Implementing dynamic paged queries - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 420

which has startingIndex and pageSize parameters that specify which page of the
result set to return, as well as a OrderSearchCriteria parameter that contains the
search criteria entered by the user and the selected sort order. It has properties
that represent the order number, phone number, email address, and date range.
The findOrders() method returns a PagedQueryResult object, which contains the
list of OrderSummary DTO objects, and a boolean flag indicating whether there are
more orders.
OrderDAOIBatisImpl , which implements the OrderDAO interface, calls SqlMap-
ClientTemplate to generate and execute the findOrders mapped statement,
which is defined in the Order.xml descriptor file. findOrders is an i BATIS dynamic
mapped statement. It contains conditional XML elements that use the values from
the OrderSearchCriteria JavaBean to determine whether to include one or more
SQL fragments in the statement. Using this mechanism to dynamically generate
SQL queries significantly simplifies the DAO by eliminating conditional logic and
code that concatenates SQL fragments. In fact, because i BATIS does all of the
work, findOrders() consists of a few lines of code that call SqlMapClientTem-
plate.queryForList() , which executes the query and returns a list of beans con-
structed from the result set.
We have seen earlier that, depending on the query, we will want to select a page
of results by either navigating through the result set or by executing a SELECT state-
ment that uses a ROWNUM -like feature. Accordingly, i BATIS defines two versions of
the queryForList() method. One version takes parameters that specify the range
of rows to return. It navigates through the JDBC result to extract the specified rows.
The other version of queryForList() returns a list containing all of the rows found
by the query. It's useful when the SQL query returns just the required rows by using
a ROWNUM -like feature. Let's look at how to use each of these methods.

11.2.1 Using queryForList() to select the rows

The first version of queryListForList() that we will examine is the one that takes
parameters specifying the range of rows to return. Here is the implementation
of the OrderDAO.findOrders() method that executes a mapped statement using
this version:

public class OrderDAOIBatisImpl extends SqlMapClientDaoSupport
implements OrderDAO {
public PagedQueryResult findOrders(int startingIndex,
int pageSize, OrderSearchCriteria criteria) {
Map map = new HashMap();
map.put("pageSize",
new Integer(pageSize + startingIndex + 1));
map.put("criteria", criteria);