java.lang.ClassNotFoundException: net.spy.memcached.compat.log.SLF4JLogger

Question

I added to Java opts -Dnet.spy.log.LoggerImpl=net.spy.memcached.compat.log.SLF4JLogger to set spymemcached to use slf4j as the logger. But I am getting the following WARNING in tomcat6 logs and I am puzzled over the error

net.spy.memcached.compat.log.SLF4JLogger not found while initializing net.spy.compat.log.LoggerFactory java.lang.ClassNotFoundException: net.spy.memcached.compat.log.SLF4JLogger

How can it be possible that the class SLF4JLogger is not found. That it was initializing LoggerFactory implies that the net.spy package was available and more generally the spy memcache jar was available. So how could it fail to find the other class.

log4j: setFile ended log4j: Adding appender named [SecurityAuditAppender] to category [SecurityAuditLogger]. Warning:  net.spy.memcached.compat.log.SLF4JLogger not found while initializing net.spy.compat.log.LoggerFactory java.lang.ClassNotFoundException: net.spy.memcached.compat.log.SLF4JLogger
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1680)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1526)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:191)
        at net.spy.memcached.compat.log.LoggerFactory.getConstructor(LoggerFactory.java:131)
        at net.spy.memcached.compat.log.LoggerFactory.getNewInstance(LoggerFactory.java:115)
        at net.spy.memcached.compat.log.LoggerFactory.internalGetLogger(LoggerFactory.java:98)
        at net.spy.memcached.compat.log.LoggerFactory.getLogger(LoggerFactory.java:87)
        at net.spy.memcached.compat.log.LoggerFactory.getLogger(LoggerFactory.java:73)
        at net.spy.memcached.compat.SpyThread.getLogger(SpyThread.java:60)
        at net.spy.memcached.MemcachedConnection.createConnections(MemcachedConnection.java:152)
        at net.spy.memcached.MemcachedConnection.<init>(MemcachedConnection.java:128)
        at net.spy.memcached.DefaultConnectionFactory.createConnection(DefaultConnectionFactory.java:176)
        at net.spy.memcached.MemcachedClient.<init>(MemcachedClient.java:193)
        at net.spy.memcached.spring.MemcachedClientFactoryBean.getObject(MemcachedClientFactoryBean.java:72)
        at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:142)
        at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:102)
        at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:1442)
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:248)
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
        at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:322)
        at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:106)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1360)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1118)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:517)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
        at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:294)
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225)
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:291)
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:585)
        at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:913)
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:464)
        at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:385)
        at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:284)
        at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:111)
        at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4210)
        at org.apache.catalina.core.StandardContext.start(StandardContext.java:4709)
        at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:799)
        at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:779)
        at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:583)
        at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:675)
        at org.apache.catalina.startup.HostConfig.deployDescriptors(HostConfig.java:601)
        at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:502)
        at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1317)
        at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:324)
        at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:142)
        at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1065)
        at org.apache.catalina.core.StandardHost.start(StandardHost.java:822)
        at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1057)
        at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:463)
        at org.apache.catalina.core.StandardService.start(StandardService.java:525)
        at org.apache.catalina.core.StandardServer.start(StandardServer.java:754)
        at org.apache.catalina.startup.Catalina.start(Catalina.java:595)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:606)
        at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289)
        at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)

Answer 1

If the WebAppClassLoader is throwing a ClassNotFoundException, then that class is not in your web application. Get the latest version of the spymemcached client jar (2.12.1 at the time of this writing) and put it in the WEB-INF/lib directory of your web application. Remove any other spymemcached jars from that directory to avoid classloading conflicts.

net.spy.memcached.compat.log.SLF4JLogger was not introduced until version 2.9.0, so if you're using an older version of net.spy:spymemcached, that would explain why it could find LoggerFactory but not SLF4JLogger.

Answer 2

You can check your dependency tree with Dependency Plugin

mvn dependency:tree -Dverbose -Dincludes=spymemcached

if you see any other version beside 2.12.1, check it's top reference and add the exclude tag into it's maven dependency element like:

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-beans</artifactId>
    <version>3.0.3.RELEASE</version>
    <exclusions>
      <exclusion>
             <groupId>net.spy</groupId>
             <artifactId>spymemcached</artifactId>
      </exclusion>
    </exclusions>
</dependency