L19 Application Architecture

transcript

HÖNNUN OG SMÍÐI HUGBÚNAÐAR 2015L19 Application Architecture

Agenda▪ Architecture Considerations▪ Architecture Decisions▪ Play Framework Exercise

Architecture Considerations

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

Domain Data Source

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

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

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

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

Different user motivations

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

App vs. Web

Don’t ask a developer which is better - it’s a management decision

MOBILE WEB MOBILE APPUsing a mobile web browser

Downloaded, runson 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/

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

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

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

Editablecontent

Staticcontent

Dynamiccontent

Staticcontent

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

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

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 Layercontrollers

Lightweight Container

DomainLayer

Data SourceLayer DB

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

Data Source Layer▪ Domain Model uses gateway

Domain Layer

Data Source Layer

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

The Big Picture

Client

DomainData

Source

RESTWeb

Server DB

The Big Picture with Services

Client

DomainData

Source

RESTWeb

Server DB

DomainData

SourceREST

Web Server DB

Frameworks LibrariesShared Objects

SERVICE

Architecture Decisions

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

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

Domain Layer▪ Transaction Script▪ Domain Model▪ Table Module

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

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

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

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

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

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

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

Domain Layer

The Big Picture

Presentation Layer

Service Layer

Data Source

DomainDB

Wehavearelativelysimpledomainlogicthatmapsnicelytothedataschema,andwehavegoodtoolsforRecordSethandling.WhatDomainLayerpatternwouldmakesense?

A) ServiceLayer B) DomainModel C) TransactionScript D) TableModule

Play Framework Exercise

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

Overview

Controller

Service Layer

Domain Model

Table Data Gateway

routes ApplicationConext.xml

SignupAs a user, I want to be able to sign up

RegistrationFields: name, username, password, email

Validation: all fields are requiredusername must be at least 4 characterspassword must be confirmed (typed in twice)

Play setup

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

The Database▪ Table users

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), )

Application.java

package controllers;

import play.*; import play.mvc.*;

import views.html.*;

public class Application extends Controller { public Result index() { return ok(index.render()); } }

index▪ View is views/index.scala.html

▪ Compiled: views/html/index

@main("RuNews") { <h2>Registration</h2> <p> Here you can sign up: </p> <p> <a class="btn" href="@routes.SignupController.blank">Sign up</a> </p>}

Routing▪ conf/routes contains the routing information

# Routes# This file defines all application routes (Higher priority routes first) # ~~~~# Home pageGET / controllers.Application.index() # Sign UpGET /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)

RuNews Example▪ User

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; } ...

RuNews Example▪ UserService is a Service Layer interface

▪ UserServiceData contains the implementation

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); }

Adding Domain and Data Layers▪ Domain Layer– Service Layer in service– Domain Model (very simple) in

domain▪ Data Source Layer– Table Data Gateway

Adding Domain and Data Layers▪ app.xml added to conf– data.xml not used

<?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>

Adding Domain and Data Layers

▪ Table Data Gateway injected into service

public class UserServiceData implements UserService { RuDataAccessFactory factory; UserDataGateway userDataGateway;

public UserServiceData() { }

public void setUserDataGateway(UserDataGateway UserDataGateway) { this.userDataGateway = UserDataGateway; }

RuNews Example▪ SignupController is a Controller

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)); }

RuNews Example▪ SignupController is a Controller

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)); }}

RuNews Example▪ signup.scala.html is the view

@(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." )

RuNews Example▪ summary.scala.html displayes the user

@(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> }

RuNews Example▪ index.scala.html is default “/“ view

▪ All views use @main with title as parameter

@main("RuNews") { <h2>Registration</h2> <p> Here you can sign up: </p> <p> <a class="btn" href="@routes.SignupController.blank">Sign up</a> </p>}

RuNews Example▪ main.scala.html is layout template

@(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>

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>

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>

L19 Application Architecture

Software