Properties files (with the file extension .properties) can be used to either specify values for substitution variables in YAML files (see also Using YAML configuration files) or to configure EPL. A properties file must be either in ISO-8859-1 encoding or in UTF-8 encoding if it begins with an UTF-8 byte order mark (BOM).

You can specify one or more properties files using the --config option when you start the correlator. See Starting the correlator. The properties files are processed in the order in which they appear on the command line. Each properties file can refer to properties that have already been defined by a previously processed properties file, using ${varname} syntax.

The properties file format is the same as the standard Java .properties file format, with # for comments and \\ used to escape any occurrences of \. For example:

Properties files are by default parsed using the ISO-8859-1 encoding (Latin-1). To use characters from other character sets, you have two options. You can use a \uXXXX escape sequence, which uses the UCS-2 character codes. This allows you to encode any character from the Basic Multilingual Plane (BMP). However, we do not support UTF-16 surrogate pairs to access characters outside the BMP. Alternatively, you can provide a UTF-8 BOM as the first characters of the file. In this case, you can use any Unicode sequence in UTF-8 directly in the file without any escaping.

You can use the following predefined properties:

All properties are applied to all YAML files, although conventionally, there is often a .properties file named the same as each .yaml file. Properties files, however, are not actually tied in to YAML files in any way. It is therefore recommended that you prefix each property key with a unique string, such as the identifier of the chain to which it applies.