Stack trace as String

You need to call the Throwable#printStackTrace(PrintWriter);

try{

}catch(Exception ex){
    String message = getStackTrace(ex);
}

public static String getStackTrace(final Throwable throwable) {
     final StringWriter sw = new StringWriter();
     final PrintWriter pw = new PrintWriter(sw, true);
     throwable.printStackTrace(pw);
     return sw.getBuffer().toString();
}

You can also use commons-lang-2.2.jar Apache Commons Lang library which provides this functionality:

public static String getStackTrace(Throwable throwable)
Gets the stack trace from a Throwable as a String.

ExceptionUtils#getStackTrace()