Java, JDBC

[Solved] ClassNotFoundException: com.mysql.jdbc.Driver

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java.lang.ClassNotFoundException is Checked Exception which is subclass of  java.lang.ReflectiveOperationException. This  is thrown when application load a class by String name whose definition is not found. This exception occurs by below methods :

  • The forName method in the class Class.

                 Class.forName(java.lang.String)

  • The findSystemClass method in the class ClassLoader.

                ClassLoader.findSystemClass()

  • The loadClass method in class ClassLoader.

                ClassLoader.loadClass(java.lang.String, boolean)

 Difference between Class.forName() and ClassLoader.loadClass()

Example 1: ClassNotFoundException

Below is example of connecting with database and retrieve data from sql table. This will throw ClassNotFoundException because sql driver jar is not in classpath. After this example also mentioned solution.

package example;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class ClassNotFoundException1 {

	public static void main(String[] args) {
		try {
			Class.forName("com.mysql.jdbc.Driver");

			Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/university", "root", "");

			Statement stmt = con.createStatement();
			ResultSet rs = stmt.executeQuery("select name from employee");
			String dbtime;
			while (rs.next()) {
				dbtime = rs.getString(1);
				System.out.println(dbtime);
			}

			con.close();

		} catch (ClassNotFoundException | SQLException e) {
			System.out.println("Connection Failed! Check output console");
			e.printStackTrace();
		}

	}

}

Output:

Connection Failed! Check output console
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
	at java.net.URLClassLoader.findClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Unknown Source)
	at example.ClassNotFoundException1.main(ClassNotFoundException1.java:13)

Solutions:

For solving ClassNotFoundException by Class.ForName() method  considering above example to load MySQL driver same way you can follow for other classes and different DB drivers.

Solution in Eclipse :Follow below steps :

  • Right click your project folder and open up Properties.
  • From the right panel, select Java Build Path then go to Libraries tab.
  • Select Add External JARs to import the MySql driver.
  • From the right panel, select Deployment Assembly.
  • Select Add…, then select Java Build Path Entries and click Next.
  • You should see the SQL driver on the list. Select it and click first.

Tomcat :

If directly running from tomcat.Just copy the MySql-Connector.jar into Tomcat’s lib folder/directory, and then remove the jar from the webApp’s lib folder, and then, run the project.

Summary :

  • Define what is ClassNotFoundException.
  • What are methods throws ClassNotFoundException?
  • Example for ClassNotFoundException.
  • How to fix ClassNotFoundException in Eclipse and Tomcat.