Gain insights into Camel Enterprise Integration Patterns, delve into foundational, Error Handling, Deployment, and Configuration patterns, and learn to implement them in varied scenarios with real-world examples.

The Camel Enterprise Integration Patterns (EIP) provide the interfaces to communicate with large component-based distributed systems. When designing the best integration solution for message-oriented applications, these patterns help save time and effort.

In this course, you'll learn about all four foundational patterns. You'll be introduced to Error Handling patterns, Deployment patterns, and Configuration patterns. Each pattern is discussed in detail to be used in distinct settings. You'll also gain a deep understanding of how each pattern works under different circumstances, and implement them appropriately when necessary using real-world examples to illustrate the design specifics. Camel EIPs offer advantages over traditional frameworks such as REST or SOAP regarding integration problems within an organization.

By the end of this course, you'll have hands-on practice with valuable interfaces and the simplification processes for integrating applications across an organization's services.

Using Apache Camel with Enterprise Integration Patterns

# Intent

This pattern allows agnostic business logic to be repeatedly used in different service contexts. **Reusability** is one of the main tenets of object-oriented and functional programming paradigms. It is also one of the main promises of component-based and service-oriented architectures. In this lesson, we will look at this principle from a Camel application point of view, where it expresses itself as the Reusable Route pattern.

# Context and problem

Reuse is a common and overrated goal in many software projects to avoid redundancy. It can be implemented at many levels, starting from methods and class level reuse to complex processing flow reuse and complete service reuse (as advertised by SOA). When implementing a complex system composed of multiple services, there might be bits of logic repeated in multiple places, in the same service, or different services. That repetition can vary from small endpoint configuration to complex sets of processing steps. Rather than duplicating the implementation (through copy and paste) and making it harder to maintain in the long term, it is better to reuse a single implementation in multiple places.




# Forces and solution

There are two main strategies for reusing an implementation in different places:

## Development time reuse

With this approach, we need access to the reusable logic (the source code or the compiled binary artifact) at build time. At the end of the build process, the reusable logic becomes part of the using service itself. With this mechanism, business logic can be included and reused in multiple services. It is not always the case that reusable implementation is needed at build time. It is possible to use some abstraction such as a Java interface rather than the concrete implementing class and have the dependency provided at deployment rather than build time. Despite that, the principle remains the same: an instance of the reusable logic is included in the main service and becomes part of it at development or deployment time.


## Runtime reuse

This approach has no direct dependency on the reusable logic at build or deployment time. Despite that, multiple services access and reuse the same service-agnostic business logic at runtime.

# Mechanics

In the Camel world, the business logic is implemented in the form of Camel routes. So we will look at the different ways for reusing routes primarily.

## Development time reuse

This is a quite common way of reusing Camel routes. It is similar to having a Java class with the routing logic implementation and then instantiating it (either directly or by extending it) multiple times for different `CamelContexts`. Let’s look at an example where two services that implement different business logic are required to perform the same validation steps. The validation is not a single component (such as Filter EIP or validator) but consists of a couple of steps. We can encapsulate the validation logic in a Camel route and reuse it across both services.

Learn the Reusable Route design pattern and its usage.

About This Course

Foundational Patterns

Error Handling Patterns

Deployment Patterns

Conclusion

Reusable Route Pattern

Intent

Context and problem

Forces and solution

Development time reuse