The Users Resource in Java

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The Users Resource
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View (indexhtmlerb)
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@users
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Controller (users_controllerrb) 5 2 index
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Userall 3
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Model (userrb)
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Table 22 RESTful routes provided by the Users resource in Listing 22 HTTP request
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GET GET GET POST GET PUT DELETE
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/users /users/1 /users/new /users /users/1/edit /users/1 /users/1
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Action
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index show new create edit update destroy
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Purpose page to list all users page to show user with id 1 page to make a new user create a new user page to edit user with id 1 update user with id 1 delete user with id 1
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2: A Demo App
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architectural style for developing distributed, networked systems and software applications such as the World Wide Web and web applications Although REST theory is rather abstract, in the context of Rails applications REST means that most application components (such as users and microposts) are modeled as resources that can be created, read, updated, and deleted---operations that correspond both to the CRUD operations of relational databases and the four fundamental HTTP request methods: POST, GET, PUT, and DELETE (We ll learn more about HTTP requests in Section 322 and especially Box 31) The RESTful style of development helps you as a Rails application developer make choices about which controllers and actions to write: you simply structure the application using resources that get created, read, updated, and deleted In the case of users and microposts, this process is straightforward, since they are naturally resources in their own right In 12, we ll see an example where REST principles allow us to model a subtler problem, following users , in a natural and convenient way
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To examine the relationship between the Users controller and the User model, let s focus on a simplified version of the index action, shown in Listing 249
Listing 24 The simplified user index action for the demo application
app/controllers/users_controllerrb
class UsersController < ApplicationController def index @users = Userall end end
This index action has the line @users = Userall (Step 3), which asks the User model to retrieve a list of all the users from the database (Step 4), and then places them in the variable @users (pronounced at-users ) (Step 5) The User model itself appears in Listing 25; although it is rather plain, it comes equipped with a large amount of functionality because of inheritance (Section 234 and Section 44) In particular, by using the Rails library called Active Record, the code in Listing 25 arranges for Userall to return all the users
9 The scaffold code is ugly and confusing, so I ve suppressed it
The Users Resource
Listing 25 The User model for the demo application
app/models/userrb
class User < ActiveRecord::Base end
Once the @users variable is defined, the controller calls the view (Step 6), shown in Listing 26 Variables that start with the @ sign, called instance variables, are automatically available in the view; in this case, the indexhtmlerb view in Listing 26 iterates through the @users list and outputs a line of HTML for each one10
Listing 26 The view for the user index (You are not expected to understand it now)
app/views/users/indexhtmlerb
<h1>Listing users</h1> <table> <tr> <th>Name</th> <th>Email</th> <th></th> <th></th> <th></th> </tr> <% @userseach do |user| %> <tr> <td><%= username %></td> <td><%= useremail %></td> <td><%= link_to 'Show', user %></td> <td><%= link_to 'Edit', edit_user_path(user) %></td> <td><%= link_to 'Destroy', user, :confirm => 'Are you sure ', :method => :delete %></td> </tr> <% end %> </table> <br /> <%= link_to 'New User', new_user_path %>
10 Remember, you aren t supposed to understand this code right now It is shown only for purposes of illustration
2: A Demo App
The view converts its contents to HTML (Step 7), which is then returned by the controller to the browser for display (Step 8)
223 Weaknesses of This Users Resource
Though good for getting a general overview of Rails, the scaffold Users resource suffers from a number of severe weaknesses
No data validations Our User model accepts data such as blank names and invalid
email addresses without complaint
No authentication We have no notion signing in or out, and no way to prevent
any user from performing any operation
No tests This isn t technically true the scaffolding includes rudimentary tests
but the generated tests are ugly and inflexible, and they don t test for data validation, authentication, or any other custom requirements
No layout There is no consistent site styling or navigation No real understanding If you understand the scaffold code, you probably shouldn t
be reading this book
23 The Microposts Resource
Having generated and explored the Users resource, we turn now to the associated Microposts resource Throughout this section, I recommend comparing the elements of the Microposts resource with the analogous user elements from Section 22; you should see that the two resources parallel each other in many ways The RESTful structure of Rails applications is best absorbed by this sort of repetition of form; indeed, seeing the parallel structure of Users and Microposts even at this early stage is one of the prime motivations for this chapter (As we ll see, writing applications more robust than the toy example in this chapter takes considerable effort we won t see the Microposts resource again until 11 and I didn t want to defer its first appearance quite that far)