Drools Tutorial for Beginners
What is Drools Rule Engine?
Drools is a Business Rule Management System BRMS or a production rule system PRS that use an enhanced implementation of the Rete pattern matching Algorithm, designed with a rule engine, and maintained by JBoss and Red Hat, Inc. Drools is an open-source project written in Java Programming and supports Java Rules Engine API Java Specification Request 94 standard for its business rules engine and framework to construct, maintain, and enforce business policies in an organization, application or service.
Logic and Data are the two crucial existed keywords in Drools.
Drools exist as a standard way for Java enterprise level application to handle that's business logic- a part of the program that
- encodes the real-world business rules (determine how data can be created, stored, and modified).
- prescribes how business objects interact with each other.
Some basic concepts of Drools:
Rules are the declarative statements that govern the conduct of business processes. A rule defines a condition and actions such as "When some conditions occur, then do some tasks."when <condition is true> then <take desired Action> When is the most important part of a rule body such that if it gets satisfied, then the then part is triggered. rule <rule_name> <attribute><value> when <conditions> then <actions> endFacts: are theJava objects (beans)that you assert in the working memory and upon which rules operate. These are the POJO classes (Plain Old Java Object) from the Java perspective. Working memory: It is the main class in Drools that use rule engine at runtime. It is the storage with Facts and holds references to all the data "asserted" into it (until retracted). Knowledge Session: Created from Knowledge Base is the core component in Drools to fire the rules. It holds all resources for firing the rules such that for the working of the rule engine, all facts are inserted into session and when the condition met, the matching rules get fired. A session is of two types:
- Stateless Knowledge Session
- Stateful Knowledge Session
Pattern Matching
Pattern Matching is the process of matching the new or existing facts against Production Rules with the help of an Inference Engine. Pattern matching can be done by implementing any of the algorithm given below:- Linear
- Rete
- Treat
- Leaps
Why use Drools Rule Engine?
There are many benefits of using Drools Rule Engine as follows:- Declarative Programming
- Logic and Data Separation
- Speed and Scalability
- Centralization of Knowledge
- Tool Integration