google web toolkit as modern ajax framework for - Theseus

56 Pages·2012·0.79 MB·English

GOOGLE WEB TOOLKIT AS MODERN AJAX
FRAMEWORK FOR DEVELOPMENT OF RIAS.

Grzegorz Nowak

Bachelor’s Thesis
April 2011

Degree Program in Information Technology
School of Technology
DESCRIPTION
Author(s) Type of publication Date
NOWAK, Grzegorz Bachelor´s Thesis 13.05.2011
Pages Language
54 English
Confidential Permission for web publication
( ) Until (X)
Title
GOOGLE WEB TOOLKIT AS MODERN AJAX FRAMEWORK FOR DEVELOPMENT OF RIAS.

Degree Program
Information Technology (Data Network Technology)

Tutor(s)
Peltomäki, Juha

Assigned by
Bitcomp Oy

Abstract
Google Web Toolkit is an Ajax based framework for development of interactive web pages – Rich Internet
Applications. With additional libraries that add support for handling geographical data it allowed creating a
user-friendly experience comparable to most popular web applications in the net.

The main objective was to develop an application which allows publishing of spatial data over the web using
modern technologies. The most important part was the map widget which should support full user interaction
with presented data.

The project’s implementation was split into several phases. Analysis of requirements and architecture gave
detailed knowledge about the project itself and the tools needed. Prepared development environment and
project’s structure was a signal that the implementation of actual features might get started. Displaying data
on the map was the subsequent step after implementing the application’s business logic.

The result of the process was a fully functional application, entirely compliant with placed requirements.
Additionally, the documentation of the project was created to allow faster adaptation of the application to
future needs.

Developed solution offers great functionality in its category. The products offered by competitive companies
were comparable or worse than the presented application.

Keywords
Google Web Toolkit, Ajax, RIA, Smart Client, GIS, GeoServer, GeoTools, OpenLayers, Maven

Miscellaneous
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CONTENTS
1 INTRODUCTION ........................................................................................................................ 6
2 THEORETICAL BASIS ................................................................................................................. 7
2.1 Ajax ..................................................................................................................................... 7
2.1.1 General Information .................................................................................................. 7
2.1.2 Evaluation .................................................................................................................. 7
2.2 Google Web Toolkit .......................................................................................................... 8
2.2.1 Compatibility with Java and libraries ....................................................................... 9
2.2.2 JavaScript Native Interfaces ................................................................................... 10
2.2.3 Modularity ............................................................................................................... 10
2.2.4 Deferred binding ..................................................................................................... 11
2.2.5 Threads and timers ................................................................................................. 11
2.2.6 GWT-RPC .................................................................................................................. 11
2.2.7 Logging ..................................................................................................................... 13
2.2.8 Localization .............................................................................................................. 13
2.2.9 History support ........................................................................................................ 14
2.2.10 Patterns .................................................................................................................... 14
2.2.11 Testing ...................................................................................................................... 16
2.2.12 Launching and compilation details ........................................................................ 17
2.2.13 Smart GWT ............................................................................................................... 18
2.2.14 Evaluation ................................................................................................................ 19
2.3 Geographic Information System .................................................................................... 19
2.3.1 Open Geospatial Consortium ................................................................................. 19
2.3.2 Web Feature Service ............................................................................................... 19
2

2.3.3 Web Map Service .................................................................................................... 20
2.3.4 GeoServer ................................................................................................................ 20
2.3.5 GeoTools .................................................................................................................. 20
2.3.6 GWT OpenLayers ..................................................................................................... 21
2.4 Development environment ............................................................................................ 21
2.4.1 Integrated development environment .................................................................. 21
2.4.2 Source configuration management ....................................................................... 22
2.4.3 Source quality management................................................................................... 23
2.4.4 Continuous integration ........................................................................................... 24
2.4.5 Component repository management .................................................................... 24
2.5 Maven .............................................................................................................................. 24
2.5.1 Project Object Model .............................................................................................. 25
2.5.2 Build lifecycle ........................................................................................................... 27
2.5.3 Profiles ..................................................................................................................... 28
2.5.4 Archetype ................................................................................................................. 28
2.5.5 Other plug-ins .......................................................................................................... 28
3 PRACTICAL IMPLEMENTATION ............................................................................................. 30
3.1 Bitcomp Oy ...................................................................................................................... 30
3.2 Analysis of the requirements ......................................................................................... 30
3.3 Analysis of the architecture ........................................................................................... 32
3.4 Workspace setup ............................................................................................................ 34
3.5 Project structure ............................................................................................................. 35
3.6 Application layout ........................................................................................................... 40
3.7 Address search ................................................................................................................ 42
3.8 Search .............................................................................................................................. 44
3

3.9 Map .................................................................................................................................. 45
3.10 Documentation ................................................................................................................ 50
4 RESULTS .................................................................................................................................. 51
5 DISCUSSION ............................................................................................................................ 52
REFERENCES .................................................................................................................................... 53

FIGURES
FIGURE 1 GWT-RPC class diagram (GWT Dev Guide, 2011.) ....................................................... 12
FIGURE 2 Model View Controller diagram ................................................................................... 15
FIGURE 3 Model View Presenter diagram .................................................................................... 16
FIGURE 4 Maven POM structure (O’Brien T, Casey J & Fox B, 2010.) ........................................ 25
FIGURE 5 Maven POM inheritance diagram (O’Brien T, Casey J & Fox B, 2010.) ...................... 26
FIGURE 6 Use case diagram ........................................................................................................... 32
FIGURE 7 Architecture diagram..................................................................................................... 33
FIGURE 8 Browser popularity diagram (StatCounter, 2011) ....................................................... 35
FIGURE 9 Skeleton of the application layout................................................................................ 40
FIGURE 10 Final look of the application. ...................................................................................... 51

TABLES
TABLE 1 Maven default lifecycle for WAR and JAR packages ..................................................... 27
TABLE 2 Functional requirements ................................................................................................. 31
TABLE 3 Non functional requirements ......................................................................................... 31
4

TERMS
AJAX – Asynchronous JavaScript and XML
API – Application Programming Interface
CI – Continuous Integration
CRS – Coordinate Reference System
CRUD – Create Read Update Delete
CSS – Cascading Style Sheets
DTO – Data Transfer Object
ERM – Electronic Resource Management
GET – type of HTTP request
GIS – Geographic Information System
GML – Geography Markup Language
GWT – Google Web Toolkit
HTML – Hypertext Markup Language
HTTP – Hypertext Transfer Protocol
IDE – Integrated Development Environment
JAXB – Java Architecture for XML Binding
JNI – Java Native Interfaces
JSNI – JavaScript Native Interfaces
JSON – JavaScript Object Notation
JVM – Java Virtual Machine
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MVC – Model View Controller
MVP – Model View Presenter
OSM – Open Street Map
PHP – PHP: Hypertext Preprocessor
POM – Project Object Model
RIA – Rich Internet Application
RMI – Remote Method Invocation
RPC – Remote Procedure Call
SCM – Source Code Management
SDK – Software Development Kit
TDD – Test Driven Development
URL – Uniform Resource Locator
WFS – Web Feature Service
WMS – Web Map Service
XLS – XML for Location Services.
XML – Extensible Markup Language
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1 INTRODUCTION
Rich Internet Application as the name suggests is a type of interactive and dynamic web page
the functionality of which is usually comparable with features provided by standalone
desktop applications. There are different technologies allowing development of such
including Flash, Java, Silver Light and Ajax based frameworks. Ajax is the only methodology
from those mentioned above, which does not require any additional plug-ins in most of
modern browsers. Unfortunately developing applications for different browsers using Ajax is
a laborious process. The main reasons for such situation are the differences in the
implementations of technologies used in Ajax across browsers. To allow development
without worrying about those differences, JavaScript frameworks were created: Prototype,
jQuery, Dojo, Google Web Toolkit and many more.
The main objective of this thesis is to report development of RIA for publishing of spatial data
over the web. The application allows visitors to view published data on the map, and also
search it using provided tools. The overall usability should be as high as possible to support
visitors with different levels of technical knowledge
The project is implemented using Google Web Toolkit and managed by Maven. The user
interface is based on Smart GWT widget library, except the map component which is part of
OpenLayers library. Spatial data is provided using WFS hosted by GeoServer. During the
development process several tools were used to improve the quality of final result.
This thesis was created during the internship in Bitcomp Oy. The company creates a suite of
tools to manage resources electronically. The whole process of forest management has been
completely covered including mobile access. When one of the clients reported a need for an
application which allows publishing of already stored data, the company decided to develop
such solution using the technologies mentioned above.
The thesis was developed during a double degree program, and because of that, it was
evaluated in two independent universities: JAMK University of Applied Sciences and Cracow
University of Technology.
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2 THEORETICAL BASIS
2.1 Ajax
2.1.1 General Information
Ajax is a set of technologies used to create dynamic web pages. It consists of following:
 Asynchronous calls using XMLHttpRequest object
 XML for data transfer
 HTML and CSS for displaying the data
 DOM for modifying the structure of the document
 JavaScript that ties together all above technologies. (Moore D, Budd R & Benson E,
2007, 35-36)
The XMLHttpRequest is a special object that allows downloading content in the background
without forcing the user to wait or reload the page. XML is not the only possible carrier of
information. It is possible to use others, for example plain text or JSON which in JavaScript
environment is very handy. The JavaScript is not the only option but it is also widely
integrated into many popular web browsers in contrast to Flash or Java.
2.1.2 Evaluation
There are many advantages and drawbacks of using Ajax.
The advantages with Ajax are listed below:
 Only changing content is transferred so the data transfer and time needed is lower
than during full page reload
 User has the impression of an interactive web page – an application in which
functionalities are sometimes same or even richer than standalone applications
 Most of the technologies used in Ajax are open source and easily accessible for
developers.
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The disadvantages are listed as follows:
 The browser history is unable to store a dynamically created webpage
 Bookmarking of such application is also limited to the state in which it starts
 In case of slow and unreliable internet connection the responsiveness of the
application might be really low in comparison to a regular web page which will load
longer but its runtime will not be interrupted
 To allow web crawlers to index the content there should be a way to access it without
using Ajax
 Some web browsers might not support JavaScript or it may be turned off. Even in
such case the user should be able to view the content
 Too many server requests with XMLHttpRequest may put the servers under bigger
stress.
As it is clearly visible above, the advantages of Ajax are totally obscured by disadvantages.
One of the reasons why so many frameworks based on Ajax were created was to overcome
these drawbacks easily and to make the development faster.
2.2 Google Web Toolkit
GWT is a powerful Ajax framework that gives the ability to develop RIAs without worrying
about the drawbacks of Ajax. The application is developed in Java language, but it is also
possible to add fragments of code in JavaScript. The source might be launched in two ways:
 Development mode – Java classes are being compiled to byte code and then run on
custom JVM which redirects the output into the browser (GWT Developer Plug-in is
required)
 Production mode – GWT Compiler translates the Java source into highly optimized
(adjustable) and obfuscated (optional) JavaScript, tailored for different browsers and
languages.
The development mode is a very important part since it enables the developers to use
standard Java tools to debug the code.