Tip 1 - Exception Logging in Java

TIP #1 - Always Use The toString() Method Of The Exception Class Instead Of getMessage().

One of the common patterns in exception logging that I see a lot (and I've used it myself) is

catch(Exception e)
{
    logger.error ("Exception Message : " + e.getMessage());
}

The problem with e.getMessage() is that for lot of Exceptions (including many thrown by in build java classes) its value is either null or a cryptic string. Without any information on the exception type it makes it very difficult to determine what actually went wrong.

Consider these rather simple example

• when a null pointer exceptions is thrown
  
  

  //Exception Message : null
  System.out.println("Exception Message : " + e.getMessage());
  
  //Exception Message : java.lang.NullPointerException
  System.out.println("Exception Message : " + e.toString());
  

  
  
• when an Number Format Exception is thrown
  
  

  //Exception Message : For input string: "x"
  System.out.println("Exception Message : " + e.getMessage());
  
  //Exception Message : java.lang.NumberFormatException: 
  For input string: "x"
  System.out.println("Exception Message : " + e.toString());
  

Which of the two messages would you rather see in your logs?

These example are typical of what e.getMessage() returns and without the Exception type the message-text is just a cryptic text value.