JFake

Introduction

JFake is a simple system to generate fake data to databases by writing set specifications liberally licenced under the MIT licence.

It has 2 usage modes, either it runs as a command line tool or as a library for a web application. When run as an web application library it will automatically generate the data only if there exists a config file (WEB-INF/auto.jfake) and ALL tables pointed to by the config file are empty (this is so that production data should not be overwritten!).

Downoad

A binary package is available at JFake JAR download

JFake specifications

Basic idea

The main idea is to write a specification on HOW the data should be generated rather than specific data. For example one can write [5000,5001,5002,5003] to generate a list of numbers but if one wants a range it could also be described as the range 5000:5003 .

A full sample is at the end of this README.md (also samples can be found under the samples directory)

Syntax

The Jfake syntax is built up as the following.

Comments are single line and everything after a # is a comment.

Sample: # This is a comment

A value is defined with the equals sign, a value defined outside a class is usually a constant or configuration value while all values inside a class definition defines a column to be generated.

Sample: @datasource="jdbc/mysource" sets a special configuration values so that JFake knows what datasource to connect to

A class is defined by an identfier followed by the definition inside a couple of curly braces, each value set inside the curly braces contributes to creating a column.

Sample: To create a product table with automatic ID values and 3 columns of names one defines it like this,

product {
  id=@autoid
  name="Product nr "+1:3
}

Numbers and strings are the basic data types, numbers are alphanumeric integers and strings are enclosed with paired ' or " characters.

Sample: 123 "Hello world"

A sequence is a linear numeric sequence of integer values, with this one can specify any range of (64bit) integers.

Sample: 1:1000 generates the numbers 1:1000 or 20:30 generates the numbers 20 to 30

A list is a sequence of user specified values, these are used to produce a defined set of values. A list specification will also include any sub-sets of values to produce a unified list.

Sample: [1,2,3] is a list with 3 members containing the values 1,2,3, ["Hello","World"] is a list containing the values "Hello" and "World" and finally a list that takes the contents of subsequences will be defined like [1:3,10:13] to generate a list with 1,2,3,10,11,12,13

Sample

A full sample file follows:

# Simple product/receipt jfake file

# What datasource do we use to talk to the database
@datasource="java:app/jdbc/ejb1"

# We want to start generating ID's at this ID (to avoid initial conflicts with JPA)
@startid=5000

# Generate product table
product {
  # Generate automatic ID
  id = @autoid
  
  # Generate some sample data
  name = ["Ferrari","Folka","Dator"]
}
                
# Generate data for receipt table
receipt {
  # Generate ID table
  id = @autoid
                        
  # Generate some sequential addresses.
  address = "Database road "+1:20
                                
  # Generate a random product ID link
  product_id = product.id.random
}