tomcat中类路径

from tomcat's online help.

l $CATALINA_HOME/common/lib - JAR files placed here are
visible both to web applications and internal Tomcat code. This is
a good place to put JDBC drivers that are required for both your
application and internal Tomcat use (such as for a JDBCRealm).

l $CATALINA_HOME/shared/lib - JAR files placed here are
visible to all web applications, but not to internal Tomcat code.
This is the right place for shared libraries that are specific to your
application.