The Script Component (SC) is a user-defined block of JavaScript code that we can drop any place in the AssemblyLine data Flow list, alongside your Connectors and Function Components, causing the script code within to be executed for each cycle at this point in the AssemblyLine workflow.
task.dumpEntry( work ); system.skipEntry();
When placed at the appropriate point in the flow of an AssemblyLine, this SC then displays the contents of the work object by writing it to log output and then skip the rest of the AssemblyLine for this cycle. By moving the SC up and down the component list, you control how much of the AssemblyLine is actually executed. If you swap out the system.skipEntry() call with system.skipTo("ALComponentName"), you directly pass control to a specific AssemblyLine Component.
We can also use SCs to drive other components. A typical scenario when doing directory or database synchronization is having to handle both updated and deleted information. Since Connectors powered by the built-in AssemblyLine workflow can only operate in one mode at a time (Update or Delete) we will need to extend this logic a bit with our own code. One method is to add two Connectors, one in Update mode and one in Delete mode, and then put code in the Before Execute Hook in each Connector's to tell it to skip change operations that it should not handle. For example, in the Before Execute Hook of the Update Connector you would write something like this:
// The LDAP change log contains an attribute called "changeType"
if (work.getString("changeType").equals("delete"))
system.ignoreEntry();
This will cause your Update mode
Connector to skip deleted Entries. You would have complementary code
in the Before Execute Hook of the Delete mode Connector, skipping
everything but deletes.
However, if you are synchronizing updates to multiple targets, this would require you to have two Connectors per data source. Another approach is to have a single Connector in Passive state that you power from script. As an example, let's say we have a Passive AssemblyLine Connector called synchIDS. We can then add an SC with the following code to run it:1
if (work.getString("changeType").equals("delete"))
synchIDS.deleteEntry( work )
else
synchIDS.update( work );
As long as you label your SC
clearly, indicating that it is running Passive Connectors, this approach
will result in shorter AssemblyLines that will be easier to read and
maintain. This is an example of having to choose between two best
practices: keeping the AssemblyLine short, and using built-in logic versus custom
script. However, in this case the goals of legibility and simplicity
are best served by writing a little script.
The Script Component also comes in handy when we want to test logic and script code. Just create an AssemblyLine with a single Script Component in the data Flow list, put in your code and run it.
Parent topic: The AssemblyLine
1 Since
Passive Connectors are not run by the AssemblyLine logic, it does not matter
where they appear in the Data Flow list.