We'll now write our first Drools rule. Let's say that we have the Account bean that has one property called balance. For every Account bean whose balance is less than 100, we want to write a message to the standard output:
package droolsbook;
rule "basic rule"
when
Account( balance < 100 ) // condition
then
System.out.println("Account balance is " +
"less than 100"); // consequence
endCode listing 1: Basic rule file (basic.drl)
The rule file mentioned earlier starts with a package name. The package acts as a namespace for rules. The rule names within a package must be unique. This concept is similar to Java's packages (classes within a Java package must have different names). After the package definition comes the rule definition. It starts with the rule name, following with the conditions and consequence sections. rule, when, then, and end are the Drools keywords. This rule is triggered for every bean instance of type Account, whose balance is less than...