Hello, Heiko, and welcome to chatbots.org.
When you say “Java”, I’m assuming that you mean JavaScript, and not actually Java itself. The two are very different languages, really, and are often confused. JavaScript (more accurately called ECMAScript) is a scripting language built into all modern browsers to facilitate functionality in web pages, while Java… Well, the explanation about the differences can take up multiple posts, so I don’t think I’ll get into it right now. For now I’m going to assume you mean JavaScript.
There are a lot of web-based chatbots out there, as well as a number that can be accessed from a web page through an API. The options are many, and the “best” choice will depend on the skillsets available to the person(s) who will be maintaining the website. For the most part I can really only speak of one of those options Program O, mainly because I’m the lead developer for the project
Program O is a web-based chatbot that is powered by PHP/MySQL. It runs well on most (if not all) OS/web server platforms with PHP 5.4+, is easy to install, and has an API that allows web pages to access the chatbot dynamically. It’s actively maintained (I just pushed a new set of bug fixes this morning), and is used in enterprise level sites.
Be warned, however. There is a bit of a learning curve involved with the administration of the chatbot, and if you want to have something more than just a generic ALICE clone chatbot you’re going to need a skilled creative staff to author the bot’s responses, and that will take several hundred man-hours to create a set of usable responses for your needs. however, I should point out that this part of the job will be the same no matter which chatbot you end up using.
I hope this bit of insight helps.