Lua Transformation

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Lua is a lightweight, high-level, multi-paradigm programming language designed primarily for embedded use in applications.

HTTP transformation rules that are used to control the processing of a request by WebSEAL can be easily written as a Lua script.

Detailed information on Lua scripting can be found in the Lua reference manual: Lua 5.4 Reference Manual. In addition to this, due to the fact that Lua is a widely used scripting language, there are many resources available on the Web to assist you with learning Lua. You can start learning Lua with Programming in Lua. It is available in paperback and as an e-book. The first edition is available for free at Programming in Lua (first edition).

WebSEAL provides custom Lua modules to control the processing of the request. See Custom Lua modules.

Since Lua is a lightweight and performant scripting language, and the custom Lua modules operate on 'live' data, the impact performance of calling simple Lua transformation rules is negligible. This means that it is acceptable to invoke Lua transformation rules on every request to handle things such as the insertion of custom HTTP headers into responses.
Note:
  • The Lua script is contained in a rules file. If a rules file is changed, you must restart the WebSEAL server for the changes to take effect.
  • The name of the rules file must have a .lua extension, otherwise WebSEAL treats the file as an XSLT transformation.