Java异常消息长度

Question

I am designing a database table, which will log Java exception messages.

For this case (and also out of interest) I want to know the (max.) message sizes I will encounter.

At the moment I am only interested in standard java language exceptions.

• Is there any technical limitation on the message size?
• What are the message lengths of the most common exceptions?
• What is the average message length of all standard java exceptions?
• Did the messages change a lot between different Java Versions?

Example:

try {
  //Some code, which throws an Exception
} catch(Exception ex) {
  String msg = ex.toString();    //Use toString, because sometimes there is no message
  int size = msg.length();       //How large can this be?
}

Throwable toString() implementation:

  public String toString() {
    String var1 = this.getClass().getName();
    String var2 = this.getLocalizedMessage();
    return var2 != null ? var1 + ": " + var2 : var1;
  }

---

Thanks for the replies. Bonus question: Is there a list with all the java language exception messages (in English), so I do not have to check the source files manually?

Answer 1

The Exception.getMessage() returns a String which doesn't have a length limit. There is no such thing as "standard" message length, it will depend on whatever libraries you are using in your codebase eg validation exceptions from javax.validation could be very long while NullPointerException often has no message.

You should get few days of logs from your application and write a regex to measure the expected length of an exception. Having this value you can make an educated guess.

Either define a VARCHAR column with given length and truncate the exception message when it's too long or define a blob/clob column and store the whole String . The deciding factor could be your database performance eg Oracle allows VARCHAR to have only 4000 bytes .

Answer 2

As far as I know there is no limitation on message length, nut in most cases The message is short in order to be practical. You probably will be safe with max size 2000 chars, but make it in DB as varchar so it takes only the space equal to the size of actual message in each case. Also exception's method toString() wouldn't give you any meaningful info. If there is no message then just store it as null or empty string "".