6.3.3.2 JDBC Uniform Resource Locators (URLs)
A JDBC url provides all information for applications to access a special resource, such as a data-base. Generally, a url contains three parts: protocol name, sub-protocol and subname for the data-base to be connected. Each of these three segments has a different function when they work together to provide unique information for the target database.
The syntax for a JDBC url can be presented as:
protocol:sub-protocol:subname
The protocol name works as an identifier to show what kind of protocol should be adopted when connecting to the desired database. For a JDBC driver, the name of the protocol should be jdbc. The protocol name is used to indicate the kind of items to be delivered or connected.
The sub-protocol is generally used to indicate the type of the database or data source to be con-nected, such as oracle or sqlserver.
The subname is used to indicate the address to which the item supposed to be delivered or the location where the database resides. Generally, a subname contains the following information for an address of a resource:
- Network host name/IP address
- The database server name
- The port number
- The name of the database
As we discussed in Section 6.2, a JDBC url can be considered a string used to define the address of the Oracle database to which we need to connect from our Java application. The protocol of this string, especially for an Oracle database, can be represented as:
jdbc:oracle:driver _ type:@database where
- driver _ type: indicates the type of JDBC driver to be used for the database connec-tion. Three options exist for Oracle JDBC drivers:
- oci: for Oracle9i and 10g OCI drivers
- thin: for the Oracle thin driver
- kprb: for the Oracle internal driver
- database: indicates the address to which the database will be connected. The following options exist:
- host:port:sid: this option works for thin and OCI drivers. The host is the host name or IP address of a database server, and the port is the port number of the Oracle listener. Both are similar to those in the SQL Server database. The sid is the Oracle system identifier or Oracle service name of the database.
- Net service name: this is only used for the OCI driver. It is a tnsnames.ora file entry that resolves to a connect descriptor.
- Connect descriptor: this is only used for the OCI or thin driver. It is the Net8 address specification.
In our application, the driver _ type is thin, since we are using a thin driver. The database is represented as: localhost:1521:XE. The database server is built on our host computer; therefore, the name is localhost. The listener port number is 1521, which can be found from the Oracle database configuration file tnsnames.ora, which is located at the folder C:\app\yingb\prod-uct\18.0.0\dbhomeXE\NETWORK\ADMIN in my case. The path after C:\app, yingb, is the user name on the author’s computer, and it should be replaced by your user name on your computer.
After a target database has been connected, the next job is to build a database query to requestor retrieve information or records from the selected Table in that database. In Java database applica-tions, the statement class is one of the most popular components and widely used to access and manipulate the target database.