If your application runs in tomcat, place any and all jarfiles that it needs into the WEB-INF/lib directory of the application. You should know what the jars are, since you are the one writing the application. If you can no longer remember the name of a specific jar, then download it again. If, after placing the jar(s) in WEB-INF/lib, you still get a ClassNotFoundException, then you have either copied it to the WEB-INF/lib directory of the wrong application, or you have done something to the Tomcat configuration which prevents it from loading libraries in that directory. What that might be, I cannot even begin to tell you. All of this, of course, assumes that you are accessing the application through Tomcat, and a browser, of course. If you are attempting to execute something from the command line, then you should use the -cp option to specify the classpath (specifying the full complete path to each individual jarfile needed) when you type java (if the class will even function from the command line, which Servlets and JSPs definately will not (and most, if not all Beans, also should not, except indirectly, i.e. accessed from a different class which is executed).