How to fix java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory

java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory or "Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory" exception comes when you don't apache commons-logging-1.1.1.jar in your Classpath. I have faced this exception many times while using open-source frameworks like Struts, Spring, and Displaytag which uses a commons-logging framework for logging. commons-logging is not an actual java logging framework but provides a wrapper so that you can use log4j, java logging, or any other Java logging framework.

The commons-logging is also smart enough to detect which logging framework are you using e.g if you are using log4j it can detect it by looking log4j.jar in your classpath.

Btw if you don't have commons-logging.jar in your classpath you may get java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory at runtime even if your application gets deployed successfully.

Cause of java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory

Real cause of "Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory" or "java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory" is JVM not able to locate commons-logging-1.1.1.jar in classpath but it may surface differently on different environment. Some time even you get this error even if you already have commons-logging-1.1.1.jar in classpath and many times it different reasons for different environment. 

It gets more difficult on the managed environments like J2EE web servers and application servers where different classloaders load different classes e.g. AppClassLoader is responsible for loading web application but classes inside lib directory of web server e.g. tomcat are loaded by another classloader. 

So you can also get "java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory" if commons-logging.jar is not visible to App classloader. some times this jar can also cause a memory leak in tomcat.

here I have outlined some steps to fix "java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory" these are based on the approach I used to resolve such kind of error. it may help you as well.

java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory Solution

1.Check your classpath for commons-logging-1.1.1.jar, if you are using spring MVC and working in a web application it must be on /WEB-INF/lib directory.

2.Check if your Java program has sufficient permission to access that jar file (I faced this issue in Unix machine when a user who copied that jar does override the default permission and the application was not able to read this jar file so make sure to check permissions if you are copying commons-logging-1.1.1.jar into Java Classpath.

3.See if commons-logging-1.1.1.jar contains org.apache.commons.logging.LogFactory class or not this may happen if commons-logging-1.1.1.jar is corrupt or not downloaded completely or may be downloaded from an incorrect source.

4.See if your Classpath is getting overridden by any start-up Script as suggested in my post on how to solve java.lang.ClassNotFoundException

5.If you are using maven for managing dependency on your project then check if your pom.xml file contains the following entry or not and if it doesn't then include the following dependency for commons-logging-1.1.1.jar in pom.xml:

Maven dependency for Apache commons-logging:

<dependency>
        <groupId>commons-logging</groupId>
        <artifactId>commons-logging</artifactId>
        <version>1.1.1</version>
</dependency>

That's all on How to fix java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory Error, it may surface as "Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory" also but mostly cause of both errors are same. 

If you have any other useful step to figure out ClassNotFoundException suggest it here.

Here are few more Java tutorials you may like.

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And lastly one question for you? What is your approach to solve any exception in Java? Do you get panicked? or do you start checking log files then stack trace and then try to make sense of it?