Harald: Created page with "
= MicroHTTP Library: Using Server Side Includes = On this page I will explain how to create dynamic web content with the uhttplib.html|MicroHTTP library..."

2017-07-13T08:31:51Z

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= MicroHTTP Library: Using Server Side Includes =

On this page I will explain how to create dynamic web content with the [[uhttplib.html|MicroHTTP library's]] SSI capabilities.

== Enabling SSI ==

To enable SSI, the application must register a handler for it. The easiest way to do this is to enable default SSI support in the Configurator. The application simply needs to call

<pre class="coding">int MediaTypeInitDefaults(void);</pre>
to activate all configured handlers. For SSI, it will register the internal default handler

<pre class="coding">int HttpSsiHandler(HTTPD_SESSION *hs, const MEDIA_TYPE_ENTRY *mt, const char *ext);</pre>
When the browser requests a file with extension ''shtml'', the web server will redirect the request to the SSI handler. The handler parses the file for SSI elements and replaces them according to the SSI syntax rules.

At the time of this writing, the following SSI elements are recognized by the server:

* echo
* exec
* include

Support for ''if-then-else'' is not provided, probably the most missing feature. If implemented once, we would also miss the ''set'' command.

CGI scripts had been discussed on [[uhttplib_forms.html|the previous page]]. Including external files is straight forward and a simple way to add common parts like menus to all your webpages. Retrieving the value of variables will be explained now.

== Predefined Variables ==

The library offers a number of predefined SSI variables, for example the current date and time. The following HTTP snippet displays the local time as well as the Greenwich Mean Time.

<pre class="coding"><p>Local time </p>
<p>GMT time </p></pre>
To enable these variables, applications must call

<pre class="coding">int EnvInitDefaults(void);
HTTP_SSI_VARHANDLER HttpRegisterSsiVarHandler(HTTP_SSI_VARHANDLER handler);</pre>
The first call adds all predefined variables to the environment and the second call is used to register a handler. MicroHTTP offers a default handler named ''EnvHandler'', which can be registered with

<pre class="coding">HttpRegisterSsiVarHandler(EnvHandler);</pre>
The library supports the following variables:

* SERVER_PORT
* SERVER_NAME
* SERVER_ADDR
* SCRIPT_NAME
* SCRIPT_FILENAME
* REQUEST_URI
* REQUEST_METHOD
* REMOTE_PORT
* REMOTE_ADDR
* QUERY_STRING_UNESCAPED
* QUERY_STRING
* HTTP_USER_AGENT
* HTTP_REFERER
* HTTP_HOST
* HTTP_COOKIE
* HTTP_CONNECTION
* HTTP_ACCEPT_ENCODING
* DOCUMENT_ROOT
* DOCUMENT_NAME
* DATE_LOCAL
* DATE_GMT

== User Defined Variables ==

The following HTML snippet should display the application's name and version:

<pre class="coding"><p> </p></pre>
The default SSI variable handler, that was used for our predefined variables above, also allows to add user defined variables with

<pre class="coding">int EnvRegisterVariable(char *name, HTTP_ENVVAR_HANDLER handler, int item);</pre>
* ''name'' points to the name of the variable.
* ''handler'' points to the handler for this variable.
* ''item'' is an index starting from 1. It will be passed to the handler.

Here is the complete initialization part:

<pre class="coding">#define APPVAR_NAME 1
#define APPVAR_VERSION 2

StreamInit();
MediaTypeInitDefaults();
EnvRegisterVariable("APPNAME", AppVarHandler, APPVAR_NAME);
EnvRegisterVariable("APPVERSION", AppVarHandler, APPVAR_VERSION);
HttpRegisterSsiVarHandler(EnvHandler);
StreamClientAccept(HttpdClientHandler, NULL);</pre>
We can create a single handler for all our user defined variables:

<pre class="coding">const char *AppVarHandler(HTTPD_SESSION *hs, int item)
{
static char value[128];

value[0] = '\0';
switch (item) {
case APPVAR_NAME:
strcpy(value, "SSI Sample");
break;
case APPVAR_VERSION:
sprintf(value, "%d.%d", MAJOR_VERSION, MINOR_VERSION);
break;
}
return value;
}</pre>
Note, that the application must make sure, that each variable, which is sharing the same handler, must have a unique index.

== Next Step ==

CGIs and server side includes are most useful to create a web interface to remotely configure your embedded device. Probably, you do not want to grant access to everyone and need some kind of [[uhttplib_auth.html|authentication]].

</div>

Documents/uHTTP Lib SSI - Revision history

Harald: Created page with " = MicroHTTP Library: Using Server Side Includes = On this page I will explain how to create dynamic web content with the uhttplib.html|MicroHTTP library..."

Harald: Created page with "
= MicroHTTP Library: Using Server Side Includes = On this page I will explain how to create dynamic web content with the uhttplib.html|MicroHTTP library..."