Data Visualization in Ext Js 3.4
White Paper
Data Visualization in Ext Js 3.4
Ext JS is a client-side javaScript framework for rapid development of cross-browser interactive Web applications using techniques such as Ajax, DHTML and
DOM scripting. In 2006, Jack Slocum began working on a set of extension utilities for the Yahoo! User Interface
(YUI) library. These extensions were later organized into an independent library of codes, named as "yui-ext".
In the same year, Jack released its final version, whose name was changed to Ext.
Ext JS framework is a highly robust, scalable and
Open Source javaScript framework. It provides many utility functions, which help in DOM traversal and
DOM manipulation along with stable and crossbrowser User Interface (UI) components. Some of the components are like grids, charts, trees, forms, drag and drop and so on.
About the Author
Kali Prasanna Mishra
The author, Kali Prasanna Mishra, is Systems Engineer, working with
TCS. He has more than three years of experience in developing and managing Rich Internet Application (RIA) for various domains.
He also has the expertise in User Experience space. His competency includes RIA technologies like Ext JS, jQuery, Flex; etc. He has worked on different RIA Web applications and has helped in making the websites Browser Compatible and Usable.
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Table of Contents
1. Introduction
2. Setting up Ext JS
3. Problem statement/key challenges
4. Defining Data Source for Charts
5. Creating Html Pages for Displaying Charts
6. Creating Line Chart
7. Creating Column Chart
8. Creating Bar Chart
9. Creating a Pie Chart
10. Customizing Charts
I.
Creating Multi Series Chart
II. Displaying the Legend for a Chart
III. Customizing the Tool Tip for Charts
11. Conclusion
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Introduction
Ext JS framework is a highly robust, scalable and Open Source javaScript framework. It provides many utility functions, which help in DOM traversal and DOM manipulation along with stable and cross-browser User
Interface (UI) components. Some of the components are like grids, charts, trees, forms, drag and drop and so on.
Data visualization in Ext JS includes the chart package. The chart package contains bar chart, column chart, line chart, pie chart, etc. This paper explores the customization possible with the charts. Paper also explains how to connect to a server side component like a servlet/php file/asp.net and some of the Ext JS concepts like
Store, Proxy API, Reader, Writer, etc.
Setting up Ext JS
The following is a step-by-step procedure to set up the Ext JS.
To set up Ext JS:
1. Download Ext JS 3.4.0 from the link, “http://www.sencha.com/”.
2. Unzip its content into your Integrated Development Environment (IDE).
3. Unzipped content contains several folders and files, out of which ext-all.css, ext-base.js and ext-all.js are important for development perspective. Refer them in the <head> part of the page.
4. Include “charts.swf” file to load the chart controls on the Web page as mentioned here. The .swf file is present in the resources directory of the Ext 3.x versions.
Ext.chart.Chart.CHART_URL='../ext-3.4.0/resources/charts.swf';
All the examples are created and tested on the following platforms: n n
OS : Windows XP
IDE : Eclipse 3.6
n n n n
Server : tomcat 6.0
Database : MySQL 5.0
Ext JS versions : 3.4
Project type: Java dynamic Web application with servlet as server-side component
Problem statement/key challenges
In modern Rich Internet Applications (RIA) the focus has shifted from traditional tabular display to classy widgets. Web applications are now consisting of modular units capable of executing functionalities, called widgets. Widgets not only change the UI but also make the applications more modular. Widgets display data to user in a better manner by using different data layout components like grid, charts, tree, forms, and so on.
In widgets based RIA, the focus is on data visualization and arrangements of widgets on the screen. On the other hand widgets are created keeping an eye on better user experience. So the search is now the technologies which can provide ways of creating better widgets in small span of time. On RIA space, many of the Open Source javaScript frameworks have evolved, tested and proven to be stable across platforms.
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Ext JS provides many user friendly widgets. Widgets are also easy to develop and easy to integrate with existing applications. In this white paper, we will explore the data visualization capabilities of Ext JS which will help other developers in rapidly creating amazing widgets.
Ext JS has the support for different types of charts. These charting components follow a certain method to get data and to send data across the server. So defining a data source for charts is an important aspect in Ext JS.
Defining Data Source for Charts
Ext JS supports different data sources like XML, JSON and ARRAY. To understand the process, we can create a data source (of type xml) and use the same data source in all the subsequent cases. The xml to be used gets generated from the servlet. However, at the same time, Ext JS can connect to different server-side components like .php or .asp files for generating the data. A process to create a store which has a proxy and reader is as follows:
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The servlet ForLineChart gives response XML as follows.
Thus the data source is ready to be used by Ext JS widgets.
Creating HTML Pages for Displaying Charts
Ext JS widgets can be created for Java based applications or MS. Net based applications. Widgets are generally placed over a user interface. Let us consider that to be a simple HTML page. Ext JS widgets follow a certain rendering mechanism by which they get attached to a particular place on the HTML. So let us create place holders for the charts to be created soon.
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Creating Line Chart
Ext JS is developed with oops concepts and 'new' keyword is used for creating objects. Ext JS provides short hand notations for complete package names as given here.
xtype: 'linechart', // for creating a line chart whose package structure is Ext.chart.LineChart
Figure 1: Line chart with single series and default styling
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Creating Column Chart
Ext JS provides support for 2 types of column charts, simple column charts and stacked column charts. Ext JS provides xtype for almost all of its components.
Xtype for both of them is as follows.
xtype: 'columnchart', // for creating a column chart,
xtype: stackedcolumnchart // for creating stacked column chart
Figure 2: Column chart with single series and default styling
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Creating Bar Chart
Ext JS provides support for 2 types of bar charts. They are simple bar chart and stacked bar chart. Ext JS provides xtype for all most all of its components.
Xtype for both of them as follows: xtype: 'barchart', // for creating a bar chart, xtype: 'stackedbarchart' // for creating stacked bar chart
Figure 3: Bar chart with single series and default styling
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Creating a Pie Chart
Only a single data field can be shown at a time in Pie chart. Available data fields break up into 360 degree. Tool tip shows % of volume consumed by the each data field.
Xtype of type ‘piechart’ creates a Pie chart.
Figure 4: Pie chart with default styling
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Customizing Charts
We can customize a chart in Ext JS by using config objects. Config objects are nothing but the name and value pairs. A single attribute may contain an array of values as its key value. The customizing properties are same for all the chart types. Let us, therefore, consider a Line chart as shown in Figure 1 for demonstrating the customizing capabilities of Ext JS.
I. Creating Multi Series Chart
So far we have created single series charts. Now let us see how to create a multi series chart. Each series represents a unique set of data like profit across months, loss across months, and so on. The following code snippets are the add-ons for the already discussed charts and are not to be used as standalone items.
Figure 5: Multiseries line chart
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II. Displaying the Legend for a Chart
The legend is displayed using the 'extraStyle' property of the chart components as mentioned below.
Legend displays more textual information alongside of the charts.
Figure 6: Multiseries line chart with legend
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III. Customizing the Tool Tip for Charts
Ext JS provides default tooltip, which doesn’t fit to all situations. So there is a quest for changing the default tooltip. This can be achieved by 'tipRenderer' property is used to create custom tooltip for the charts as mentioned below:
Figure 7: Multiseries line chart with custom tooltip
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Conclusion
Ext JS 3.4 is an Open Source javaScript framework. These chart components are robust and easy to customize and are supported by all platforms and browsers. As discussed above, these chart components are customizable and easy to connect to server side components. So we can summarize its advantages as follows: n n
Is easy to customize with the help of attributes
Supports all OS platforms n n n
Does not need any proprietary tool to develop the Ext JS based component
Supports a wide range of data sources like XML, JSON and Array
Supports static as well as dynamic data.
References
[1] http://docs.sencha.com/ext-js/3-4/
[2] http://w3techs.com/technologies/details/js-extjs/all/all
[3] http://en.wikipedia.org/wiki/Comparison_of_JavaScript_frameworks
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Contact
For more information about TCS’ consulting services, contact at ntdg.ux@tcs.com
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