[cgiapp] Announcing Titanium 0.90_1

Mark Stosberg mark at summersault.com
Sat Aug 9 09:11:46 EDT 2008


Announcing Titanium, a next generation web framework based on CGI::Application.

Titanium is designed to provide the underlying strength and flexibility of the
CGI::Application framework, while being more user-friendly to deploy and
develop with. 

To this end, several useful plugins for CGI::Application are bundled by default
with CGI::Application and are documented directly in Titanium.

Several practices are specifically recommended and documented, such as using
dispatching, redirect() and forward(), while details for alternative and
advanced functionality for CGI::Application are not included here. Those
advanced docs remain available in CGI::Application.

Several useful development and testing tools are installed along with Titanium as well.
Here's the full list modules that come with it:

   CGI::Application::Dispatch           
   CGI::Application::Server
   CGI::Application::Plugin::ConfigAuto
   CGI::Application::Plugin::DBH         
   CGI::Application::Plugin::DebugScreen 
   CGI::Application::Plugin::DevPopup    
   CGI::Application::Plugin::ErrorPage
   CGI::Application::Plugin::FillInForm  
   CGI::Application::Plugin::Forward
   CGI::Application::Plugin::LogDispatch
   CGI::Application::Plugin::Redirect    
   CGI::Application::Plugin::Session     
   CGI::Application::Plugin::Stream      
   CGI::Application::Plugin::ValidateRM
   CGI::Application::Standard::Config
   Module::Starter::Plugin::CGIApp
   Test::WWW::Mechanize::CGIApp

The first release should hit CPAN soon, and a text-only version of the docs is
available below until then.

I don't have a public SCM repo set up yet, but can do that soon.  Feedback
welcome!

    Mark

###############

    * NAME
    * SYNOPSIS
          o Coding
          o Development and Testing
          o Dispatching with Clean URIs
    * Elements of Titanium
    * DESCRIPTION
          o Script/Dispatching Methods
                + new()
                + run()
          o Essential Method to Override
                + setup()
          o Essential Application Methods
                + load_tmpl()
                + param()
                + query()
                + run_modes()
                + start_mode()
                + tmpl_path()
          o More Methods to override
                + teardown()
                + cgiapp_init()
                + cgiapp_prerun()
                + cgiapp_postrun()
                + cgiapp_get_query()
          o More Application Methods
                + error_mode()
                + header_add()
                + header_props()
                + redirect()
                + forward()
                + dbh()
                + session()
                + cfg()
                + log()
                + check_rm()
                + fill_form()
                + error()
                + stream_file()
                + prerun_mode()
          o Dispatching Clean URIs to run modes
          o Offline website development
          o Automated Testing
    * PLUGINS
    * COMMUNITY
    * FUTURE and TODO
    * SEE ALSO
    * MORE READING
    * AUTHORS
    * LICENSE

---------------------------------------------------------------

NAME
    Titanium - A strong, lightweight web application famework

SYNOPSIS
  Coding
      # In "WebApp.pm"...
      package WebApp;
      use base 'Titanium';

      sub setup {
            my $c = shift;

            $c->start_mode('form_display');
            $c->run_modes([qw/
            form_display
            form_process
            /);
      }
      sub form_display { 
            my $c = shift;
            my $errs = shift;

            my $t = $c->load_tmpl;
            $t->param($errs) if $errs;
            return $t->output;
      }
      sub form_process {
           my $ c= shift;

           # Validate the form against a profile. If it fails validation, re-display
           # the form for the user with their data pre-filled and the errors highlighted. 
           my ($results, $err_page) = $c->check_rm('form_display','_form_profile');
           return $err_page if $err_page; 

           return $c->forward('form_success');   
      }

      # Return a Data::FormValidator profile
      sub _form_profile {
        my $c = shift;
        return {
            required => 'email',
        };
      }

      sub form_success { ... } 

      1;

      ### In "webapp.cgi"...
      use WebApp;
      my $c = WebApp->new();
      $c->run();

    Inside the run modes, the following methods are available:

        $c->query;                               # A query object. CGI.pm by default.
        $c->redirect('http://othersite.com');    # Basic redirection
        $c->dbh;                                 # DBI database handle
        $c->session();                           # A CGI::Session object
        $c->check_rm;                            # Form validation with Data::FormValidator
        $c->cfg('root_uri');                     # Config file access (YAML, Perl or INI formats)
        $c->fill_form;                           # Form filling with HTML::FillInForm
        $c->error( title => '..', msg => '..' ); # Easy error page generation
        $c->stream_file($file);                  # file streaming
        $c->log;                                 # A Log::Dispatch object

  Development and Testing
    Easily setup the project skeleton using the bundled cgiapp-starter
    script.

    In development you can turn on a debugging screen and a developer pop-up
    to quickly catch code, html and performance issues, thanks to
    CGI::Application::Plugin::DebugScreen and
    CGI::Application::Plugin::DevPopup.

    For automated testing, Test::WWW::Mechanize::CGIApp is bundled, allowing
    you to functionally test your web application without involving a full
    web server. If you'd rather test against full web server,
    Test::WWW::Mechanize is there, too.

  Dispatching with Clean URIs
    Modern web frameworks dispense with cruft in URIs. Instead of:

     /cgi-bin/item.cgi?rm=view&id=15

    A clean URI to describe the same resource might be:

     /item/15/view

    The process of mapping these URIs to run modes is called dispatching and
    is handled by CGI::Application::Dispatch. It comes with a default
    dispatch table that automatically creates URLs in this pattern for you:

     /app/module_name/run_mode

    There's plenty of flexibility to design your own URIs if you'd like.

Elements of Titanium
    * Titanium is solid and mature. While it has a new name, the reality is
    that Titanium is simply a more user-friendly packaging of the mature
    CGI::Application framework and some useful plugins. These packages have
    already been refined and vetted. The seed framework was first released
    in 2000 and by 2005 was mature. Titanium contains no real code of its
    own, and there is no intention to do so in the future. Instead, we may
    select other mature plugins to include in the future. Other "Titanium
    alloys" in the "Titanium::Alloy::" name space may also come to exist,
    following the same philosophy, but choosing to bundle a different
    combination of plugins.

    * Titanium is lightweight. Titanium has a very light core and the
    plugins it uses employ lazy-loading whenever possible. That means that
    while we have built-in database plugin, we don't have to load DBI or
    make a database connection until you actually use the database
    connection. Titanium runs well in a plain CGI environment and provides
    excellent performance in a persistent environment such as FastCGI or
    mod_perl. Titanium apps are compatible with the dozens of published
    plugins for CGI::Application, so you can add additional features as your
    needs evolve.

DESCRIPTION
    It is intended that your Application Module will be implemented as a
    sub-class of Titanium. This is done simply as follows:

        package My::App; 
        use base 'Titanium';

    Notation and Conventions

    For the purpose of this document, we will refer to the following
    conventions:

      WebApp.pm  : The Perl module which implements your Application Module class.
      WebApp     : Your Application Module class; a sub-class of Titanium.
      webapp.cgi : The Instance Script which implements your Application Module.
      $c         : Used in instance methods to pass around the
                   current object. (Sometimes referred as "$self" in other projects.)
                   Think of the "$c" as short for "controller". 

  Script/Dispatching Methods
    By inheriting from Titanium you have access to a number of built-in
    methods. The following are those which are expected to be called from
    your Instance Script or through your CGI::Application::Dispatch
    dispatcher.

   new()
    The new() method is the constructor for a Titanium. It returns a blessed
    reference to your Application Module class. Optionally, new() may take a
    set of parameters as key => value pairs:

        my $c = WebApp->new(
                    TMPL_PATH => 'App/',
                    PARAMS => {
                            'custom_thing_1' => 'some val',
                            'another_custom_thing' => [qw/123 456/]
                    }
        );

    This method may take some specific parameters:

    TMPL_PATH - This optional parameter defines a path to a directory of
    templates. This is used by the load_tmpl() method (specified below), and
    may also be used for the same purpose by other template plugins. This
    run-time parameter allows you to further encapsulate instantiating
    templates, providing potential for more re-usability. It can be either a
    scalar or an array reference of multiple paths.

    QUERY - This optional parameter allows you to specify an already-created
    CGI query object. Under normal use, Titanium will instantiate its own
    CGI.pm query object. Under certain conditions, it might be useful to be
    able to use one which has already been created.

    PARAMS - This parameter, if used, allows you to set a number of custom
    parameters at run-time. By passing in different values in different
    instance scripts which use the same application module you can achieve a
    higher level of re-usability. For instance, imagine an application
    module, "Mailform.pm". The application takes the contents of a HTML form
    and emails it to a specified recipient. You could have multiple instance
    scripts throughout your site which all use this "Mailform.pm" module,
    but which set different recipients or different forms.

    One common use of instance scripts is to provide a path to a config
    file. This design allows you to define project wide configuration
    objects used by many several instance scripts. There are several plugins
    which simplify the syntax for this and provide lazy loading. Here's an
    example using CGI::Application::Plugin::ConfigAuto, which uses
    Config::Auto to support many configuration file formats.

     my $app = WebApp->new(PARAMS => { cfg_file => 'config.pl' });

     # Later in your app:
     my %cfg = $c->cfg()
     # or ... $c->cfg('HTML_ROOT_DIR');

    See the list of of plugins below for more config file integration
    solutions.

   run()
    The run() method is called upon your Application Module object, from
    your Instance Script. When called, it executes the functionality in your
    Application Module.

        my $c = WebApp->new;
        $c->run;

    This method determines the application state by looking at the dispatch
    table, as described in CGI::Application::Dispatch.

    Once the mode has been determined, run() looks at the hash stored in
    run_modes() and finds the subroutine which is tied to a specific hash
    key. If found, the function is called and the data returned is
    print()'ed to STDOUT and to the browser. If the specified mode is not
    found in the run_modes() table, run() will croak(). This 'death' can
    possibly be captured and handled using "error_mode()", described below.

  Essential Method to Override
    Titanium implements some methods which are expected to be overridden by
    implementing them in your sub-class module. One of these is essential to
    do:

   setup()
    This method is called by the inherited new() constructor method. The
    setup() method should be used to define the following property/methods:

        start_mode() - string containing the default run mode.
        run_modes()  - hash table containing mode => function mappings.

        error_mode() - string containing the error mode.
        tmpl_path()  - string or array reference containing path(s) to template directories.

    Your setup() method may call any of the instance methods of your
    application. This function is a good place to define properties specific
    to your application via the $c->param() method.

    Your setup() method might be implemented something like this:

            sub setup {
                    my $c = shift;
                    $c->start_mode('putform');
                    $c->run_modes([qw/
                    form
                    form_process
                    /]);
            }

  Essential Application Methods
    The following methods are inherited from Titanium, and are available to
    be called by your application within your Application Module. They are
    called essential because you will use all are most of them to get any
    application up and running. These functions are listed in alphabetical
    order.

   load_tmpl()
        my $tmpl_obj = $c->load_tmpl;
        my $tmpl_obj = $c->load_tmpl('some.html');
        my $tmpl_obj = $c->load_tmpl( \$template_content );
        my $tmpl_obj = $c->load_tmpl( FILEHANDLE );

    This method takes the name of a template file, a reference to template
    data or a FILEHANDLE and returns an HTML::Template object. If the
    filename is undefined or missing, Titanium will default to trying to use
    the current run mode name, plus the extension ".html".

    If you use the default template naming system, you should also use
    CGI::Application::Plugin::Forward, which simply helps to keep the
    current name accurate when you pass control from one run mode to
    another.

    ( For integration with other template systems and automated template
    names, see "Alternatives to load_tmpl() below. )

    When you pass in a filename, the HTML::Template->new_file() constructor
    is used for create the object. When you pass in a reference to the
    template content, the HTML::Template->new_scalar_ref() constructor is
    used and when you pass in a filehandle, the
    HTML::Template->new_filehandle() constructor is used.

    Refer to HTML::Template for specific usage of HTML::Template.

    If tmpl_path() has been specified, load_tmpl() will set the
    HTML::Template "path" option to the path(s) provided. This further
    assists in encapsulating template usage.

    The load_tmpl() method will pass any extra parameters sent to it
    directly to HTML::Template->new_file() (or new_scalar_ref() or
    new_filehandle()). This will allow the HTML::Template object to be
    further customized:

        my $tmpl_obj = $c->load_tmpl('some_other.html',
             die_on_bad_params => 0,
             cache => 1
        );

    Note that if you want to pass extra arguments but use the default
    template name, you still need to provide a name of "undef":

        my $tmpl_obj = $c->load_tmpl(undef',
             die_on_bad_params => 0,
             cache => 1
        );

    Alternatives to load_tmpl()

    If your application requires more specialized behavior than this, you
    can always replace it by overriding load_tmpl() by implementing your own
    load_tmpl() in your Titanium sub-class application module.

    First, you may want to check out the template related plugins.

    CGI::Application::Plugin::TT focuses just on Template Toolkit
    integration, and features pre-and-post features, singleton support and
    more.

   param()
        $c->param('pname', $somevalue);

    The param() method provides a facility through which you may set
    application instance properties which are accessible throughout your
    application.

    The param() method may be used in two basic ways. First, you may use it
    to get or set the value of a parameter:

        $c->param('scalar_param', '123');
        my $scalar_param_values = $c->param('some_param');

    Second, when called in the context of an array, with no parameter name
    specified, param() returns an array containing all the parameters which
    currently exist:

        my @all_params = $c->param();

    The param() method also allows you to set a bunch of parameters at once
    by passing in a hash (or hashref):

        $c->param(
            'key1' => 'val1',
            'key2' => 'val2',
            'key3' => 'val3',
        );

    The param() method enables a very valuable system for customizing your
    applications on a per-instance basis. One Application Module might be
    instantiated by different Instance Scripts. Each Instance Script might
    set different values for a set of parameters. This allows similar
    applications to share a common code-base, but behave differently. For
    example, imagine a mail form application with a single Application
    Module, but multiple Instance Scripts. Each Instance Script might
    specify a different recipient. Another example would be a web bulletin
    boards system. There could be multiple boards, each with a different
    topic and set of administrators.

    The new() method provides a shortcut for specifying a number of run-time
    parameters at once. Internally, Titanium calls the param() method to set
    these properties. The param() method is a powerful tool for greatly
    increasing your application's re-usability.

   query()
        my $q = $c->query();
        my $remote_user = $q->remote_user();

    This method retrieves the CGI.pm query object which has been created by
    instantiating your Application Module. For details on usage of this
    query object, refer to CGI. Titanium is built on the CGI module.
    Generally speaking, you will want to become very familiar with CGI.pm,
    as you will use the query object whenever you want to interact with form
    data.

    When the new() method is called, a CGI query object is automatically
    created. If, for some reason, you want to use your own CGI query object,
    the new() method supports passing in your existing query object on
    construction using the QUERY attribute.

   run_modes()
        # The common usage: an arrayref of run mode names that exactly match subroutine names
        $c->run_modes([qw/
            form_display
            form_process
        /]);

       # With a hashref, use a different name or a code ref
       $c->run_modes(
               'mode1' => 'some_sub_by_name', 
               'mode2' => \&some_other_sub_by_ref
        );

    This accessor/mutator specifies a lookup table for the application
    states, using the syntax examples above. It returns the dispatch table
    as a hash.

    The run_modes() method may be called more than once. Additional values
    passed into run_modes() will be added to the run modes table. In the
    case that an existing run mode is re-defined, the new value will
    override the existing value. This behavior might be useful for
    applications which are created via inheritance from another application,
    or some advanced application which modifies its own capabilities based
    on user input.

    The run() method uses the data in this table to send the application to
    the correct function as determined by the dispatcher, as described in
    CGI::Application::Dispatch. These functions are referred to as "run mode
    methods".

    The hash table set by this method is expected to contain the mode name
    as a key. The value should be either a hard reference (a subref) to the
    run mode method which you want to be called when the application enters
    the specified run mode, or the name of the run mode method to be called:

        'mode_name_by_ref'  => \&mode_function
        'mode_name_by_name' => 'mode_function'

    The run mode method specified is expected to return a block of text
    (e.g.: HTML) which will eventually be sent back to the web browser. The
    run mode method may return its block of text as a scalar or a
    scalar-ref.

    An advantage of specifying your run mode methods by name instead of by
    reference is that you can more easily create derivative applications
    using inheritance. For instance, if you have a new application which is
    exactly the same as an existing application with the exception of one
    run mode, you could simply inherit from that other application and
    override the run mode method which is different. If you specified your
    run mode method by reference, your child class would still use the
    function from the parent class.

    An advantage of specifying your run mode methods by reference instead of
    by name is performance. Dereferencing a subref is faster than eval()-ing
    a code block. If run-time performance is a critical issue, specify your
    run mode methods by reference and not by name. The speed differences are
    generally small, however, so specifying by name is preferred.

    Specifying the run modes by array reference:

        $c->run_modes([ 'mode1', 'mode2', 'mode3' ]);

    Is is the same as using a hash, with keys equal to values

        $c->run_modes(
            'mode1' => 'mode1',
            'mode2' => 'mode2',
            'mode3' => 'mode3'
        );

    Often, it makes good organizational sense to have your run modes map to
    methods of the same name. The array-ref interface provides a shortcut to
    that behavior while reducing verbosity of your code.

    Note that another importance of specifying your run modes in either a
    hash or array-ref is to assure that only those Perl methods which are
    specifically designated may be called via your application. Application
    environments which don't specify allowed methods and disallow all others
    are insecure, potentially opening the door to allowing execution of
    arbitrary code. Titanium maintains a strict "default-deny" stance on all
    method invocation, thereby allowing secure applications to be built upon
    it.

    IMPORTANT NOTE ABOUT RUN MODE METHODS

    Your application should *NEVER* print() to STDOUT. Using print() to send
    output to STDOUT (including HTTP headers) is exclusively the domain of
    the inherited run() method. Breaking this rule is a common source of
    errors. If your program is erroneously sending content before your HTTP
    header, you are probably breaking this rule.

    THE RUN MODE OF LAST RESORT: "AUTOLOAD"

    If Titanium is asked to go to a run mode which doesn't exist it will
    usually croak() with errors. If this is not your desired behavior, it is
    possible to catch this exception by implementing a run mode with the
    reserved name "AUTOLOAD":

      $c->run_modes(
            "AUTOLOAD" => \&catch_my_exception
      );

    Before Titanium calls croak() it will check for the existence of a run
    mode called "AUTOLOAD". If specified, this run mode will in invoked just
    like a regular run mode, with one exception: It will receive, as an
    argument, the name of the run mode which invoked it:

      sub catch_my_exception {
            my $c = shift;
            my $intended_runmode = shift;

            my $output = "Looking for '$intended_runmode', but found 'AUTOLOAD' instead";
            return $output;
      }

    This functionality could be used for a simple human-readable error
    screen, or for more sophisticated application behaviors.

   start_mode()
        $c->start_mode('mode1');

    The start_mode contains the name of the mode as specified in the
    run_modes() table. Default mode is "start". The mode key specified here
    will be used whenever the value of the CGI form parameter specified by
    mode_param() is not defined. Generally, this is the first time your
    application is executed.

   tmpl_path()
        $c->tmpl_path('/path/to/some/templates/');

    This access/mutator method sets the file path to the directory (or
    directories) where the templates are stored. It is used by load_tmpl()
    to find the template files, using HTML::Template's "path" option. To set
    the path you can either pass in a text scalar or an array reference of
    multiple paths.

  More Methods to override
    Several more non-essential methods are useful to declare in your
    application class, or in a project "super class" that inherits from your
    Titanium only to serve in turn as a base class for project modules.
    These additional methods are as follows:

   teardown()
    If implemented, this method is called automatically after your
    application runs. It can be used to clean up after your operations. A
    typical use of the teardown() function is to disconnect a database
    connection which was established in the setup() function, or flush open
    session data. You could also use the teardown() method to store state
    information about the application to the server.

   cgiapp_init()
    If implemented, this method is called automatically right before the
    setup() method is called. The cgiapp_init() method receives, as its
    parameters, all the arguments which were sent to the new() method.

    An example of the benefits provided by utilizing this hook is creating a
    custom "application super-class" from which which all your web
    applications would inherit, instead of directly from Titanium.

    Consider the following:

      # In MySuperclass.pm:
      package MySuperclass;
      use base 'Titanium';
      sub cgiapp_init {
            my $c = shift;
            # Perform some project-specific init behavior
            # such as to load settings from a database or file.
      }

      # In MyApplication.pm:
      package MyApplication;
      use base 'MySuperclass';
      sub setup { ... }
      sub teardown { ... }
      # The rest of your Titanium-based follows...

    By using Titanium and the cgiapp_init() method as illustrated, a suite
    of applications could be designed to share certain characteristics,
    creating cleaner code.

   cgiapp_prerun()
    If implemented, this method is called automatically right before the
    selected run mode method is called. This method provides an optional
    pre-runmode hook, which permits functionality to be added at the point
    right before the run mode method is called. The value of the run mode is
    passed into cgiapp_prerun().

    This could be used by a custom "application super-class" from which all
    your web applications would inherit, instead of Titanium.

    Consider the following:

      # In MySuperclass.pm:
      package MySuperclass;
      use base 'Titanium';
      sub cgiapp_prerun {
            my $c = shift;
            # Perform some project-specific init behavior
            # such as to implement run mode specific
            # authorization functions.
      }

      # In MyApplication.pm:
      package MyApplication;
      use base 'MySuperclass';
      sub setup { ... }
      sub teardown { ... }
      # The rest of your Titanium-based follows...

    It is also possible, within your cgiapp_prerun() method, to change the
    run mode of your application. This can be done via the prerun_mode()
    method, which is discussed elsewhere.

   cgiapp_postrun()
    If implemented, this hook will be called after the run mode method has
    returned its output, but before HTTP headers are generated. This will
    give you an opportunity to modify the body and headers before they are
    returned to the web browser.

    A typical use for this hook is pipelining the output of a
    CGI-Application through a series of "filter" processors. For example:

      * You want to enclose the output of all your CGI-Applications in
        an HTML table in a larger page.

      * Your run modes return structured data (such as XML), which you
        want to transform using a standard mechanism (such as XSLT).

      * You want to post-process CGI-App output through another system,
        such as HTML::Mason.

      * You want to modify HTTP headers in a particular way across all
        run modes, based on particular criteria.

    The cgiapp_postrun() hook receives a reference to the output from your
    run mode method, in addition to the CGI-App object. A typical
    cgiapp_postrun() method might be implemented as follows:

      sub cgiapp_postrun {
        my $c = shift;
        my $output_ref = shift;

        # Enclose output HTML table
        my $new_output = "<table border=1>";
        $new_output .= "<tr><td> Hello, World! </td></tr>";
        $new_output .= "<tr><td>". $$output_ref ."</td></tr>";
        $new_output .= "</table>";

        # Replace old output with new output
        $$output_ref = $new_output;
      }

    Obviously, with access to the CGI-App object you have full access to use
    all the methods normally available in a run mode. You could, for
    example, use "load_tmpl()" to replace the static HTML in this example
    with HTML::Template. You could change the HTTP headers (via
    "header_add()" ). You could also use the objects properties to apply
    changes only under certain circumstance, such as a in only certain run
    modes, and when a "param()" is a particular value.

   cgiapp_get_query()
     my $q = $c->cgiapp_get_query;

    Override this method to retrieve the query object if you wish to use a
    different query interface instead of CGI.pm.

    CGI.pm is only loaded to provided query object is only loaded if it used
    on a given request.

    If you can use an alternative to CGI.pm, it needs to have some
    compatibility with the CGI.pm API. For normal use, just having a
    compatible "param" method should be sufficient.

    If use the "path_info" option to the mode_param() method, then we will
    call the "path_info()" method on the query object.

    If you use the "Dump" method in Titanium, we will call the "Dump" and
    "escapeHTML" methods on the query object.

  More Application Methods
    You can skip this section if you are just getting started.

    The following additional methods are inherited from Titanium, and are
    available to be called by your application within your Application
    Module. These functions are listed in alphabetical order.

   error_mode()
        $c->error_mode('my_error_rm');

    If the runmode dies for whatever reason, "run() will" see if you have
    set a value for "error_mode()". If you have, "run()" will call that
    method as a run mode, passing $@ as the only parameter.

    No "error_mode" is defined by default. The death of your "error_mode()"
    run mode is not trapped, so you can also use it to die in your own
    special way.

    For a complete integrated logging solution, check out
    CGI::Application::Plugin::LogDispatch.

   header_add()
        # add or replace the 'type' header
        $c->header_add( -type => 'image/png' );

        - or -

        # add an additional cookie
        $c->header_add(-cookie=>[$extra_cookie]);

    The "header_add()" method is used to add one or more headers to the
    outgoing response headers. The parameters will eventually be passed on
    to the CGI.pm header() method, so refer to the CGI docs for exact usage
    details.

    Unlike calling "header_props()", "header_add()" will preserve any
    existing headers. If a scalar value is passed to "header_add()" it will
    replace the existing value for that key.

    If an array reference is passed as a value to "header_add()", values in
    that array ref will be appended to any existing values values for that
    key. This is primarily useful for setting an additional cookie after one
    has already been set.

   header_props()
        $c->header_props(-type=>'image/gif',-expires=>'+3d');

    The "header_props()" method expects a hash of CGI.pm-compatible HTTP
    header properties. These properties will be passed directly to CGI.pm's
    "header()" or "redirect()" methods. Refer to CGI for exact usage
    details.

    Calling header_props any arguments will clobber any existing headers
    that have previously set.

    "header_props()" return a hash of all the headers that have currently
    been set. It can be called with no arguments just to get the hash
    current headers back.

    To add additional headers later without clobbering the old ones, see
    "header_add()".

    IMPORTANT NOTE REGARDING HTTP HEADERS

    It is through the "header_props()" and "header_add()" method that you
    may modify the outgoing HTTP headers. This is necessary when you want to
    set a cookie, set the mime type to something other than "text/html", or
    perform a redirect. Understanding this relationship is important if you
    wish to manipulate the HTTP header properly.

   redirect()
      return $c->redirect('http://www.example.com/');

    Redirect to another URL.

   forward()
      return $c->forward('rm_name');

    Pass control to another run mode and return its output. This is
    equivalent to calling $self->$other_runmode, except that the internal
    value of the current run mode is updated. This bookkeeping is important
    to load_tmpl() when called with no arguments and some other plugins.

   dbh()
      sub cgiapp_init  {
          my $c = shift;
  
          # use the same args as DBI->connect();
          $c->dbh_config($data_source, $username, $auth, \%attr);
  
      }

     sub form_process {
        my $c = shift;

        my $dbh = $c->dbh;
     } 

    Easy access to a DBI database handle. The database connection is not
    created until the first call to "dbh()". See
    CGI::Application::Plugin::DBH for more features and details.

   session()
     # in cgiapp_init()
     $c->session_config(
              CGI_SESSION_OPTIONS => [ "driver:PostgreSQL;serializer:Storable", $self->query, {Handle=>$dbh} ],
     );

     # in a run mode 
     my $ses = $c->session->param('foo');

    Easy access to a CGI::Session object, so you can store user data between
    requests. The session is not accessed or created until the first call to
    session() in a given request. See CGI::Application::Plugin::Session for
    more features and details.

   cfg()
        $c->cfg('root_uri'); 

    Easy access to parameters loaded from a config file, which can be stored
    in one of several formats, including YAML and Pure Perl. For more
    features and details see CGI::Application::Plugin::ConfigAuto.

   log()
       $c->log->info('Information message');
       $c->log->debug('Debug message');

    Easy access to a Log::Dispatch logging object, allowing you to log to
    different locations with different locations of severity. By adjusting
    the logging level for your application, you make "debug" messages appear
    or disappear from your logs without making pervasive code changes. See
    CGI::Application::Plugin::LogDispatch for more features and details.

   check_rm()
      my ($results, $err_page) = $c->check_rm('form_display','_form_profile');
      return $err_page if $err_page; 

    Easy form validation with Data::FormValidator. If the validation fails,
    we'll re-display the form for the user with their data pre-filled and
    the errors highlighted. You'll have full control over the design of the
    errors with HTML and CSS in your templates, although we provide some
    intelligent defaults. See CGI::Application::Plugin::ValidateRM for
    features and details.

   fill_form()
     # fill an HTML form with data in a hashref or from an object with with a param() method
     my $filled_html = $self->fill_form($html, $data);

     # ...or default to getting data from $self->query()
     my $filled_html = $self->fill_form($html);

    HTML::FillInForm is a useful when you want to fill in a web form with
    default values from a database table. Like many CPAN modules, you can
    use directly from CGI::Application without any special plugin. The value
    of this plugin is that it defaults to finding values through
    $self->query(). Besides that, it is just a bit of synatic sugar that was
    mostly created work-around weaknesses in the HTML::FillInForm 1.x
    interface, which were fixed with HTML::FillInForm 2.0 release. See
    CGI::Application::Plugin::FillInForm for details.

   error()
      $c->error( title => '..', msg => '..' ); 

    Provide quick error messages back to the user for exceptional cases. You
    can provide your own custom designed template or use the default one
    built-in. See CGI::Application::Plugin::ErrorPage.

   stream_file()
     $c->stream_file($file);                  
 
    If your run mode is outputing an image or a spreadsheet instead of an
    HTML page, you may want to stream the output. This method takes care of
    the boring details of buffering, headers and MIME types. See
    CGI::Application::Plugin::Stream for details.

   prerun_mode()
        $c->prerun_mode('new_run_mode');

    The prerun_mode() method is an accessor/mutator which can be used within
    your cgiapp_prerun() method to change the run mode which is about to be
    executed. For example, consider:

      # In WebApp.pm:
      package WebApp;
      use base 'Titanium';
      sub cgiapp_prerun {
            my $c = shift;

            # Get the web user name, if any
            my $q = $c->query();
            my $user = $q->remote_user();

            # Redirect to login, if necessary
            unless ($user) {
                    $c->prerun_mode('login');
            }
      }

    In this example, the web user will be forced into the "login" run mode
    unless they have already logged in. The prerun_mode() method permits a
    scalar text string to be set which overrides whatever the run mode would
    otherwise be.

    The prerun_mode() method should be used in cases where you want to use
    Titanium's normal run mode switching facility, but you want to make
    selective changes to the mode under specific conditions.

    Note: The prerun_mode() method may ONLY be called in the context of a
    cgiapp_prerun() method. Your application will die() if you call
    prerun_mode() elsewhere, such as in setup() or a run mode method.

  Dispatching Clean URIs to run modes
    Modern web frameworks dispense with cruft in URIs, providing in clean
    URIs instead. Instead of:

     /cgi-bin/item.cgi?rm=view&id=15

    A clean URI to describe the same resource might be:

     /item/15/view

    The process of mapping these URIs to run modes is called dispatching and
    is handled by CGI::Application::Dispatch. Dispatching is not required
    and is a layer you can fairly easily add to an application later.

  Offline website development
    You can work on your Titanium project on your desktop or laptop without
    installing a full-featured web-server like Apache. Instead, install
    CGI::Application::Server from CPAN. After a few minutes of setup, you'll
    have your own private application server up and running.

  Automated Testing
    There a couple of testing modules specifically made for Titanium.

    Test::WWW::Mechanize::CGIApp allows functional testing of a
    CGI::App-based project without starting a web server.
    Test::WWW::Mechanize could be used to test the app through a real web
    server.

    Test::WWW::Selenium is similar, but uses Selenium for the testing,
    meaning that a local web-browser would be used, allowing testing of
    websites that contain JavaScript.

    Direct testing is also easy. Titanium will normally print the output of
    it's run modes directly to STDOUT. This can be surprised with an
    enviroment variable, CGI_APP_RETURN_ONLY. For example:

      $ENV{CGI_APP_RETURN_ONLY} = 1;
      $output = $c->run;
      like($output, qr/good/, "output is good");

    Examples of this style can be seen in our own test suite.

PLUGINS
    Titanium has a plug-in architecture that is easy to use and easy to
    develop new plug-ins for. Plugins made for CGI::Application are directly
    compatible. The CGI::Application should be referenced for those who wish
    to write plugins.

    Select plugins are listed below. For a current complete list, please
    consult CPAN:

    http://search.cpan.org/search?m=dist&q=CGI%2DApplication%2DPlugin

    *   CGI::Application::Plugin::Apache - Use Apache::* modules without
        interference

    *   CGI::Application::Plugin::AutoRunmode - Automatically register
        runmodes

    *   CGI::Application::Plugin::CompressGzip - Add Gzip compression

    *   CGI::Application::Plugin::TT - Use Template::Toolkit as an
        alternative to HTML::Template.

    Consult each plug-in for the exact usage syntax.

COMMUNITY
    Therese are primary resources available for those who wish to learn more
    about Titanium and discuss it with others.

    Wiki

    This is a community built and maintained resource that anyone is welcome
    to contribute to. It contains a number of articles of its own and links
    to many other Titanium related pages. It is currently branded as
    CGI::Application, but the code is the same.

    <http://www.cgi-app.org>

    Support Mailing List

    If you have any questions, comments, bug reports or feature suggestions,
    post them to the support mailing list! To join the mailing list, simply
    send a blank message to "cgiapp-subscribe at lists.openlib.org".

    IRC

    You can also drop by "#cgiapp" on "irc.perl.org" with a good chance of
    finding some people involved with the project there.

    Source Code

    This project is managed using the darcs source control system (
    http://www.darcs.net/ ). The darcs archive is here:
    http://mark.stosberg.com/darcs_hive/titanium

TODO
    * I would like Titanium to be easier to install and get started with.
    Rather than depending on the large CPAN dependency chain being
    installed, I would like an option for users to download the full stack
    of dependencies, so that you can just unpack a single file and go.

    * Titanium depends on Module::Starter::Plugin::CGIApp which provides
    "cgiapp-starter", a project kick-start tool. I'd like to provide
    'titanium-starter'

    * I'd like a plugin to cope with the URI-encoding that Dreamweaver does
    to templates that may just mean packing and releasing the following code
    as a plug-in:

      CGI::Application->add_callback('load_tmpl',sub {
            my ($c, $ht_params, $tmpl_params, $tmpl_file) = @_;
  
            require HTML::Template::Filter::URIdecode;
            import HTML::Template::Filter::URIdecode 'ht_uri_decode';
  
            # If you already have a filter defined, don't do anything. 
            # If you want to add more of your own filters later, be mindful
            # about whether you add to this arrayref, or replace it. 
            unless ($ht_params->{filter}) {
                    $ht_params->{filter} = [\&ht_uri_decode] 
            }
      });
 
SEE ALSO
    *   CGI::Application

MORE READING
    If you're interested in finding out more about Titanium, the following
    articles are available on Perl.com, providing context about the
    underlying CGI::Application framework

        Using CGI::Application
        http://www.perl.com/pub/a/2001/06/05/cgi.html

        Rapid Website Development with CGI::Application
        http://www.perl.com/pub/a/2006/10/19/cgi_application.html

    Thanks to O'Reilly for publishing these articles, and for the incredible
    value they provide to the Perl community!

AUTHORS
    Many.

    Mark Stosberg, "mark at summersault.com" published the original Titanium
    module, while many another contributed to CGI::Application and the
    related plugins.

LICENSE
    This module is free software; you can redistribute it and/or modify it
    under the terms of either:

    a) the GNU General Public License as published by the Free Software
    Foundation; either version 1, or (at your option) any later version,

    or

    b) the "Artistic License" which comes with this module.

    This program is distributed in the hope that it will be useful, but
    WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See either the GNU
    General Public License or the Artistic License for more details.

    You should have received a copy of the Artistic License with this
    module, in the file ARTISTIC. If not, I'll be glad to provide one.

    You should have received a copy of the GNU General Public License along
    with this program; if not, write to the Free Software Foundation, Inc.,
    59 Temple Place, Suite 330, Boston, MA 02111-1307 USA





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