2.1.3 JDBC URLs

A JDBC URL provides a way of identifying a data source so that the appropriate driver will recognize it and establish a connection with it. Driver writers are the ones who actually determine what the JDBC URL that identifies a particular driver will be. Users do not need to worry about how to form a JDBC URL; they simply use the URL supplied with the drivers they are using. JDBC's role is to recommend some conventions for driver writers to follow in structuring their JDBC URLs.
Since JDBC URLs are used with various kinds of drivers, the conventions are, of necessity, very flexible. First, they allow different drivers to use different schemes for naming databases. The odbc subprotocol, for example, lets the URL contain attribute values (but does not require them).
Second, JDBC URLs allow driver writers to encode all necessary connection information within them. This makes it possible, for example, for an applet that wants to talk to a given database to open the database connection without requiring the user to do any system administration chores.
Third, JDBC URLs allow a level of indirection. This means that the JDBC URL may refer to a logical host or database name that is dynamically translated to the actual name by a network naming system. This allows system administrators to avoid specifying particular hosts as part of the JDBC name. There are a number of different network name services (such as DNS, NIS, and DCE), and there is no restriction about which ones can be used.

The standard syntax for JDBC URLs is shown here. It has three parts, which are separated by colons.
jdbc::

The three parts of a JDBC URL are broken down as follows:

1. jdbc-the protocol. The protocol in a JDBC URL is always jdbc.
2. -the name of the driver or the name of a database connectivity mechanism, which may be supported by one or more drivers. A prominent example of a subprotocol name is odbc, which has been reserved for URLs that specify ODBC-style data source names. For example, to access a database through a JDBC-ODBC bridge, one might use a URL such as the following:
jdbc:odbc:fred
In this example, the subprotocol is odbc, and the subname fred is a local ODBC data source.
If one wants to use a network name service (so that the database name in the JDBC URL does not have to be its actual name), the naming service can be the subprotocol. So, for example, one might have a URL like:
jdbc:dcenaming:accounts-payable
In this example, the URL specifies that the local DCE naming service should resolve the database name accounts-payable into a more specific name that can be used to connect to the real database.
3. -a way to identify the data source. The subname can vary, depending on the subprotocol, and it can have any internal syntax the driver writer chooses, including a subsubname. The point of a subname is to give enough information to locate the data source. In the previous example, fred is enough because ODBC provides the remainder of the information. A data source on a remote server requires more information, however. If the data source is to be accessed over the Internet, for example, the network address should be included in the JDBC URL as part of the subname and should adhere to the following standard URL naming convention:
//hostname:port/subsubname
Supposing that dbnet is a protocol for connecting to a host on the Internet, a JDBC URL might look like this:
jdbc:dbnet://wombat:356/fred