From 8782e0926fca8ba82f2cdd5e60cba2b66bf51ca8 Mon Sep 17 00:00:00 2001
From: opa <vincent.letarouilly@itsfactory.fr>
Date: Fri, 20 Sep 2019 16:04:09 +0200
Subject: [PATCH] KEYCLOAK-6698 - Add documentation for substitution of system
 properties and environment variables in theme.properties file

Enhanced doc
---
 server_development/topics/themes.adoc | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
 mode change 100644 => 100755 server_development/topics/themes.adoc

diff --git a/server_development/topics/themes.adoc b/server_development/topics/themes.adoc
old mode 100644
new mode 100755
index 0d6c0b6164..d3010d480f
--- a/server_development/topics/themes.adoc
+++ b/server_development/topics/themes.adoc
@@ -114,6 +114,25 @@ file in the corresponding type of the keycloak theme (`themes/keycloak/<THEME TY
 
 You can also add your own custom properties and use them from custom templates.
 
+When doing so, you can substitute system properties or environment variables by using these formats:
+
+* `${some.system.property}` - for system properties
+* `${env.ENV_VAR}` - for environment variables.
+
+A default value can also be provided in case the system property or the environment variable is not found with `${foo:defaultValue}`.
+
+NOTE: If no default value is provided and there's no corresponding system property or environment variable, then nothing is replaced and you end up with the format in your template.
+
+Here's an example of what is possible:
+
+[source,properties]
+----
+javaVersion=${java.version}
+
+unixHome=${env.HOME:Unix home not found}
+windowsHome=${env.HOMEPATH:Windows home not found}
+----
+
 ==== Stylesheets
 
 A theme can have one or more stylesheets. To add a stylesheet create a file in the `<THEME TYPE>/resources/css` directory of your theme. Then add it to the `styles`