Controlling the classpath in a servlet

Question

My servlet application includes a number of library .jars, some of which contain embedded log4j.xml or log4j.properties files. I\'d like to ensure that log4j finds my log4j.

Answer 1

Tomcat 8.5

Ditto Tomcat 8.0.

See documentation: Class Loader HOW-TO.

Tomcat 8.0

The answer is simple, taken from the Tomcat documentation page, Class Loader HOW-TO. In particular notice the use of the /WEB-INF/ directory/folder.

Therefore, from the perspective of a web application, class or resource loading looks in the following repositories, in this order:

• Bootstrap classes of your JVM
• /WEB-INF/classes of your web application
• /WEB-INF/lib/*.jar of your web application
• System class loader classes (described above)
• Common class loader classes (described above)

If the web application class loader is configured with then the order becomes:

• Bootstrap classes of your JVM
• System class loader classes (described above)
• Common class loader classes (described above)
• /WEB-INF/classes of your web application
• /WEB-INF/lib/*.jar of your web application

Tomcat 6

Excerpted from Tomcat 6 page, Class Loader HOW-TO.

Therefore, from the perspective of a web application, class or resource loading looks in the following repositories, in this order:

• Bootstrap classes of your JVM
• System class loader classes (described above)
• /WEB-INF/classes of your web application
• /WEB-INF/lib/*.jar of your web application
• $CATALINA_HOME/lib
• $CATALINA_HOME/lib/*.jar