Java, passing database connection into different classes.

Question

I don't understand the purpose of DatabaseAccess class. I'm curious about how did the object name "conDA" contains the database connection even without using the getConnection() method I created. Example "con2 = new Connection2(conDA);" how is that "conDA" object name can be understood as a connection of database? Here are the codes:

import java.sql.*;
public class Connection1 
{
    static Connection connection;
    static ConnectionDA conDA;
    static Connection2 con2;

    public static void main(String args[]) throws ClassNotFoundException, SQLException
    {
        conDA = new ConnectionDA(getConnection());
        System.out.println("Con1 Connected!!");
        con2 = new Connection2(conDA);  
    }

    public static Connection getConnection() throws ClassNotFoundException, SQLException
    {
        Class.forName("com.ibm.db2.jcc.DB2Driver");
        connection =  DriverManager.getConnection("jdbc:db2://localhost:50000/Sample", "ZeroCool","siliconvalley"); 

        return connection;
    }
}

2nd Class

import java.sql.*;
public class Connection2
{
    ConnectionDA conDA;
    Connection3 con3;

    public Connection2(ConnectionDA conDA) throws ClassNotFoundException
    {
        this.conDA = new ConnectionDA(conDA.getConnection());
        this.conDA = conDA;
        System.out.println("Con2 Connected!!");
        con3 = new Connection3(conDA);
    }
}

3rd Class

import java.sql.*;
public class Connection3 
{
    ConnectionDA conDA;

    public Connection3(ConnectionDA conDA) throws ClassNotFoundException
    {
        this.conDA = new ConnectionDA(conDA.getConnection());
        this.conDA = conDA;
        System.out.println("Con3 Connected!!");
    }
}

Database Access Class

import java.sql.*;
public class ConnectionDA 
{
    Connection connection;

    public ConnectionDA(Connection connection) throws ClassNotFoundException
    {
        this.connection = connection;
        System.out.println("ConDA Established!!!");
    }

    public Connection getConnection() 
    {
        return connection;
    }
}

SQL.injection · Accepted Answer · 2015-03-02 13:47:38Z

1

how is that "conDA" object name can be understood as a connection of database?

because the class ConnectionDA have the method getConnection implement that returns an object of the type connection.

public Connection3(ConnectionDA conDA) throws ClassNotFoundException
{
    this.conDA = new ConnectionDA(conDA.getConnection());
}

And here the implementation of the getConnection() method.

public class ConnectionDA 
{
    public Connection getConnection() 
    {
        return connection;
    }
}

I'm curious about how did the object name "conDA" contains the database connection even without using the getConnection() method I created

this is because, the class receive an connection on the constructor

public class ConnectionDA 
{
    Connection connection;

    public ConnectionDA(Connection connection) throws ClassNotFoundException
    {
        this.connection = connection;
    }

}

edited Mar 2, 2015 at 13:47

answered Mar 2, 2015 at 13:41

SQL.injection

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2 Comments

ZeroCool Over a year ago

So, I just need to call the ConnectionDA to establish connection to other classes? If that's the case, what is the use of getConnection() method everytime I initialize a conDA object name?

SQL.injection Over a year ago

you have the method getConection() to get the connection in the case you need it for some reason.

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