jBPM and Spring - Spring Enterprise Recipes: A Problem Solution Approach - page 424

<java name="send-verification-email" expr="#{customerService}"
method="sendCustomerVerificationEmail">
<arg> <object expr="#{customerId}" /> </arg>
<transition to="confirm-receipt-of-verification-email" />

</java>

<state name="confirm-receipt-of-verification-email">
<transition to="send-welcome-email" />

</state>

<java name="send-welcome-email"
expr="#{customerService}" method="sendWelcomeEmail">
<arg> <object expr="#{customerId}" /> </arg>

</java>

</process>

In the customerService bean, a client will use createCustomer to create a customer record. In a real-
world example, you might imagine exposing these services as a SOAP endpoint to be consumed by
various clients such as a web application or other business applications. You can imagine it being called
as a result of a successful form on a web site. When it executes, it creates a new Customer object and uses
Hibernate to persist it. Inside the createCustomer method, we use jBPM to start the business process to
track the Customer . This is done with the startProcessInstanceByKey method. In the invocation, we give
jBPM variables through a Map<String,Object> instance (acting as something of a context for the process
variables). Those variables are accessible inside the business process as Expression Language
expressions and allow you to parameterize the business process in much the same way you might
parameterize a macro or a Java method. We give the process instance a custom business key, instead of
letting it generate its own.

executionService.startProcessInstanceByKey(
REGISTER_CUSTOMER_PROCESS_KEY, vars, Long.toString(customer.getId()));

The last parameter is the key. Here we're using the String id of the customer as the key. This makes it
easy to find the process instance later, though you could also query for the process instance, predicating
on process variables that, taken together, should make the process instance unique. You might also
query by roles or users assigned to certain tasks, or simply note the id of the business process itself in
your domain model and reference that later when looking up the process instance. Here, we know that
there's only ever going to be one sign-up process for a customer, so we key it with a valid ID that will
only work once: the Customer 's id value.
When the process starts, it will start executing the steps in your process definition. First, it will go to
the <start> element. It will evaluate the one transition it has and proceed through that transition to the
next step, send-verification-email .
Once in the java element named send-verification-email , jBPM will invoke
sendCustomerVerificationEmail on the customerService bean in Spring. It uses an Expression
Language construct to reference the Spring bean by name:

<java name="send-verification-email"
expr="#{customerService}"
method="sendCustomerVerificationEmail">
…

</java>