5 Enterprise integration patterns

Today’s businesses aren’t run on a single monolithic system, and most businesses have a full range of disparate systems. There’s an ever-increasing demand for those systems to integrate with each other and with external business partners and government systems.

Let’s face it: integration is hard. To help deal with its complexity, enterprise integration patterns (EIPs) have become the standard way to describe, document, and implement complex integration problems. We explain the patterns we discuss in this book, but to learn more about them and others, see the Enterprise Integration Patterns website and the associated book: www.enterpriseintegrationpatterns.com.

5.1 Introducing enterprise integration patterns

Apache Camel implements EIPs, and because the EIPs are essential building blocks in the Camel routes, you’ll bump into EIPs throughout this book, starting in chapter 2. It would be impossible for this book to cover all the EIPs Camel supports, which currently total about 70 patterns. This chapter is devoted to covering five of the most powerful and feature-rich patterns, listed in table 5.1.

5.1.1 The Aggregator and Splitter EIPs

5.1.2 The Routing Slip and Dynamic Router EIPs

5.1.3 The Load Balancer EIP

5.2 The Aggregator EIP

5.2.1 Using the Aggregator EIP

5.2.2 Completion conditions for the Aggregator

5.2.3 Using persistence with the Aggregator

5.2.4 Using recovery with the Aggregator

5.3 The Splitter EIP

5.3.1 Using the Splitter

5.3.2 Using beans for splitting

5.3.3 Splitting big messages

5.3.4 Aggregating split messages

5.3.5 When errors occur during splitting

5.4 The Routing Slip EIP

5.4.1 Using the Routing Slip EIP

5.4.2 Using a bean to compute the routing slip header

5.4.3 Using an Expression as the routing slip

5.4.4 Using @RoutingSlip annotation

5.5 The Dynamic Router EIP

5.5.1 Using the Dynamic Router

5.5.2 Using the @DynamicRouter annotation

5.6 The Load Balancer EIP

5.6.1 Introducing the Load Balancer EIP

5.6.2 Using load-balancing strategies

5.6.3 Using the failover load balancer

5.6.4 Using a custom load balancer