Tools for Designing Web Based Interfaces for Erlang/OTP

Martin Gustafsson

Program

Why Web Based User Interfaces. httpd the Webserver in Erlang/OTP. How to use and develop with WebTool. Best Desing of Web Based Tools, with

Erlang/OTP.

Why Web Based User Interfaces

Easy for the user. Fast development,

– Easy to Learn.– Fast Development.

The tool can be used from the network. Easy to generate printable reports.

Problems with Web based User Interfaces

Takes little more time to start than command-line tools.

Interaction with the files system. Browser incompabilities. Security is problem,

– Functionality that can stop the Erlang node.– Data transfer between server and client is not

secure.

httpd -The Webserver in Erlang/OTP

Support for Basic User Authentication. Support for SSL. Support for creation of Dynamic Web Pages. httpd is a Apache styled Webserver.

The functionality of httpd

httpd

s

mod_xxx

HTTP-request

{response{statuscode,Body}}

HTTP-Response

Creation of dynamic Web Pages

CGI Eval Scheme

– Ex: http://server:port/EvalSchemAlias/mod:func(AnyArg)

Erl SchemeEx: http://server:port/ErlSchemeAlias/mod/func

The Webserver will return the result of calling

mod:func(Env,Input).

Example index(Env,Input) ->

[“\r\n\r\n”,html_head(),htmlbody(),

createMenu(Env),”</HTML>”].

createMenu(Env)->

Ag=httpd_util:key1search(

Env, http_user_agent,other), case

mod_browser:getBrowser(Ag) of

{{msie,_},_} ->

menu(ie);

{{netscape,_},_} ->

menu(nav)

end.

menu(nav) ->

“<LAYER NAME=\”popup\”

VISIBILITY=\”hidden\”>

<TABLE>

<TR><TD>

<A HREF=./start>

Start tool

</A>

</TD></TR>

….

</TABLE>

</LAYER>”;

Starting WebTool

Create a *.tool file for each tool and save it in the directory MyTool-vsn/priv/FileName.tool– Ex: {version,1.2},

[{config_func,{webappmon,configData,[]}}] Start WebTool.

– Ex: webtool:start().webtool:start(Path,Port).

Point a browser to http://HostName:Port/

Callback function for WebTool

WebTool use the callback function to receive configuration data for the tool.

Configuration data is needed for:– Creating links from WebTool to the tool.– Configuration of the Webserver.– Data about how to start and stop the tool.

Developing tools to be used via WebTool

The tools must export a callback function that returns the configuration data needed by WebTool.– Example:configData()-> Application=my_app RealPath=code:priv_dir(Application), {mytool,[{web_data,{“URL”,”Linktext”}},

{alias,{erl_alias,”VPath”,[“Module”]}}, {alias,{“VirtualPath2”,RealPath}},

{start{{Mod,Func,Arg},{Mod,Func,Arg}}}]}.

Design principles for Web based Tools

A N-layered solution has many advantages– Easier to update the code– If well designed the logic module might be

possible to use as a command-line version.

logic ModuleModule that generates the

User Interface

HTTP-Request

WebPage