Using Database Metadata
Sometimes, in addition to querying and updating the data
in a database, you also want to retrieve information about the
database itself and its contents. This information is called
metadata. The DatabaseMetaData interface allows you to
retrieve this kind of information. You can obtain an object that
implements this interface by calling the getMetaData( ) method of the Connection object, as shown in Example 18-2.
After GetDBInfo opens
a database Connection and obtains a
DatabaseMetaData object, it
displays some general information about the database server and JDBC
driver. Then, if the user just specified a database name on the
command line, the program lists all the tables in that database. If
the user specified a database name and a table name, however, the
program lists the name and data type of each column in that
table.
An interesting feature of this GetDBInfo program is how it obtains the
parameters needed to connect to the database. The example operates on
the premise that at any given site, it is typically used to connect to
the same database server, using the same database driver, and may also
be used with the same database username and password. So, instead of
requiring the user to type all this cumbersome information on the
command line each time the program is run, the program reads default
values from a file named DB.props that is stored
in the same directory as the GetDBInfo.class
file. In order to run Example
18-2, you have to create an appropriate ...
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