Mastering Apache Camel

Table of Contents

Mastering Apache Camel

Credits

About the Author

About the Reviewers

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Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Errata

Piracy

Questions

1. Key Features

What is Apache Camel?

Components and bean support

Predicates and expressions

Data format and type conversion

Easy configuration and URI

Lightweight and different deployment topologies

Quick prototyping and testing support

Management and monitoring using JMX

Active community

Summary

2. Core Concepts

Messages

Exchange

Camel context

Processor

Routes

Channels

Domain Specific Languages (DSL)

Component, endpoint, producer, and consumer

Data format

Type converter

Summary

3. Routing and Processors

What is a processor?

An example of Camel routes containing processors

Prefixer processor

Creating a route using Java DSL

Route using Camel Blueprint DSL

Summary

4. Beans

Registry

SimpleRegistry

JndiRegistry

ApplicationContextRegistry

OsgiServiceRegistry

Creating CompositeRegistry

Service activator

Bean and method bindings

Annotations

Annotations for expression languages

Example – creating an OSGi bundle with a bean

Creating the MyBean class

Writing a route definition using the Camel Blueprint DSL

Building and deploying

Summary

5. Enterprise Integration Patterns

EIP processors

Messaging systems EIPs

Message Channel

Message

Pipeline

The implicit pipeline

The explicit pipeline

Message router

Message Translator

The transform notation

Using processor or bean

Marshalling/umarshalling

Message Endpoint

Messaging channels EIPs

Point To Point Channel

Publish Subscribe Channel

Dead Letter Channel

Guaranteed Delivery

Message Bus

Message Construction EIPs

The Event Message EIP

The Request Reply EIP

The Correlation Identifier EIP

The Return Address EIP

Message Routing

The Content Based Router EIP

The Message Filter EIP

The Dynamic Router EIP

Multicast and Recipient List EIPs

The Multicast EIP

The Recipient List EIP

The Splitter and Aggregator EIPs

The Splitter EIP

Aggregator

The Resequencer EIP

The Composed Message Processor EIP

The Scatter-Gather EIP

The Routing Slip EIP

The Throttler and Sampling EIPs

The Throttler EIP

The Sampling EIP

The Delayer EIP

The Load Balancer EIP

The Loop EIP

Message Transformation EIPs

The Content Enricher EIP

The Content Filter EIP

The Claim Check EIP

The Normalizer EIP

The Sort EIP

The Validate EIP

The Messaging Endpoints EIPs

The Messaging Mapper EIP

The Event Driven Consumer EIP

The Polling Consumer EIP

The Competing Consumer EIP

The Message Dispatcher EIP

The Selective Consumer EIP

The Durable Subscriber EIP

The Idempotent Consumer EIP

The Transactional Client EIP

The Message Gateway and Service Activator EIPs

System Management EIPs

The ControlBus EIP

The Detour EIP

The Wire Tap EIP

The Message History EIP

The Log EIP

Summary

6. Components and Endpoints

Components

Bootstrapping a component

Endpoint

A custom component example

Summary

7. Error Handling

Types of errors

Recoverable errors

Irrecoverable errors

Camel error handlers

Non-transacted error handlers

DefaultErrorHandler

DeadLetterChannel

LoggingErrorHandler

NoErrorHandler

TransactedErrorHandler

Error handlers scopes

Error handler features

Redelivery

Exception policy

Handling and ignoring exceptions

A failover solution

onWhen

onRedeliver

retryWhile

Try, Catch, and Finally

Summary

8. Testing

Unit test approach with the Camel test kit

ProducerTemplate

JUnit extensions

CamelTestSupport

CamelSpringTestSupport

CamelBlueprintTestSupport

The mock component

Using MockComponent

A complete example

Additional annotations

Mocking OSGi services

Summary

Index

Mastering Apache Camel

Mastering Apache Camel

Copyright © 2015 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: June 2015

Production reference: 1250615

Published by Packt Publishing Ltd.

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ISBN 978-1-78217-315-1

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Credits

Author

Jean-Baptiste Onofré

Reviewers

Volker Kueffel

Carsten Ringe

Phil Wilkins

Commissioning Editor

Amarabha Banerjee

Acquisition Editor

Meeta Rajani

Content Development Editor

Anand Singh

Technical Editors

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Copy Editors

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Proofreader

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Indexer

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Production Coordinator

Melwyn D'sa

Cover Work

Melwyn D'sa

About the Author

Jean-Baptiste Onofré is a member of the Apache Software Foundation, and he has been involved in Apache projects for about 10 years. He's the PMC chair of Apache Karaf and its subprojects, including Cellar, Cave, and EIK.

He's also a PMC member of Apache ACE, Apache ServiceMix, and Apache Syncope, and he is a committer for Apache ActiveMQ, Apache Archiva, Apache Aries, Apache Camel, and Apache jClouds.

He's currently working at Talend (http://www.talend.com) as a software architect and is a member of the Talend Apache team.

He has provided articles on Java technologies for GNU/Linux magazine France and has worked as an author and a reviewer on different books, such as Learning Karaf Cellar and Apache Karaf Cookbook, both by Packt Publishing.

He has also given talks on Apache projects, such as Karaf and Camel, at different conferences, especially ApacheCon NA and Europe, CamelOne, and so on.

I would like to thank the whole Camel and Karaf team, especially Guillaume Nodet, Achim Nierbeck, Jamie Goodyear, Ioannis Canellos, Claus Ibsen, and all the others. We are a great team, and you do a great job.

I would also like to thank my wife, Lucile, who accepted that I spent some nights on this book.

About the Reviewers

Volker Kueffel has been a software engineer and architect for almost two decades and has been developing software since he was a teenager. A physicist by trade, he has worked on large-scale data systems in various verticals of the software industry, spanning from online travel, mobile, and enterprise applications to online advertising. He introduced Apache Camel into one of his projects where it has successfully served as a major system component for several years. Volker is a native of Germany and currently lives with his family in San Francisco, California.

Carsten Ringe is a software developer by heart and has been working in different industries, from defense to agriculture and logistics, in the last 10 years. Over the last couple of years, he has spent his time with Apache Camel building a scalable integration platform for a large logistics enterprise.

Phil Wilkins has spent over 25 years in the software industry, working for both multinationals and software startups. He started out as a developer and has worked his way up through technical and development leadership roles, primarily in Java-based environments. He now works as an enterprise technical architect within the IT group for a global optical healthcare manufacturer and retailer using Oracle Middleware, Cloud and RedHat JBoss technologies.

Outside of his work commitments, he has contributed his technical capabilities to supporting others in a wide range of activities from the development of community websites, to providing input and support to people authoring books and developing software ideas and businesses, including reviewing a range of technical books for Packt and other publishers. He is also a blogger and a participant in the Oracle middleware community.

When not immersed in work and technology, he spends his time pursuing his passion for music and with his wife and two boys.

I'd like to take this opportunity to thank my wife, Catherine, and our two sons, Christopher and Aaron, for their tolerance and for the innumerable hours that I've spent in front of a computer, contributing to activities for both, my employer and many other IT-related activities that I've supported over the years.

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Preface

Apache Camel has slowly emerged as the main framework for integration. It provides a very flexible and efficient way to integrate applications and systems all together.

Camel provides a complete set of features, based on simple but powerful concepts, allowing you to easily implement very rich integration logic.

Using this book, you will have a detailed understanding, with how to steps to implement integration logics.

What this book covers

Chapter 1, Key Features, introduces what Camel is and the provided key features.

Chapter 2, Core Concepts, introduces the basis of all the functionalities provided by Camel.

Chapter 3, Routing and Processors, introduces Camel routing and the usage of processors.

Chapter 4, Beans, explains how to use beans in Camel routes and the different registries in which the beans live.

Chapter 5, Enterprise Integration Patterns, introduces one of the most interesting features of Camel—the ready-to-use patterns, which serve as an answer to classic integration problems.

Chapter 6, Components and Endpoints, introduces Camel components and endpoints, both how to use them and implement your own.

Chapter 7, Error Handling, introduces how to deal with errors in Camel routes.

Chapter 8, Testing, introduces how to implement both unit tests and integration tests on your Camel routes.

What you need for this book

For this book, the software required will be as follows:

Operating systems (any system supporting Java):

Windows 7 or superior

Unix (Linux)

Java DK 1.7

Apache Karaf 3.0.3

Who this book is for

This book is for developers who want to implement integration logic using Apache Camel. They will get details about Camel, from basic usage, up to the custom development of their own components.

Thanks to the first few chapters, even beginners unfamiliar with Camel will receive a comprehensive look into Camel before jumping into the details.

Conventions

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: A message is described in the org.apache.camel.Message interface.

A block of code is set as follows:

public class MyProcessor implements Processor {

  public void process(Exchange exchange) {

System.out.println(Hello + exchange.getIn().getBody(String.class));

  }

}

Any command-line input or output is written as follows:

$ mvn clean install

Note

Warnings or important notes appear in a box like this.

Tip

Tips and tricks appear like this.

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Downloading the example code

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Errata

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Questions

If you have a problem with any aspect of this book, you can contact us at <questions@packtpub.com>, and we will do our best to address the problem.

Chapter 1. Key Features

After a quick introduction about what Apache Camel is, this chapter will introduce the key features provided by Camel. It provides just an overview of these features; the details will come in dedicated chapters.

In an enterprise, you see a lot of different software and systems in the IT ecosystem. In order to consolidate the data and sync the systems, the enterprise would want to implement communication and integration of these systems. This communication or integration is not so easy, as we have to deal with the specifications on each system the protocol and the message's data format are different most of the time, so we have to transform and adapt to