Java Reference
In-Depth Information
Notice that inside the body of the
<sql:query>
tag we added a
<sql:param>
tag, this tag is used to dynamically substitute items in the
WHERE
clause of the
SQL
SELECT
statement in the tag, in a matter similar to the way the
java.sql.
PreparedStatement
interface works. In the query, question marks are used to
indicate parameters that need to be substituted with
<sql:param>
tags. Should
our query have multiple parameters (for example, when the values of two or
more columns are used in its
WHERE
clause), we can use a question mark for each
parameter in the query. The body of the
<sql:query>
tag must have a
<sql:param>
tag for each question mark in the query; the first
<sql:param>
will contain the value
for the first question mark, the second one will contain the value for the second
question mark, and so forth. The
value
attribute of the
<sql:param>
tag can contain
a String literal or a JSTL expression.
By deploying our application and pointing the browser to our page (or simply
right-clicking on the page and selecting
Run File
), we can see the
<sql:update>
tag
in action.
Every time we reload our page, a new row is added to the database, and the table on
the page is updated accordingly.
