Mnesia is a scalable database system designed to work as a storage system for large, distributed applications. In my previous post I showed you how to set up a Mnesia cluster using Erlang shell. Unfortunately, Mnesia cannot be easily accessed from languages other than Erlang. If you are a web developer, there is even an MVC framework for you - Erlyweb. But what if you are a mainstream programmer who would like to use the power of Mnesia, but is not willing to learn another language and change the whole way of thinking in order to understand the functional programming philosophy?

This is why I created Mnapi - API for Java and PHP, which provides basic methods to create, fetch, update and delete records in Mnesia. It is licensed under LGPL, which means that you can get it and use it in any commercial or non-commercial applications, and you are only obliged to publish only the source code of Mnapi if you extend it or modify it (the license does not affect an application which makes a use of it). You can download Mnapi here.

Please bear in mind that Mnesia does not support creating multiple databases or schemas within one instance, joining tables, etc. - and the API reflects those restrictions. You can learn more about it reading documentation attached to the source code and running example applications, so I will not be describing it here in detail. What you need to start using Mnapi is to compile Erlang driver for Mnesia:

erlc mnapi.erl

then start an Erlang shell:

erl -sname erl -setcookie mysecretcookie

and run Mnapi server from the shell:

mnapi:start().

Now you can use Java or PHP to talk to Mnesia through Mnapi libraries.

Note that to use Mnapi from PHP you first need to install and configure Erlang extension for PHP. Read instructions provided with the extension to learn how to configure you PHP installation.

To compile Java api you need Jinterface. If you cannot find Jinterface in lib folder of your standard Erlang installation, you can either download Erlang source code distribution or install it as a package from CEAN.