JarCastingvirgo
Virgo is a Java Business Rule Engine, based on Libra. It supports an easy-to-use syntax for defining business rule.
install
<dependency>
<groupId>org.dungba</groupId>
<artifactId>joo-virgo</artifactId>
<version>0.1.0</version>
</dependency>
how to use
// create a business rule
BusinessRule rule = new DefaultBusinessRule("IF customer.age > 50 THEN SET seniorCitizen = true");
// create a rule context
RuleContext context = new RuleContext(someObject);
// execute it
ExecutionResult result = rule.execute(ruleContext).orElseThrow(() -> new NullPointerException("result is null"));
// get the result. this will get the first value in the result map
Object resultValue = result.getValue();
// get a specific result
resultValue = result.getValue("seniorCitizen");
You can also merge multiple business rules into a single rule
// create some business rules
BusinessRule rule1 = new DefaultBusinessRule("IF customer.age > 50 THEN SET seniorCitizen = true");
BusinessRule rule2 = new DefaultBusinessRule("IF order.price > 100 THEN SET discount = 0.1");
// merge into a single rule
BusinessRule rule = new MultiBusinessRule(rule1, rule2);
// execute it
ExecutionResult result = rule.execute(ruleContext).orElseThrow(() -> new NullPointerException("result is null"));
// get the merged results
boolean seniorCitizen = result.getValue("seniorCitizen");
double discount = result.getValue("discount");
grammar
These are the supported grammar of Virgo
Single condition:
IF <condition> THEN <actions>
Branched conditions:
IF <condition> THEN <actions>
ELSE IF <condition> THEN <actions>
ELSE <actions>
Nested conditions:
IF <condition> THEN
IF <condition> THEN
<actions>
ELSE
<actions>
Nested conditions with braces:
IF <condition> THEN {
IF <condition> THEN
<actions>
ELSE
<actions>
} ELSE {
<actions>
}
No condition at all:
<action>
Multiple actions can be separated by semicolons:
IF <condition> THEN
<action>;
<action>;
Currently only assignment action is supported:
SET <someVariable> = <someExpression>
The syntax for condition and expression can be found in Libra repository.
Note: The line break is not required, it's just to make it easier to read
examples
The following are valid examples:
IF 1 + 1 == 2 THEN SET result = 1
IF customer.age > 50 THEN SET seniorCitizen = true ELSE SET seniorCitizen = false
SET seniorCitizen = customer.age > 50
IF order.price > 100 THEN SET discount = 0.1
IF product.brand is 'Apple' THEN SET discount = 0.2
ELSE IF product.brand is 'Samsung' THEN SET discount = 0.3
ELSE SET discount = 0.1
license
This library is distributed under MIT license, see LICENSE