How to store override method in a variable in Scala - scala

Question

Here is My Code Snippet
package SimpleDruidOperation
import java.sql.{Connection, Driver, DriverManager, SQLException, Statement}
class ConnectionEstablishment {
var conn:Connection=_
var dr:Driver=_
def connEstablishment() =
{
try {
dr = new com.mysql.jdbc.Driver()
DriverManager.registerDriver(dr)
conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/deven","root","root")
if(conn!=null)
println("!!Database Connected Succesfully!!!")
else
println("!!Check your Database Connection !!")
}
catch
{
case e:SQLException=>println("Exception is "+e.getMessage)
}
finally
{
conn.close()
}
}
}
class InsertintoDatabase extends ConnectionEstablishment {
var stmt:Statement=_
// override def connEstablishment():co = super.connEstablishment()
val conn:Connection=connEstablishment()//it is not going to override
def insertintoDatabase(): Unit =
{
println("Checking Conection Establishment")
try {
stmt = conn1.createStatement()
var sql = "insert into emp (eid,ename,eadd,emob) values (101,'Mohit','Pune',9156369938) "
var i = stmt.executeUpdate(sql)
if (i > 0)
println(i + "Value Inserted Successfully into Databaes")
else
println("!!Not Inserted Check something is going wrong!!")
}
catch
{
case e:SQLException=>println("Exception is "+e.getMessage)
}
finally
{
println("Closing Connection Establishment "+conn1.close())
println("CLosing Statement Connection "+conn1.close())
}
}
}
How to store override method in a variable in Scala
Here in my first class ConnectionEstablishment this class is to make connection and second class is for insert into database but the problem is I am unable to override the connEstablisment method because if I want override it then I am unable to establish a connection for insert
because I need it, so that i can call statement stmt=conn,createStatement().
How can I do it?

Answer 1

The problem here is that you have created a class hierarchy when you actually need two separate classes. The ConnectionEstablishment class represents a database connection and the InsertintoDatabase class represents an operation on that database, and there is no natural hierarchy between them.
Class hierarchies should have an "is a" relationship: If D inherits from C then it should make sense to say that a D is a C. So it makes sense for Circle to inherit from Shape because a circle is a shape. It does not make sense for a database operation to inherit from a database connection because a database operation is not a database connection.
A database operation needs a database connection, and this is a containment relationship, not a hierarchy.
So you should have a ConnectionEstablishment class that creates and manages the database connection, and an InsertintoDatabase class that takes a ConnectionEstablishment instance and uses it to insert items into the database.
With this arrangement you can create different subclasses of ConnectionEstablishment that connect to the database in different ways, and the InsertintoDatabase class will work with any of those subclasses. Likewise you can create new classes that use the database connection, such as DeleteFromDatabase, without having to inherit from the existing InsertintoDatabase class.