Eu uso o Eclipse Juno. Eu tenho mysql-connector-java-5.1.22-bin.jar no meu buildpath e tento estabelecer uma conexão de banco de dados para o meu banco de dados mysql. Aqui está meu código

public Connection getConnectionToDB() {
    try {
        Class.forName(driver);
        Connection con = DriverManager.getConnection(url + dbName,
                userName, password);
        return con;
    } catch (Exception e) {
        e.printStackTrace();
    }
    return null;
}

Quando eu depurar, descobri que o problema é:

Class.forName(driver);

Eu também tentei substituí-lo com:

Class.forName(driver).newInstance();

Nesta linha, ele se rompe na exceção e lança essa exceção:

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1676)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1521)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:169)
at main.jdbc.BaseJdbc.getConnectionToDB(BaseJdbc.java:18)
at main.jdbc.UserDriverJdbc.queryUserById(UserDriverJdbc.java:15)
at main.drivers.UserDriver.findUserById(UserDriver.java:50)
at main.drivers.UserDriver.isLoginValid(UserDriver.java:56)
at main.controllers.LoginController.doPost(LoginController.java:33)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
at org.apache.catalina.core.StandardContextValve.__invoke(StandardContextValve.java:164)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
at org.apache.catalina.core.StandardHostValve.__invoke(StandardHostValve.java:164)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:250)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:166)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)