How to log as much information as possible for a Java Exception

Question

There s a common problem I ve come across a few times when logging Exceptions  There seem to be various different types to deal with  E g  some wrap other Exceptions  some don t have a message at all - just a type   Most code I ve seen logs Exceptions using either getMessage   or toString   but these don t always capture all the information needed to pinpoint the problem - other methods such as getCause   and getStackTrace   sometimes provide additional info   As an example  the Exception I m looking at right now in my Eclipse Inspect window is an InvocationTargetException  The Exception itself has no cause  no message  no stacktrace     but the target from getCause   is InvalidUseOfMatchersException with these details populated   So my question is  Given an Exception of any type as an input please provide a single method that will output a nicely formatted String containing all relevant information about the Exception  e g  possibly recursively calling getCause   amongst other things   Before posting this question I was nearly going to have a stab at this myself but don t really want to reinvent the wheel - surely such a thing must have been done many times before      Please don t point me at any particular logging or utility framework to do this  I m looking for a fragment of code rather than a library since I don t have the right to add external dependencies on the project I m working on and it s actually being logged to part of a webpage rather than a file  If it s a case of copying the code fragment out of such a framework  and attributing it  that s fine  -

User · Answer

A logging script that I have written some time ago might be of help, although it is not exactly what you want. It acts in a way like a System.out.println but with much more information about StackTrace etc. It also provides Clickable text for Eclipse:

private static final SimpleDateFormat   extended    = new SimpleDateFormat( "dd MMM yyyy (HH:mm:ss) zz" );

public static java.util.logging.Logger initLogger(final String name) {
    final java.util.logging.Logger logger = java.util.logging.Logger.getLogger( name );
    try {

        Handler ch = new ConsoleHandler();
        logger.addHandler( ch );

        logger.setLevel( Level.ALL ); // Level selbst setzen

        logger.setUseParentHandlers( false );

        final java.util.logging.SimpleFormatter formatter = new SimpleFormatter() {

            @Override
            public synchronized String format(final LogRecord record) {
                StackTraceElement[] trace = new Throwable().getStackTrace();
                String clickable = "(" + trace[ 7 ].getFileName() + ":" + trace[ 7 ].getLineNumber() + ") ";
                /* Clickable text in Console. */

                for( int i = 8; i < trace.length; i++ ) {
                    /* 0 - 6 is the logging trace, 7 - x is the trace until log method was called */
                    if( trace[ i ].getFileName() == null )
                        continue;
                    clickable = "(" + trace[ i ].getFileName() + ":" + trace[ i ].getLineNumber() + ") -> " + clickable;
                }

                final String time = "<" + extended.format( new Date( record.getMillis() ) ) + "> ";

                StringBuilder level = new StringBuilder("[" + record.getLevel() + "] ");
                while( level.length() < 15 ) /* extend for tabby display */
                    level.append(" ");

                StringBuilder name = new StringBuilder(record.getLoggerName()).append(": ");
                while( name.length() < 15 ) /* extend for tabby display */
                    name.append(" ");

                String thread = Thread.currentThread().getName();
                if( thread.length() > 18 ) /* trim if too long */
                    thread = thread.substring( 0, 16 ) + "..."; 
                else {
                    StringBuilder sb = new StringBuilder(thread);
                    while( sb.length() < 18 ) /* extend for tabby display */
                        sb.append(" ");
                    thread = sb.insert( 0, "Thread " ).toString();
                }

                final String message = "\"" + record.getMessage() + "\" ";

                return level + time + thread + name + clickable + message + "\n";
            }
        };
        ch.setFormatter( formatter );
        ch.setLevel( Level.ALL );
    } catch( final SecurityException e ) {
        e.printStackTrace();
    }
    return logger;
}

Notice this outputs to the console, you can change that, see http://docs.oracle.com/javase/1.4.2/docs/api/java/util/logging/Logger.html for more information on that.

Now, the following will probably do what you want. It will go through all causes of a Throwable and save it in a String. Note that this does not use StringBuilder, so you can optimize by changing it.

Throwable e = ...
String detail = e.getClass().getName() + ": " + e.getMessage();
for( final StackTraceElement s : e.getStackTrace() )
    detail += "\n\t" + s.toString();
while( ( e = e.getCause() ) != null ) {
    detail += "\nCaused by: ";
    for( final StackTraceElement s : e.getStackTrace() )
        detail += "\n\t" + s.toString();
}

Regards,
Danyel

User · Answer

What s wrong with the printStacktrace   method provided by Throwable  and thus every exception   It shows all the info you requested  including the type  message  and stack trace of the root exception and all  nested  causes  In Java 7  it even shows you the information about  supressed  exceptions that might occur in a try-with-resources statement   Of course you wouldn t want to write to System err  which the no-argument version of the method does  so instead use one of the available overloads   In particular  if you just want to get a String     Exception e         StringWriter sw   new StringWriter      e printStackTrace new PrintWriter sw      String exceptionDetails   sw toString      If you happen to use the great Guava library  it provides a utility method doing this  com google common base Throwables getStackTraceAsString Throwable

User · Answer

It should be quite simple if you are using LogBack or SLF4J  I do it as below    imports import org slf4j Logger  import org slf4j LoggerFactory     Initialize logger Logger logger   LoggerFactory getLogger  lt classname gt  class   try        try something   catch Exception e        Actual logging of error    logger error  some message   e

User · Answer

The java util logging package is standard in Java SE  Its Logger includes an overloaded log method that accepts Throwable objects  It will log stacktraces of exceptions and their cause for you   For example   import java util logging Level  import java util logging Logger          Logger logger   Logger getAnonymousLogger    Exception e1   new Exception    Exception e2   new Exception e1   logger log Level SEVERE   an exception was thrown   e2     Will log   SEVERE  an exception was thrown java lang Exception  java lang Exception     at LogStacktrace main LogStacktrace java 21  Caused by  java lang Exception     at LogStacktrace main LogStacktrace java 20    Internally  this does exactly what  philipp-wendler suggests  by the way  See the source code for SimpleFormatter java  This is just a higher level interface

User · Answer

You can also use Apache s ExceptionUtils    Example   import org apache commons lang exception ExceptionUtils  import org apache log4j Logger    public class Test        static Logger logger   Logger getLogger Test class        public static void main String   args             try              String   avengers   null              System out println  Size    avengers length             catch  NullPointerException e               logger info ExceptionUtils getFullStackTrace e                         Console output   java lang NullPointerException     at com aimlessfist avengers ironman Test main Test java 11

User · Answer

Something that I do is to have a static method that handles all exceptions and I add the log to a JOptionPane to show it to the user  but you could write the result to a file in FileWriter wraped in a BufeeredWriter  For the main static method  to catch the Uncaught Exceptions I do   SwingUtilities invokeLater  new Runnable          Override     public void run               Initializations                Thread setDefaultUncaughtExceptionHandler       new Thread UncaughtExceptionHandler              Override         public void uncaughtException  Thread t  Throwable ex                 handleExceptions  ex  true                         And as for the method   public static void handleExceptions  Throwable ex  boolean shutDown         JOptionPane showMessageDialog  null           A CRITICAL ERROR APPENED  n            SYSTEM FAIL           JOptionPane ERROR MESSAGE         StringBuilder sb   new StringBuilder ex toString         for  StackTraceElement ste   ex getStackTrace              sb append   n tat    append ste               while   ex   ex getCause       null             sb append   n            for  StackTraceElement ste   ex getStackTrace                  sb append   n tat    append ste                        String trace   sb toString         JOptionPane showMessageDialog  null           PLEASE SEND ME THIS ERROR SO THAT I CAN FIX IT   n n    trace           SYSTEM FAIL           JOptionPane ERROR MESSAGE        if  shutDown             Runtime getRuntime   exit  0              In you case  instead of  screaming  to the user  you could write a log like I told you before   String trace   sb toString     File file   new File  mylog txt    FileWriter myFileWriter   null  BufferedWriter myBufferedWriter   null   try         with FileWriter File file  boolean append  you can writer to        the end of the file     myFileWriter   new FileWriter  file  true        myBufferedWriter   new BufferedWriter  myFileWriter         myBufferedWriter write  trace      catch   IOException ex1           Do as you want  Do you want to use recursive to handle        this exception  I don t advise that  Trust me      finally       try           myBufferedWriter close              catch   IOException ex1               Idem               try           myFileWriter close              catch   IOException ex1               Idem              I hope I have helped   Have a nice day

[java] How to log as much information as possible for a Java Exception?

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