Skip to content

zefaker is a command-line tool for generating CSV, Excel, JSON and SQL files from a Groovy DSL


Notifications You must be signed in to change notification settings


Repository files navigation

Zé Faker

zefaker is a command-line tool that helps developers generate and export data into CSV, Excel and SQL files for testing their applications.


  • Random data generation via java-faker with Locale support
  • Export to CSV
  • Export to Excel Sheet
  • Export to SQL INSERTS
  • Export to SQL COPY (for PostgreSQL)
  • Export to JSON
  • Export to JSON Lines

Why would I use this?

Short answer to generate (test) data.

If you ever need to have a CSV, Excel file with (random*) data or need to populate a database with development/dummy data you can use zefaker to generate the data, leveraging the power of Groovy

We created it because we deal with a lot of Excel files (with lots of columns!) and SQL data and often have to generate files to test the code that processes those files or data.

* the generated data does not have to be random

Example Usage

NOTE: Checkout the examples for even more examples, and "advanced" usage

Let's go straight to an example:

Create a file named person.groovy and place the following content:

// person.groovy

locale("en-GB") // tells Java Faker to use the given tag for the Locale.

// You can also use a custom faker
// import net.datafaker.Faker
// useFaker(new Faker(Locale.getLanguageTag("en-GB")))

    "FirstName": { faker -> },
    "LastName": { faker -> },
    "Age": { faker -> faker.number().numberBetween(18, 70) },
    "AccountStatus": { faker -> faker.options().option("Open", "Closed") },
    "Plan": { faker -> "FREE" } // doesn't necessarily have to be a faker value

Once you have this, you can pass it to the zefaker command to generate a file:

Exporting as a CSV File

$ zefaker -f person.groovy -rows 1000 -output people.csv -csv 

The example command, above, generates a file named people.csv with 1000 rows populated with data generated using the Faker functions specified in the Groovy script.

Exporting as an Excel file

$ zefaker -f person.groovy -rows 1000 -output people.xlsx -sheet People

The example command, above, generates a file named people.xlsx with 1000 records.

Bonus / Shameless plug: If you're using Java, you can process the generated files quickly and efficiently using zerocell.

Exporting as an SQL file

$ zefaker -f person.groovy -rows 1000 -output people.sql -sql -table people 

The example command, above, generates a file named people.sql with 1000 INSERT statements which have random data in the VALUES clause.

Exporting as a JSON file

$ zefaker -f person.groovy -rows 1000 -output people.json -json 

The example command, above, generates a file named people.json with 1000 JSON objects.


Download a copy of zefaker from the Releases page.

NOTE: Requires at least Java 8 to be installed


The build archive contains start scripts, zefaker and zefaker.bat for UN*X and Windows environments, respectively.

Command Line

Usage: zefaker [options]
  -f=FILE         Groovy file with column definitions
  -rows=ROWS      Number of rows to generate
  -output=FILE    File to write to, e.g. generated.xlsx
  -sheet=NAME     Sheet name in the generated Excel file
  -table=NAME     The name of the table to use in SQL INSERT mode
  -sql            Use SQL INSERT export mode
  -vvv            Show verbose output
  -x              Overwrite existing file

Web based UI

You can run the following java -jar zefaker.jar -web to start a webserver at port 4567:


In the Groovy Script

Within your Groovy script you are required to use the generateFrom() function to generate the Excel file.


The following are the only methods that are required in the groovy script for Zefaker to run.

ColumnDef column(int index, String name)

This method defines a new Column that has a name and an index (position)

void generateFrom(ColumnDef[] columns)

This method actually initiates the generation of the Excel file. If you don't call this method you won't actually get any result.

Example: generateFrom([ (firstName) : { faker -> } ])


Inside the Groovy script you can set some variables or properties that affect the output of zefaker. These variables, consequently, take precedence over arguments specified on the command-line.

The following special variables are available, and are therefore reserved names:

  • sheetName - Change the name of the target Sheet in Excel. Overrides -sheet
  • tableName - Change the name of the target table in SQL INSERTS. Overrides -table
  • outputFile - The name/path of the file to write output to. Overrides -f
  • verbose - Show verbose output. Overrides -vvv
  • maxRows - Sets the maximum number of rows to generate in the file. Overrides -rows
  • overwriteExisting - Whether to overrite an existing file with the new Workbook. Overrides -x


We are using Gradle for this, so follow the instructions below to build it.

$ git clone
$ cd zefaker
$ gradlew clean build

After this, the build file will be in build/libs/zefaker-all.jar - it is an executable Jar file.

Using Docker

You will have to build the image locally at the moment, :). Then run:

$ docker run --volume "$(pwd):/tmp:rw" zefaker -f /tmp/example.groovy -output /tmp/first.sql -sql 


Help out by resolving an issue in the issue tracker. Pull Requests are welcome. If you run into a problem, create an issue and we will try to resolve it.

Copyright (c) 2022, Credit Data CRB Ltd