Working with Databases - Java 8 Recipes - page 456

ber string variable was equal to "13-1", the results of executing the query in the ex-
ample would look something like the following:
13-1: Connecting to a Database - DriverManager and
DataSource Implementations
Of course, if the substitution variable is not set correctly or if there is an issue with
the SQL string, an exception will be thrown. This would cause the code that is con-
tained within the catch block to be executed. You should also be sure to clean up
after using PreparedStatement s by closing the statement when you are finished
using it. If you're not using a try-with-resources construct, it is a good practice
to put all the cleanup code within a finally block to be sure that the Pre-
paredStatement is closed properly even if an exception is thrown. In the example,
the finally block looks like the following :
finally {
if (pstmt != null){
try {
pstmt.close();
} catch (SQLException ex) {
ex.printStackTrace();
}
}
}
You can see that the PreparedStatement object that was instantiated, pstmt ,
is checked to see whether it is NULL . If not, it is closed by calling the close() meth-
od.
Working through the code in the solution to this recipe, you can see that similar
code is used to process database INSERT , Update , and DELETE statements. The
only difference in those cases is that the PreparedStatement executeUp-
date() method is called rather than the executeQuery() method. The ex-
ecuteUpdate() method will return an int value representing the number of rows
affected by the SQL statement.
The use of PreparedStatement objects is preferred over JDBC Statement
objects. This is due to the fact that they are more secure and perform better. They can
also make your code easier to follow and maintain.