Connecting to number of databases.

[jagan raja]

I have got five different databases i.e 5 different hosts.

I have to connect to them and retrieve data without making a performance hit.

My Code for establishing connection with single database is as follows.

public class Database 
{
	private static Connection con = null;
	public static Connection makeConnection() throws Exception
	{
		try{
		Class.forName("oracle.jdbc.driver.OracleDriver");
		if(con==null){
			con=DriverManager.getConnection("jdbc:oracle:thin:@host:1521:SID","USERNAME","PASSWORD");
		}
		else
				return con;
		}catch(Exception e){
			e.printStackTrace();
			throw e;
		}
		return con;
		
	}  
}
 

Can any one help me out ???

[Paul Sturrock]

What is the question?

[jagan raja]

How to establish connection with 5 different host's at a time?

[Paul Sturrock]

Do the above five times, with a different variable for each connection.

[Vinod Tiwari]

You can write a generic code and pass database details (which can be stored in some property of XML file) as parameter to establish connection....

[jagan raja]

I did that 5 times and it works fine.

But i want to know if there is any other simpler way of doing it.

Now my code is as below.

public static ArrayList<Connection> makeConnection() throws Exception
	{
		try{
		Class.forName("oracle.jdbc.driver.OracleDriver");
		if(conc2==null && cons1==null){
			conc2=DriverManager.getConnection("jdbc:oracle:thin:@host:1521:sid","username","password");
			cons1=DriverManager.getConnection("jdbc:oracle:thin:@host:1521:sid","username","password");
			coni=DriverManager.getConnection("jdbc:oracle:thin:@host:1521:sid","username","password");
			coni1=DriverManager.getConnection("jdbc:oracle:thin:@host:1521:sid","username","password");
			cons=DriverManager.getConnection("jdbc:oracle:thin:@host:1521:sid","username","password");
			conArray=new ArrayList<Connection>();
			conArray.add(conc2);
			conArray.add(cons1);
			conArray.add(coni);
			conArray.add(coni1);
			conArray.add(cons);
		}
		else
				return conArray;
		}catch(Exception e){
			e.printStackTrace();
			throw e;
		}
		return conArray;
		
	}
	public static void closeConnection()
	{
		try{
		conc2.close();
		cons1.close();
		coni.close();
		coni1.close();
		cons.close();
		}catch(Exception e){System.out.println(e.getLocalizedMessage());};
	}
}

How to store these details in some property of XML file and use it?

Thanks in advance

[Jan Cumps]

(assuming this is a stand alone application)

You could create an XML file with contents like this:

<connections>

  <connection 
    name="connection1" 
    driver="oracle.jdbc.driver.OracleDriver"
    url=""jdbc:oracle:thin:@host:1521:sid" 
    user="username" 
    password="password"/>

  <connection 
    name="connection2" 
    driver="oracle.jdbc.driver.OracleDriver"
    url=""jdbc:oracle:thin:@otherhost:1521:sid" 
    user="username" 
    password="password"/>

</connections>

And then, in your java code, use one of the XML APIs to read the file and create a connection for each occurrence of the <connection> tag.
You can store these connections in conArray.

[Peter Johnson]

Do you want several connections to the same database with the same login credentials? That is what you have. Or if the literal strings you posted were just examples, then you have a fixed number of connections.

I would have changed the makeConnection() method to pass the URL, username and password strings, and had the DriverManager.getConnection() method used the passed arguments. Or I would have wrapped all of this in a Connection wrapper class. Then each connection could use a different database and different credentials.