Lutris: The Enhydra Java/XML Application Server

A group of men from Lutris <www.lutris.com> introduced their Open Source Application Server called Enhydra <www.enhydra.org> to the Java SIG. Enhydra is general, flexible, and scalable. Because it is written in Java, it is platform independent and amenable towards group development.

David Young gave us an overview of the company and introduced Enhydra. Lutris was founded in July of 1995 and now boasts 145 employees located over the hill in Santa Cruz. They are a pre-IPO company whose early customers include FedEx and Kinkos.

Enhydra got its start in 1997 because there were not any commercial products available. The goal was to produce a generic application server so that Lutris could offer its customers a shorter time-to-market value. Enhydra uses the FreeBSD license to encourage developers around the world to use, fix, and extend the application server so that it could be better and more robust than any proprietary offering. David is hoping that the world jumps on the Enhydra bandwagon so that Lutris can "do the `Red Hat' thing."

Wayne Stidolph discussed the architecture of Enhydra. The application is represented by a super servlet which is the window into the system. A session manager keeps every session straight via cookies or URL rewriting and allows processing to occur on multiple machines for load-sharing. The software uses a wide range of standards, and the Enhydra developers move into new standards as they become available.

Douglas McArthur talked about Enhydra application development. An Enhydra application consists of the servlet class, the business logic and the database classes, the presentation class, and a class to render the presentation in HTML. Tools are provided to generate stub files for these components easily. Once the classes are written and installed, a simple configuration file, which is mostly generated automatically by the administration utility, is used to enable the application.

Finally, Matt Schwartz talked about XMLC, an XML Compiler which can be used to generate Java classes from HTML files. The beauty of this tool is that the graphic designer and programmer are completely insulated from each other since the designer does not have to touch a line of code and the programmer does not have to write any HTML. This separation also makes both the code and HTML templates much easier to maintain, unlike JSP (Java Server Pages) whose code and HTML are intermingled. An "id" attribute is added to the HTML tags which XMLC uses to create Java methods which can be called by Java to get and set the contents of a page of HTML. XMLC is not tied to Enhydra, so anyone who writes servlets to render HTML can take advantage of XMLC.

Enhydra 3.0 will be released in April. The future of Enhydra reveals movement towards J2EE (Java 2 Enterprise Edition), use of EJB (Enterprise Java Beans) and CORBA, and inclusion of JMS (Java Messaging System), and others. This future release is slotted for July.


Bill is a Senior Software Engineer who much prefers programming in Java. His interests are graphics, visualization, and UIs. He can be reached at wohler@newt.com.


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