Unable to create class org.apache.logging.log4j.core.impl.Log4jContextFactory

Question

I am using spring boot application for a project and getting the following error while running the project from jar using java -jar build/libs/com.user.admin.rest.services.jar. But its not a blocker and i was able to access the api's, and the logger is working fine as intended. I just want to resolve this error.

ERROR StatusLogger Unable to create class org.apache.logging.log4j.core.impl.Log4jContextFactory specified in jar:file:/Users/Samuel/UserMgmt/com.user.admin.rest.services/build/libs/com.user.admin.rest.services.jar!/META-INF/log4j-provider.properties
 java.lang.ClassNotFoundException: org.apache.logging.log4j.core.impl.Log4jContextFactory
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at org.apache.logging.log4j.spi.Provider.loadLoggerContextFactory(Provider.java:96)
    at org.apache.logging.log4j.LogManager.<clinit>(LogManager.java:91)
    at com.user.admin.rest.services.api.UserServiceResource.<clinit>(UserServiceResource.java:32)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:142)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:89)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1147)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1099)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:513)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:866)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:542)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:737)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:370)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:314)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1162)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1151)
    at com.user.admin.rest.services.api.Application.main(Application.java:27)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:48)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:87)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:50)
    at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:51)

I have added the following lines for logger in the build.gradle file.

compile 'org.apache.logging.log4j:log4j-api:2.8.2' compile 'org.apache.logging.log4j:log4j-core:2.8.2'

And my log4j2.xml file is given below

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE xml>
<Configuration status="ERROR" name="example-config">
    <Properties>
        <Property name="PATTERN">%-5level %d [%t] %c:%M(%L): %m%n</Property>
    </Properties>
    <Appenders>
        <Console name="STDOUT" target="SYSTEM_OUT">
            <PatternLayout pattern="${PATTERN}" />
        </Console>
    </Appenders>
    <Loggers>
        <Root level="TRACE">
            <AppenderRef ref="STDOUT" />
        </Root>
    </Loggers>
</Configuration>

Answer 1

Generally speaking, you should never need to switch logging implementations; Logback should suit you fine. However, if you decide that you’d rather use Log4j or Log4j2, you’ll need to change your dependencies to include the appropriate starter for the logging implementation you want to use and to exclude Logback.
Spring Boot in Action

Swapping out Logback for Log4j2 in Gradle

1. Exclude the default logging

configurations {
  all*.exclude group:'org.springframework.boot',
               module:'spring-boot-starter-logging'
}

2. Add Log4j2 logging

compile("org.springframework.boot:spring-boot-starter-log4j2")

You can find details of spring-boot-starter-log4j2 dependency version that is provided by Spring Boot here.

Answer 2

I have met the similar problem. The version of log4j-api and log4j-core have to match (and ClassNotFound is a strange exception here). As you have said in comment, you have found log4j-core-2.7.jar, but I may guess your log4j-api is in version of 2.8.2 as your above description shows.

Check your dependency, remove old version of log4j-core and add new version should fix the problem.