Expert Spring MVC and Web Flow

AttributeMappers

The org.springframework.binding.AttributeMapper, shown in Listing 12-8, is a generic serv-

ice interface for mapping attributes from one source to another. Spring Web Flow uses it to

map objects and properties from one flow to another.

Listing 12-8.AttributeMapper Interface

public interface AttributeMapper {

void map(Object source, Object target, Map context);

}

Example

Let’s look again at the subflow state and attribute mappings from Listing 12-7:

<subflow-state id="enterShippingInformation" flow="shipping-flow">

<attribute-mapper>

<input-mapping name="purchase.requiresShipping" as="requiresShipping"/>

<output-maping name="shipping" as="purchase.shipping"/>

</attribute-mapper>

<transition on="end" to="placeOrder"/>

</subflow-state>

The <input-mapping>element instructs Spring Web Flow to map the value of the

requiresShippingproperty of the purchaseobject in theparent flow scopeto an attribute in

the subflow scope with the name requiresShipping.

The <output-mapping>element instructs Spring Web Flow to map the result of

the shippingsubflow output attributeto the shipping property on the purchaseobject in the

parent flow scope.

Figure 12-1 graphically represents this.

Figure 12-1.Graphical representation of mapping attributes to and from a subflow

Purchase Flow Shipping Flow

requires Shipping

shipping

purchase.requiresShipping

requiresShipping

requiresShipping

shipping

purchase.requiresShipping

purchase.shipping

342 CHAPTER 12 ■ADVANCED SPRING WEB FLOW