Benjamin Schmaus

NAME

WWW::Form - Simple, extendable OO module for HTML form validation and display

SYNOPSIS

Simple and extendable module that allows developers to handle HTML form validation and display flexibly and consistently.

DESCRIPTION

This module:

  • provides functionality to handle all of the various types of HTML form inputs this includes displaying HTML for the various form inputs)

  • handles populating form inputs with user entered data or progammer specified default values

  • provides robust validation of user entered input

  • handles presenting customizable error feedback to users

  • is easily extended, the WWW::Form module is designed to be easily inherited from, so you can add your own features.

The most time consuming process (and it's not too bad) is creating the data structure used for instantiating a WWW::Form object. Once you have a WWW::Form object almost all your work is done, as it will have enough information to handle just about everything.

Before we get too involved in the details, let's take a look at a sample usage of the WWW::Form module in a typical setting. The following example uses CGI instead of mod_perl, so if you're using mod_perl, certain pieces of the code would look a little different. The WWW::Form module is used the same way in both environments (CGI or mod_perl), though.

    #!/usr/bin/perl
    use strict;
    use warnings;

    use CGI;
    use WWW::Form;

    # Used by WWW::Form to perform various validations on user entered input
    use WWW::FieldValidator;

    # Define values for form input name attributes as constants
    use constant EMAIL_FIELD_NAME => 'emailAddress';
    use constant PASSWORD_FIELD_NAME => 'password';

    # Gets us access to the HTTP request data
    my $q = CGI->new();

    # Hash ref of HTTP vars, would be $r->param() if you're using mod_perl
    my $params = $q->Vars() || {};

    my $form = WWW::Form->new(
        get_form_fields(),
        $params,
        [&EMAIL_FIELD_NAME, &PASSWORD_FIELD_NAME]
    );

    # Check to see that the form was submitted by the user if you're using
    # mod_perl, instead of $ENV{REQUEST_METHOD} you'd have $r->method()
    if ($form->is_submitted($ENV{REQUEST_METHOD})) {

        # Validate user entered data
        $form->validate_fields();

        # If the data was good, do something
        if ($form->is_valid()) {
            # Do some stuff with params because we know the user entered data
            # passed all of its validation
        }
    }

    # Display the HTML web page
    print <<HTML;
    Content-Type: text/html

    <html>
    <head>
    <title>A Simple HTML Form</title>
    </head>
    <body>
    HTML
        # Display the HTML form content
        print $form->get_form_HTML(action => './form_test.pl');
    print <<HTML;
    </body>
    </html>
    HTML

    # Returns data structure suitable for passing to WWW::Form object
    # constructor, the keys will become the names of the HTML form inputs
    sub get_form_fields {
        my %fields = (
            &EMAIL_FIELD_NAME => {
                label        => 'Email address',
                defaultValue => 'you@emailaddress.com',
                type         => 'text',
                validators   => [WWW::FieldValidator->new(
                    WWW::FieldValidator::WELL_FORMED_EMAIL,
                    'Make sure email address is well formed'
                )]
            },
            &PASSWORD_FIELD_NAME => {
                label        => 'Password',
                defaultValue => '',
                type         => 'password',
                validators   => [WWW::FieldValidator->new(
                    WWW::FieldValidator::MIN_STR_LENGTH,
                    'Password must be at least 6 characters',
                    6
                )]
            }
        );
        return \%fields;
    }

Instantiating A WWW::Form Object

As I said, instantiating a form object is the trickiest part. The WWW::Form constructor takes three parameters. The first parameter called $fieldsData, is a hash reference that describes how the form should be built. $fieldsData should be keyed with values that are suitable for using as the value of the form inputs' name HTML attributes. That is, if you call a key of your $fieldsData hash 'full_name', then you will have some type of form input whose name attribute will have the value 'full_name'. The values of the $fieldsData keys (i.e., $fieldsData->{$fieldName}) should also be hash references. This hash reference will be used to tell the WWW::Form module about your form input. All of these hash references will be structured similarly, however, there are a couple of variations to accommodate the various types of form inputs. The basic structure is as follows:

 {
     # UI presentable value that will label the form input
     label => 'Your name',
     # If set, the form input will be pre-populated with this value
     # you could hard code a default value or use a value retrieved
     # from a data base table, for example
     defaultValue => 'Homer Simpson',
     # The type of form input, i.e. text, checkbox, textarea, etc.
     # (more on this later)
     type => 'text',
     # An array ref of various validations that should be performed on the
     # user entered input
     validators => []
 }

So to create a WWW::Form object with one text box you would have the following data structure:

 my $fields = {
     emailAddress => {
         label        => 'Email address',
         defaultValue => 'you@emailaddress.com',
         type         => 'text',
         validators   => [WWW::FieldValidator->new(
             WWW::FieldValidator::WELL_FORMED_EMAIL,
             'Make sure email address is well formed
         )]
     }
 };

You could then say the following to create that WWW::Form object:

  my $form = WWW::Form->new($fields);

Now let's talk about the second parameter. If a form is submitted, the second parameter is used. This parameter should be a hash reference of HTTP POST parameters. So if the previous form was submitted you would instantiate the WWW::Form object like so:

  my $params = $r->param(); # or $q->Vars if you're using CGI
  my $form   = WWW::Form->new($fields, $params);

At this point, let me briefly discuss how to specify validators for your form inputs.

The validators keys in the $fieldsData->{$fieldName} hash reference can be left empty, which means that the user entered input does not need to be validated at all, or it can take a comma separated list of WWW::FieldValidator objects. The basic format for a WWW::FieldValidator constructor is as follows:

  WWW::FieldValidator->new(
      $validatorType,
      $errorFeedbackIfFieldNotValid,
      # Optional, depends on type of validator, if input is entered validation
      # is run, if nothing is entered input is OK
      $otherVarThatDependsOnValidatorType,
      $isOptional
  )

The FieldValidator types are:

  WWW::FieldValidator::WELL_FORMED_EMAIL
  WWW::FieldValidator::MIN_STR_LENGTH
  WWW::FieldValidator::MAX_STR_LENGTH
  WWW::FieldValidator::REGEX_MATCH
  WWW::FieldValidator::USER_DEFINED_SUB

So to create a validator for a field that would make sure the input of said field was a minimum length, if any input was entered, you would have:

  WWW::FieldValidator->new(
      WWW::FieldValidator::MIN_STR_LENGTH,
      'String must be at least 6 characters',
      6, # input must be at least 6 chars
      # input is only validated if user entered something if field left blank,
      # it's OK
      1 # field is optional
  )

Now for the third parameter. The third parameter is simply an array reference of the keys of the $fieldsData hash, but the order of elements in the array ref should be the order that you want your form inputs to be displayed in. This array ref is used by the get_form_HTML method to return a form block that can be displayed in an HTML page.

  # The third parameter will be used to generate an HTML form whose inputs
  # will be in the order of their appearance in the array ref, note this is
  # the constructor format you should use when instantiating form objects
  my $form = WWW::Form->new(
      $fieldsData,
      $params,
      ['name', 'emailAddress', 'password']
  );

How To Create All The Various Form Inputs

The following form input types are supported by the WWW::Form module (these values should be used for the 'type' key of your $fieldsData->{$fieldName} hash ref):

  text
  password
  hidden
  file
  checkbox
  radio
  select
  textarea

The following structure can be used for text, password, hidden, file, and textarea form inputs:

  $fieldName => {
      label => 'Your name',
      defaultValue => 'Homer Simpson',
      type => 'text', # or file, password, hidden, textarea
      validators => []
  }

The following structure should be used for radio and select form inputs:

The data structure for input types radio and select use an array of hash references called optionsGroup. The optionsGroup label is what will be displayed in the select box or beside the radio button, and the optionsGroup value is the value that will be in the hash of HTTP params depending on what the user selects. To pre-select a select box option or radio button, set its defaultValue to a value that is found in the optionsGroup hash ref. For example, if you wanted the option 'Blue' to be selected by default in the example below, you would set defaultValue to 'blue'.

  $fieldName => {
      label => 'Favorite color',
      defaultValue => '',
      type => 'select',
      optionsGroup => [
          {label => 'Green', value => 'green'},
          {label => 'Red',   value => 'red'},
          {label => 'Blue',  value => 'blue'}
      ],
      validators => []
  }

The following structure should be used for checkboxes:

Note: All checkbox form inputs need a defaultValue to be specified, this is the value that will be used if the checkbox is checked when the form is submitted. If a checkbox is not checked then there will not be an entry for it in the hash of HTTP POST params. If defaultChecked is 1 the checkbox will be selected by default, if it is 0 it will not be selected by default.

  $fieldName => {
      label => 'Do you like spam?',
      defaultValue => 'Yes, I love it!',
      defaultChecked => 0, # 1 or 0
      type => 'checkbox',
      validators => []
  }

Function Reference

NOTE: For style conscious developers all public methods are available using internalCapsStyle and underscore_separated_style. So 'isSubmitted' is also available as 'is_submitted', and 'getFieldHTMLRow' is also available as 'get_field_HTML_row', and so on and so forth.

new

Creates a WWW::Form object. $fieldsData is a hash reference that describes your WWW::Form object. (See instantiating a WWW::Form object above.) $fieldsValues (i.e., $params below) has keys identical to $fieldsData. $fieldsValues is a hash reference of HTTP POST variables. $fieldsOrder is an array reference of $fieldsData keys that is used to determine the order that form inputs are displayed in when getFormHTML() is called. If you don't use this parameter you should use the other public methods provided and display your form inputs by hand.

  Example:

  my $params = $r->param() || {};
  my $form = WWW::Form->new($fieldsData, $params, $fieldsOrder);

validateFields

Validates field's values input according to the validators (WWW::FieldValidators) that were specified when the WWW::Form object was created. This will also set error feedback as necessary for form inputs that are not valid.

Returns hash reference of all the fields that are valid (generally you don't need to use this for anything though because if all the validation passes you can just use your hash ref of HTTP $params, i.e. $r->param()).

  Example:

  if ($form->isSubmitted($r->method)) {
      # validate fields because form was POSTed
      $form->validateFields();
  }

getFields

Returns hash ref of fields data.

  Example:

  my $fields = $form->getFields();

resetFields

Resets values and default values for all fields

  Example:

  $form->resetFields(include_defaults => 1);

getField

Returns hash ref of field data that describes the form input that corresponds to the passed $fieldName ($fieldName should be a value of a key in the $fieldsData hash ref you used to construct your WWW::Form instance).

  Example:

  my $field = $form->getField('address');

getFieldErrorFeedback

Returns an array of all the error feedback (if any) for the specified $fieldName.

  Example:

  my $name_feedback = $form->getFieldErrorFeedback('fullName');

getFieldsOrder

Returns array ref of field names in the order they should be displayed.

  Example:

  $form->getFieldsOrder();

getFieldValue

Returns the current value of the specified $fieldName.

  Example:

  $form->getFieldValue('comments');

isFieldValue

Returns 1 or 0 depending on whether or not the specified field name is valid.

  Example:

  $form->isFieldValid('zip_code');

getFieldValidators

Returns array ref of validators for the passed field name.

  Example:

  $validators = $form->getFieldValidators($fieldName);

getFieldType

Returns value of a field's 'type' key for the specified $fieldName.

  Example:

  my $input_type = $form->getFieldType('favoriteColor');

getFieldLabel

Returns the label associated with the specified $fieldName.

  Example:

  my $ui_label = $form->getFieldLabel('favoriteBand');

setFieldValue

Sets the value of the specified $fieldName to $value. You might use this if you need to convert a user entered value to some other value.

  Example:

  $form->setFieldValue('fullName', uc($form->getFieldValue('fullName')));

isValid

Returns true is all form fields are valid or false otherwise.

  Example:

  if ($form->isSubmitted($r->method)) {
      # validate fields because form was POSTed
      $form->validateFields($params);

      # now check to see if form inputs are all valid
      if ($form->isValid()) {
          # do some stuff with $params because we know
          # the validation passed for all the form inputs
      }
  }

isSubmitted

Returns true if the HTTP request method is POST. If for some reason you're using GET to submit a form then this method won't be of much help. If you're not using POST as the method for submitting your form you may want to override this method in a subclass.

  Example:

  # Returns true if HTTP method is POST
  if ($form->isSubmitted($r->method())) {
      print "You submitted the form.";
  }

Returns a string representation of the current instance.

  Example:

  &LOG->debug("WWW::Form instance: " . $form->asString());

getFieldFormInputHTML

Returns an HTML form input for the specified $fieldName. $attributesString is an (optional) arbitrary string of HTML attribute key='value' pairs that you can use to add attributes to the form input, such as size='20' or onclick='someJSFunction()', and so forth.

  Example:

  $html .= $form->getFieldFormInputHTML(
      'password',
      " size='6' class='PasswordInput' "
  );

getFieldHTMLRow

Returns HTML to display in a web page. $fieldName is a key of the $fieldsData hash that was used to create a WWW::Form object. $attributesString is an (optional) arbitrary string of HTML attribute key='value' pairs that you can use to add attributes to the form input.

The only caveat for using this method is that it must be called between <table> and </table> tags. It produces the following output:

  <!-- NOTE: The error feedback row(s) are only displayed if the field -->
  <!-- input was not valid -->
  <tr>
  <td colspan="2">$errorFeedback</td>
  </tr>
  <tr>
  <td>$fieldLabel</td>
  <td>$fieldFormInput</td>
  </tr>

  Example:

  $form->getFieldHTMLRow('name', " size='6' class='FormField' ");

getFieldFeedbackHTML

Returns HTML error content for each vaildator belonging to $fieldName that doesn't pass validation.

Returns following HTML:

  <div class='feedback'>
  $validatorOneErrorFeedback
  </div>
  <div class='feedback'>
  $validatorTwoErrorFeedback
  </div>
  <div class='feedback'>
  $validatorNErrorFeedback
  </div>

Note: If you use this, you should implement a CSS class named 'feedback' that styles your error messages appropriately.

  Example:

  $html .= $form->getFieldFeedbackHTML('emailAddress');

startForm

Returns an opening HTML form tag.

Arguments:

name - Value of HTML name attribute.

action - Value of action HTML attribute.

attributes - Optional hash ref of HTML attribute name value pairs.

is_file_upload - Optional, boolean, should be true if your form contains file inputs.

  Example:

  $form->start_form(
      action => '/some_script.pl',
      name   => 'MyFormName',
      attributes => {class => 'MyFormClass'}
  );

Returns HTML similar to:

  <form action='/some_script.pl'
        method='post'
        name='MyFormName'
        id='MyFormName'
        class='MyFormClass'>

endForm

Returns HTML to close form.

  Example:

  $html .= $form->endForm();

getFormHTML

Loops through the fieldsOrder array and builds markup for each form input in your form.

Returns HTML markup that when output will display your form.

Arguments:

action - Value of form's action attribute.

name - Value that will be used for form's name and id attribute.

attributes - hashref of key value pairs that can be used to add arbitrary attributes to the opening form element.

submit_label - Optional label for your form's submit button.

submit_name - Optional Value of your submit button's name attribute. This value will also be used for your submit button's id attribute.

submit_type - Optional string value, defaults to submit, if you want to use an image submit button pass submit_type as 'image'.

submit_src - Optional unless submit_type is 'image' then an image src should be specified with submit_src, e.g. submit_src => './img/submit_button.png'.

submit_class - Optional string that specifies a CSS class.

submit_attributes - Optional hash ref of arbitrary name => 'value' HTML attributes.

is_file_upload - Optional boolean that should be true if your form contains a file input.

  Example:

  print $form->getFormHTML(
      action => './my_form.pl',
      name => 'LoginForm',
      attributes => {
          class => 'FormBlueBackground'
      },
      submit_label => 'Login',
      is_file_upload => 1
  );

SEE ALSO

WWW::FieldValidator

AUTHOR

Ben Schmaus

If you find this module useful or have any suggestions or comments please send me an email at perlmods@benschmaus.com.

CHANGELOG

July 2, 2003

Code formatting and cleanup.

Adds support for file inputs.

July 3, 2003

Adds code examples to documentation for public methods.

September 25, 2003

Adds new methods including: resetFields(), isFieldValid(), and getFieldValidators().

Changes _setFields method to handle empty user values. That is, in previous releases, if a form is submitted and the value for a field is empty, the value of the field will be set to the field's default value if it has one. This release updates _setFields to prefer submitted values over default values.

TODO

Add more helpful error logging.

Add functionality for generating client side validation.

BUGS

None that I know of, but please let me know if you find any.

Send email to perlmods@benschmaus.com.

COPYRIGHT

Copyright 2003, Ben Schmaus. All Rights Reserved.

This program is free software. You may copy or redistribute it under the same terms as Perl itself.