Getting Startedwith pureQuery

Chapter 13 – Handlers 267
constructor, and uses the same instance every time your application calls the annotated
methods. pureQuery recommends that you use this approach as much as you can
because your application will not have to manage instances of the handler, and only one
instance of the handler will be instantiated, no matter how many times your application
invokes the annotated method. However, you might have handlers that do not have public
no-argument constructors. You also might have handlers that store information about the
query result of a query, preventing you from using a single handler for multiple invocations
of an annotated method. For these handlers, you will need to specify the handlers as
parameters to the annotated methods.
13.3.2 Specifying handlers as method parameters
When you want to specify a handler for an annotated method, if you do not want to (or
cannot) specify it by using the @Handler annotation, specify it as a parameter to the
annotated method. When you specify handlers as parameters for an annotated method,
they must be the last parameters to the method. That is, you must first provide any
parameters that provide the information for setting the parameters in the SQL statement,
and then you can provide one or two handlers. Listing 13.6 shows an example of
specifying the IteratorPagingResultHandler for an annotated method.
@Select(sql = "SELECT * FROM EMPLOYEE WHERE WORKDEPT = ?)
Iterator selectEmployeesInDepartment (String workDept,
IteratorPagingResultHandler resultHandler);
Listing 13.6 - An example of specifying a handler as a parameter to an annotated
method
13.3.2.1 In practice: Add an annotated method to HumanResourcesData that
executes the SQL and uses a handler for the query result
The “Company Employees” screen displays all of the employees in the company in pages
of 10 employees each. Let’s use the IteratorPagingResultHandler to retrieve
the employees, one page at a time. Modify the displayAllEmployees method in
hrm.inProgress.pdqMethodStyleWithHandlers.HumanResourcesManager,
along with the utility method selectPageOfEmployees. You will also need to modify the
interface
hrm.inProgress.pdqMethodStyleWithHandlers.HumanResourcesData. Refer
to Section 8.2.1 for the SQL statement that we need to execute.
13.3.2.1.3 Specify annotated method
Declare an annotated method that executes the SQL statement and uses the
IteratorPagingResultHandler to return the results. The
IteratorPagingResultHandler does not have a no-argument constructor, so we
will specify it as a parameter to the annotated method. The return type of the handle
method is ResultIterator. We can use that as the return type of our method, or
we can use Iterator, which is a superinterface of ResultIterator. We