Spring Webflow: Can Validators Be Manually Set Per Flow? - spring-webflow

Question

I have multiple flow configured in my application:
<flow:flow-registry id="flowRegistry" flow-builder-services="flowBuilderServices" >
<flow:flow-location id="reservation1" path="/WEB-INF/flows/flow1.xml" />
<flow:flow-location id="reservation2" path="/WEB-INF/flows/flow2.xml" />
</flow:flow-registry>
These two flows use separate classes for their model attribute, call them Flow1DTO.java and Flow2DTO.java. However, they use a set of common JSPs/Tiles for their actual interface.
<form:form modelAttribute="reservationForm">
<!-- etc -->
</form:form>
Is it possible to define a separate Validator class per flow?

Answer 1

You can define a multiple validation methods for the same Model class for each specific view-state id. Where each custom validation method maps to a specific webflow view-state id.
Your validator class name for your model needs to be defined with the name "${model}Validator" (and have #Component annotation) and each validation method name needs to be named like this "validate${state} ([ModelClassType] model, ValidationContext context)"
So lets say you have a model class called "Reservation.java" and 2 different flows definition that use this model and each flow definition having a view-state definitions of
<!-- defined in your first flow file -->
<view-state id="ReservationSameDayViewState" view="sumting" model="reservationForm">
</view-state>
....
<!-- defined in your 2nd flow file -->
<view-state id="ReservationFutureViewState" view="sumting" model="reservationForm">
</view-state>
The validator class for Reservation model would like this:
#Component
public class ReservationValidator {
public void validateReservationSameDayViewState(Reservation reservation, ValidationContext context) {
// perform custom validation for first flow
}
public void validateReservationFutureViewState(Reservation reservation, ValidationContext context) {
// perform custom validation for 2nd flow
}
}
http://docs.spring.io/autorepo/docs/webflow/2.4.x/reference/html/views.html#view-validation-programmatic-validator
Also, it is bad practice to define your flows with integer increments. Change your flow registry definition to look like this. This way you don't have to keep manually adding flows to it every time you create new flows.
<flow:flow-registry id="flowRegistry" flow-builder-services="flowBuilderServices" base-path="/WEB-INF/flows">
<flow-location-pattern value="/**/*-flow.xml" />
</flow:flow-registry>
note: the flow names end with "-flow.xml". This is the unofficial standard way to define a flow-registry and flow names.

Answer 2

I figured out a solution that allowed me to validate multiple forms with a single implementation of a form validator.
The code looked something like this:
public void validateMethodName(Flow1DTO dto, ValidationContext context) {
valMethodName(dto, context);
}
public void validateMethodName(Flow2DTO dto, ValidationContext context) {
valMethodName(dto, context);
}
private void valMethodName(CommonFlowDTO dto, ValidationContext context) {
// do stuff
}
Putting validation methods in the DTO classes themselves was not an option. Validation required calls to the database, which would have coupled the DTO objects to the business logic and made the creation of the DTOs somewhat more complex.
I discovered that the validation methods could not specify an interface, leading to the duplicate methods for each concrete DTO class.