Three key points about the document: 1. It discusses architecture considerations for building applications, including separating an application into presentation, domain, and data source layers. 2. It examines different patterns that can be used in the domain and data source layers, such as transaction script, domain model, table module, and different gateway patterns. 3. It provides an example of designing a news application called RuNews that demonstrates some of these patterns, including a domain model, table data gateway, and service layer.

1. HÖNNUN OG SMÍÐI HUGBÚNAÐAR 2015
L19 Application Architecture

2. Agenda
▪ Architecture Considerations
▪ Architecture Decisions
▪ Play Framework Exercise

3. Architecture Considerations

4. Three Layers
▪ Presentation Layer for the User Interface
▪ Domain Layer for the domain logic
▪ Data Source Layer for the data access
– Separation of concern
Client
Client
Domain Data Source

5. Presentation Layer
▪ Consideration
– Separating the Presentation Logic from the Domain Logic
– Simple vs. Rich user interface
– Should content be editable frequently
▪ Content Management System
– View templates with HTML and JS

6. User Interfaces
▪ Clear separation of concerns is important
– Define the Presentation Logic
– Design the domain layer so the presentation can get the information
needed
– Semantics – or the meaning of things is important
– Presentation logic must avoid making assumptions on the domain –
the semantics should be a part of the domain
• Use Data Transfer Objects to store semantics
Presentation Semantics Domain

7. Client Types
▪ Native OS Applications
– Windows, iOS, Android, Linux
▪ Embedded
– Run inside Web Browsers
– Flash, Java Applets
▪ Interactive Web Applications
– HTML with JavaScript
▪ HTML Presentation in Browsers
– Simple HTML

8. Client Types
▪ Mobile is not a client type
– It’s just smaller screen
– Which 60% people hold vertically
▪ People have their phones with them all the time
▪ Check their phone about 110 times per day

10. Different user motivations

11. Responsive Web Design
▪ Web pages that automatically adjust to the screen size
– Should be the default design
▪ Problems with RWD
– Does not deal with context
– What would a persons be
looking for when using
a mobile phone?
– Excuse to avoid apps, when app might be a better choice

12. App vs. Web
Don’t ask a developer which is better - it’s a management decision

13. MOBILE WEB MOBILE APP
Using a mobile
web browser
Downloaded, runs
on native hardware
PROS
Content is indexable
Device independent (almost)
Easier/Faster development & update
Easier to measure
CONS
Connection Dependence
Limited hardware integration
Bandwidth & browser limited UX
PROS
Connection independence
Better hardware integration
Better graphic performance & UX
CONS
Content is not web indexable
Device dependence
More expensive development & update
More complex to measure
Source: moz.com/blog/

14. Content Delivery
▪ Native, Embedded and Interactive Web Apps
– Require HTTP API call for dynamic content
– For example SOAP, REST with Json or XML
▪ HTML Presentation in Browsers
– Server side generated

15. Content Type
▪ Static Content such as graphic assets, doesn’t change frequently
▪ Editable Content such as text, layout, mashed-up content, editable by content
owners, frequently
▪ Dynamic Content stored in database and manipulated by the domain logic

16. Content Management Systems
▪ Content is separated form the Enterprise system
– Managed by CMS software with its own database
– HTTP API calls for dynamic content from the enterprise system
CLIENT
Web Browser
HTML
JavaScript CMS
Enterprise
Application
HTTP/REST/Json
OPERATOR
Editable
content
Static
content
Dynamic
content
Static
content

17. Domain Layer
▪ Where is the domain logic?
– Application Servers
– Lightweight Containers

18. Application Servers
▪ Domain Components are deployed on Application Servers
– Distributed Multi-tiered Applications
– Example:
• Web Servers, EJB Servers

19. Lightweight Containers
▪ Assemble components from different projects into a cohesive
application
– Wiring is done with “Inversion of Control” - config
– Provide life-cycle management of objects
– Provide context
Web Browser
Native App
Web Server
Web Layer
controllers
view
Lightweight Container
Domain
Layer
Data Source
Layer
DB

20. Data Source Layer
▪ How to create the mapping from the domain to the Data Source Layer
– Gateways with no domain logic
– Records managed with some domain logic
– Data Mappers

21. Data Source Layer
▪ Domain Model uses gateway
Domain
Layer
Data
Source
Layer

22. Object Relational Mapping (ORM)
▪ Use a mapping layer to map between objects and tables
– Mapping a data representation from an object model to a relational
data model with a SQL-based schema
▪ Mapping requires
metadata
– XML
▪ Authoring and maintaining
metadata is less work than
maintaining SQL code

23. The Big Picture
Client
Domain
Data
Source
CMS
REST
Web
Server DB

24. The Big Picture with Services
Client
Domain
Data
Source
CMS
REST
Web
Server DB
Domain
Data
Source
REST
Web
Server DB
Frameworks Libraries
Shared
Objects
SERVICE
SERVICE

25. Architecture Decisions

26. Advice is a dangerous gift
There are no right answers
“Use the advice to prod your thinking, but don’t use it as a
replacement for your thinking” — Martin Fowler

27. Three Layers
▪ Presentation Layer for the User Interface
▪ Domain Layer for the domain logic
▪ Data Source Layer for the data access
– What patterns to use?
Presentation
Layer
Domain Data Source

28. Domain Layer
▪ Transaction Script
▪ Domain Model
▪ Table Module

29. Domain Layer
▪ Transaction Script
– Procedural
– Encapsulates the logic of each transaction
– Works well for systems that are transactional in nature
▪ Drawbacks
– Does not handle complexity of logic
– Code duplications

30. Domain Layer
▪ Domain Model
– Works nicely for any type of domain logic
– Flexibility in creating an object oriented classes that use
abstractions and polymorphism
– Beautiful code
▪ Drawbacks
– Learning curve – understanding the model
– Requires skills
– Doesn’t always map easily to relational database

31. Domain Layer
▪ Table Module
– Works well for data driven applications
– Fits well with relational databases
– Requires Record Set functionality
▪ Drawbacks
– Structured around the database
– Needs tooling support, for example Record Set
– Can become dependent on the environment

32. Data Source Layer
▪ Data Source for Transaction Script
– Fits well to use the Gateway patterns
– Row Data Gateway or Table Data Gateway
– Depends on the applications
– If the transactions are dealing with each row per transactions, then
Row Data Gateway works
– If working with tables, Table Data Gateway works

33. Data Source Layer
▪ Data Source for Table Module
– Table Module requires good support from Record Set
– Table Data Gateway fits this well

34. Data Source Layer
▪ Data Source for Domain Model
– If the Domain Model is fairly simple, and maps the database, Active
Record works well
– If you want to provide abstraction the gateway patterns become
better choice, Row Data Gateway and Table Data Gateway
– If things get more complication and there is need to keep the model
independent from the data source, Data Mapper should be
considered

35. Model View Controller
▪ For all types MVC architectural patterns applies
▪ Web Frameworks are usually implemented using some sort of
Front Controller pattern
▪ Each request has an Action or a Controller
▪ Views are handle by Template View

36. Domain Layer
The Big Picture
Presentation
Layer
Service
Layer
Data Source
Domain
DB

37. We have a relatively simple domain logic that maps nicely to the
data schema, and we have good tools for Record Set handling.
What Domain Layer pattern would make sense?
A) Service Layer
B) Domain Model
C) Transaction Script
D) Table Module
QUIZ

38. Play Framework Exercise

39. Exercise
▪ Design Web Application RuNews
– Front page displays RSS news items
– Content read with ImportContentProcess
– User can sign up and login

40. Overview
Controller
View
Service Layer
Domain Model
Table Data
Gateway
routes ApplicationConext.xml
users

41. Signup
As a user, I want to be able to sign up
Registration
Fields: name, username, password, email
Validation:
all fields are required
username must be at least 4 characters
password must be confirmed (typed in twice)

43. Play setup
43
▪ Project is created: RuNews
– activator new RuNews
– Import in IntelliJ IDEA
▪ Structure
– controllers
– is.ru.honn.news
– views

44. The Database
▪ Table users
44
CREATE TABLE users
(
id int Identity (1, 1) primary key NOT NULL,
name varchar(128),
username varchar(128) unique,
password varchar(128),
email varchar(128),
)

45. Application.java
45
package controllers;
import play.*;
import play.mvc.*;
import views.html.*;
public class Application extends Controller
{
public Result index()
{
return ok(index.render());
}
}

46. index
▪ View is views/index.scala.html
▪ Compiled: views/html/index
46
@main("RuNews") {
<h2>Registration</h2>
<p>
Here you can sign up:
</p>
<p>
<a class="btn" href="@routes.SignupController.blank">Sign up</a>
</p>
}

47. Routing
▪ conf/routes contains the routing information
# Routes
# This file defines all application routes (Higher priority routes first)
# ~~~~
# Home page
GET / controllers.Application.index()
# Sign Up
GET /signup controllers.SignupController.blank()
POST /signup controllers.SignupController.submit()
GET /users/:username controllers.UserController.getUser(username: String)
GET /userinfo controllers.UserController.blank()
# Map static resources from the /public folder to the /assets URL path
GET /assets/*file controllers.Assets.versioned(path="/public", file: Asset)

48. RuNews Example
▪ User
48
public class User
{
protected int id;
protected String name;
protected String username;
protected String password;
protected String email;
public User()
{
}
public User(int id, String name, String username, String password,
String email)
{
this.id = id;
this.name = name;
this.username = username;
this.password = password;
this.email = email;
}
...

49. RuNews Example
▪ UserService is a Service Layer interface
▪ UserServiceData contains the implementation
49
public interface UserService
{
public int signup(User user);
public User login(String username, String password);
public User getUser(String username);
public void setUserDataGateway(UserDataGateway userDataGateway);
}

50. Adding Domain and Data Layers
▪ Domain Layer
– Service Layer in service
– Domain Model (very simple) in
domain
▪ Data Source Layer
– Table Data Gateway

51. Adding Domain and Data Layers
▪ app.xml added to conf
– data.xml not used
51
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://
www.springframework.org/schema/beans/spring-beans.xsd">
<bean id="userService" class="is.ru.honn.news.service.UserServiceData">
<property name="userDataGateway" ref="userDataGateway"/>
</bean>
<bean id="userDataGateway" class="is.ru.honn.news.data.UserData">
<property name="dataSource" ref="dataSource"/>
</bean>
<bean id="dataSource"
class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="net.sourceforge.jtds.jdbc.Driver"/>
<property name="url" value="jdbc:jtds:sqlserver://hrnem.ru.is:1433"/>
<property name="username" value=“###”/>
<property name="password" value=“###”/>
</bean>
</beans>

52. Adding Domain and Data Layers
▪ Table Data Gateway injected into service
52
public class UserServiceData implements UserService
{
RuDataAccessFactory factory;
UserDataGateway userDataGateway;
public UserServiceData()
{
}
public void setUserDataGateway(UserDataGateway UserDataGateway)
{
this.userDataGateway = UserDataGateway;
}

53. RuNews Example
▪ SignupController is a Controller
53
package controllers;
import ...
import play.mvc.*;
import play.data.*;
import views.html.signup;
import views.html.summary;
import static play.data.Form.form;
public class SignupController extends Controller
{
final static Form<UserRegistration> signupForm =
form(UserRegistration.class);
protected ApplicationContext ctx = new
FileSystemXmlApplicationContext("/conf/app.xml");
public Result blank()
{
return ok(signup.render(signupForm));
}

54. RuNews Example
▪ SignupController is a Controller
54
public Result submit()
{
Form<UserRegistration> filledForm = signupForm.bindFromRequest();
if (!"true".equals(filledForm.field("accept").value()))
{
filledForm.reject("accept", "You must accept the terms and conditions");
}
...
if (filledForm.hasErrors())
{
return badRequest(signup.render(filledForm));
}
else
{
UserRegistration created = filledForm.get();
UserService service = (UserService) ctx.getBean("userService");
service.signup(created);
return ok(summary.render(created));
}
}

55. RuNews Example
▪ signup.scala.html is the view
55
@(signupForm: Form[is.ru.honn.news.domain.UserRegistration])
@import helper._
@main("Signup", nav = "signup") {
@helper.form(action = routes.SignupController.submit) {
<fieldset>
<legend>Account informations</legend>
@inputText(
signupForm("name"),
'_label -> "Name",
'_help -> "Please enter your name.",
'_error -> signupForm.globalError
)
@inputText(
signupForm("username"),
'_label -> "Username",
'_help -> "Please choose a valid username.",
'_error -> signupForm.globalError
)
@inputText(
signupForm("email"), '_label -> "Email",
'_help -> "Enter a valid email address."
)

56. RuNews Example
▪ summary.scala.html displayes the user
56
@(user: is.ru.honn.news.domain.User)
@main("Account created!", nav = "signup") {
<h2>Your account:</h2>
<p>Name: @user.getName()</p>
<p>Username: @user.getUsername()</p>
<p>Email: @user.getEmail()</p>
}

57. RuNews Example
▪ index.scala.html is default “/“ view
▪ All views use @main with title as parameter
57
@main("RuNews") {
<h2>Registration</h2>
<p>
Here you can sign up:
</p>
<p>
<a class="btn" href="@routes.SignupController.blank">Sign up</a>
</p>
}

58. RuNews Example
▪ main.scala.html is layout template
58
@(title: String = "Welcome", nav: String = "")(content: Html)
<!DOCTYPE html>
<html>
<head>
<title>RuNews</title>
<link rel="stylesheet" media="screen"
href="@routes.Assets.versioned("stylesheets/bootstrap.css")">
<link rel="stylesheet" media="screen"
href="@routes.Assets.versioned("stylesheets/main.css")">
<link rel="shortcut icon" type="image/png"
href="@routes.Assets.versioned("images/favicon.png")">
</head>

59. RuNews Example
▪ main.scala.html is layout template
<body>
<nav class="navbar navbar-default">
<div class="container-fluid">
<div class="navbar-header">
<a class="navbar-brand" href="@routes.Application.index()">RuNews</a>
</div>
<div>
<ul class="nav navbar-nav">
<li class="@("active".when(nav == "signup"))">
<a href="@routes.SignupController.blank">Sign up</a>
</li>
<li class="@("active".when(nav == "details"))">
<a href="@routes.UserController.blank">User details</a>
</li>
</ul>
</div>
</div>
</nav>

60. RuNews Example
▪ main.scala.html is layout template
<div class="container">
<div class="content">
<div class="page-header">
<h1>@title</h1>
</div>
<div class="row">
<div class="span14">
@content
</div>
</div>
</div>
<footer>
<p>
<a href="http://www.playframework.org">www.playframework.org</a>
</p>
</footer>
</div>
</body>
</html>