Fix log4j No appenders could be found for logger of a dependency's class in Spring Boot

Question

I'm building a backend using Spring Boot 3.1.0-SNAPSHOT with the spring-boot-starter-log4j2 for logging.

Due to we are using log4j2 and not Logback, we have excluded it as follows:

configurations {     
    all*.exclude module: 'spring-boot-starter-logging'
}

So far, all is working as expected.

Now I have a necessity to add an internal dependency of another department to my gradle file, example:

implementation 'com.test.ws:example:5.4'

Warning:

log4j:WARN No appenders could be found for logger (com.test.ws.jaxrpc.ExamplePortProxyFactoryBean). log4j:WARN Please initialize the log4j system properly. log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.

Looking at the class of the dependency that is causing this warning, I can see that indeed it has a Logger:

import org.apache.log4j.Logger;
import org.springframework.remoting.jaxrpc.JaxRpcPortProxyFactoryBean;

public class ExamplePortProxyFactoryBean extends JaxRpcPortProxyFactoryBean {
    private static final Logger logger = Logger.getLogger(ExamplePortProxyFactoryBean.class);

    public ExamplePortProxyFactoryBean() {
    }

    protected void postProcessJaxRpcService(Service arg0) {
        if (logger.isDebugEnabled()) {
            logger.debug("postProcessJaxRpcService(Service arg0=" + arg0 + ") - start");
        }

        TypeMappingRegistry registry = arg0.getTypeMappingRegistry();
        TypeMapping mapping = registry.createTypeMapping();
        PortProxyFactoryBeanUtil.registerBeanMapping(mapping, List.class, "List", this.getNamespaceUri());
        registry.register("http://schemas.xmlsoap.org/soap/encoding/", mapping);
        if (logger.isDebugEnabled()) {
            logger.debug("postProcessJaxRpcService(Service arg0=" + arg0 + ") - end ${message_user}");
        }

    }
}

Inside the dependency's pom.xml file, I cannot see any reference to the org.apache.log4j library.

The warning is just a warning, not an error, the app works fine, but I feel that I need to fix this warning because is ugly to see it at service start up.

I have tried to exclude log4j as follows:

implementation('com.orange:odo-ws-endpoints:5.4') {
      exclude group: 'log4j', module: 'log4j'
}

Error:

Caused by: java.lang.ClassNotFoundException: org.apache.log4j.Logger
    at jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641) ~[?:?]
    at jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188) ~[?:?]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:521) ~[?:?]
    at com.test.ws.jaxrpc.ExamplePortProxyFactoryBean.<clinit>(ContractPortProxyFactoryBean.java:28)

Not the best idea I guess.

Other threads indicate (questions already on Stack Overflow) that I should create a file called log4j.properties inside the /resources folder.

log4j.properties:

# Root logger option
log4j.rootLogger=DEBUG, console

# Redirect log messages to console
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{yyyy-MM-dd'T'HH:mm:ss.SSSXXX} %5p %c{1} : %msg%n

Now with this file, the error is gone and I can see the logs that the class above is firing. The thing is that is weird for me to have this file because of that class, guilty.

This thread https://stackoverflow.com/a/12532442/10977224 talks about another option to configure a basic appender by adding this line in my main method:

BasicConfigurator.configure();

Effectively, the warning is gone and I can see the logs of the class. But still, why do I need to handle a necessity of a class that is not under my power.

Questions:

What other things can I do to fix the warning without having a log4j.properties or adding more code?
There is a way to avoid showing the warnings of that class in the console?
To avoid confusion within my team and weird future log behaviours, if any, of having things related to log4j while we use spring-boot-starter-log4j2, there is a way to apply a fix only to the guilty class (or package)?

Any other approach or advice will be appreciated. I'm not sure how to handle this correctly.

Fix log4j No appenders could be found for logger of a dependency's class in Spring Boot

0 Answers0