page contains temporary result from dicussions on error handling.

These guidelines must be reviewed and approved before being promoted to the Error Handling page.

Best practices

Human readable logs : fields organized in aligned columns, standard date format
Redefine toSring() method : using Guava Objects.ToStringHelper for instance. It helps a lot to improve log readability.

Anti patterns

Multi-line log messages. Messages must be grouped in a single log.

Huge try-catch block complicates refactoring

try {
  is = new FileInputStream(fileName); // throws FileNotFoundException
  ... // a lot of other stuff, which can't throw FileNotFoundException
  ... // also you can imagine that one day after refactorings this block will contain call to method, which also may throw FileNotFoundException
} catch (FileNotFoundException e) {
  ...
}

Re-wrapping exceptions

Not correct propagation :

try {
  // do risky stuff
} catch (Exception e) {
  throw new RuntimeException(e); // unnecessary wrapping in case if e instanceof RuntimeException
}

Better :

try {
  doRiskyStuff();
} catch (RuntimeException e) {
  throw e;
} catch (Exception e) {
  throw new RuntimeException(e.getMessage(), e);
}

With Google Guava :

try {
  // do risky stuff
} catch (Exception e) {
  throw Throwables.propagate(e);
}

Logback advanced features

Display class packaging information in stacktrace with the option xThrowable{level}.

Integration tests

Regressions are frequently introduced on error handling. Integration tests must verify behaviors on error as much as possible. Most of time they need to access generated logs. See ORCH-66.