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Chapter 18 JDBC and Database Connection Pooling

Sometimes the queries follow a fixed format even though certain values

change. You should make use of prepared statements in such a case; see Sec 

tion 18.6 for details. Other times, however, even the query format is variable.

Fortunately, this situation presents no problem, since 

ResultSetMetaData

can be used to determine the number, names, and types of columns in a

ResultSet

, as was discussed in Section 18.1 (Basic Steps in Using JDBC). In

fact, the database utilities of Listing 18.6 store that metadata in the

DBResults

 object that is returned from the 

showQueryData

 method. Access

to this metadata makes it straightforward to implement an interactive graphi 

cal query viewer as shown in Figures 18 1 through 18 5. The code to accom 

plish this result is presented in the following subsection.

Figure 18 1 Initial appearance of the query viewer.

Figure 18 2 Query viewer after a request for the complete employees table from an 

Oracle database.

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