TDIing out loud

Ramblings on the paradigm-shift that is TDI.

Monday, September 30, 2013

Using a Connector Loop to replace Connectors in Lookup Mode - and Why

Although our motto has been 'make no assumptions', TDI makes an assumption about Connectors in Lookup mode: One and only entry will be matched successfully. Period. If none are found, you have to script (or at least enable) the On No Match Hook. If multiple are found, then the On Multiple Found Hook must be dealt with. And if you want to perform some operation repeatedly for all entries in the result set, you have to script your way through connector functions like getNextDuplicateEntry(). And you have to make sure the Lookup Limit is set high enough, since TDI will buffer this many entries in memory.

This gets simpler if you turn your Connector into a Connector Loop. In other words, Add a Connector Loop and attach your Lookup Connector to it.

A Connector Loop will not cycle at all if the search returns no entries. Otherwise it cycles once for each entry found. You control what is found each time through the Link Criteria tab of the Loop. The Loop also gives you the option to Initialize each time it starts up each AL cycle, also performing the Lookup. Or you can set the Loop to just perform the Lookup. This latter option can save time by avoiding having to set up time-consuming connections each cycle.

You can still code the On No Match and On Multiple Found Hooks if you want, but these are not mandatory for a Lookup Loop.

The Loop supports both Lookup and Iterator modes if the attached Connector supports them. In order to perform specific actions on each entry returned (like deleting them) you need to add another Connector under the Loop and set the Link Criteria to search for a unique attribute - which should be one of those returned by the Loop Input Map.

The observant reader will have noted that the Lookup Limit setting is still an issue. You solve this by changing the Mode of the Loop from Lookup mode to Iterator, since Iterator mode does not buffer entries. Then you control the search by setting the relevant search filter parameter of the Connector via the Loop's Connector Parameters tab. So for LDAP you would map the ldapSearchFilter parameter like you would any attribute, for example using Javascript.

Or you could do this using a literal Text with Substitution tokens: uid={work.EmpId}.

For for JDBC it could look like this:

Note that the names that show up in the Schema area of the Connector Parameters map are the internal names of the parameters. You see this if you click on the label for a parameter, or the pencil button out to the right of it.

Normally, a Connector gets the values from its Connection Form only when it initializes. After that point, changing a parameter value (which just changes the configuration) will have no affect. However, some Connectors refresh the value for their search criteria parameter, for example the LDAP and JDBC Connectors. As a result, you do not need to tell the Connector to re-initialize, but merely to perform the Select each time.

For those parameters that do require a re-initialization to pick up changes, just tell the Loop to Initialize each time.

It's as easy as spittin'.

1 comment:

Eddie Hartman said...

You can make a Connector automatically re-initialize each time a parameter changes by setting the Initialize drop-down of the Connector to 'whenever configuration changes'. Forgot to mention that :)