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Mastering JBoss Drools 6

By : Mariano De Maio, Salatino, Aliverti

3 (1)

Mastering JBoss Drools 6

3 (1)

By: Mariano De Maio, Salatino, Aliverti

Overview of this book

Mastering JBoss Drools 6 will provide you with the knowledge to develop applications involving complex scenarios. You will learn how to use KIE modules to create and execute Business Rules, and how the PHREAK algorithm internally works to drive the Rule Engine decisions. This book will also cover the relationship between Drools and jBPM, which allows you to enrich your applications by using Business Processes. You will be briefly introduced to the concept of complex event processing (Drools CEP) where you will learn how to aggregate and correlate your data based on temporal conditions. You will also learn how to define rules using domain-specific languages, such as spreadsheets, database entries, PMML, and more. Towards the end, this book will take you through the integration of Drools with the Spring and Camel frameworks for more complex applications.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

1. Rules Declarative Nature

1. Rules Declarative Nature

What are rules?

Why do we use rules?

When should we use rules?

When not to use a rule engine

Summary

2. Writing and Executing Rules

2. Writing and Executing Rules

Setting up our environment

Creating our first Drools project

Writing and executing our first rule

The Rule language

Organizing our projects

Summary

3. Drools Runtime

3. Drools Runtime

Understanding the Drools runtime instances

KieModule configurations (KieBases, KieSessions & StatelessKieSessions)

KieScanner

Summary

4. Improving Our Rule Syntax

4. Improving Our Rule Syntax

Adding external interactions with global variables

Modifying the data in the working memory

Rule attributes

Controlling loops in rules

Special Drools operations

Working memory breakdown: the from clause

Drools syntactic sugar

Decorating our objects in memory

Logical insertion of elements

Rule inheritance

Summary

5. Understanding KIE Sessions

5. Understanding KIE Sessions

Stateless and stateful Kie Sessions

Kie runtime components

Kie Base components

Summary

6. Complex Event Processing

6. Complex Event Processing

What is complex event processing?

Declaring CEP-based Rules

Event-driven architecture

Running CEP-based Scenarios

Drools CEP limitations

Summary

7. Human-Readable Rules

7. Human-Readable Rules

Domain Specific Languages

Decision tables

Rule templates

PMML

Summary

8. Rules' Testing and Troubleshooting

8. Rules' Testing and Troubleshooting

Create loosely coupled DRLs

Prefer KieHelper over a KieContainer classpath

Benefits of using globals

Debugging the left-hand side of a rule

Debugging the right-hand side of a rule

Reporting a bug in Drools

Summary

9. Introduction to PHREAK

9. Introduction to PHREAK

Introducing PHREAK

Special nodes in the network

Queries and backward-chaining

PHREAK improvements over RETE

Phreak Inspector

Summary

10. Integrating Rules and Processes

10. Integrating Rules and Processes

jBPM – the process engine

Simple business process example

Drools and jBPM: integration patterns

Persistence and transactions

Summary

11. Integrating Drools with our Apps

11. Integrating Drools with our Apps

Architecture considerations

Integrating with the rest of an application

CDI integration

Spring integration

Camel integration

Kie Execution Server

Kie Workbench

Drools and beyond: extending our functionality

Summary

Index

Index

Customer Reviews

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Writing and executing our first rule

Now that we have our project structure ready, we can write our first rule. For that, we will create a new empty text file. This will be a static resource, therefore, we need to place it in the src/main/resources directory. This text file needs to have the .drl extension so that it can be picked up as a rule file. In the .drl files, we will write as many rules as we want. Now, we will start easy with just one rule.

Let's write our first rule to classify the items based on what they cost us. Our rules.drl text file will look similar to the following:

package myfirstproject.rules
import org.drools.devguide.eshop.model.Item;
import org.drools.devguide.eshop.model.Item.Category;
rule "Classify Item - Low Range"
    when
        $i: Item(cost < 200)
    then
        $i.setCategory(Category.LOW_RANGE);
end

This rule checks for each item that costs less than 200 USD and automatically tags it with a category, in this case, LOW_RANGE. For our shop...

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