Getting Startedwith pureQuery

13
Chapter 13 - Handlers
In this chapter, you will learn how to use handlers to modify how pureQuery returns query
results, and how pureQuery sets the values of SQL parameters.
13.1 Handlers: The big picture
pureQuery provides a wide variety of ways to specify parameters for the SQL statements
that you execute, along with many formats for returning query results. However, there
might be times when the built-in functionality does not meet the needs of your application.
In these cases, you can use handlers to customize various aspects of pureQuery
processing by writing classes that implement the handler interfaces. pureQuery provides
the following types of handlers:
Customizing input:
Customizing output:
• com.ibm.pdq.runtime.handlers.ParameterHandler: You can
use a ParameterHandler object to determine how the pureQuery sets the
values of parameters in prepared SQL statement. The interface defines a
method named handleParameters that pureQuery calls to set the
values of the parameters in the SQL statement.
• com.ibm.pdq.runtime.handlers.RowHandler: You can use
a RowHandler object to determine how pureQuery returns each
row of a query result. Use this when you want to use one of pureQuery's
built-in objects for returning all the rows, but you want to modify the way
pureQuery returns each row. The RowHandler interface defines a
method named handle. pureQuery processes each row of the query
result by calling this method. The handle method returns an object of
type ROW, which pureQuery uses to represent the row in the object that
the annotated or inline method returns. If you are using the annotatedmethod
style to execute an SQL INSERT statement, and if you use a
single pureQuery bean to provide the values of the SQL parameters,
pureQuery can update properties in the bean with values generated by