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.
来源：https://stackoverflow.com/questions/40857681/java-lang-classerror-while-initializing-log4j-properties-file-in-java-program