java - Using GWT and a library that uses log4j in the same project -

i'm developing gwt web app. gwt, i'm using .jar uses logj4, call "bob". if don't add log4j jar war/web-inf/lib folder, error described here: java.lang.noclassdeffounderror: org/apache/log4j/logmanager.

if put .jar in lib folder, java.lang.noclassdeffounderror, time org/apache/log4j/appender. error comes within "bob", other library. bob.jar on classpath of project, in war/web-inf/lib.

is there obvious fix this?