Bundling WSO2 ESB Mediator JAR in a CAR file
Prior to WSO2 ESB 4.8.1, when a class mediator was created or modified, the corresponding JAR needed to be manually copied to <ESB_HOME>/repository/components/lib and the ESB instance needed to be restarted before using the class mediator in any sequence. In other words, hot deployment of class mediators were not possible prior to version 4.8.1.
From ESB 4.8.1 onward, we can bundle class mediators in Composite Application Archive (CAR) files thanks to the URL class loader. But there is one limitation when using this approach. We cannot use the mediator in sequences outside of the CAR file. i.e. you have to include all the sequences that use the class mediator in a single CAR file. This is not actually bad limitation since we can have a sequence in the mediator CAR file as a proxy to call that mediator.