WSO2 ESB Pass Registry file into Custom Mediator

Question

In WSO2 ESB registry I have a DRL file

/opt/config/rules.drl

rule ""
when
    ...
then
    ...
end

I want to use this file to fire Drools rules using a custom mediator with Kie

DroolsMediator.java

class DroolsMediator extends AbstractMediator {
    public boolean mediate(MessageContext context) {
        KnowledgeBuilder builder...
        URL url = new URL("path/to/registry/rules.drl");
        builder.add(ResourceFactory.newUrlResource(url), ResourceType.DRL);
        ...
    }
}

I have tried to get as a property but with no success:

<property name="REGISTRY-VALUE"
          expression="get-property('registry', '/opt/config/rules.drl')"/>

What approach should I take to passing registry items into custom mediators?

Answer 1

The problem wasn't so much with the code as it was with where I was placing resources within the WSO2 Registry.

Inside the WSO2, there are three kinds of registries:

Local Registry

Entries are stored on the local filesystem and accessed as follows:

<localEntry key="Drools" src="/path/to/rules.drl" />

These can only be accessed by the ESB on the same machine as the resource.

Configuration Registry

Entries are uploaded to the WSO2 ESB and actually stored in a database, not the filesystem. They can be accessed under the registry location /_system/config/ as follows:

<property name="Drools" expression="get-property('conf:/path/to/rules.drl')" />

Governance Registry

Entries are uploaded and stored just like in the configuration registry. They can be accessed under the registry location /_system/config/ as follows:

<property name="Drools" expression="get-property('gov:/path/to/rules.drl')" />

The primary difference between the configuration and governance registries seems to be that configuration entries should be "product-specific" whereas governance entries are "global". This isn't enforced.