Customizing Apache Camel Routes
Here, you can find instructions on how to customize Apache Camel within the Dataspace Connector.
The Dataspace Connector uses Camel routes to execute the logic of message handlers - the components responsible for processing incoming IDS messages. The logic for each message handler is split into small steps, where each step is executed by its own Camel processor. Thus, the message handling process becomes modular. Therefore, custom steps, like e.g. sending a confirmed agreement to another service, can easily be integrated into this process. This documentation describes how to achieve this.
Adding a custom processor
Creating the processor
To add custom logic to a route, you have to create your own implementation of a Camel processor. This is down by implementing the org.apache.camel.Processor interface and overriding the process method that is of type void and takes an org.apache.camel.Exchange as parameter. An exchange is used in Camel routes to transfer information between endpoints. It has a getIn() method that returns the message held by the exchange. Calling getBody() on that message returns the current body, setBody(Object object) sets a new body. In the process method, you can now execute custom logic based on the body and modify it, if desired.
The processor implementations in the package io.dataspaceconnector.camel.processor can be used for reference.
Note: All processors already defined use io.dataspaceconnector.service.message.handler.dto.Request and io.dataspaceconnector.service.message.handler.dto.Response as the message bodies. So if you set any other object as the body in your processor’s process method, the following processors in the route will fail!
Using the processor in a route
To be able to reference a processor in a route, it first has to be added as a Spring Bean. Simply annotate your processor class with @Component("yourProcessorsName") to achieve this. Afterwards, you can call it anywhere in a route using:
<process ref="yourProcessorsName"/>
Modifying routes without recompilation
As the Dataspace Connector uses the Spring XML DSL instead of the Java DSL for defining Camel routes, routes can be modified without recompiling the code. All routes used by the connector reside in the directory /src/main/resources/camel-routes and are loaded from there at application start. The directory from which the routes are loaded can be changed in the application.properties, so that it is possible to load the routes from external directories residing somewhere in the file system.
Default setting:
camel.xml-routes.directory=classpath:camel-routes
Example for using an external directory:
camel.xml-routes.directory=/some/directory
When using an external directory, the Camel routes can be modified and reloaded by just restarting the connector, instead of recompiling the whole project.
Note: The Dataspace Connector requires all routes present in the camel-routes directory to run correctly. If any of the routes or any steps in the routes are missing, this may lead to unforeseen errors! So if you want to load routes from a custom directory, the best way to do so is to copy all files from the camel-routes directory to the desired directory and then modify them there.