<?xml version="1.0" encoding="latin1" ?>
<!DOCTYPE chapter SYSTEM "chapter.dtd">
<chapter>
<header>
<copyright>
<year>2001</year><year>2009</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
The contents of this file are subject to the Erlang Public License,
Version 1.1, (the "License"); you may not use this file except in
compliance with the License. You should have received a copy of the
Erlang Public License along with this software. If not, it can be
retrieved online at http://www.erlang.org/.
Software distributed under the License is distributed on an "AS IS"
basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
the License for the specific language governing rights and limitations
under the License.
</legalnotice>
<title>WebTool User Guide</title>
<prepared></prepared>
<docno></docno>
<date></date>
<rev></rev>
<file>webtool_chapter.xml</file>
</header>
<section>
<title>Introduction </title>
<p>WebTool provides an easy and efficient way to implement web
based tools with Erlang/OTP. WebTool configures and starts the
webserver and the various web based tools.</p>
<p>All tools that shall run under WebTool must have a *.tool
file in the code path or in its priv directory. When WebTool
starts it searches the code path for such files. For each
<c>ebin</c> directory in the path, the <c>priv</c> directory is
also searched. The *.tool files contain the configuration data
for each web based tool.</p>
</section>
<section>
<title>Starting WebTool</title>
<p>Start WebTool by calling the function <c>webtool:start/0</c> or
<c>webtool:start/2</c>. If <c>webtool:start/0</c> is used the
start page of WebTool is available at
<em>http://localhost:8888/</em> or
<em>http://127.0.0.1:8888/</em>, and the directory containing
the root directory for the webserver, is assumed to be
<c><![CDATA[webtool-<vsn>/priv]]></c>.</p>
<p>Use <c>webtool:start/2</c> if the default path for the root
directory, port, ip-number or server name can not be used. See
the Reference Manual for <seealso marker="webtool">webtool</seealso> for more information.</p>
<p>WebTool, with the default configuration as in <c>start/0</c>,
can also be started with the <c>start_webtool</c> script which
is available in the <c>priv</c> directory of the WebTool
application. See the Reference Manual for <seealso marker="start_webtool">start_webtool</seealso> for further
information about this script. For Windows users, the batch file
<c>start_webtool.bat</c> can be used for the same purpose.</p>
</section>
<section>
<title>Using WebTool</title>
<p>Start WebTool and point the browser to the corresponding URL.
At the top of the page there is a frame with a link named
<em>WebTool</em>. Click that link and a page where it is
possible to start the available tools will appear in the main
frame.</p>
</section>
<section>
<title>Start a web based tool</title>
<p>Click on the link labeled <em>WebTool</em> in the topmost frame,
select the checkbox for each tool to start and
click on the button labeled <em>Start</em>. A link to each tool
that WebTool succeeded to start will appear in the topmost frame.</p>
</section>
<section>
<title>Stop a web based tool</title>
<p>Click on the link labeled <em>WebTool</em> in the topmost
frame. Select <em>Stop Tools</em> in the left frame. Select the
checkbox for each tool to stop and click on the button labeled
<em>Stop</em>.</p>
</section>
<section>
<title>Develop new web based tools</title>
<p>WebTool can be used as a framework when developing new web based
tools.</p>
<p>A web based tool running under WebTool will typically consist of
three parts.</p>
<list type="bulleted">
<item>A *.tool file which defines how WebTool can find the tool's
configuration data</item>
<item>The Erlang code generating the web interface to the tool (HTML
code)</item>
<item>The tool itself.</item>
</list>
<p>In most cases it is a good idea to separate the code for
creation of the html-pages and the code for the logic. This
increases the readability of the code and the logic might be
possible to reuse.</p>
<section>
<title>The *.tool file</title>
<p>When WebTool starts it searches the current path for
<c>*.tool</c> files to find all available tools. The *.tool
file contains a version identifier and a list of tuples which
is the configuration data. The version identifier specifies
the *.tool file version, i.e. not the version of
webtool. Currently the only valid version is "1.2" and the
only valid configuration tag is
<c>config_func</c>. <c>config_func</c> specifies which
function WebTool must call to get further configuration data
for the tool. This means that a *.tool file generally must
look like this:</p>
<code type="none">
{version,"1.2"}.
[{config_func,{Module,Function,Arguments}}]. </code>
<p><c>Module</c> is the name of the module where the callback
function is defined. <c>Function</c> is the name of the
callback function, and <c>Arguments</c> is the list of
arguments to the callback function.</p>
</section>
<section>
<title>The configuration function</title>
<p>The *.tool file points out a configuration function. This
function must return a list of configuration parameters (see
the Reference Manual for <seealso marker="webtool">webtool</seealso>).</p>
<p>The <c>web_data</c> parameter is mandatory and it specifies
the name of the tool and the link to the tool's start
page. All other parameters are optional.</p>
<p>If the tool requires any processes to run, the <c>start</c>
parameter specifies the function that WebTool must call in
order to start the process(es).</p>
<p>The <c>alias</c> parameters are passed directly on to the
webserver (INETS). The webserver has three ways to create
dynamic web pages CGI, Eval Scheme and Erl Scheme. All tools
running under WebTool must use Erl Scheme.</p>
<p>Erl Scheme tries to resemble plain CGI. The big difference is
that Erl Scheme can only execute Erlang code. The code will
furthermore be executed on the same instance as the webserver.</p>
<p>An URL which calls an Erlang function with Erl Scheme can have
the following syntax:</p>
<code type="none"><![CDATA[
http://Servername:Port/ErlScriptAlias/Mod/Func<?QueryString> ]]></code>
<p>An <c>alias</c> parameter in the configuration function can be
an ErlScriptAlias as used in the above URL. The definition of
an ErlScripAlias shall be like this:</p>
<p><c>{alias,{erl_alias,Path,[Modules]}}</c>, e.g.</p>
<p><c>{alias,{erl_alias,"/testtool",[helloworld]}}</c></p>
<p>The following URL will then cause a call to the function
helloworld:helloworld/2 (if WebTool is started with default
settings i.e. servername "localhost" and port 8888):</p>
<p><c>http://localhost:8888/testtool/helloworld/helloworld</c></p>
<p>Note that the module <c>helloworld</c> must be in the code
path of the node running WebTool.</p>
<p>Functions that are called via the Erl Scheme must take two
arguments, <c>Environment</c> and <c>Input</c>.
</p>
<list type="bulleted">
<item><c>Environment</c> is a list of key/value tuples.</item>
<item><c>Input</c> is the part of the URL after the "?", i.e. the
part of the URL containing name-value pairs. If the page was
called with the URL:
<br></br>
<c><![CDATA[http://localhost:8888/testtool/helloworld/helloworld?input1=one&input2=two]]></c> <br></br>
<c>Input</c> will be the string
<c><![CDATA["input1=one&input2=two"]]></c>. In the module
<c>httpd</c> in the INETS application there is a function
<c>parse_query</c> which will parse such a string and return
a list of key-value tuples.</item>
</list>
<p>An <c>alias</c> parameter in the configuration function can
also be a normal path alias. This can e.g. be used to point
out a directory where HTML files are stored. The following
definition states that the URL
<c>http://localhost:8888/mytool_home/</c> really points to the
directory <c>/usr/local/otp/lib/myapp-1.0/priv</c>:</p>
<p><c>{alias,{"/mytool_home","/usr/local/otp/lib/myapp-1.0/priv"}}</c></p>
<p>See the INETS documentation, especially the module
<c>mod_esi</c>, for a more in depht coverage of Erl Scheme.</p>
</section>
<section>
<title>A small example</title>
<p>A Hello World example that uses Erl Scheme would look like
this. Note that this example does not have a process running
and thus does not need a <c>start</c> parameter in the
configuration function.
</p>
<p><em>helloworld.erl:</em></p>
<pre>
-module(helloworld).
-export([config_data/0]).
-export([helloworld/2]).
config_data()->
{testtool,
[{web_data,{"TestTool","/testtool/helloworld/helloworld"}},
{alias,{erl_alias,"/testtool",[helloworld]}}]}.
helloworld(_Env,_Input)->
[header(),html_header(),helloworld_body(),html_end()].
header() ->
header("text/html").
header(MimeType) ->
"Content-type: " ++ MimeType ++ "\r\n\r\n".
html_header() ->
"<HTML>
<HEAD>
<TITLE>Hello world Example </TITLE>
</HEAD>\n".
helloworld_body()->
"<BODY>Hello World</BODY>".
html_end()->
"</HTML>".
</pre>
<p>To use this example with WebTool a *.tool file must be created
and added to a directory in the current path, e.g. the same
directory as the compiled <c>helloworld.beam</c>.</p>
<p><em>testtool.tool:</em></p>
<code type="none">
{version,"1.2"}.
[{config_func, {helloworld,config_data,[]}}].
</code>
<p>When <c>helloworld.erl</c> is compiled, start WebTool by
calling the function <c>webtool:start()</c> and point your
browser to <em>http://localhost:8888/</em>. Select WebTool in
the topmost frame and start TestTool from the web page. Click
on the link labeled <em>TestTool</em> in the topmost frame.</p>
</section>
</section>
</chapter>
