13.13. Options and Operators in JBoss Rules

Table 13.2. Options and Operators in JBoss Rules

Option Description Example
Date literal
The date format dd-mmm-yyyy is supported by default. You can customize this by providing an alternative date format mask as the System property named drools.dateformat. If more control is required, use a restriction. 
Cheese( bestBefore < "27-Oct-2009" )
List and Map access
You can directly access a List value by index. 
// Same as childList(0).getAge() == 18
Person( childList[0].age == 18 )
Value key
You can directly access a Map value by key. 
// Same as credentialMap.get("jsmith").isValid()
Person( credentialMap["jsmith"].valid )
Abbreviated combined relation condition
This allows you to place more than one restriction on a field using the restriction connectives && or ||. Grouping via parentheses is permitted, resulting in a recursive syntax pattern. 
// Simple abbreviated combined relation condition using a single &&
Person( age > 30 && < 40 )
// Complex abbreviated combined relation using groupings
Person( age ( (> 30 && < 40) ||
              (> 20 && < 25) ) )
// Mixing abbreviated combined relation with constraint connectives
Person( age > 30 && < 40 || location == "london" )
Operators
Operators can be used on properties with natural ordering. For example, for Date fields, < means before, for String fields, it means alphabetically lower. 
Person( firstName < $otherFirstName )
Person( birthDate < $otherBirthDate )
Operator matches
Matches a field against any valid Java regular expression. Typically that regexp is a string literal, but variables that resolve to a valid regexp are also allowed. It only applies on String properties. Using matches against a null value always evaluates to false. 
Cheese( type matches "(Buffalo)?\\S*Mozarella" )
Operator not matches
The operator returns true if the String does not match the regular expression. The same rules apply as for the matches operator. It only applies on String properties. 
Cheese( type not matches "(Buffulo)?\\S*Mozarella" )
The operator contains
The operator contains is used to check whether a field that is a Collection or array contains the specified value. It only applies on Collection properties. 
CheeseCounter( cheeses contains "stilton" ) // contains with a String literal
CheeseCounter( cheeses contains $var ) // contains with a variable
The operator not contains
The operator not contains is used to check whether a field that is a Collection or array does not contain the specified value. It only applies on Collection properties. 
CheeseCounter( cheeses not contains "cheddar" ) // not contains with a String literal
CheeseCounter( cheeses not contains $var ) // not contains with a variable
The operator memberOf
The operator memberOf is used to check whether a field is a member of a collection or array; that collection must be a variable. 
CheeseCounter( cheese memberOf $matureCheeses )
The operator not memberOf
The operator not memberOf is used to check whether a field is not a member of a collection or array. That collection must be a variable. 
CheeseCounter( cheese not memberOf $matureCheeses )
The operator soundslike
This operator is similar to matches, but it checks whether a word has almost the same sound (using English pronunciation) as the given value. 
// match cheese "fubar" or "foobar"
Cheese( name soundslike 'foobar' )
The operator str
The operator str is used to check whether a field that is a String starts with or ends with a certain value. It can also be used to check the length of the String. 
Message( routingValue str[startsWith] "R1" )
Message( routingValue str[endsWith] "R2" )
Message( routingValue str[length] 17 )
Compound Value Restriction
Compound value restriction is used where there is more than one possible value to match. Currently only the in and not in evaluators support this. The second operand of this operator must be a comma-separated list of values, enclosed in parentheses. Values may be given as variables, literals, return values or qualified identifiers. Both evaluators are actually syntactic sugar, internally rewritten as a list of multiple restrictions using the operators != and ==. 
Person( $cheese : favouriteCheese )
Cheese( type in ( "stilton", "cheddar", $cheese ) )
Inline Eval Operator (deprecated)
An inline eval constraint can use any valid dialect expression as long as it results to a primitive boolean. The expression must be constant over time. Any previously bound variable, from the current or previous pattern, can be used; autovivification is also used to auto-create field binding variables. When an identifier is found that is not a current variable, the builder looks to see if the identifier is a field on the current object type, if it is, the field binding is auto-created as a variable of the same name. This is called autovivification of field variables inside of inline eval's. 
Person( girlAge : age, sex = "F" )
Person( eval( age == girlAge + 2 ), sex = 'M' ) // eval() is actually obsolete in this example
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