“When a Driver class is loaded, it should create an instance of itself and register it with the DriverManager”-the Driver interface of JDBC API has made it very clear about its intentions. So the user now can register the Driver by calling Class.forName(the driver name).This is a simplest case of dynamic class loading and is used extensively in implementing Enterprise systems. For others, there are two choices: either call Class.forName() or call DriverManager.registerDriver().
Let us do the latter.
Driver driver=new com.mysql.jdbc.Driver();
DriverManager.registerDriver(driver);
The point which I am curious about is that now the DriverManager has two Driver instances registered with it and every time we try to get a connection, it iterates over the list containing these two drivers.Well! Our intention was to have a single driver instance and we end up having two. Why we have two driver instances is simple as in Driver class we have a static block as
static
{
try
{
DriverManager.registerDriver(new Driver());
}
catch(SQLException E)
{
throw new RuntimeException("Can't register driver!");
}
}
So when we call new Driver(), first registration happens and the next is performed by us.
Well! After this long story, the only thing which I am curious about is “Why we have a register method in DriverManager class where we can do our job with Class.forName() or just calling new Driver()”.
Since I have never used DriverManager.registerDriver() nor I have seen somebody using it.I would appreciate if someone comes up with its usage.
