What is wrong with the code there are lots of error while debugging. I am writing a code for a singleton class to connect with the database mysql.
Here is my code
package com.glomindz.mercuri.util;
import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
public class MySingleTon {
String url = "jdbc:mysql://localhost:3306/";
String dbName = "test";
String driver = "com.mysql.jdbc.Driver";
String userName = "root";
String password = "";
private static MySingleTon myObj;
private Connection Con ;
private MySingleTon() {
System.out.println("Hello");
Con= createConnection();
}
@SuppressWarnings("rawtypes")
public Connection createConnection() {
Connection connection = null;
try {
// Load the JDBC driver
Class driver_class = Class.forName(driver);
Driver driver = (Driver) driver_class.newInstance();
DriverManager.registerDriver(driver);
connection = DriverManager.getConnection(url + dbName);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
}
return connection;
}
/**
* Create a static method to get instance.
*/
public static MySingleTon getInstance() {
if (myObj == null) {
myObj = new MySingleTon();
}
return myObj;
}
public static void main(String a[]) {
MySingleTon st = MySingleTon.getInstance();
}
}
I am new to java. Please help.
The exception can also occur because of the class path not being defined.
After hours of research and literally going through hundreds of pages, the problem was that the class path of the library was not defined.
Set the class path as follows in your windows machine
It seems the mysql connectivity library is not included in the project. Solve the problem following one of the proposed solutions:
Add the mysql-connector dependency to the pom.xml project file:
Here you are all the versions: https://mvnrepository.com/artifact/mysql/mysql-connector-java
Add the jar library manually to the project.
Right Click the project -- > build path -- > configure build path
In
Libraries Tab
pressAdd External Jar
andSelect
your jar.You can find zip for mysql-connector here
When building the project, java throws you an exception because a file (the com.mysql.jdbc.Driver class) from the mysql connectivity library is not found. The solution is adding the library to the project, and java will find the com.mysql.jdbc.Driver
For Gradle-based projects you need a dependency on MySQL Java Connector:
check for jar
(mysql-connector-java-bin)
in your classpath download from hereYou will have to include driver jar for MySQL MySQL Connector Jar in your classpath.
If you are using Eclipse: How to add dependent libraries in Eclipse
If you are using command line include the path to the driver jar using the -cp parameter of java.
Trivial as it may seem in my case netbeans version maven project 7.2.1 was different. There is a folder in the project called dependencies. Right click and then it brings up a popup window where you can search for packages. In the query area put
It will bring up the matches (it seems it does this against some repository). Double click then install.