How to send a stacktrace to log4j

Question

Say you catch an exception and get the following on the standard output  like  say  the console  if you do a e printStackTrace      java io FileNotFoundException  so txt         at java io FileInputStream  lt init gt  FileInputStream java          at ExTest readMyFile ExTest java 19          at ExTest main ExTest java 7    Now I want to send this instead to a logger like  say  log4j to get the following   31947  AWT-EventQueue-0  ERROR Java io FileNotFoundException  so txt 32204  AWT-EventQueue-0  ERROR    at java io FileInputStream  lt init gt  FileInputStream java  32235  AWT-EventQueue-0  ERROR    at ExTest readMyFile ExTest java 19  32370  AWT-EventQueue-0  ERROR    at ExTest main ExTest java 7    How can I do this   try            catch  Exception e        final String s               lt -- What goes here      log error  s

User · Answer

In Log4j 2  you can use Logger catching   to log a stacktrace from an exception that was caught       try           String msg   messages messages length           logger error  An exception should have been thrown          catch  Exception ex            logger catching ex

User · Answer

You can use bellow code   import org apache logging log4j Logger  import org apache logging log4j LogManager   public class LogWriterUtility       Logger log       public LogWriterUtility Class lt   gt  clazz            log   LogManager getLogger clazz          public void errorWithAnalysis  Exception exception             String message  No Message on error           StackTraceElement   stackTrace   exception getStackTrace            if stackTrace  null  amp  amp  stackTrace length gt 0                message                 for  StackTraceElement e   stackTrace                    message      n    e toString                                    log error message                Here you can just call   LogWriterUtility errorWithAnalysis  YOUR EXCEPTION INSTANCE    It will print stackTrace into your log

User · Answer

Just because it happened to me and can be useful  If you do this  try            catch  Exception e        log error   failed       e        you will get the header of the exception and not the whole stacktrace  Because the logger will think that you are passing a String  Do it without    as skaffman said

User · Answer

Create this class    public class StdOutErrLog    private static final Logger logger   Logger getLogger StdOutErrLog class    public static void tieSystemOutAndErrToLog         System setOut createLoggingProxy System out        System setErr createLoggingProxy System err       public static PrintStream createLoggingProxy final PrintStream realPrintStream        return new PrintStream realPrintStream            public void print final String string                logger info string                     public void println final String string                logger info string                          Call this in your code  StdOutErrLog tieSystemOutAndErrToLog

User · Answer

The answer from skaffman is definitely the correct answer  All logger methods such as error    warn    info    debug   take Throwable as a second parameter   try          catch  Exception e    logger error  error     e       However  you can extract stacktrace as a String as well  Sometimes it could be useful if you wish to take advantage of formatting feature using      placeholder - see method void info String var1  Object    var2   In this case say you have a stacktrace as String  then you can actually do something like this   try          catch  Exception e    String stacktrace   TextUtils getStacktrace e   logger error  error occurred for usename    and group     details      username  group  stacktrace       This will print parametrized message and the stacktrace at the end the same way it does for method  logger error  error     e    I actually wrote an open source library that has a Utility for extraction of a stacktrace as a String with an option to smartly filter out some noise out of stacktrace  I e  if you specify the package prefix that you are interested in your extracted stacktrace would be filtered out of some irrelevant parts and leave you with very consized info  Here is the link to the article that explains what utilities the library has and where to get it  both as maven artifacts and git sources  and how to use it as well  Open Source Java library with stack trace filtering  Silent String parsing Unicode converter and Version comparison  See the paragraph  Stacktrace noise filter

User · Answer

You can also get stack trace as string via ExceptionUtils getStackTrace   See  ExceptionUtils java  I use it only for log debug  to keep log error simple

User · Answer

This answer may be not related to the question asked but related to title of the question    public class ThrowableTest        public static void main String   args             Throwable createdBy   new Throwable  Created at main              ByteArrayOutputStream os   new ByteArrayOutputStream            PrintWriter pw   new PrintWriter os           createdBy printStackTrace pw           try               pw close                os close              catch  IOException e                e printStackTrace                      logger debug os toString               OR  public static String getStackTrace  Throwable t        StringWriter stringWriter   new StringWriter        PrintWriter  printWriter    new PrintWriter stringWriter       t printStackTrace printWriter       printWriter close         surprise no IO exception here     try           stringWriter close              catch  IOException e              return stringWriter toString        OR  StackTraceElement   stackTraceElements   Thread currentThread   getStackTrace    for StackTraceElement stackTrace  stackTraceElements       logger debug stackTrace getClassName          stackTrace getMethodName       stackTrace getLineNumber

User · Answer

Try this   catch  Throwable t        logger error  any message    t       StackTraceElement   s   t getStackTrace        for StackTraceElement e   s           logger error   tat     e

User · Answer

You pass the exception directly to the logger  e g   try            catch  Exception e        log error   failed    e        It s up to log4j to render the stack trace

User · Answer

If you want to log a stacktrace without involving an exception just do this    String message        for StackTraceElement stackTraceElement   Thread currentThread   getStackTrace                                   message   message   System lineSeparator     stackTraceElement toString         log warn  Something weird happened  I will print the the complete stacktrace even if we have no exception just to help you find the cause    message

User · Answer

this would be good log4j error exception logging - readable by splunk other logging monitoring s w  everything is form of key-value pair  log4j would get the stack trace from Exception obj e      try             ---           ---       catch  Exception e            log error  api name    method     message   error description    msg                         new Object    api name    method name   e getMessage    e

[java] How to send a stacktrace to log4j?

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