Develop Reference

How to configure log4j in Eclipse to view debug messages of Maven dependency library?

I have a Maven project in Eclipse that has the following dependencies, among others:
<dependency>
<groupId>org.hyperledger.fabric-sdk-java</groupId>
<artifactId>fabric-sdk-java</artifactId>
<version>1.4.13</version>
</dependency>
<dependency>
<groupId>org.hyperledger.fabric</groupId>
<artifactId>fabric-gateway-java</artifactId>
<version>2.2.2</version>
</dependency>
As part of my troubleshooting efforts, I would like to use log4j (or a similar library) to view the debug output that originates from these libraries. In my src/main/resources folder I have the following log4j.properties file:
# Root logger option
log4j.rootLogger=DEBUG, 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
I have changed the level of rootLogger to DEBUG but I am still unable to see the debug messages.
I would like to look at the debug messages of one or more specific classes - org.hyperledger.fabric.sdk.NetworkConfig for instance. How should I configure my log4j.properties to achieve this?
Update: I have just been made aware of the log4j security vulnerability. Nevertheless, I would like to continue with seeking help for my question as I have confidence that the situation will be resolved soon.

DailyRollingFileAppender not creating daily log file

DailyRollingFileAppender is not creating daily backup log file.
I am using the below config, which works on my local machine but it not working on the machine where my project has been deployed.
log4j.rootLogger=DEBUG, Appender2
log4j.appender.Appender2=org.apache.log4j.DailyRollingFileAppender
log4j.appender.Appender2.File=C:/Logs/AppLog.log
log4j.appender.Appender2.DatePattern='.'dd-MM-yyyy
log4j.appender.Appender2.layout=org.apache.log4j.PatternLayout
log4j.appender.Appender2.layout.ConversionPattern=%-7p %d [%t] %c %x - %m%n
log4j.appender.Appender2.rootLogger = DEBUG
Framework - Spring MVC
I am not able to understand which part of the config is bloking DailyRollingFileAppender to create date wise log on my server machine.
Edit-
I updated my file as per the suggestion and it is not creating a new backup file at 12 am next day. means it updated AppLog.l‌​og till 12 then there was no backup file and all the previous day logs are gone and it starts writing from the beginning.
This is log4j properties now-
log4j.rootLogger=DEBUG, Appender2
log4j.appender.Appender2=org.apache.log4j.DailyRollingFileAppender
log4j.appender.Appender2.File=${catalina.home}/Logs/AppLog.log
log4j.appender.Appender2.DatePattern='.'yyyy-MM-dd
log4j.appender.Appender2.layout=org.apache.log4j.PatternLayout
log4j.appender.Appender2.Append=false
log4j.appender.Appender2.layout.ConversionPattern=%-7p %d [%t] %c %x - %m%n

The issue is with the file path here:
log4j.appender.Appender2.File=C:/Logs/AppLog.log
Please make sure that this path exists on the server where you have deployed your project.

I faced with this problem before, the cause turned to be I used wrong log4j dependency in pom.xml. The previous dependency is:
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
I use spring boot in my project, so I changed it to the following, it worked.
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-logging</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-log4j</artifactId>
<version>1.3.8.RELEASE</version>
</dependency>

your DatePattern should be '.'yyyy-MM-dd
refer to https://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/DailyRollingFileAppender.html

u can use this for get the daily rolling log file,
########## Appender Daily Rolling
log4j.logger.appender=Daily
log4j.appender.Daily=org.apache.log4j.DailyRollingFileAppender
log4j.appender.Daily.Threshold=INFO
log4j.appender.Daily.File=D:/backup/RFLI1010.log
log4j.appender.Daily.DatePattern='.'yyyy-MM-dd
# Append to the end of the file or overwrites the file at start.
log4j.appender.Daily.Append=true
log4j.appender.Daily.MaxBackupIndex=20
log4j.appender.Daily.layout=org.apache.log4j.PatternLayout
log4j.appender.Daily.layout.ConversionPattern= [%5p] %d %r %t (%F:%M:%L)%m%n%n

Maven project log4j not working

I have a simple maven project and trying to get log4j implemented.
deploying to local tomcat. Nothing printing in console of eclipse where I have logger.debug().
Am I missing something?
This is my structure:
pom.xml:
<!-- http://mvnrepository.com/artifact/log4j/log4j -->
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
Class:
final static Logger logger = Logger.getLogger(myclass.class);
.properties file
# Root logger option
log4j.rootLogger=INFO, stdout
log4j.rootLogger=DEBUG, stdout
log4j.rootLogger=ERROR, 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

Simply remove the superfluous rootLogger declarations:
# Root logger option
log4j.rootLogger=DEBUG, 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
Logging levels are inclusive of those levels "above" them. For example, setting the logging level to DEBUG will include DEBUG, INFO, WARN, ERROR, and FATAL messages automatically. There is no need to declare logging levels for each one.

Enabling complete Path Logging in Spring MVC

I wrote the following in my log4j.properties file
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{ABSOLUTE} %5p %c{1}:%L - %m%n
log4j.logger.org.springframework.web = TRACE, stdout
But I'm just getting the init logging. What should I do so as to get detailed logging so as to get the trace whenever i enter a url in my browser.

Its very simple to log the execution of program :
1) Add log4j dependency in pom.xml
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.4.2</version>
</dependency>
2) Add the one Listner class in web.xml
<listener>
<listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>
</listener>
3) Then add log4jConfigLocation in web.xml
<context-param>
<param-name>log4jConfigLocation</param-name>
<param-value>/WEB-INF/classes/log4j.properties</param-value>
</context-param>
and then add your log4j properties as follows :
# Direct log messages to a log file
log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.File=C:\\loging.log
log4j.appender.file.MaxFileSize=1MB
log4j.appender.file.MaxBackupIndex=1
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n
# 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{ABSOLUTE} %5p %c{1}:%L - %m%n
# Root logger option
log4j.rootLogger=debug, file, stdout
4) Go to the particular java file in your application import log4j package
and then implement your logging mechanism
5) Now you should be able to trace the log

How to get SLF4J "Hello World" working with log4j?

The "Hello World" example from SLF4J is not working for me. I guess this is because I added slf4j-log4 to my classpath. Should I configure log4j directly for the hello world to work?
log4j:WARN No appenders could be found for logger (HelloWorld).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
Update: I added log4j initialization, and it still doesn't work:
public static void main(String[] params) {
org.apache.log4j.Logger.getRootLogger().addAppender(new ConsoleAppender());
Logger logger = org.slf4j.LoggerFactory.getLogger(TestBase.class);
logger.info("Hello World");
}
And I'm getting:
log4j:ERROR No output stream or file set for the appender named [null].

If you want to use slf4j simple, you need these jar files on your classpath:
slf4j-api-1.6.1.jar
slf4j-simple-1.6.1.jar
If you want to use slf4j and log4j, you need these jar files on your classpath:
slf4j-api-1.6.1.jar
slf4j-log4j12-1.6.1.jar
log4j-1.2.16.jar
No more, no less. Using slf4j simple, you'll get basic logging to your console at INFO level or higher. Using log4j, you must configure it accordingly.

Following is an example. You can see the details http://jkssweetlife.com/configure-slf4j-working-various-logging-frameworks/ and download the full codes here.
Add following dependency to your pom if you are using maven, otherwise, just download the jar files and put on your classpath
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.7</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.7</version>
</dependency>
Configure log4j.properties
log4j.rootLogger=TRACE, 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'T'HH:mm:ss.SSS} %-5p [%c] - %m%n
Java example
public class Slf4jExample {
public static void main(String[] args) {
Logger logger = LoggerFactory.getLogger(Slf4jExample.class);
final String message = "Hello logging!";
logger.trace(message);
logger.debug(message);
logger.info(message);
logger.warn(message);
logger.error(message);
}
}

you need to add 3 dependency ( API+ API implementation + log4j dependency)
Add also this
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<version>2.5</version>
</dependency>
# And to see log in command line , set log4j.properties
# Root logger option
log4j.rootLogger=INFO, file, 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
#And to see log in file , set log4j.properties
# Direct log messages to a log file
log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.File=./logs/logging.log
log4j.appender.file.MaxFileSize=10MB
log4j.appender.file.MaxBackupIndex=10
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n

Here a working example to use slf4j as façade with log4j in the backend:
pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>xxx</groupId>
<artifactId>xxx</artifactId>
<version>0.0.1-SNAPSHOT</version>
<dependencies>
<!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-api -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.30</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-log4j12 -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.30</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-core -->
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<version>2.13.3</version>
</dependency>
</dependencies>
</project>
src/main/resources/log4j.properties
# Root logger option
log4j.rootLogger=DEBUG, 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
src/main/java/Main.java
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class Main {
private static final Logger logger = LoggerFactory.getLogger(Main.class);
/**
* Default private constructor.
*/
private Main() {
}
/**
* Main method.
*
* #param args Arguments passed to the execution of the application
*/
public static void main(final String[] args) {
logger.info("Message to log");
}
}

I had the same problem. I called my own custom logger in the log4j.properties file from code when using log4j api directly. If you are using the slf4j api calls, you are probably using the default root logger so you must configure that to be associated with an appender in the log4j.properties:
# Set root logger level to DEBUG and its only appender to A1.
log4j.rootLogger=DEBUG, A1
# A1 is set to be a ConsoleAppender.
log4j.appender.A1=org.apache.log4j.ConsoleAppender