Welcome!

Java IoT Authors: Sematext Blog, Elizabeth White, Liz McMillan, AppDynamics Blog, Akhil Sahai

Related Topics: Java IoT, Linux Containers, Open Source Cloud, Eclipse

Java IoT: Tutorial

Using Ext JS, Servlets, JSON, MySQL and Tomcat on Fedora

A simple how to

Java Developer Magazine on Ulitzer

These days the popularity of Ext JS (a JavaScript library) is gaining momentum. One of the most popular widgets within Ext JS is the DataGrid. The reason - displaying data from a database is one of the most common tasks of a web application. "Out of the box" the DataGrid has functionality (for instance, ascending or descending sorting and reordering of columns by dragging it) that otherwise would require some effort from developers. Another attractive feature of the DataGrid is that it can use JSON (JavaScript Object Notation), which allows you to reduce traffic in comparison with full Swing HTML or XML formatting on the server.

Examples from Ext JS site [1] and Ext JS books such as Learning Ext JS.Packt Publishing [2] are focused on PHP in conjunction with Ext JS.

However, what if your organization already uses servlets for web applications?

Googling the problem will lead to a number of "spotted" solutions in which key details are often missed. Besides, there is no "out of the box" JSON support in Java. Sure, you can do it manually but why reinvent the wheel?

This article will show you how to build a servlet-based web application with Ext JS from scratch, and will save you a lot of time on configuration issues that are usually hard to fix.

Example: Phone Book
The following describes how a phone book will be used within this article as it is usually easy to learn by example.

Suppose you need to create a web application to read a phone book for your organization.

As your clients and/or customers can be located all over the world, you need to have a "country" column within a database table in which the phone book is stored. Also suppose it's required to have a First Name, Last Name, Middle Name, Phone Number, Type of phone (home, office, etc.), Description (in here some useful information about a phone can be placed). Foreign names and phones (as dialed from the U.S.) can be long, so it's reasonable to store said information in lengthy enough fields.

For production, the possible length of fields should be researched carefully, but for our example let's assume it will be 250 characters. Of course, you will be able to easily change it if necessary. All names, companies and phones used in this example are entirely fictional. Any possible coincident with reality is by accident only. Data for the example will be stored in a table called phone1 of the MySQL phonebook database.

MySQL and Fedora
MySQL is a popular free open source database for Internet applications. At the time of writing the possible future of MySQL within Oracle was widely discussed (please see for example [3]). However, consider a big installation base and the fact that MySQL packages can be found for most Linux distributions, it will be safe to assume that MySQL will be used at least in the short term.

As an example of Linux, the popular Fedora distribution will be used within the article. With minimal effort, results can be reproduced in other distributions such as Ubuntu.

Configuration in which methods from this article were developed includes a virtual machine with Fedora on a Windows host. Please see my articles [4, 5] on how to use it effectively.

The installation procedure for MySQL on Fedora with yum is described in [6]. If you don't want to start MySQL each time you start Fedora, you may want to create a launcher with the following command:

service mysqld start

and place it, for instance, on your GNOME desktop.

Another useful script given below will allow you to easily start the mysql command within your terminal window

mysql -u <yourUserName> -p<yourPassword>

in the above script <yourUserName> and <yourPassword> should be substituted with your user name and password, respectively. Please note that there is a blank between -u and <yourUserName> but there is no blank between -p and <yourPassword>. You may want to place the script under some directory from your path. If you want a GUI tool for MySQL, it is recommended that you use Oracle SQL developer [7] rather than native MySQL GUI tools. The reason is the flexibility of Oracle SQL developer (for instance you can use it both with MySQL 5.x and Oracle 11g). Download the latest release of Oracle SQL developer  from [7]. At the time of writing Linux RPM of the release is sqldeveloper-1.5.4.59.40-1.noarch.rpm.

Installation can be performed by running the following command:

rpm -Uhv sqldeveloper-1.5.4.59.40-1.noarch.rpm

within the Fedora terminal window.

After that SQL Developer can be found under Applications | Programming of the GNOME menu. From here SQL Developer launchers can be added to the desktop or panel by right-clicking and making a corresponding choice.

The only additional thing that you will need to use is the JDBC driver for MySQL. At the time of writing it is recommended you select from the Oracle SQL developer menu Help | Check for updates, click Next. Than select Third-Party Extensions, click Next and select MySQL JDBC driver (assuming that your computer is connected to Internet). Please visit [7] for latest updates on Oracle SQL developer. Both mysql command, Oracle SQL developer and described below Ganymede Data Source Explorer can be used together as convenient.

Tomcat 6, MySQL and Dolphin
It is assumed within the article that Java SDK from Sun is used rather than the native Java that comes with Fedora. At the time of writing it was possible to use http://www.mjmwired.net/resources and select your Fedora release (say Fedora 10) for a "how to" on this subject. If this resource will not be available, you may want to Google for "Personal Fedora <your release number here> installation guide".

The easiest way to install Tomcat 6 on Fedora is to issue the following command within terminal window:

yum install tomcat6

The above command will install Tomcat 6 as a service. Assuming that you don't want to run Tomcat 6 each time you start Fedora, use the following commands within the terminal window. To start Tomcat 6 use:

service tomcat6 start

To stop Tomcat 6 use:

service tomcat6 stop

You may want to create launchers with these commands to conveniently start and stop Tomcat 6.

Web applications by default are located under /var/lib/tomcat6/webapps. Tomcat 6 libraries are located under /usr/share/tomcat6/lib. To work with MySQL you will need to download MySQL Connector/J tarball from the appropriate mirror mentioned here.

At the time of writing, a file with the latest connector is mysql-connector-java-5.1.7-bin.jar (tarball file name is mysql-connector-java-5.1.7.tar.gz). Check the site in question for updates.

It's convenient to use Dolphin (a file manager for KDE) to extract files from a tarball. Dolphin can be used under GNOME as well. You can start a Dolphin, navigate to the location of a tarball and double-click on the tarball. Dolphin will open the tarball just like a regular folder. Then you may locate the needed file, files or folders, select them (if the entire contents of a certain folder is needed, just select the folder or open the folder and press CTRL+A) and press CTRL + C. Then navigate to your destination and press CTRL + V to copy files selected from a tarball. That's it.

This way you can copy mysql-connector-java-5.1.7-bin.jar from the tarball to /usr/share/tomcat6/lib.

Ganymede
It's convenient to use an IDE to develop servlets. One of the most popular is Eclipse. The latest release of Eclipse at the time of writing is Ganymede, which can be downloaded from http://www.eclipse.org/downloads/. It's recommended to use at least the Eclipse IDE for Java EE Developers distribution of Ganymede. To install Ganymede just open Ganymede tarball (which is eclipse-jee-ganymede-SR2-linux-gtk.tar.gz at the time of writing) with Dolphin and copy the Eclipse folder under the desired location. A detailed description of Ganymede options is far beyond the scope of this article. However, one of them, namely the GUI, for work in particular with databases (in Ganymede terms it is Data Source Explorer) will be described.

  • To get to the Data Source Explorer select Window | Show View | Data Source Explorer from the Ganymede menu. Within Data Source Explorer navigate to Data Base Connections.
  • Once in here right-click and select New.
  • Select MySQL from a drop-down list and click Next.
  • Click the New Driver Definition button, which is a little circle with lines in it.
  • Select the MySQL JDBC driver MySQL 5.1.
  • Click the Jar List tab. Click Add Jar/Zip button.
  • Browse to /usr/share/tomcat6/lib/mysql-connector-java-5.1.7-bin.jar and select it.
  • Click Remove Jar/Zip button to remove mysql-connector-java-5.1.0-bin.jar, which is the Ganymede default.
  • Click the Properties tab to set up the correct connection URL, database name, password and user ID.

In Ganymede terms, the previously described operation is known as a connection profile creation.

  • Within the Data Source Explorer window click on the triangle that is located left of Data Base Connection folder. The name of your database will appear under your connection.
  • Click on a triangle left of the name. Authorization IDs and Schemas folders will appear.
  • Click on a triangle left of the Schemas folder. A representation of the schema of your database will appear.
  • Click on a triangle left of it. Folders named Dependencies, Stored Procedures and Tables will appear among others. Click on a triangle left of Tables. A list of tables from your database will appear. Select the needed table.
  • Right-click on it and select Data | Edit from the pop-up menu.

That's it. From this point you will be able to view and edit data directly from your table within the window named after the table in question. There is no Save button within said window so how do you save your work? Suppose you edited data, clicked on a row next to one in which data was changed, and after that attempted to close said window. In this case a Save Resource window will appear. You will be offered three options: Yes, No and Cancel. If you select Yes, said data will be saved. In this case Ganymede will generate and execute a corresponding SQL Update command for you. Ganymede will also report on results of the execution.

MySQL Stored Procedure for the Example
Usage of stored procedures rather than direct SQL statements in JDBC is highly recommended. The reasons are high execution speed, reduction of traffic (only needed parameters are transferred to a database, not a whole SQL statement) and improvements in security. The creation of stored procedures within MySQL is simple. Just set the delimiter to some symbol that you will not use in your procedure (say to "|"). In this simple example we will just select data from phone1 table. The reaction of our stored procedure within the MySQL command is shown below:

mysql> delimiter | ;
mysql> create procedure read_phonebook()
-> begin
-> select * from phone1;
-> end;
-> |

After that a delimiter can be set back to ";" and a procedure checked for accuracy by using

call read_phonebook();
statement.

Servlet with JSON-type Response
The source code of the servlet is given in Listing 1. Here are some comments for your convenience.

To bring JSON-type results to the HTML page with Ext JS one can use:

res.setContentType("text/html");

In the previous sentence res is an instance of HttpServletResponse. The result set using stored procedure described in the previous section can be obtained as follows:

CallableStatement stExtJS = connExtJS.prepareCall("{call read_phonebook()}");
stExtJS.execute();
ResultSet rsExtJS = stExtJS.getResultSet();

Please note that the datasource used in Listing 1 should be described within META-INF/context.xml

To interact with Ext JS we need to put "[" at the beginning  and "]" at the end of the information produced by the servlet.

Java (and specifically servlets) do not support JSON notation "out of the box." Rather than develop a "homemade" solution, it is recommended you use the free open source library, which is proven to be effective. For our example, json_simple-1.1.jar is chosen for its simplicity and effectiveness. The file can be obtained from this at the time of writing. Please contact me, if this resource is not available. You will need to include this file both in Build Path for your Ganymede project and in WEB-INF/lib for the servlet.

json_simple-1.1 automatically encloses the appropriate data with curly brackets; however, it is your job to put a comma (",") between said data (please see Listing 1 for more details on this).

Please note that of course json_simple-1.1 is not a "silver bullet." You need to research other libraries that implement JSON on Java to see what will fit your needs (for instance google-gson from http://code.google.com/p/google-gson/).

Putting It All Together: Ext JS, JSON, Tomcat
As a standalone, Tomcat is used both as a web server and a sevlet/JSP container, you may want to place your HTML page (or pages) for Ext JS under /var/lib/tomcat6/webapps/<YourApplicationName>. Replace <YourApplicationName> from previous sentence with the needed name of your application.

In the same directory, the corresponding war file or META-INF, WEB-INF for the servlet in question as well as extjs (a folder with Ext JS distribution that you downloaded from [1] and unzipped) and  JavaScript file(s) that will be used by the page(s) will be located.

In this case, the necessary HTML link elements for Ext JS components will be made like this one:

<link rel="stylesheet" href="extjs/resources/css/ext-all.css" />

Please note that path starts with extjs. Using the given link element as an example, you can easily write similar ones for ext-base.js and ext-all.js.

For our example, the name of the page is phone_book.html. This page uses phonebook.js JavaScript file, which in turn works with Ext JS and the servlet in question. Page and JavaScript file do not use any complicated constructions and are very much self-explanatory (please see Listing 2 and Listing 3 for details). It should be mentioned, however, that instead of the traditional PHP scripts, a reference to the URL for the servlet from the previous section (as it is described in web.xml) is used within the JavaScript file. Said reference has the following form:

url: '<nameOfTheServletAsItDescribedInWebXML>'.

Replace  < nameOfTheServletAsItDescribedInWebXML > from the previous sentence with the needed name.

What Do We Have?
Now when all the groundwork is done, what do we get in exchange?

With Ext JS a user can drag and drop columns, sort columns in the desired order and decide which columns to display as shown in Figure 1. Note that only checked columns from Figure 1 are displayed. If, for instance, we uncheck some of the columns, the result will be given in Figure 2.

Without writing any additional code that handles drag-and-drop, sorting, and partial displaying logic, we obtained the mentioned functionality by using simple methods described in this article together with Ext JS JSON, MySQL, Tomcat, and Fedora.

Resources

  1. Ext JS site
  2. Frederic S., Ramsay C. and Blades S.'C'. Learning Ext JS.Packt Publishing. 2008. ISBN-10: 1847195148.
  3. Schutzberg A. Oracle Buys Sun: What Happens to MySQL?
  4. Krivitsky A. Running Fedora Core 5 Under Windows XP - Tips and Tricks, LinuxWorld magazine, vol.4, issue 5, 2006, pp. 28 - 30
  5. Krivitsky A. The 'Best of Both Worlds': Running Fedora 8 on Legacy Windows XP.
  6. Negus C. Fedora 9 and Red Hat Enterprise Linux Bible. Wiley Publishing Inc. 2008. ISBN: 978-0-470-37362-0
  7. Oracle SQL Developer

More Stories By Anatoly Krivitsky

Anatoly Krivitsky has a PhD in computer science and has more than 24 years of working experience in the IT field. He's the author of 20 published papers and books and five patents. For more information, please visit http://www.myjavaserver.com/~akrivitsky/index.html.

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


@ThingsExpo Stories
I wanted to gather all of my Internet of Things (IOT) blogs into a single blog (that I could later use with my University of San Francisco (USF) Big Data “MBA” course). However as I started to pull these blogs together, I realized that my IOT discussion lacked a vision; it lacked an end point towards which an organization could drive their IOT envisioning, proof of value, app dev, data engineering and data science efforts. And I think that the IOT end point is really quite simple…
"My role is working with customers, helping them go through this digital transformation. I spend a lot of time talking to banks, big industries, manufacturers working through how they are integrating and transforming their IT platforms and moving them forward," explained William Morrish, General Manager Product Sales at Interoute, in this SYS-CON.tv interview at 18th Cloud Expo, held June 7-9, 2016, at the Javits Center in New York City, NY.
You think you know what’s in your data. But do you? Most organizations are now aware of the business intelligence represented by their data. Data science stands to take this to a level you never thought of – literally. The techniques of data science, when used with the capabilities of Big Data technologies, can make connections you had not yet imagined, helping you discover new insights and ask new questions of your data. In his session at @ThingsExpo, Sarbjit Sarkaria, data science team lead ...
Extracting business value from Internet of Things (IoT) data doesn’t happen overnight. There are several requirements that must be satisfied, including IoT device enablement, data analysis, real-time detection of complex events and automated orchestration of actions. Unfortunately, too many companies fall short in achieving their business goals by implementing incomplete solutions or not focusing on tangible use cases. In his general session at @ThingsExpo, Dave McCarthy, Director of Products...
WebRTC is bringing significant change to the communications landscape that will bridge the worlds of web and telephony, making the Internet the new standard for communications. Cloud9 took the road less traveled and used WebRTC to create a downloadable enterprise-grade communications platform that is changing the communication dynamic in the financial sector. In his session at @ThingsExpo, Leo Papadopoulos, CTO of Cloud9, discussed the importance of WebRTC and how it enables companies to focus...
Verizon Communications Inc. (NYSE, Nasdaq: VZ) and Yahoo! Inc. (Nasdaq: YHOO) have entered into a definitive agreement under which Verizon will acquire Yahoo's operating business for approximately $4.83 billion in cash, subject to customary closing adjustments. Yahoo informs, connects and entertains a global audience of more than 1 billion monthly active users** -- including 600 million monthly active mobile users*** through its search, communications and digital content products. Yahoo also co...
A critical component of any IoT project is what to do with all the data being generated. This data needs to be captured, processed, structured, and stored in a way to facilitate different kinds of queries. Traditional data warehouse and analytical systems are mature technologies that can be used to handle certain kinds of queries, but they are not always well suited to many problems, particularly when there is a need for real-time insights.
Amazon has gradually rolled out parts of its IoT offerings in the last year, but these are just the tip of the iceberg. In addition to optimizing their back-end AWS offerings, Amazon is laying the ground work to be a major force in IoT – especially in the connected home and office. Amazon is extending its reach by building on its dominant Cloud IoT platform, its Dash Button strategy, recently announced Replenishment Services, the Echo/Alexa voice recognition control platform, the 6-7 strategic...
The best-practices for building IoT applications with Go Code that attendees can use to build their own IoT applications. In his session at @ThingsExpo, Indraneel Mitra, Senior Solutions Architect & Technology Evangelist at Cognizant, provided valuable information and resources for both novice and experienced developers on how to get started with IoT and Golang in a day. He also provided information on how to use Intel Arduino Kit, Go Robotics API and AWS IoT stack to build an application tha...
IoT generates lots of temporal data. But how do you unlock its value? You need to discover patterns that are repeatable in vast quantities of data, understand their meaning, and implement scalable monitoring across multiple data streams in order to monetize the discoveries and insights. Motif discovery and deep learning platforms are emerging to visualize sensor data, to search for patterns and to build application that can monitor real time streams efficiently. In his session at @ThingsExpo, ...
SYS-CON Events announced today that LeaseWeb USA, a cloud Infrastructure-as-a-Service (IaaS) provider, will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. LeaseWeb is one of the world's largest hosting brands. The company helps customers define, develop and deploy IT infrastructure tailored to their exact business needs, by combining various kinds cloud solutions.
SYS-CON Events announced today that 910Telecom will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Housed in the classic Denver Gas & Electric Building, 910 15th St., 910Telecom is a carrier-neutral telecom hotel located in the heart of Denver. Adjacent to CenturyLink, AT&T, and Denver Main, 910Telecom offers connectivity to all major carriers, Internet service providers, Internet backbones and ...
Big Data, cloud, analytics, contextual information, wearable tech, sensors, mobility, and WebRTC: together, these advances have created a perfect storm of technologies that are disrupting and transforming classic communications models and ecosystems. In his session at @ThingsExpo, Erik Perotti, Senior Manager of New Ventures on Plantronics’ Innovation team, provided an overview of this technological shift, including associated business and consumer communications impacts, and opportunities it ...
SYS-CON Events announced today that Venafi, the Immune System for the Internet™ and the leading provider of Next Generation Trust Protection, will exhibit at @DevOpsSummit at 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Venafi is the Immune System for the Internet™ that protects the foundation of all cybersecurity – cryptographic keys and digital certificates – so they can’t be misused by bad guys in attacks...
It’s 2016: buildings are smart, connected and the IoT is fundamentally altering how control and operating systems work and speak to each other. Platforms across the enterprise are networked via inexpensive sensors to collect massive amounts of data for analytics, information management, and insights that can be used to continuously improve operations. In his session at @ThingsExpo, Brian Chemel, Co-Founder and CTO of Digital Lumens, will explore: The benefits sensor-networked systems bring to ...
Manufacturers are embracing the Industrial Internet the same way consumers are leveraging Fitbits – to improve overall health and wellness. Both can provide consistent measurement, visibility, and suggest performance improvements customized to help reach goals. Fitbit users can view real-time data and make adjustments to increase their activity. In his session at @ThingsExpo, Mark Bernardo Professional Services Leader, Americas, at GE Digital, discussed how leveraging the Industrial Internet a...
There will be new vendors providing applications, middleware, and connected devices to support the thriving IoT ecosystem. This essentially means that electronic device manufacturers will also be in the software business. Many will be new to building embedded software or robust software. This creates an increased importance on software quality, particularly within the Industrial Internet of Things where business-critical applications are becoming dependent on products controlled by software. Qua...
In addition to all the benefits, IoT is also bringing new kind of customer experience challenges - cars that unlock themselves, thermostats turning houses into saunas and baby video monitors broadcasting over the internet. This list can only increase because while IoT services should be intuitive and simple to use, the delivery ecosystem is a myriad of potential problems as IoT explodes complexity. So finding a performance issue is like finding the proverbial needle in the haystack.
The 19th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Digital Transformation, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportuni...
Large scale deployments present unique planning challenges, system commissioning hurdles between IT and OT and demand careful system hand-off orchestration. In his session at @ThingsExpo, Jeff Smith, Senior Director and a founding member of Incenergy, will discuss some of the key tactics to ensure delivery success based on his experience of the last two years deploying Industrial IoT systems across four continents.