Avoid printStackTrace use a logger call instead

Question

In my application  I am running my code through PMD It shows me this message         Avoid printStackTrace    use a logger call instead        What does that mean

User · Answer

Almost every logging framework provides a method in which we can pass the throwable object along with a message. Like:

public trace(Marker marker, String msg, Throwable t);

They print the stacktrace of the throwable object.

User · Answer

It means you should use logging framework like logback or log4j and instead of printing exceptions directly   e printStackTrace      you should log them using this frameworks  API   log error  Ops    e     Logging frameworks give you a lot of flexibility  e g  you can choose whether you want to log to console or file - or maybe skip some messages if you find them no longer relevant in some environment

User · Answer

In Simple e printStackTrace   is not good practice because it just prints out the stack trace to standard error  Because of this you can t really control where this output goes

User · Answer

A production quality program should use one of the many logging alternatives  e g  log4j  logback  java util logging  to report errors and other diagnostics   This has a number of advantages    Log messages go to a configurable location  The end user doesn t see the messages unless you configure the logging so that he she does  You can use different loggers and logging levels  etc to control how much little or much logging is recorded  You can use different appender formats to control what the logging looks like  You can easily plug the logging output into a larger monitoring   logging framework  All of the above can be done without changing your code  i e  by editing the deployed application s logging config file    By contrast  if you just use printStackTrace  the deployer   end user has little if any control  and logging messages are liable to either be lost or shown to the end user in inappropriate circumstances    And nothing terrifies a timid user more than a random stack trace

User · Answer

Let s talk in from company concept  Log gives you flexible levels  see Difference between logger info and logger debug   Different people want to see different levels  like QAs  developers  business people  But e printStackTrace   will print out everything  Also  like if this method will be restful called  this same error may print several times  Then the Devops or Tech-Ops people in your company may be crazy because they will receive the same error reminders  I think a better replacement could be log error  errors happend in XXX   e  This will also print out whole information which is easy reading than e printStackTrace

User · Answer

If you call printStackTrace   on an exception the trace is written to System err and it s hard to route it elsewhere  or filter it   Instead of doing this you are adviced to use a logging framework  or a wrapper around multiple logging frameworks  like Apache Commons Logging  and log the exception using that framework  e g  logger error  some exception message   e     Doing that allows you to    write the log statement to different locations at once  e g  the console and a file filter the log statements by severity  error  warning  info  debug etc   and origin  normally package or class based  have some influence on the log format without having to change the code etc

User · Answer

The main reason is that Proguard would remove Log calls from production  Because by logging or printing StackTrace  it is possible to see them  information inside stack trace or Log  inside the Android phone by for example Logcat Reader application  So that it is a bad practice for security  Also  we do not access them during production  it would better to get removed from production  As ProGuard remove all Log calls not stackTrace  so it is better to use Log in catch blocks and let them removed from Production by Proguard

[java] Avoid printStackTrace(); use a logger call instead

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