Log4j configuring a Web App to use a relative path

Question

I have a java webapp that has to be deployed on either Win or Linux machines  I now want to add log4j for logging and I d like to use a relative path for the log file as I don t want to change the file path on every deployment  The container will most likely be Tomcat but not necessarily   What s the best way of doing this

User · Accepted Answer

I ve finally done it in this way   Added a ServletContextListener that does the following   public void contextInitialized ServletContextEvent event        ServletContext context   event getServletContext        System setProperty  rootPath   context getRealPath            Then in the log4j properties file   log4j appender file File   rootPath WEB-INF logs MyLog log   By doing it in this way Log4j will write into the right folder as long as you don t use it before the  rootPath  system property has been set  This means that you cannot use it from the ServletContextListener itself but you should be able to use it from anywhere else in the app   It should work on every web container and OS as it s not dependent on a container specific system property and it s not affected by OS specific path issues  Tested with Tomcat and Orion web containers and on Windows and Linux and it works fine so far   What do you think

User · Answer

Doesn t log4j just use the application root directory if you don t specify a root directory in your FileAppender s path property   So you should just be able to use   log4j appender file File logs MyLog log  It s been awhile since I ve done Java web development  but this seems to be the most intuitive  and also doesn t collide with other unfortunately named logs writing to the   catalina home  logs directory

User · Answer

You can specify relative path to the log file  using the work directory   appender file fileName     sys user dir  log application log   This is independent from the servlet container and does not require passing custom variable to the system environment

User · Answer

Tomcat sets a catalina home system property   You can use this in your log4j properties file   Something like this   log4j rootCategory DEBUG errorfile  log4j appender errorfile File   catalina home  logs LogFilename log   On Debian  including Ubuntu     catalina home  will not work because that points at  usr share tomcat6 which has no link to  var log tomcat6  Here just use   catalina base    If your using another container  try to find a similar system property  or define your own   Setting the system property will vary by platform  and container   But for Tomcat on Linux Unix I would create a setenv sh in the CATALINA HOME bin directory   It would contain   export JAVA OPTS  -Dcustom logging root  var log webapps    Then your log4j properties would be   log4j rootCategory DEBUG errorfile  log4j appender errorfile File   custom logging root  LogFilename log

User · Answer

In case you re using Maven I have a great solution for you    Edit your pom xml file to include following lines    lt profiles gt       lt profile gt           lt id gt linux lt  id gt           lt activation gt               lt os gt                   lt family gt unix lt  family gt               lt  os gt           lt  activation gt           lt properties gt               lt logDirectory gt  var log tomcat6 lt  logDirectory gt           lt  properties gt       lt  profile gt       lt profile gt           lt id gt windows lt  id gt           lt activation gt               lt os gt                   lt family gt windows lt  family gt               lt  os gt           lt  activation gt           lt properties gt               lt logDirectory gt   catalina home  logs lt  logDirectory gt           lt  properties gt       lt  profile gt   lt  profiles gt    Here you define logDirectory property specifically to OS family  Use already defined logDirectory property in log4j properties file   log4j appender FILE org apache log4j RollingFileAppender log4j appender FILE File   logDirectory  mylog log log4j appender FILE MaxFileSize 30MB log4j appender FILE MaxBackupIndex 10 log4j appender FILE layout org apache log4j PatternLayout log4j appender FILE layout ConversionPattern  d ISO8601    x   -5p   t    c 1    m n  That s it    P S   I m sure this can be achieved using Ant but unfortunately I don t have enough experience with it

User · Answer

As a further comment on https   stackoverflow com a 218037 2279200 - this may break  if the web app implicitely starts other ServletContextListener s  which may get called earlier and which already try to use log4j - in this case  the log4j configuration will be read and parsed already before the property determining the log root directory is set    the log files will appear somewhere below the current directory  the current directory when starting tomcat    I could only think of following solution to this problem  - rename your log4j properties  or logj4 xml  file to something which log4j will not automatically read  - In your context filter  after setting the property  call the DOM PropertyConfigurator helper class to ensure that your log4j-  xml properties  is read - Reset the log4j configuration  IIRC there is a method to do that   This is a bit brute force  but methinks it is the only way to make it watertight

User · Answer

Tomcat sets a catalina home system property   You can use this in your log4j properties file   Something like this   log4j rootCategory DEBUG errorfile  log4j appender errorfile File   catalina home  logs LogFilename log   On Debian  including Ubuntu     catalina home  will not work because that points at  usr share tomcat6 which has no link to  var log tomcat6  Here just use   catalina base    If your using another container  try to find a similar system property  or define your own   Setting the system property will vary by platform  and container   But for Tomcat on Linux Unix I would create a setenv sh in the CATALINA HOME bin directory   It would contain   export JAVA OPTS  -Dcustom logging root  var log webapps    Then your log4j properties would be   log4j rootCategory DEBUG errorfile  log4j appender errorfile File   custom logging root  LogFilename log

User · Answer

Doesn t log4j just use the application root directory if you don t specify a root directory in your FileAppender s path property   So you should just be able to use   log4j appender file File logs MyLog log  It s been awhile since I ve done Java web development  but this seems to be the most intuitive  and also doesn t collide with other unfortunately named logs writing to the   catalina home  logs directory

User · Answer

My suggestion is the log file should always be logged above the root context of the webApp  so in case we redeploy the webApp  we don t want to override the existing log files

User · Answer

My solution is similar to Iker Jimenez s solution  but instead of using System setProperty      I use org apache log4j PropertyConfigurator configure Properties   For that I also need log4j to be unable to find its configuration on its own and I load it manually  both points described in Wolfgang Liebich s answer    This works for Jetty and Tomcat  standalone or run from IDE  requires zero configuration  allows to put each app s logs in their own folder  no matter how many apps inside the container  which is the problem with the System-based solution   This way one can also put the log4j config file anywhere inside the web app  e g  in one project we had all config files inside WEB-INF     Details    I have my properties in the log4j-no-autoload properties file in the classpath  e g  in my Maven project it s originally in src main resources  gets packaged into WEB-INF classes   It has the file appender configured as e g    log4j appender MyAppFileAppender   org apache log4j FileAppender log4j appender MyAppFileAppender file     webAppRoot  WEB-INF logs my-app log      And I have a context listener like this  gets much shorter with Java 7 s  try-with-resource  syntax     WebListener public class ContextListener implements ServletContextListener        Override     public void contextInitialized final ServletContextEvent event            Properties props   new Properties            InputStream strm               ContextListener class getClassLoader                    getResourceAsStream  log4j-no-autoload properties            try               props load strm             catch  IOException propsLoadIOE                throw new Error  can t load logging config file   propsLoadIOE             finally               try                   strm close                  catch  IOException configCloseIOE                    throw new Error  error closing logging config file   configCloseIOE                                   props put  webAppRoot   event getServletContext   getRealPath                PropertyConfigurator configure props              from now on  I can use LoggerFactory getLogger

User · Answer

Doesn t log4j just use the application root directory if you don t specify a root directory in your FileAppender s path property   So you should just be able to use   log4j appender file File logs MyLog log  It s been awhile since I ve done Java web development  but this seems to be the most intuitive  and also doesn t collide with other unfortunately named logs writing to the   catalina home  logs directory

User · Answer

In case you re using Maven I have a great solution for you    Edit your pom xml file to include following lines    lt profiles gt       lt profile gt           lt id gt linux lt  id gt           lt activation gt               lt os gt                   lt family gt unix lt  family gt               lt  os gt           lt  activation gt           lt properties gt               lt logDirectory gt  var log tomcat6 lt  logDirectory gt           lt  properties gt       lt  profile gt       lt profile gt           lt id gt windows lt  id gt           lt activation gt               lt os gt                   lt family gt windows lt  family gt               lt  os gt           lt  activation gt           lt properties gt               lt logDirectory gt   catalina home  logs lt  logDirectory gt           lt  properties gt       lt  profile gt   lt  profiles gt    Here you define logDirectory property specifically to OS family  Use already defined logDirectory property in log4j properties file   log4j appender FILE org apache log4j RollingFileAppender log4j appender FILE File   logDirectory  mylog log log4j appender FILE MaxFileSize 30MB log4j appender FILE MaxBackupIndex 10 log4j appender FILE layout org apache log4j PatternLayout log4j appender FILE layout ConversionPattern  d ISO8601    x   -5p   t    c 1    m n  That s it    P S   I m sure this can be achieved using Ant but unfortunately I don t have enough experience with it

User · Answer

My solution is similar to Iker Jimenez s solution  but instead of using System setProperty      I use org apache log4j PropertyConfigurator configure Properties   For that I also need log4j to be unable to find its configuration on its own and I load it manually  both points described in Wolfgang Liebich s answer    This works for Jetty and Tomcat  standalone or run from IDE  requires zero configuration  allows to put each app s logs in their own folder  no matter how many apps inside the container  which is the problem with the System-based solution   This way one can also put the log4j config file anywhere inside the web app  e g  in one project we had all config files inside WEB-INF     Details    I have my properties in the log4j-no-autoload properties file in the classpath  e g  in my Maven project it s originally in src main resources  gets packaged into WEB-INF classes   It has the file appender configured as e g    log4j appender MyAppFileAppender   org apache log4j FileAppender log4j appender MyAppFileAppender file     webAppRoot  WEB-INF logs my-app log      And I have a context listener like this  gets much shorter with Java 7 s  try-with-resource  syntax     WebListener public class ContextListener implements ServletContextListener        Override     public void contextInitialized final ServletContextEvent event            Properties props   new Properties            InputStream strm               ContextListener class getClassLoader                    getResourceAsStream  log4j-no-autoload properties            try               props load strm             catch  IOException propsLoadIOE                throw new Error  can t load logging config file   propsLoadIOE             finally               try                   strm close                  catch  IOException configCloseIOE                    throw new Error  error closing logging config file   configCloseIOE                                   props put  webAppRoot   event getServletContext   getRealPath                PropertyConfigurator configure props              from now on  I can use LoggerFactory getLogger

User · Answer

If you use Spring you can   1  create a log4j configuration file  e g    WEB-INF classes log4j-myapp properties  DO NOT name it  log4j properties   Example   log4j rootLogger ERROR  stdout  rollingFile  log4j appender stdout org apache log4j ConsoleAppender log4j appender stdout layout org apache log4j PatternLayout log4j appender stdout layout ConversionPattern  d  p   c  -  lt  m gt  n  log4j appender rollingFile org apache log4j RollingFileAppender log4j appender rollingFile File   myWebapp-instance-root  WEB-INF logs application log log4j appender rollingFile MaxFileSize 512KB log4j appender rollingFile MaxBackupIndex 10 log4j appender rollingFile layout org apache log4j PatternLayout log4j appender rollingFile layout ConversionPattern  d  p   c  -  m n log4j appender rollingFile Encoding UTF-8   We ll define  myWebapp-instance-root  later on point  3   2  Specify config location in web xml    lt context-param gt     lt param-name gt log4jConfigLocation lt  param-name gt     lt param-value gt  WEB-INF classes log4j-myapp properties lt  param-value gt   lt  context-param gt    3  Specify a unique variable name for your webapp s root  e g   myWebapp-instance-root    lt context-param gt     lt param-name gt webAppRootKey lt  param-name gt     lt param-value gt myWebapp-instance-root lt  param-value gt   lt  context-param gt    4  Add a Log4jConfigListener    lt listener gt     lt listener-class gt org springframework web util Log4jConfigListener lt  listener-class gt   lt  listener gt    If you choose a different name  remember to change it in log4j-myapp properties  too   See my article  Italian only    but it should be understandable   http   www megadix it content configurare-path-relativi-log4j-utilizzando-spring  UPDATE  2009 08 01  I ve translated my article to English  http   www megadix it node 136

User · Answer

Just a comment on Iker s solution    ServletContext is a good solution for your problem  But I don t think it is good for maintains  Most of the time log files are required to be saved for long time    Since ServletContext makes the file under the deployed file  it will be removed when server is redeployed  My suggest is to go with rootPath s parent folder instead of child one

User · Answer

Tomcat sets a catalina home system property   You can use this in your log4j properties file   Something like this   log4j rootCategory DEBUG errorfile  log4j appender errorfile File   catalina home  logs LogFilename log   On Debian  including Ubuntu     catalina home  will not work because that points at  usr share tomcat6 which has no link to  var log tomcat6  Here just use   catalina base    If your using another container  try to find a similar system property  or define your own   Setting the system property will vary by platform  and container   But for Tomcat on Linux Unix I would create a setenv sh in the CATALINA HOME bin directory   It would contain   export JAVA OPTS  -Dcustom logging root  var log webapps    Then your log4j properties would be   log4j rootCategory DEBUG errorfile  log4j appender errorfile File   custom logging root  LogFilename log

User · Answer

If you use Spring you can   1  create a log4j configuration file  e g    WEB-INF classes log4j-myapp properties  DO NOT name it  log4j properties   Example   log4j rootLogger ERROR  stdout  rollingFile  log4j appender stdout org apache log4j ConsoleAppender log4j appender stdout layout org apache log4j PatternLayout log4j appender stdout layout ConversionPattern  d  p   c  -  lt  m gt  n  log4j appender rollingFile org apache log4j RollingFileAppender log4j appender rollingFile File   myWebapp-instance-root  WEB-INF logs application log log4j appender rollingFile MaxFileSize 512KB log4j appender rollingFile MaxBackupIndex 10 log4j appender rollingFile layout org apache log4j PatternLayout log4j appender rollingFile layout ConversionPattern  d  p   c  -  m n log4j appender rollingFile Encoding UTF-8   We ll define  myWebapp-instance-root  later on point  3   2  Specify config location in web xml    lt context-param gt     lt param-name gt log4jConfigLocation lt  param-name gt     lt param-value gt  WEB-INF classes log4j-myapp properties lt  param-value gt   lt  context-param gt    3  Specify a unique variable name for your webapp s root  e g   myWebapp-instance-root    lt context-param gt     lt param-name gt webAppRootKey lt  param-name gt     lt param-value gt myWebapp-instance-root lt  param-value gt   lt  context-param gt    4  Add a Log4jConfigListener    lt listener gt     lt listener-class gt org springframework web util Log4jConfigListener lt  listener-class gt   lt  listener gt    If you choose a different name  remember to change it in log4j-myapp properties  too   See my article  Italian only    but it should be understandable   http   www megadix it content configurare-path-relativi-log4j-utilizzando-spring  UPDATE  2009 08 01  I ve translated my article to English  http   www megadix it node 136

User · Answer

Tomcat sets a catalina home system property   You can use this in your log4j properties file   Something like this   log4j rootCategory DEBUG errorfile  log4j appender errorfile File   catalina home  logs LogFilename log   On Debian  including Ubuntu     catalina home  will not work because that points at  usr share tomcat6 which has no link to  var log tomcat6  Here just use   catalina base    If your using another container  try to find a similar system property  or define your own   Setting the system property will vary by platform  and container   But for Tomcat on Linux Unix I would create a setenv sh in the CATALINA HOME bin directory   It would contain   export JAVA OPTS  -Dcustom logging root  var log webapps    Then your log4j properties would be   log4j rootCategory DEBUG errorfile  log4j appender errorfile File   custom logging root  LogFilename log

User · Answer

If you use Spring you can   1  create a log4j configuration file  e g    WEB-INF classes log4j-myapp properties  DO NOT name it  log4j properties   Example   log4j rootLogger ERROR  stdout  rollingFile  log4j appender stdout org apache log4j ConsoleAppender log4j appender stdout layout org apache log4j PatternLayout log4j appender stdout layout ConversionPattern  d  p   c  -  lt  m gt  n  log4j appender rollingFile org apache log4j RollingFileAppender log4j appender rollingFile File   myWebapp-instance-root  WEB-INF logs application log log4j appender rollingFile MaxFileSize 512KB log4j appender rollingFile MaxBackupIndex 10 log4j appender rollingFile layout org apache log4j PatternLayout log4j appender rollingFile layout ConversionPattern  d  p   c  -  m n log4j appender rollingFile Encoding UTF-8   We ll define  myWebapp-instance-root  later on point  3   2  Specify config location in web xml    lt context-param gt     lt param-name gt log4jConfigLocation lt  param-name gt     lt param-value gt  WEB-INF classes log4j-myapp properties lt  param-value gt   lt  context-param gt    3  Specify a unique variable name for your webapp s root  e g   myWebapp-instance-root    lt context-param gt     lt param-name gt webAppRootKey lt  param-name gt     lt param-value gt myWebapp-instance-root lt  param-value gt   lt  context-param gt    4  Add a Log4jConfigListener    lt listener gt     lt listener-class gt org springframework web util Log4jConfigListener lt  listener-class gt   lt  listener gt    If you choose a different name  remember to change it in log4j-myapp properties  too   See my article  Italian only    but it should be understandable   http   www megadix it content configurare-path-relativi-log4j-utilizzando-spring  UPDATE  2009 08 01  I ve translated my article to English  http   www megadix it node 136

User · Answer

As a further comment on https   stackoverflow com a 218037 2279200 - this may break  if the web app implicitely starts other ServletContextListener s  which may get called earlier and which already try to use log4j - in this case  the log4j configuration will be read and parsed already before the property determining the log root directory is set    the log files will appear somewhere below the current directory  the current directory when starting tomcat    I could only think of following solution to this problem  - rename your log4j properties  or logj4 xml  file to something which log4j will not automatically read  - In your context filter  after setting the property  call the DOM PropertyConfigurator helper class to ensure that your log4j-  xml properties  is read - Reset the log4j configuration  IIRC there is a method to do that   This is a bit brute force  but methinks it is the only way to make it watertight

User · Answer

Just a comment on Iker s solution    ServletContext is a good solution for your problem  But I don t think it is good for maintains  Most of the time log files are required to be saved for long time    Since ServletContext makes the file under the deployed file  it will be removed when server is redeployed  My suggest is to go with rootPath s parent folder instead of child one

User · Answer

My suggestion is the log file should always be logged above the root context of the webApp  so in case we redeploy the webApp  we don t want to override the existing log files

User · Answer

If you use Spring you can   1  create a log4j configuration file  e g    WEB-INF classes log4j-myapp properties  DO NOT name it  log4j properties   Example   log4j rootLogger ERROR  stdout  rollingFile  log4j appender stdout org apache log4j ConsoleAppender log4j appender stdout layout org apache log4j PatternLayout log4j appender stdout layout ConversionPattern  d  p   c  -  lt  m gt  n  log4j appender rollingFile org apache log4j RollingFileAppender log4j appender rollingFile File   myWebapp-instance-root  WEB-INF logs application log log4j appender rollingFile MaxFileSize 512KB log4j appender rollingFile MaxBackupIndex 10 log4j appender rollingFile layout org apache log4j PatternLayout log4j appender rollingFile layout ConversionPattern  d  p   c  -  m n log4j appender rollingFile Encoding UTF-8   We ll define  myWebapp-instance-root  later on point  3   2  Specify config location in web xml    lt context-param gt     lt param-name gt log4jConfigLocation lt  param-name gt     lt param-value gt  WEB-INF classes log4j-myapp properties lt  param-value gt   lt  context-param gt    3  Specify a unique variable name for your webapp s root  e g   myWebapp-instance-root    lt context-param gt     lt param-name gt webAppRootKey lt  param-name gt     lt param-value gt myWebapp-instance-root lt  param-value gt   lt  context-param gt    4  Add a Log4jConfigListener    lt listener gt     lt listener-class gt org springframework web util Log4jConfigListener lt  listener-class gt   lt  listener gt    If you choose a different name  remember to change it in log4j-myapp properties  too   See my article  Italian only    but it should be understandable   http   www megadix it content configurare-path-relativi-log4j-utilizzando-spring  UPDATE  2009 08 01  I ve translated my article to English  http   www megadix it node 136

User · Answer

You can specify relative path to the log file  using the work directory   appender file fileName     sys user dir  log application log   This is independent from the servlet container and does not require passing custom variable to the system environment

User · Answer

Doesn t log4j just use the application root directory if you don t specify a root directory in your FileAppender s path property   So you should just be able to use   log4j appender file File logs MyLog log  It s been awhile since I ve done Java web development  but this seems to be the most intuitive  and also doesn t collide with other unfortunately named logs writing to the   catalina home  logs directory

[java] Log4j, configuring a Web App to use a relative path

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