To create web pages with dynamic data, you need a convenient and powerful server-side scripting
environment. Using the legacy CGI protocol is slow and difficult to create great looking web
pages because you cannot see the result until it is rendered. In contrast, environments such as
Embedded Server Pages or PHP allow you to see what the page will look like
in WSYWIG tools like Dreameweaver.
Appweb provides a rich set of options to use when creating web pages or web applications. This
document compares the alternatives and suggests where each option is best deployed.
 Embedded Server Pages (ESP)
Embedded Server Pages (ESP) are a collection of technologies developed by Mbedthis to
provide embeddable, standards-based dynamic web page generation. Similar in its ultimate goal
to PHP, Active Server Pages (ASP) and Java Server Pages (JSP), Embedded Server Pages enables
the elegant creation of web pages by embedding scripting in the HTML page to access and compute
dynamic data. This allows the use of page layout tools such as Dreamweaver to create and
layout the page.
Embedded Server Pages was designed exclusively to be suitable for embedding in applications
and devices. It provides a close binding between your application and the web page to be
displayed, making it very easy to generate dynamic data. The Appweb ESP architecture allows
multiple scripting engines to be used at the same time. Appweb is provided with server-side
Embedded JavaScript which implements a subset of the ECMA-262 standard ECMAScript. Other
scripting engines such as TCL, Perl or Python may also leverage this open scripting
architecture in the future.
Embedded Server pages has a very small memory footprint (~45K including the JavaScript) and
yet offeres powerful features like:
- Expressions (variables, assignment, +, -, /, *, ++, --, <<, >> etc)
- Variables (local and global)
- Session variables
- Control flow (if, else, while)
- Control of redirection
- Post back to the same page
- Scripted generation and iteration of HTML text
- Include Javascript libraries
- Ability to call C/C++ procedures
- Ability to access C/C++ variables
PHP
PHP is a
widely-used general-purpose scripting language that is especially suited for enterprise Web
development. It provides an object oriented programming language, numerous extensions and a
broad developer community. The power of PHP comes at a price, it typically has a memory
footprint of 1-2 MB for the PHP code alone. For embedded systems, this is often too big and so
we recommend using Embedded Server Pages for such systems.
CGI
CGI stands for the Common Gateway Interface and it is the legacy extension interface for
running external programs to generate dynamic data. It is standard but slow. Unless you have
legacy CGI programs or need to run a scripting language via CGI, you are better served by using
either PHP or ESP.
EGIThe Embedded Gateway Interface (EGI) was
implemented by Mbedthis as an in-memory, faster replacement for CGI. It can be used to migrate
and accelerate CGI programs by running them inside the Appweb address space. However, in most
cases ESP can do everything that EGI could be used for and so ESP or PHP is a better choice.
Custom HandlersOccasionally, you may require total
control over how the HTTP server should respond to a request. Appweb allows you to create your
own custom HTTP handler that can respond and process selective HTTP requests. This is useful if
you have custom HTTP protocol extensions, proprietary authentication or authorization
procedures or specific request timeout requirements.
Comparison
In summary, We recommend using ESP for embedded applications and
PHP for enterprise applications. The following table summarizes the
differences between the various page creation alternatives.
Â
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| Target Use |
Legacy dynamic pages and forms |
In-memory form processing |
Dynamic embedded web pages and forms |
Enterprise web pages and forms |
Custom URL processing |
| Typical memory footprint |
External program |
10K
|
50K
|
1-2MB |
Handler code |
| Performance |
Slow |
Very fast form processing |
Very fast page and form processing |
Fast page and form processing |
Fastest possible |
| Advantages |
Standard in wide-use |
Simple fast forms processing |
Easy creation of dynamic web pages
|
Large base of PHP code and developers |
Allow any URL handling desired |
| Disadvantages |
Slow. Limit to forms. Can't design page WYSIWYG |
Limit to forms. Can't design page WYSIWYG |
Not quite the feature set of PHP
|
Large memory footprint |
Must build functionality |
Remarks
|
Use just for legacy CGI programs and scripts. Use ESP or PHP
instead.
|
Use ESP instead.
|
Use where memory footprint matters. Useful in embedded systems.
|
Use where memory footprint is not a major concern. Useful for
enterprise web applications.
|
Use for custom HTTP processing.
|
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