javax.servlet.ServletException: java.sql.SQLException: No suitable driver found for jdbc:mysql://localhost:3306/testdb

This error occurs when the JDBC driver for MySQL is not found or not added to the classpath. To fix this error, follow these steps:

1. Download the JDBC driver for MySQL from the official website. The driver file should be in the form of a JAR file.

2. Add the JDBC driver JAR file to the classpath of your project. You can do this by adding the JAR file to the "lib" directory of your project or by adding it to the classpath through your IDE's project settings.

3. Make sure that the JDBC driver class name is correct in your code. The class name should be "com.mysql.jdbc.Driver".

4. Check the URL of the MySQL database connection. Make sure that it is correct and that the database is running on the specified port.

5. Test the database connection by running a simple query. If the query executes successfully, the connection should be working fine.

6. If the problem persists, try restarting your IDE or application server.

By following these steps, you should be able to fix the "No suitable driver found" error and establish a successful connection to your MySQL database.