How to initialize log4j properly

Question

After adding log4j to my application I get the following output every time I execute my application    log4j WARN No appenders could be found for logger  slideselector facedata FaceDataParser   log4j WARN Please initialize the log4j system properly    It seems this means a configuration file is missing  Where should this config file be located and what is a good start content    I m using plain java for developing a desktop application  So no webserver etc

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What are you developing in  Are you using Apache Tomcat   log4j appender CONSOLE org apache log4j ConsoleAppender log4j appender CONSOLE target System out log4j appender CONSOLE layout org apache log4j PatternLayout log4j appender CONSOLE layout ConversionPattern  d yyyyMMdd HH mm ss SSS     5p   c 1    t    m n   I have a properties like this in a Java app of mine

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Find a log4j properties or log4j xml online that has a root appender  and put it on your classpath       direct log messages to stdout     log4j appender stdout org apache log4j ConsoleAppender log4j appender stdout Target System out log4j appender stdout layout org apache log4j SimpleLayout log4j rootLogger debug  stdout   will log to the console  I prefer logging to a file so you can investigate afterwards   log4j appender file org apache log4j RollingFileAppender log4j appender file maxFileSize 100KB log4j appender file maxBackupIndex 5 log4j appender file File test log log4j appender file threshold debug log4j appender file layout org apache log4j PatternLayout log4j appender file layout ConversionPattern  d ABSOLUTE   5p  c 1   L -  m n log4j rootLogger debug file   although for verbose logging applications 100KB usually needs to be increased to 1MB or 10MB  especially for debug   Personally I set up multiple loggers  and set the root logger to warn or error level instead of debug

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Try to set debug attribut in log4j configuration node to true    lt log4j configuration xmlns log4j  http   jakarta apache org log4j   debug  true  gt    It prints out information as the configuration file is read and used to configure the log4j environment  You may be got more details to resolve your problem

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I just did this and the issue was fixed   Followed the below blog  https   intellij-support jetbrains com hc en-us community posts 206875685-How-to-fix-log4j-WARN-console-messages-when-running-an-Application-inside-IntelliJ-Idea  But here he says like below  To fix that just enter the following log4j resources file into main resources folder of your project   instead of creating log4j resources  create log4j properties  Right Click on Resource in IntelliJ -  New -  Resource Bundle - Just name it as log4j

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To enable -Dlog4j debug  I go to System  Advanced system settings  Environment variables and set system variable  JAVA OPTIONS to -Dlog4j debug

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Logging API - The Java Logging API facilitates software servicing and maintenance at customer sites by producing log reports suitable for analysis by end users  system administrators  field service engineers  and software development teams  The Logging APIs capture information such as security failures  configuration errors  performance bottlenecks  and or bugs in the application or platform  The core package includes support for delivering plain text or XML formatted log records to memory  output streams  consoles  files  and sockets  In addition  the logging APIs are capable of interacting with logging services that already exist on the host operating system   Package java util logging    Provides the classes and interfaces of the Java platform s core logging facilities     Log4j 1 x    log4j is a popular Java-based logging utility  Log4j is an open source project based on the work of many authors  It allows the developer to control which log statements are output to a variety of locations by using Appenders  console  files  DB and email   It is fully configurable at runtime using external configuration files      Log4j has three main components          Loggers   -  OFF  FATAL  ERROR  WARN  INFO  DEBUG  TRACE    Appenders                Apache Commons Logging  ConsoleAppender  FileAppender  RollingFileAppender  DailyRollingFileAppender  JDBCAppender-Driver  SocketAppender     Log4J Appender for MongoDB  MongoDbAppender - Driver           Layouts   -  PatternLayout  EnhancedPatternLayout         Configuration files can be written in XML or in Java properties  key value  format         log4j External properties    Java properties  key value  format         The string between an opening      and closing     is interpreted as a key  The value of the substituted variable can be defined as a system property or in the configuration file itself    Set appender specific options     log4j appender appenderName option value  For each named appender you can configure its Layout      log4j rootLogger INFO  FILE  FILE PER SIZE  FILE PER DAY  CONSOLE  MySql   log path    log path E  Logs    https   logging apache org log4j 1 2 apidocs org apache log4j PatternLayout html     -5p -  WARN  INFO  ERROR    5p 0-   WARN  INFO ERROR   log patternLayout org apache log4j PatternLayout log pattern  -5p -  d yyyy-MM-dd HH mm ss SSS   C 1   12 20M  L -  m  n    System out   System err log4j appender CONSOLE org apache log4j ConsoleAppender log4j appender CONSOLE Target System err log4j appender CONSOLE layout   log patternLayout  log4j appender CONSOLE layout ConversionPattern   log pattern     File Appender log4j appender FILE org apache log4j FileAppender log4j appender FILE File   log path  logFile log  log4j ERROR setFile null false  call failed  - Defaults setFile null true   log4j appender FILE Append   false log4j appender FILE layout   log patternLayout  log4j appender FILE layout ConversionPattern   log pattern     BackUP files for every Day  log4j appender FILE PER DAY org apache log4j DailyRollingFileAppender      Current File   - logRollingDayFile log       BackUPs  logRollingDayFile log 2017-12-10        log4j appender FILE PER DAY File   log path  logRollingDayFile log log4j appender FILE PER DAY DatePattern    yyyy-MM-dd log4j appender FILE PER DAY layout   log patternLayout  log4j appender FILE PER DAY layout ConversionPattern   log pattern     BackUP files for size rotation with log cleanup  log4j appender FILE PER SIZE org apache log4j RollingFileAppender      Current File   - logRollingFile log       BackUPs  logRollingFile log 1  logRollingFile log 2  log4j appender FILE PER SIZE File   log path  logRollingFile log log4j appender FILE PER SIZE MaxFileSize 100KB log4j appender FILE PER SIZE MaxBackupIndex 2 log4j appender FILE PER SIZE layout   log patternLayout  log4j appender FILE PER SIZE layout ConversionPattern   log pattern     MySql Database - JDBCAppender log4j appender MySql org apache log4j jdbc JDBCAppender log4j appender MySql driver com mysql jdbc Driver log4j appender MySql URL jdbc mysql   localhost 3306 automationlab log4j appender MySql user root log4j appender MySql password  log4j appender MySql layout org apache log4j EnhancedPatternLayout log4j appender MySql layout ConversionPattern INSERT INTO  logdata  VALUES    p     d yyyy-MM-dd HH mm ss      C     M     L     m     log4j appender MySql sql INSERT INTO  logdata  VALUES    p     d yyyy-MM-dd HH mm ss      C     M     L     m       Direct log events Messages  to MongoDB Collection - MongoDbAppender log mongoDB hostname loalhost log mongoDB userName Yash777 log mongoDB password Yash 123 log mongoDB DB MyLogDB log mongoDB Collection Logs  log4j appender MongoDB org log4mongo MongoDbAppender log4j appender MongoDB hostname   log mongoDB hostname  log4j appender MongoDB userName   log mongoDB userName  log4j appender MongoDB password   log mongoDB password  log4j appender MongoDB port 27017 log4j appender MongoDB databaseName   log mongoDB DB  log4j appender MongoDB collectionName   log mongoDB Collection  log4j appender MongoDB writeConcern FSYNCED     MySQL Table structure for table logdata    CREATE TABLE IF NOT EXISTS  logdata       Logger Level  varchar 5  COLLATE utf8 unicode ci NOT NULL     DataTime  timestamp NOT NULL DEFAULT CURRENT TIMESTAMP ON UPDATE CURRENT TIMESTAMP     ClassName  varchar 30  COLLATE utf8 unicode ci NOT NULL     MethodName  varchar 50  COLLATE utf8 unicode ci NOT NULL     LineNumber  int 10  NOT NULL     Message  text COLLATE utf8 unicode ci NOT NULL   ENGINE InnoDB DEFAULT CHARSET utf8 COLLATE utf8 unicode ci            log4j External xml    XML log4j configuration with public DTD file         lt  xml version  1 0  encoding  iso-8859-1   gt   lt  DOCTYPE log4j configuration PUBLIC    -  APACHE  DTD LOG4J 1 2  EN   http   logging apache org log4j 1 2 apidocs org apache log4j xml doc-files log4j dtd  gt   lt log4j configuration debug  false  gt        lt appender name  CONSOLE  class  org apache log4j ConsoleAppender  gt           lt param name  target  value  System out    gt           lt param name  threshold  value  debug    gt           lt layout class  org apache log4j PatternLayout  gt               lt param name  ConversionPattern  value   -5p -  d yyyy-MM-dd HH mm ss SSS   C 1   12 20M  L -  m  n    gt           lt  layout gt       lt  appender gt        lt appender name  FILE  class  org apache log4j FileAppender  gt           lt param name  file  value  E  Logs logFile log    gt           lt param name  append  value  false    gt           lt layout class  org apache log4j PatternLayout  gt               lt param name  ConversionPattern  value   -5p -  d yyyy-MM-dd HH mm ss SSS   C 1   12 20M  L -  m  n    gt           lt  layout gt       lt  appender gt        lt appender name  FILE PER SIZE  class  org apache log4j RollingFileAppender  gt           lt param name  file  value  E  Logs logRollingFile log    gt           lt param name  immediateFlush  value  true   gt           lt param name  maxFileSize  value  100KB    gt           lt param name  maxBackupIndex  value  2   gt           lt layout class  org apache log4j PatternLayout  gt               lt param name  ConversionPattern  value   -5p -  d yyyy-MM-dd HH mm ss SSS   C 1   12 20M  L -  m  n    gt           lt  layout gt       lt  appender gt        lt appender name  FILE PER DAY  class  org apache log4j DailyRollingFileAppender  gt           lt param name  file  value  E  Logs logRollingDayFile log    gt           lt param name  datePattern  value     yyyy-MM-dd    gt           lt layout class  org apache log4j PatternLayout  gt               lt param name  ConversionPattern  value   -5p -  d yyyy-MM-dd HH mm ss SSS   C 1   12 20M  L -  m  n   gt           lt  layout gt       lt  appender gt        lt root gt           lt priority value  info    gt           lt appender-ref ref  CONSOLE    gt           lt appender-ref ref  FILE    gt           lt appender-ref ref  FILE PER SIZE    gt           lt appender-ref ref  FILE PER DAY    gt       lt  root gt   lt  log4j configuration gt              Log4j Configuration from the URL in Java program          In order to specify a custom configuration with an external file  the used class must implement the Configurator interface       when default configuration files  log4j properties    log4j xml  are not available         For  log4j properties  you can fed to the PropertyConfigurator configure java net URL  method    For  log4j xml  DOMConfigurator will be used         public class LogFiles          Define a static logger variable so that it references the Logger instance named  LogFiles       static final Logger log   Logger getLogger  LogFiles class          SuppressWarnings  deprecation       public static void main String   args            System out println  CONFIGURATION FILE      LogManager DEFAULT CONFIGURATION FILE           System out println  DEFAULT XML CONFIGURATION FILE    log4j xml     Default access modifier             String fileName                            log4j External xml                    log4j External properties           String configurationFile   System getProperty  user dir     src     fileName           if  fileName contains   xml                   DOMConfigurator configure  configurationFile                log info  Extension   xml              else if   fileName contains   properties                   PropertyConfigurator configure  configurationFile                log info  Extension   properties              else               DailyRollingFileAppender dailyRollingAppender   new DailyRollingFileAppender                dailyRollingAppender setFile  E  Logs logRollingDayFile log                dailyRollingAppender setDatePattern     yyyy-MM-dd                 PatternLayout layout   new PatternLayout                layout setConversionPattern    -5p -  d yyyy-MM-dd HH mm ss SSS   C 1   12 20M  L -  m  n                 dailyRollingAppender setLayout layout                dailyRollingAppender activateOptions                 Logger rootLogger   Logger getRootLogger                rootLogger setLevel Level DEBUG               rootLogger addAppender dailyRollingAppender                log info  Configuring from Java Class                        log info  Console Message             method2            methodException 0              static void method2             log info  method2 - Console Message               static void methodException int b            try               int a   10 b              System out println  Result      a               log info  Result      a             catch  Exception ex       ArithmeticException    by zero             log error String format   n tException occurred   s   stackTraceToString ex                         public static String stackTraceToString Exception ex            StringWriter sw   new StringWriter            PrintWriter pw   new PrintWriter sw           ex printStackTrace pw           return sw toString

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If you are having this error on Intellij IDEA even after adding the log4j properties or log4j xml file on your resources test folder  maybe the Intellij IDEA is not aware yet about the existence of the file   So  after add the file  right click on the file and choose Recompile log4j xml

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Simply  create log4j properties under src main assembly folder  Depending on if you want log messages to be shown in the console or in the file you modify your file  The following is going to show your messages in the console      Root logger option log4j rootLogger INFO  stdout    Direct log messages to stdout log4j appender stdout org apache log4j ConsoleAppender log4j appender stdout Target System out log4j appender stdout layout org apache log4j PatternLayout log4j appender stdout layout ConversionPattern  d yyyy-MM-dd HH mm ss   -5p  c 1   L -  m n

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If you just get rid of everything  e g  if you are in tests   org apache log4j BasicConfigurator configure new NullAppender

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My log4j got fixed by below property file      direct log messages to stdout     log4j appender stdout org apache log4j ConsoleAppender log4j appender stdout Target System out log4j appender stdout layout org apache log4j SimpleLayout log4j rootLogger debug  stdout log4j appender file org apache log4j RollingFileAppender log4j appender file maxFileSize 100KB log4j appender file maxBackupIndex 5 log4j appender file File   logs test log log4j appender file threshold debug log4j appender file layout org apache log4j PatternLayout log4j appender file layout ConversionPattern  d ABSOLUTE   5p  c 1   L -  m n log4j rootLogger debug file

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You can set the location of your log4j properties from inside your java app by using   org apache log4j PropertyConfigurator configure file location log4j properties    More information is available here  https   logging apache org log4j 1 2 manual html

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As per Apache Log4j FAQ page   Why do I see a warning about  quot No appenders found for logger quot  and  quot Please configure log4j properly quot   This occurs when the default configuration files log4j properties and log4j xml can not be found and the application performs no explicit configuration  log4j uses Thread getContextClassLoader   getResource   to locate the default configuration files and does not directly check the file system  Knowing the appropriate location to place log4j properties or log4j xml requires understanding the search strategy of the class loader in use  log4j does not provide a default configuration since output to the console or to the file system may be prohibited in some environments   Basically the warning No appenders could be found for logger means that you re using log4j logging system  but you haven t added any Appenders  such as FileAppender  ConsoleAppender  SocketAppender  SyslogAppender  etc   into your configuration file or the configuration file is missing  There are three ways to configure log4j  with a properties file  log4j properties   with an XML file and through Java code  rootLogger addAppender new NullAppender       log4j properties If you ve property file present  e g  when installing Solr   you need to place this file within your classpath directory  classpath Here are some command suggestions in Linux how to determine your classpath value    echo  CLASSPATH   ps wuax   grep -i classpath   grep -Ri classpath  etc tomcat   var lib tomcat  conf  usr share tomcat   or from Java  System getProperty  quot java class path quot    Log4j XML Below is a basic XML configuration file for log4j in XML format   lt  xml version  quot 1 0 quot  encoding  quot UTF-8 quot    gt   lt  DOCTYPE log4j configuration SYSTEM  quot log4j dtd quot  gt    lt log4j configuration xmlns log4j  quot http   jakarta apache org log4j  quot  gt     lt appender name  quot console quot  class  quot org apache log4j ConsoleAppender quot  gt        lt param name  quot Target quot  value  quot System out quot   gt        lt layout class  quot org apache log4j PatternLayout quot  gt          lt param name  quot ConversionPattern quot  value  quot  -5p  c 1  -  m n quot   gt        lt  layout gt      lt  appender gt       lt root gt        lt priority value   quot debug quot    gt        lt appender-ref ref  quot console quot    gt      lt  root gt      lt  log4j configuration gt   Tomcat If you re using Tomcat  you may place your log4j properties into    usr share tomcat  lib  or  var lib tomcat  webapps   WEB-INF lib  folder  Solr For the reference  Solr default log4j properties file looks like     Logging level solr log logs  log4j rootLogger INFO  file  CONSOLE  log4j appender CONSOLE org apache log4j ConsoleAppender  log4j appender CONSOLE layout org apache log4j PatternLayout log4j appender CONSOLE layout ConversionPattern  -4r   t   -5p  c  x  u2013  m n   - size rotation with log cleanup  log4j appender file org apache log4j RollingFileAppender log4j appender file MaxFileSize 4MB log4j appender file MaxBackupIndex 9   - File to log to and log format log4j appender file File   solr log  solr log log4j appender file layout org apache log4j PatternLayout log4j appender file layout ConversionPattern  -5p -  d yyyy-MM-dd HH mm ss SSS    C   m n  log4j logger org apache zookeeper WARN log4j logger org apache hadoop WARN    set to INFO to enable infostream log messages log4j logger org apache solr update LoggingInfoStream OFF   Why can t log4j find my properties file in a J2EE or WAR application   The short answer  the log4j classes and the properties file are not within the scope of the same classloader  Log4j only uses the default Class forName   mechanism for loading classes  Resources are handled similarly  See the documentation for java lang ClassLoader for more details  So  if you re having problems  try loading the class or resource yourself  If you can t find it  neither will log4j       See also   Short introduction to log4j at Apache site Apache  Logging Services  FAQ at Apache site

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For testing  a quick-dirty way including setting log level   org apache log4j BasicConfigurator configure    org apache log4j Logger getRootLogger   setLevel org apache log4j Level WARN       set to Level DEBUG for full  or Level OFF

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While setting up log4j properly is great for  real  projects you might want a quick-and-dirty solution  e g  if you re just testing a new library   If so a call to the static method  org apache log4j BasicConfigurator configure      will setup basic logging to the console  and the error messages will be gone

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import org apache log4j BasicConfigurator       Call this method   BasicConfigurator configure

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Another way to do it without putting the property file on the classpath  is to set the property from the java code directly  Here is the sample code   public class Log4JSample    public static void main String   args        Properties properties new Properties        properties setProperty  log4j rootLogger   TRACE stdout MyFile        properties setProperty  log4j rootCategory   TRACE         properties setProperty  log4j appender stdout        org apache log4j ConsoleAppender        properties setProperty  log4j appender stdout layout     org apache log4j PatternLayout        properties setProperty  log4j appender stdout layout ConversionPattern    d yyyy MM dd HH mm ss SSS    5p   t   F  -  m n         properties setProperty  log4j appender MyFile    org apache log4j RollingFileAppender        properties setProperty  log4j appender MyFile File    my example log        properties setProperty  log4j appender MyFile MaxFileSize    100KB        properties setProperty  log4j appender MyFile MaxBackupIndex    1        properties setProperty  log4j appender MyFile layout     org apache log4j PatternLayout        properties setProperty  log4j appender MyFile layout ConversionPattern    d yyyy MM dd HH mm ss SSS    5p   t   F  -  m n         PropertyConfigurator configure properties        Logger logger   Logger getLogger  MyFile         logger fatal  This is a FATAL message         logger error  This is an ERROR message         logger warn  This is a WARN message         logger info  This is an INFO message         logger debug  This is a DEBUG message         logger trace  This is a TRACE message

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If we are using apache commons logging wrapper on top of log4j  then we need to have both the jars available in classpath  Also  commons-logging properties and log4j properties xml should be available in classpath    We can also pass implementation class and log4j properties name as JAVA OPTS either using -Dorg apache commons logging Log  lt logging implementation class name gt  -Dlog4j configuration  lt file location of log4j properties xml file gt   Same can be done via setting JAVA OPTS in case of app web server   It will help to externalize properties which can be changed in deployment

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You can set up the log level by using setLevel    The levels are useful to easily set the kind of informations you want the program to display  For example  Logger getRootLogger   setLevel Level WARN     will not show debug messages  The set of possible levels are   TRACE  DEBUG  INFO  WARN  ERROR and FATAL  According to Logging Services manual

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The fix for me was to put  log4j properties  into the  src  folder

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Maven solution   I came across all the same issues as above  and for a maven solution I used 2 dependencies  This configuration is only meant for quick testing if you want a simple project to be using a logger  with a standard configuration  I can imagine you want to make a configuration file later on if you need more information and or finetune your own logging levels        lt properties gt           lt slf4jVersion gt 1 7 28 lt  slf4jVersion gt       lt  properties gt            lt dependency gt               lt groupId gt org slf4j lt  groupId gt               lt artifactId gt slf4j-api lt  artifactId gt               lt version gt   slf4jVersion  lt  version gt           lt  dependency gt           lt dependency gt               lt groupId gt org slf4j lt  groupId gt               lt artifactId gt slf4j-jdk14 lt  artifactId gt               lt version gt   slf4jVersion  lt  version gt           lt  dependency gt

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Log4j by default looks for a file called log4j properties or log4j xml on the classpath   You can control which file it uses to initialize itself by setting system properties as described here  Look for the  Default Initialization Procedure  section     For example   java -Dlog4j configuration customName        Will cause log4j to look for a file called customName on the classpath   If you are having problems I find it helpful to turn on the log4j debug   -Dlog4j debug   It will print to System out lots of helpful information about which file it used to initialize itself  which loggers   appenders got configured and how etc    The configuration file can be a java properties file or an xml file  Here is a sample of the properties file format taken from the log4j intro documentation page   log4j rootLogger debug  stdout  R  log4j appender stdout org apache log4j ConsoleAppender log4j appender stdout layout org apache log4j PatternLayout    Pattern to output the caller s file name and line number  log4j appender stdout layout ConversionPattern  5p   t    F  L  -  m n  log4j appender R org apache log4j RollingFileAppender log4j appender R File example log  log4j appender R MaxFileSize 100KB   Keep one backup file log4j appender R MaxBackupIndex 1  log4j appender R layout org apache log4j PatternLayout log4j appender R layout ConversionPattern  p  t  c -  m n

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This is an alternative way using  yaml  Logic Structure   Configuration      Properties      Appenders      Loggers    Sample   Configutation      name  Default      Properties          Property              name  log-path             value   logs       Appenders           Console          name  Console Appender         target  SYSTEM OUT         PatternLayout              pattern     -5level   d yyyy-MM-dd HH mm ss SSS    t   c 1  -  msg n          File            name  File Appender           fileName    log-path  logfile log           PatternLayout              pattern     -5level   d yyyy-MM-dd HH mm ss SSS    t   c 1  -  msg n       Loggers           Root              level  debug             AppenderRef                - ref  Console Appender          Logger              - name   lt package gt   lt subpackage gt   lt subsubpackage gt   lt     gt                level  debug               AppenderRef                   - ref  File Appender                  level  error                Ref  LOG4J 2 CONFIGURATION  USING YAML

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I ve created file log4j properties in resources folder next to hibernate cfg xml file and filled it with text below   log4j rootLogger INFO  CONSOLE  log4j appender CONSOLE org apache log4j ConsoleAppender log4j appender CONSOLE layout org apache log4j PatternLayout log4j appender CONSOLE layout ConversionPattern  d ABSOLUTE   -5p   c 1   L   m n   now I got rid of warnings and errors

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As explained earlier there are 2 approaches   First one is to just add this line to your main method   BasicConfigurator configure      Second approach is to add this standard log4j properties file to your classpath   While taking second approach you need to make sure you initialize the file properly   Eg   Properties props   new Properties     props load new FileInputStream  log4j property file path      props setProperty  log4j appender File File    Folder where you want to store log files      File Name      Make sure you create required folder to store log files

[configuration] How to initialize log4j properly?

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