The ExecutiveService adapter is used to execute a java service which utilizes the connection from the Integration Server managed connection pool to execute custom SQL statements. The adapter service input include an Object type targetServiceInput. This actually is a IS document type based on my experiment.
To properly send pipeline variables to the wrapped java service, a wrapper document type needs to be created in a map service to map to the targetServiceInput object in the adapter service and then any properties under this document, will be available to access from the wrapper java service by doing the following:
IDataMap idm = new IDataMap(pipeline); String foo = idm.getAsString("bar");
This java service has an input of bar defined in its Input tab.