From 81302aff5cf7e25674ca3af7ba79c5b3fa5f4e20 Mon Sep 17 00:00:00 2001 From: Simon Cozens Date: Tue, 6 Apr 2004 15:54:24 +0000 Subject: [PATCH] LOADS of documentation! git-svn-id: http://svn.maypole.perl.org/Maypole/trunk@123 48953598-375a-da11-a14b-00016c27c3ee --- doc/Flox.pod | 295 +++++++++++++++++++++++++++++- doc/Model.pod | 2 + doc/Request.pod | 464 +++++++++++++++++++++++++++++++++++++++++++++--- 3 files changed, 725 insertions(+), 36 deletions(-) diff --git a/doc/Flox.pod b/doc/Flox.pod index b8d3d7a..3c637cd 100644 --- a/doc/Flox.pod +++ b/doc/Flox.pod @@ -3,19 +3,300 @@ Friendster, Tribe, and now Google's Orkut - it seems like in early 2004, everyone wanted to be a social networking site. At the time, I was too busy to be a social networking site, as I was working on my own project -at the time, a web application server called Maypole. However, I -realised that if I could implement a social networking system using -Maypole, then Maypole could probably do anything. +at the time - Maypole. However, I realised that if I could implement a +social networking system using Maypole, then Maypole could probably do +anything. I'd already decided there was room for a free, open-source networking site, and then Peter Sergeant came up with the hook - localizing it to universities and societies, and tying in meet-ups with restaurant bookings. I called it Flox, partially because it flocks people together and partially because it's localised for my home town of Oxford and its -university. +university student population. -Flox is still in, uh, flux, but it does the essentials. In this chapter, -we're going to see how it was put together, and how the techniques shown -in the L chapter can help to create a sophisticated web +Flox is still in, uh, flux, but it does the essentials. We're going to +see how it was put together, and how the techniques shown in the +L chapter can help to create a sophisticated web application. Of course, I didn't have this manual available at the time, so it took a bit longer than it should have done... + +=head2 Mapping the concepts + +Any Maypole application should start with two things: a database schema, +and some idea of what the pages involved are going to look like. +Usually, these pages will be tying to displaying or editing some element +of the database, so these two concepts should come hand in hand. + +When I started looking at social networking sites, I began by +identifying the concepts which were going to make up the tables of the +application. At its most basic, a site like Orkut or Flox has two +distinct concepts: a user, and a connection between two users. +Additionally, there's the idea of an invitation to a new user, which can +be extended, accepted, declined or ignored. These three will make up the +key tables; there are an extra two tables in Flox, but they're +essentially enumerations that are a bit easier to edit: each user has an +affiliation to a particular college or department, and a status in the +university. (Undergraduate, graduate, and so on.) + +For this first run-through, we're going to ignore the ideas of societies +and communities, and end up with a schema like so: + + CREATE TABLE user ( + id int not null auto_increment primary key, + first_name varchar(50), + last_name varchar(50), + email varchar(255), + profile text, + password varchar(255), + affiliation int, + unistatus int, + status ENUM("real", "invitee"), + photo blob, + photo_type varchar(30) + ); + + CREATE TABLE connection ( + id int not null auto_increment primary key, + from_user int, + to_user int, + status ENUM("offered", "confirmed") + ); + + CREATE TABLE invitation ( + id char(32) not null primary key, + issuer int, + recipient int, + expires date + ); + +Plus the definition of our two auxilliary tables: + + CREATE TABLE affiliation ( + id int not null auto_increment primary key, + name varchar(255) + ); + + CREATE TABLE unistatus ( + id int not null auto_increment primary key, + name varchar(255) + ); + +Notice that, for simplicity, invitations and friendship connections are +quite similar: they are extended from one user to another. This means +that people who haven't accepted an invite yet still have a place in the +user table, with a different C. Similarly, a connection between +users can be offered, and when it is accepted, its status is changed to +"confirmed" and a reciprocal relationship put in place. + +We also have some idea, based on what we want to happen, of what pages +and actions we're going to define. Leaving the user aside for the +moment, we want an action which extends an invitation from the current +user to a new user. We want a page the new user can go to in order to +accept that invitation. Similarly, we want an action which offers a +friendship connection to an existing user, and a page the user can go to +to accept or reject it. This gives us five pages so far: + + invitation/issue + invitation/accept + + user/befriend + connection/accept + connection/reject + +Notice that the C action is performed on a user, not a +connection. This is distinct from C because when +befriending, we have a real user on the system that we want to do +something to. This makes sense if you think of it in terms of object +oriented programming - we could say + + Flox::Connection->create(to => $user) + +but it's clearer to say + + $user->befriend + +Similarly, we could say + + Flox::User->create({ ... })->issue_invitation_to + +but it's clearer to say + + Flox::Invitation->issue( to => Flox::User->create({ ... }) ) + +because it more accurately reflects the principal subject and object of +these actions. + +Returning to look at the user class, we want to be able to view a user's +profile, edit one's own profile, set up the profile for the first +time, upload pictures and display pictures. We also need to handle the +concepts of logging in and logging out. + +As usual, though, we'll start with a handler class which sets up the +database: + + package Flox; + use base qw(Apache::MVC); + Flox->setup("dbi:mysql:flox"); + Flox->config->{display_tables} = [qw[user invitation connection]]; + 1; + +Very simple, as these things are meant to be. Now let's build on it. + +=head2 Authentication + +The concept of a current user is absolutely critical in a site like +Flox; it represents "me", the viewer of the page, as the site explores +the connections in my world. We've described the authentication hacks +briefly in the L chapter, but now it's time to go into a +little more detail about how user handling is done. + +XXX + +=head2 Viewing a user + +The first page that a user will see after logging in will be their own +profile, so in order to speed development, we'll start by getting a +C page up. + +The only difference from a programming point of view between this action +and the default C action is that, if no user ID is given, then we +want to view "me", the current user. Remembering that the default view +action does nothing, our C action only needs to do +nothing plus ensure it has a user in the C slot, putting +C<$r-E{user}> in there if not: + + sub view :Exported { + my ($class, $r) = @_; + $r->{objects} = [ $r->{user} ] unless @{$r->{objects}||[]}; + } + +Maypole, unfortunately, is very good at making programming boring. The +downside of having to write very little code at all is that we now have +to spend most of our time writing nice HTML for the templates. + +XXX + +The next stage is viewing the user's photo. Assuming we've got the photo +stored in the database already (which is a reasonable assumption for the +moment since we don't have a way to upload a photo quite yet) then we +can use the a variation of the "Displaying pictures" hack from the +Requests chapter: + + sub view_picture :Exported { + my ($self, $r) = @_; + my $user = $r->{objects}->[0] || $r->{user}; + if ($r->{content_type} = $user->photo_type) { + $r->{output} = $user->photo; + } else { + # Read no-photo photo + $r->{content_type} = "image/png"; + $r->{output} = slurp_file("images/no-photo.png"); + } + } + +We begin by getting a user object, just like in the C action: either +the user whose ID was passed in on the URL, or the current user. Then +we check if a C has been set in this user's record. If so, +then we'll use that as the content type for this request, and the data +in the C attribute as the data to send out. The trick here is +that setting C<$r-E{output}> overrides the whole view class processing +and allows us to write the content out directly. + +In our template, we can now say + + + +and the appropriate user's mugshot will appear. + +However, if we're throwing big chunks of data around like C, it's +now worth optimizing the C class to ensure that only pertitent +data is fetched by default, and C and friends are only fetched on +demand. The "lazy population" section of C's man page +explains how to group the columns by usage so that we can optimize +fetches: + + Flox::User->columns(Primary => qw/id/); + Flox::User->columns(Essential => qw/status/); + Flox::User->columns(Helpful => qw/ first_name last_name email password/) + Flox::User->columns(Display => qw/ profile affiliation unistatus /); + Flox::User->columns(Photo => qw/ photo photo_type /); + +This means that the status and ID columns will always be retrieved when +we deal with a user; next, any one of the name, email or password +columns will cause that group of data to be retrieved; if we go on to +display more information about a user, we also load up the profile, +affiliation and university status; finally, if we're throwing around +photos, then we load in the photo type and photo data. + +These groupings are somewhat arbitrary, and there needs to be a lot of +profiling to determine the most efficient groupings of columns to load, +but they demonstrate one principle about working in Maypole: this is the +first time in dealing with Maypole that we've had to explicitly list the +columns of a table, but Maypole has so far Just Worked. There's a +difference, though, between Maypole just working and Maypole working +well, and if you want to optimize your application, then you need to +start putting in the code to do that. The beauty of Maypole is that you +can do as much or as little of such optimization as you want or need. + +So now we can view users and their photos. It's time to allow the users +to edit their profiles and upload a new photo. + +=head2 Editing users + +XXX Editing a profile + +I introduced Flox to a bunch of friends and told them to be as ruthless +as possible in finding bugs and trying to break it. And break it they +did; within an hour the screens were thoroughly messed up as users had +nasty HTML tags in their profiles, names, email addresses and so on. +This spawned another hack in the request cookbook: "Limiting data for +display". I changed the untaint columns to use C untainting, and +all was better: + + Flox::User->untaint_columns( + html => [qw/first_name last_name profile/], + printable => [qw/password/], + integer => [qw/affiliation unistatus /], + email => [qw/email/] + ); + +The next stage was the ability to upload a photo. We unleash the "Uploading +files" recipe, with an additional check to make sure the photo is of a +sensible size: + + use constant MAX_IMAGE_SIZE => 512 * 1024; + sub do_upload :Exported { + my ($class, $r) = @_; + my $user = $r->{user}; + my $upload = $r->{ar}->upload("picture"); + if ($upload) { + my $ct = $upload->info("Content-type"); + return $r->error("Unknown image file type $ct") + if $ct !~ m{image/(jpeg|gif|png)}; + return $r->error("File too big! Maximum size is ".MAX_IMAGE_SIZE) + if $upload->size > MAX_IMAGE_SIZE; + + my $fh = $upload->fh; + my $image = do { local $/; <$fh> }; + + use Image::Size; + my ($x, $y) = imgsize(\$image); + return $r->error("Image too big! ($x, $y) Maximum size is 350x350") + if $y > 350 or $x > 350; + $r->{user}->photo_type($ct); + $r->{user}->photo($image); + } + + $r->objects([ $user ]); + $r->{template} = "view"; + } + +Now we've gone as far as we want to go about user editing at the moment. +Let's have a look at the real meat of a social networking site: getting +other people involved, and registering connections between users. + +=head2 Invitations + +=head2 Friendship Connections + +=head2 diff --git a/doc/Model.pod b/doc/Model.pod index 1468de2..c5f5b18 100644 --- a/doc/Model.pod +++ b/doc/Model.pod @@ -4,6 +4,8 @@ =head2 Maypole::Model::CDBI +=head2 Extending a model class with actions + =head2 What Maypole wants from a model =head2 Building your own model class diff --git a/doc/Request.pod b/doc/Request.pod index 6af8278..80e4037 100644 --- a/doc/Request.pod +++ b/doc/Request.pod @@ -1,43 +1,89 @@ =head1 Maypole Request Hacking Cookbook +Hacks; design patterns; recipes: call it what you like, this chapter is a +developing collection of techniques which can be slotted in to Maypole +applications to solve common problems or make the development process easier. + +As Maypole developers, we don't necessarily know the "best practice" for +developing Maypole applications ourselves, in the same way that Larry Wall +didn't know all about the best Perl programming style as soon as he wrote +Perl. These techniques are what we're using at the moment, but they may +be refined, modularized, or rendered irrelevant over time. But they've +certainly saved us a bunch of hours work. + =head2 Frontend hacks +These hacks deal with changing the way Maypole relates to the outside world; +alternate front-ends to the Apache and CGI interfaces, or subclassing chunks +of the front-end modules to alter Maypole's behaviour in particular ways. + +=head3 Debugging with the command line + +You're seeing bizarre problems with Maypole output, and you want to test it in +some place outside of the whole Apache/mod_perl/HTTP/Internet/browser circus. + +B: Use the C module to go directly from a URL to +standard output, bypassing Apache and the network altogether. + +C is not a standalone front-end, but to allow you to debug your +applications without having to change the front-end they use, it temporarily +"borgs" an application. If you run it from the command line, you're expected +to use it like so: + + perl -MMaypole::CLI=Application -e1 'http://your.server/path/table/action' + +For example: + + perl -MMaypole::CLI=BeerDB -e1 'http://localhost/beerdb/beer/view/1?o2=desc' + +You can also use the C module programatically to create +test suites for your application. See the Maypole tests themselves or +the documentation to C for examples of this. + =head3 Changing how params are parsed =head3 REST -=head2 Authentication hacks +=head2 Content display hacks -=head2 Creating and editing hacks +These hacks deal primarily with the presentation of data to the user, +modifying the C template or changing the way that the results of +particular actions are displayed. -=head3 Getting data from external sources +=head3 Template Switcheroo -You want to supplement the data received from a form with additional -data from another source. +An action doesn't have any data of its own to display, but needs to display +B. -B: Munge the contents of C< $r-Eparams > before jumping -to the original C routine. For instance, in this method, -we use a C object to fill in some fields of a database row based -on an ISBN: +B: This is an B common hack. You've just issued an +action like C, which updates the database. You don't want +to display a page that says "Record updated" or similar. Lesser +application servers would issue a redirect to have the browser request +C> instead, but we can actually modify the Maypole +request on the fly and, after doing the update, pretend that we were +going to C> all along. We do this by setting the +objects in the C slot and changing the C