Working with mapped statements - iBATIS in Action - page 95

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The example in listing 4.2 uses the remapResults attribute combined with
Dynamic SQL to demonstrate how to change the data returned from a
mapped statement on the fly. While Dynamic SQL is not covered until chapter 8,
this example uses it to create a mapped statement where the value of the
includePassword property determines the fields that are in the results. Depend-
ing on its value, you may or may not get the password field back in your results.
One thing to be aware of is that the performance hit for determining a result
map each and every time a statement is run may be prohibitive, so use this fea-
ture only when it is an absolute requirement.

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4.2.5 Joining related data

There are times when you want to join multiple data tables into a single “flat-
tened-out” structure for reporting or other purposes. The i BATIS framework
makes this completely effortless, because it maps SQL statements to objects, not
tables to objects. There is literally no difference between mapping a single-table
select and a multitable select.
In chapter 7, we will look at how to perform more advanced multitable opera-
tions for the purpose of providing lists of child objects that are related to their
containing objects—such as a list of orders details for an order.
For now, we will simply restate that there is literally no difference between
mapping a single-table select and a multitable select.
We have talked about how SQL is similar to a function in that it has input val-
ues and, based on those input values, it produces output values. In the next sec-
tion, let's see how you provide those input values.

4.3 Mapping parameters

There are two ways to map parameters into your mapped statements: inline map-
ping and external mapping. Using inline parameter mapping means that you give
i BATIS some hints as to what you want, and let it figure out the details. External
parameter mapping, on the other hand, is more explicit—you tell i BATIS exactly
what you want it to do.

4.3.1 External parameter maps

You can specify up to six attributes when using an external parameter map. If you
do not specify them, i BATIS will try to decide on reasonable values using reflec-
tion, but this takes time and may not be as accurate. Table 4.4 lists the attributes
that are available for mapping parameters, and briefly describes how each is used.