[ Team LiB ] 6.3 Using SQL Directly
[ Team LiB ] 6.3 Using SQL Directly from JSPs The standard tag library contains tags that allow SQL commands to be embedded directly in a page. The most basic of these is the query tag, which allows a page to perform a select and display the results. The tag’s use is demonstrated in Listing 6.3, which selects the list of artists from the table defined in Listing 6.1. Listing 6.3 A page that gets data from a database <%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %> <%@ taglib prefix="sql" uri="http://java.sun.com/jstl/sql" %>
This example starts by importing the core library and a new SQL library that contains the new tags. Immediately after loading the library, the query tag is used to load some data. The query tag has many options, but the ones used here are the most common. First, the tag needs to be told how to connect to the database where the information lives, which is specified as the dataSource parameter. The exact form of this will make more sense after Chapter 9, but for now, think of it as naming three things: the location of the database, the kind of database, and the user name and password with which to connect to the database. These are all specified on one line, separated by commas. The sql parameter specifies the SQL to execute. The SQL used here is a simple select command. Finally, the var parameter names a variable in which the results of the query should be stored. This is somewhat similar to the var parameter in the c:forEach tag in that both make a value available elsewhere on the page. Not coincidentally, the next place this variable is seen is in a c:forEach tag on the next line. Note that this variable is used as the items, because this one variable contains something like an array, each element of which will be one row of data. The artist variable, defined in the c:forEach tag, will hold each row in turn. Within the body of the c:forEach tag, the artist variable acts like the param variable in Section 4.6, which has a different property for each value sent by a form. Similarly, artist will have one property for each column, which may be obtained by using the normal dot notation used with beans. The artist name, therefore, is obtained with
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