Singleton Connection Class

Hello,

I am trying to access a singleton connection class from a test class but I got an incompatible type error.

here is the connection class:

import java.sql.*;
import java.util.Properties;
import java.io.InputStream;

public  class DBManager
{
    private  static Connection connection = null;
    private static DBManager dbmanager;
    
   private DBManager()throws Exception
   {
        if (connection == null)
        {
            //System.out.println("MySQL Connect Example.");

String CONFIG_FILE_NAME = "mysql.properties";
            Properties dbProperties;
            try
            {
                dbProperties = new Properties();
                Class thisClass = Class.forName("dbapps.DBManager");
                InputStream is = thisClass.getResourceAsStream(CONFIG_FILE_NAME);
                dbProperties.load(is);

String url = "jdbc:mysql://"+dbProperties.getProperty("host")+":"+dbProperties.getProperty("port")+"/";
                String dbName = dbProperties.getProperty("schema")+"?useUnicode=yes&characterEncoding=UTF-8";
                String driver = "com.mysql.jdbc.Driver";
                String userName = dbProperties.getProperty("username");
                String password = dbProperties.getProperty("password");

Class.forName(driver).newInstance();
                connection = DriverManager.getConnection(url + dbName, userName, password);
               // System.out.println("Connected to the database");
            }
            catch (Exception e)
            {
                e.printStackTrace();
                connection = null;
                throw e;
            }
        }       
   }

public static Connection openDBConnection() throws Exception
    {
        dbmanager = new DBManager();
     return connection;
    }
}

and the test class

The error that I get is : incompatible type required : DBManager found: java.sql.connection.

Thanks !

You need a Connection object. The openDBConnection method returns a Connection object. So... what type of variable do you think you should assign the result of the openDBConnection method to?

Hello,

Well with the Singleton pattern I should use an object of the same type for the connection class, isn't it?

I don't follow. You have a method that returns the type java.sql.Connection and you are trying to assign it to a variable that expects the type DBManager. Perhaps the concept of a singleton is confusing the issue? Why do you want to use a singleton? What you have coded is not a singleton, by the way.

DBManager db= DBManager.openDBConnection(); returns a Connection and not a DBManager!

quote=Jothi Shankar Kumar]DBManager db= DBManager.openDBConnection(); returns a Connection and not a DBManager!

Hello,

Yes in fact the class return a connection which from Statement is inherited.

[

Paul Sturrock wrote:I don't follow. You have a method that returns the type java.sql.Connection and you are trying to assign it to a variable that expects the type DBManager. Perhaps the concept of a singleton is confusing the issue? Why do you want to use a singleton? What you have coded is not a singleton, by the way.

Hello Paul,

Well the main idea behind coding the class as a singleton pattern is because I need just a one connection object a long with the system, and also disabling creating another instance from the connection.

I solved the problem thanks !

Faiz Abdelhafid wrote:

Paul Sturrock wrote:I don't follow. You have a method that returns the type java.sql.Connection and you are trying to assign it to a variable that expects the type DBManager. Perhaps the concept of a singleton is confusing the issue? Why do you want to use a singleton? What you have coded is not a singleton, by the way.

Hello Paul,

Well the main idea behind coding the class as a singleton pattern is because I need just a one connection object a long with the system, and also disabling creating another instance from the connection.

I solved the problem thanks !

OK, but what you've got above is not a singleton, many instances of DBManager can exist using that code.

Paul Sturrock wrote:

Faiz Abdelhafid wrote:

Paul Sturrock wrote:I don't follow. You have a method that returns the type java.sql.Connection and you are trying to assign it to a variable that expects the type DBManager. Perhaps the concept of a singleton is confusing the issue? Why do you want to use a singleton? What you have coded is not a singleton, by the way.

Hello Paul,

Well the main idea behind coding the class as a singleton pattern is because I need just a one connection object a long with the system, and also disabling creating another instance from the connection.

I solved the problem thanks !

OK, but what you've got above is not a singleton, many instances of DBManager can exist using that code.

The DBManager class uses a private constructor a side with a public static method to "share" the connection but not creating a new "instance".
I will ask my trainer for further details about the connection class.

I can easily clone your class to create a new instance. I don't understand your argument. the openConnection() method returns a Connection and not a DBManager. Are you disagreeing with that?

Jothi Shankar Kumar wrote:I can easily clone your class to create a new instance. I don't understand your argument. the openConnection() method returns a Connection and not a DBManager. Are you disagreeing with that?

Hello Jothi,

The whole idea was to create a single shared instance for the application inside the static method:

which will share this object among all users with the same DBConnection object

And then you gotta only write the following in your application

Hope I clarified my point of view

BR

Is it possible for you to share the complete code...i am trying very hard from last couple of days to figure this out.

I want to have a singleton database java code loading from the property file

Thanks a bunch

Welcome to the Ranch

Since this thread is two years old, you might not get a reply, I am afraid.