Chapter 11. Seam and JBoss Rules
Seam makes it easy to call JBoss Rules (Drools) rulebases from Seam components or jBPM process definitions.
The first step is to make an instance of org.drools.RuleBase
available in a Seam context variable. In most rules-driven applications, rules need to be dynamically deployable, so you will need to implement some solution that allows you to deploy rules and make them available to Seam (a future release of Drools will provide a Rule Server that solves this problem). For testing purposes, Seam provides a built-in component that compiles a static set of rules from the classpath. You can install this component via components.xml
:
<drools:rule-base name="policyPricingRules">
<drools:rule-files>
<value>policyPricingRules</value>
</drools:rule-files>
</drools:rule-base>
This component compiles rules from a set of .drl
files and caches an instance of org.drools.RuleBase
in the Seam APPLICATION
context. Note that it is quite likely that you will need to install multiple rule bases in a rule-driven application.
If you want to use a Drools DSL, you alse need to specify the DSL definition:
<drools:rule-base name="policyPricingRules" dsl-file="policyPricing.dsl">
<drools:rule-files>
<value>policyPricingRules</value>
</drools:rule-files>
</drools:rule-base>
Next, we need to make an instance of org.drools.WorkingMemory
available to each conversation. (Each WorkingMemory
accumulates facts relating to the current conversation.)
<drools:managed-working-memory name="policyPricingWorkingMemory" auto-create="true" rule-base="#{policyPricingRules}"/>
Notice that we gave the policyPricingWorkingMemory
a reference back to our rule base via the ruleBase
configuration property.