为什么跟上个jsp课程同样的DB数据库，上一个可以用，这次这个案例却不能用

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver

at java.net.URLClassLoader$1.run(URLClassLoader.java:202)

at java.security.AccessController.doPrivileged(Native Method)

at java.net.URLClassLoader.findClass(URLClassLoader.java:190)

at java.lang.ClassLoader.loadClass(ClassLoader.java:306)

at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)

at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

at java.lang.Class.forName0(Native Method)

at java.lang.Class.forName(Class.java:171)

at util.DBHelper.<clinit>(DBHelper.java:17)

java.sql.SQLException: No suitable driver found for jdbc:mysql://localhost:3306/shopping?useUnicode=true&characterEncoding=UTF-8

at java.sql.DriverManager.getConnection(DriverManager.java:602)

at java.sql.DriverManager.getConnection(DriverManager.java:185)

at util.DBHelper.getConnection(DBHelper.java:27)

at util.DBHelper.main(DBHelper.java:35)