Script Expressions

Flowman allows to use expressions at many places in the YAML specification files. For example you can reference variables defined in the environment section or also access a set of predefined objects inside values.

Flowman uses Apache Velocity as the template engine. Please also read its documentation for advanced feature like conditional expression or recursive evaluation.

Simple Expressions

You can access the contents of a variable via a dollar sign ($), like for example:

    kind: read
    source: $weather_source

This example uses a variable weather_source to define which relation to read form. This way different environments can be supported by simply setting different values for that variable.

Variables can be set globally in a project’s environment section or in a profile of a project (which then has to be activated) or on the command line.

Predefined Objects

Flowman also provides some predefined objects, which are available in the expression language. These objects either simply hold some data (like the location of the project), or they also provide some functions (for working with date and time).


  • project.basedir
  • project.filename
  • project.version


  • Integer.parse(string) or Integer.valueOf(string)


  • Float.parse(string) or Float.valueOf(string)


  • LocalDate.parse(string) or LocalDateTime.valueOf(string)
  • LocalDate.ofEpochSeconds(int)
  • LocalDate.format(string, string)
  • LocalDate.addDays(string, int)
  • LocalDate.addWeeks(string, int)
  • LocalDate.addMonths(string, int)
  • LocalDate.addYears(string, int)


  • LocalDateTime.parse(string) or LocalDateTime.valueOf(string)
  • LocalDateTime.ofEpochSeconds(int)
  • LocalDateTime.format(string, string)
  • LocalDateTime.add(string, string)
  • LocalDateTime.subtract(string, string)
  • LocalDateTime.addSeconds(string, int)
  • LocalDateTime.addMinutes(string, int)
  • LocalDateTime.addHours(string, int)
  • LocalDateTime.addDays(string, int)
  • LocalDateTime.addWeeks(string, int)
  • LocalDateTime.addMonths(string, int)
  • LocalDateTime.addYears(string, int)


  • Timestamp.parse(string) or Timestamp.valueOf(string)
  • Timestamp.ofEpochSeconds(int)


  • Duration.ofDays(int)
  • Duration.ofHours(int)
  • Duration.ofMinutes(int)
  • Duration.ofSeconds(int)
  • Duration.ofMillis(int)
  • Duration.between(string,string)
  • Duration.parse(string) or Duration.valueOf(string)


  • Period.ofYears(int)
  • Period.ofMonths(int)
  • Period.ofWeeks(int)
  • Period.ofDays(int)
  • Period.parse(string) or Period.valueOf(string)


  • System.getenv(string) or System.getenv(string,string)
  • System.getProperty(string) or System.getProperty(string,string)


  • String.concat(string,string)