java.lang.Class:ERROR while initializing log4j pro

问题:

I am trying to run a standalone java program using log4j, but receiving below while debugging (with no log4j related logs on console):

log= {Logger@1343} "java.lang.Class:ERROR in 18b4aac2"

Can someone please suggest what is wrong here?

The code is as below:

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.core.Logger;
import java.io.IOException;
import java.sql.SQLException;

public class log4jExample {

static org.apache.logging.log4j.Logger log = LogManager.getLogger(log4jExample.class.getClass());

public static void main(String[] args)throws IOException,SQLException {
    System.out.println("in main...");

    log.debug("Hello this is a debug message");
    System.out.println("in main...2..");
    log.info("Hello this is an info message");
}

}

And the log4j.properties file is as below which is kept at src/main/resources.

log4j.rootLogger=DEBUG, stdout, 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{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n

log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.File=C:\\test\\log4j-example.log
log4j.appender.file.MaxFileSize=1MB
log4j.appender.file.MaxBackupIndex=2
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

I am running my java program with VM option

-Dlog4j.configurationFile=C:\MyFirstProject\src\main\resources\log4j.properties

回答1:

It seems to me like you have mixed up log4j versions. The configuration file you use is using log4j 1.x format. You have to convert it to log4j 2.x format. I tried your example and it works. See details below.

pom.xml file

<?xml version="1.0" encoding="UTF-8"?>
<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.bft.</groupId>
    <artifactId>test</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>2.7</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-api</artifactId>
            <version>2.7</version>
        </dependency>
    </dependencies>
</project>

Re-factored code

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

public class log4jExample {

    static final Logger logger = LogManager.getLogger(log4jExample.class);

    public static void main(String[] args) {
        System.out.println("in main...");

        logger.info("Hello this is a debug message");
        System.out.println("in main...2..");
        logger.info("Hello this is an info message");
    }
}

log4j.properties file (in log4j2.x format)

status = error
dest = err
name = PropertiesConfig

filter.threshold.type = ThresholdFilter
filter.threshold.level = debug

appender.console.type = Console
appender.console.name = STDOUT
appender.console.layout.type = PatternLayout
appender.console.layout.pattern = %m%n

rootLogger.level = info
rootLogger.appenderRef.stdout.ref = STDOUT

Output:

in main...
Hello this is a debug message
in main...2..
Hello this is an info message

Process finished with exit code 0

Refer the log4j docs.

回答2:

It is not an error !

It just says that your logger level is set to ERROR, so you will not see the messages logged to DEBUG/INFO levels.

Maybe you should check if your configuration is compatible with Log4J-2.x:

https://logging.apache.org/log4j/2.x/manual/configuration.html#Properties https://logging.apache.org/log4j/2.x/manual/appenders.html#ConsoleAppender

Use XML format is usually better.