Developing Apama Applications > Developing Apama Applications in EPL > Using Correlator Plug-ins in EPL > Using the Payload Extraction plug-in > The direct-access functions > Parameters for primary direct-access functions
Parameters for primary direct-access functions
The following table describes the parameters used by the direct-access functions:
Parameter
Description
payload_field
The payload field. For example, if the event to be analyzed has been placed in the event variable ev, then its payload field would conventionally be ev.__payload.
field_name
The name of the field to extract from the payload. This parameter takes a string literal.
default_value
The value to return if the field specified in field_name does not exist, has no value (is empty or null), is invalid (e.g. contains binary characters) or cannot be cast to the type requested. The type of this parameter depends on the particular method; it is a string for parseString, a float for parseFloat, an integer for parseInteger, and a boolean for parseBoolean. Note that all types can be cast to a string, however, the opposite might not be possible. For example a string can be only be successfully cast to a float if it contains a valid float number, for example, 1.0.
Copyright © 2013 Software AG, Darmstadt, Germany and/or Software AG USA Inc., Reston, VA, USA, and/or Terracotta Inc., San Francisco, CA, USA, and/or Software AG (Canada) Inc., Cambridge, Ontario, Canada, and/or, Software AG (UK) Ltd., Derby, United Kingdom, and/or Software A.G. (Israel) Ltd., Or-Yehuda, Israel and/or their licensors.