Log4j does not record any log file for my project-CodePudding

My log4j does not record any log file. I am not sure if this is a problem from the settings inside log4j.properties or the location of this file.

The way I built the project:

git clone https://github.com/spring-guides/gs-maven.git

Then modified: .\initial\pom.xml and added support for log4j:

    <dependencyManagement>
      <dependencies>
        <dependency>
          <groupId>org.apache.logging.log4j</groupId>
          <artifactId>log4j-bom</artifactId>
          <version>2.17.2</version>
          <scope>import</scope>
          <type>pom</type>
        </dependency>
      </dependencies>
    </dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-api</artifactId>
      </dependency>
      <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId>
      </dependency>
    </dependencies>

just before:

</project>

Added log commands to .\initial\src\main\java\hello\HelloWorld.java as follows:

package hello;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class HelloWorld {
    private static Logger logger = LogManager.getLogger(HelloWorld.class);

    public static void main(String[] args) {
        logger.error("Application status : {} ", "start");
        Greeter greeter = new Greeter();
        System.out.println(greeter.sayHello());
        logger.error("Application status : {} ", "terminated");
    }
}

Then added log4j.properties:

appender.stdout.type = Console
# ... other appender properties
appender.file.type = File
# ... other appender properties
logger.app = INFO, stdout, file
# logger.app.name = com.example.app
 
# is equivalent to:
# appender.stdout.type = Console
# appender.stdout.name = stdout
# ...
appender.file.type = File
appender.file.name = mylog
# ...
# logger.app.name = com.example.app
logger.app.level = INFO
logger.app.appenderRef.$1.ref = stdout
logger.app.appenderRef.$2.ref = file

I kept changing the location of this file to

.\initial\log4j.properties
.\initial\target\log4j.properties
.\initial\target\classes\log4j.properties
.\initial\target\classes\hello\log4j.properties

None of them have ever worked at all. I do not see mylog or any other log files.

The way I run the project is as follows:

cd initial
mvn compile
mvn package
java -jar target/gs-maven-0.1.0.jar

How should I fix this?

CodePudding user response：

There are some problems with your configuration:

As Gopinath remarked, the configuration file should be in src/main/resources. Maven will copy it to target/classes,
Log4j 1.x uses the name log4j.properties, Log4j 2.x uses log4j2.properties,
The properties configuration format is the most difficult to master. I would advise you to use any of the other format (e.g. XML, which does not require additional dependencies).

If you insist on using the properties format, here are some hints:

every configuration requires a root logger, which is the ancestor of each logger and provides the default values for the other logger configurations. You can use the shorthand notation:
```
rootLogger = INFO, stdout, file
```
introduced in version 2.17.2 or the long notation:
```
rootLogger.level = INFO
rootLogger.appenderRef.$1.ref = stdout
rootLogger.appenderRef.$2.ref = file
```
The names of the appender references must match the name properties of the appenders:
```
appender.stdout.name = stdout
appender.file.name = file
```
there is no shorthand for that.
The FileAppender needs a fileName:
```
appender.file.fileName = mylog
```