8.5. Rules

Procedure 8.10. Create a Rules Service

1. Create a new SwitchYard Rules file in the SwitchYard Editor JBoss Developer Studio plug-in.
2. The MyService interface can be as simple as this, with no SwitchYard-specific imports:

   package com.example.switchyard.docs;
   public interface Example {
       public void process(MyData data);
     }
   

3. The generated rule template looks like this:

   package com.example.switchyard.docs
   import org.switchyard.Message
   global Message message
    
   rule "RulesExample"
       when
           // insert conditional here
       then
           // insert consequence here
           System.out.println("service: ExampleService, payload: " + message.getContent());
   end
   

4. Input the values into the SwitchYard Editor's SwitchYard Rules File screen.
5. Click Finish.

1. To map the variables, hover the mouse over the Rules component in switchyard.xml and click Properties icon.

   Figure 8.3. Properties dialog for Rules Component

   
2. In the Properties dialog, click Implementation. From the right hand side panel, click Operations tab to view Operation Mapping tooling window.

   Figure 8.4. Operations Mapping

   

1. Configure the rules implementation.
   Note
   Your expression can use the variables exchange (org.switchyard.Exchange), context (org.switchyard.Context) or message (org.switchyard.Message).

   Context can be accessed in the expression as a java.util.Map. When accessing it as such, the default properties Scope is IN. This can be overridden using the contextScope attribute by changing it to OUT or EXCHANGE
2. Use these global variables in your JBoss Rules Drools Rule Language file:

   package example
    
   global java.lang.String service
   global java.lang.String messageId
   global com.example.Payload payload
    
   rule "Example"
       when
           ...
       then
           ...
           System.out.println("service: " + service + ", messageId: " + messageId + ", payload: " + payload);
   end
   

   Note
   In a more realistic scenario, the payload would be accessed in rule firing because it was inserted into the session directly by the RulesExchangeHandler, and thus evaluated (rather than being accessed as a global).