Laszlo platform

(This article is published in "Programmer" magazine 2005 No. 2)

In October 2004, Laszlo Systems opened the source code of the main product Laszlo Platform, which intentionally turned to the Rich Client's J2EE developers a choice. In addition to Laszlo, the Rich Client's implementation strategy can be divided into two categories: a faction represented by Flex adopts the display format (such as flash), which is more beautiful, and is not limited by the browser, but the performance The development of layers requires special skills. J2EE developers are often unqualified; one represented by XUL / XAML depends on the browser, and the developer only needs to write a markup similar to HTML, but the browser compatibility is very poor. Laszlo has the advantage of both.

The above is the application architecture map of Laszlo, it looks flat, any Flash-based RICH Client application has similar architectures. The difference between Laszlo is that the Flash interface running in the client is not made by the art in the Flash editor, but is compiled according to the LZLO Presentation Server (LPS), and then sends to the customer End. LZX is an interface description format containing two parts: XML tags for describing interfaces, and JavaScript scripts for event processing. The reader may say: Is this format not similar to the traditional HTML page? exactly. So J2EE developers can also complete the development of the entire RICH Client interface, do not have to go to the Usage of the Flash Editor.

Here is a typical LZX code. We describe a set of data from the server side in . The subsequent tag can be positioned to this data via XPath and display them in Flash:

John smith 617-536-7855 In order to cater to the J2EE developer's taste, Laszlo can be described as good intentions: not only use standard XML as interface description and data binding format, even event processing mechanisms Abandoned Homely ActionScript, and the programmer is more familiar with JavaScript. However, it is also obvious that the disadvantages of the XML description interface are also obvious, that is, the development efficiency is low. In response to this problem, IBM also opens an Eclipse-based editor plug-in that is specifically used to develop Laszlo applications. The reader can find this plugin at the following address: http://alphaworks.ibm.com/tech/ide4laszlo.

However, despite the characteristics of Flash, highly portable features and XUL / XAML simple, easy to develop, Laszlo still has many problems. First, the debugging of the script will be a quite trouble. Although Laszlo provides a beautiful script debugger, since LZX must be displayed after compilation of LPS, the entire debugging process must be connected to the server. When the interface logic becomes complicated, the debugging process of the script can be prejecteder to seriously affect the development efficiency. Secondly, there is a problem with the operational efficiency and stability of Laszlo, especially when accessing a new interface, compiling the Flash process is enough to scare the user, and the amount of data transmitted through the network is also large. Finally, Laszlo is quite high on server hardware, and it is quite doubtful if it is stable in a large load environment.

In summary, Laszlo does provide a convenient and highly portable solution for Rich Client application development, but this program is currently only suitable for development of internal applications. If the problem is used to develop public network applications, efficiency and transmission data volume may become very serious. Therefore, it is afraid that Laszlo is called "Rich Internet Application Platform".