Welcome!

Java IoT Authors: Elizabeth White, Pat Romanski, Harry Trott, Philippe Abdoulaye, Scott Sobhani

Related Topics: Java IoT

Java IoT: Article

Delivering JDBC-Based Applications

Delivering JDBC-Based Applications

Introduction
In this article, we take a look at using JDBC to build applications. Internet technology is changing so rapidly that some of the methods used today will become obsolete tomorrow. We are taking an approach that combines Java network programming and JDBC programming. Programming in JDBC is taking a step backward when you have mature 4GL tools like Sybase Powerbuilder. Programming in JDBC is similar to programming in any low level database library like ODBC or Sybase CT-LIB.

There is more than one way to deploy applications and applets using JDBC. The first approach is by using the JDBC-ODBC bridge that is part of JDK 1.1. You have to install ODBC Drivers and set the ODBC datasource in each client. If you are willing to do this existing client server tools will do a better job than Java. The second approach is to use a JDBC driver that is 100 Percent Java compliant. For writing Java applications, this method will work fine, but not for Java applets. Applets can not make arbitrary connection to other servers. You have to run your database server in the same machine where the Web server is running. This article will help you write Java applets or applications using JDBC without any of the above mentioned restrictions.

What are the Advantages?
This implementation follows a 3-tier client-server model. JDBC Client sends a request to JDBC server which processes the request, communicates to the database server and sends back the reply. Compatible with all Java enabled browsers. It's secure because the database server is not exposed. You can configure number of concurrent users allowed at any point of time. With little modification you can dynamically increase and decrease number of JDBC server listening for request or totally redirect the request to a different web server. You can also attach your own encryption and decryption routine before communicating with a remote client. JDBC server runs on the server side so you have total freedom to use any JDK, any ODBC driver and Java native methods. You can batch your request or can have real-time connection like any other client-server application.

There are some limitations in this implementation. If you want to have multiple connection you have to initialize multiple driver's in the client side. It will not handle blob or image data type even though it's very easy to implement one, by saving the image in the server and sending the filename back as URL. You can use the same method to transfer the whole ResultSet.

Architecture
There are three different functional pieces. Port allocator (PA) is a Java based server that listens on a predefined port. JDBC server listens for connection from client. JDBC client which makes the request. When client makes a request to Port Allocator it will send back a JDBC server port that is currently free. From that point onwards, JDBC client talks only to the JDBC server. Client sends a single byte command to server and waits for reply. The server sends back a status code and byte or string value. Commands can have arguments usually a byte or a string. While processing clients request, if server encounters an exception it converts the exception to a string and sends back an error code and the string to the client.

Let us look into the details. There are four client side classes RDriver, RConnection, Rstatement, RResultSet for connecting and fetching data. These are very similar to JDBC interfaces Driver, Connection, Statement, ResultSet. It does not implement these interfaces. JDBC client initializes the RDriver then creates a TCP socket to port allocator (PA) and gets a port to communicate to a JDBC server. It also sends command to initialize DriverManager in the server if everything is successful. This enables the client to connect directly to the JDBC server using RDriver.connect(username, password) and create a database connection. You only need username and password to create a database connection hiding all server details in the JDBC server code. You can call createStatement() method to create a RStatement() after successfully establishing a database connection. Send the SQL string to server using executeQuery function. It will create a ResultSet in the server and RResultSet in the client. Use executeUpdate() function for update and insert SQL statements. Access the ResultSet values using next() and getString() or getInt().

One of the advantages of this architecture is that all conversation between client and server happens as bytes and strings. If the client dies for some reason Driver.detach() will cleanup the connection, but if an exception occurs you have to take care of it. Rdriver has an overloaded finalize method which calls Driver.detach().

The example here shows how to connect to a Sybase SQL server using beta version of Jconnect. Before running the examples you may need to change hostname, port and any other parameters it may need in your environment.

Table 1 shows the commands, arguments and return code.

JDBC Protocol Implementation
JDBC Protocol is a layer above the Java socket layer. It hides the Java socket layer, but you have to still catch exceptions from this layer. Protocol structure follows the same structure as any other standard protocols (FTP, TELNET). JDBC protocol does session control by sending acknowledgment or negative acknowledgment after each request from client. Java takes care of presentation of data. This protocol fits in the top layers of OSI model. Like most other protocols this protocol has series of commands and expected return values. Most importantly these commands are not part of any standards. One other difference is it has only one path to the server, unlike FTP which uses a command port (21) and a data port (20).

All commands are single byte followed by a byte or string. In special cases it is more than one string. For each command sent from client JDBC server replies with a return status of SUCCESS or FAIL. If the return status from the server is SUCCESS it returns either string, byte or no value depending on type of command. If an error occurs in the server the return status is FAIL server then sends a SQLExeption string to the client.

Table 2 explains the protocol implementation.

More Stories By Paul Ananth

Paul Ananth works with Barclays Global Investors, San Francisco, as a software engineer. He is a senior member in the client/server development team, specializing in building object-oriented software using C++, Java, PowerBuilder 5.0 and PFC.

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
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life sett...
There are several IoTs: the Industrial Internet, Consumer Wearables, Wearables and Healthcare, Supply Chains, and the movement toward Smart Grids, Cities, Regions, and Nations. There are competing communications standards every step of the way, a bewildering array of sensors and devices, and an entire world of competing data analytics platforms. To some this appears to be chaos. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, Bradley Holt, Developer Advocate a...
Cognitive Computing is becoming the foundation for a new generation of solutions that have the potential to transform business. Unlike traditional approaches to building solutions, a cognitive computing approach allows the data to help determine the way applications are designed. This contrasts with conventional software development that begins with defining logic based on the current way a business operates. In her session at 18th Cloud Expo, Judith S. Hurwitz, President and CEO of Hurwitz & ...
In his general session at 18th Cloud Expo, Lee Atchison, Principal Cloud Architect and Advocate at New Relic, discussed cloud as a ‘better data center’ and how it adds new capacity (faster) and improves application availability (redundancy). The cloud is a ‘Dynamic Tool for Dynamic Apps’ and resource allocation is an integral part of your application architecture, so use only the resources you need and allocate /de-allocate resources on the fly.
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, wh...
19th Cloud Expo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy. Meanwhile, 94% of enterpri...
SYS-CON Events announced today that Bsquare has been named “Silver Sponsor” of SYS-CON's @ThingsExpo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. For more than two decades, Bsquare has helped its customers extract business value from a broad array of physical assets by making them intelligent, connecting them, and using the data they generate to optimize business processes.
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices - comp...
Machine Learning helps make complex systems more efficient. By applying advanced Machine Learning techniques such as Cognitive Fingerprinting, wind project operators can utilize these tools to learn from collected data, detect regular patterns, and optimize their own operations. In his session at 18th Cloud Expo, Stuart Gillen, Director of Business Development at SparkCognition, discussed how research has demonstrated the value of Machine Learning in delivering next generation analytics to imp...
There is little doubt that Big Data solutions will have an increasing role in the Enterprise IT mainstream over time. Big Data at Cloud Expo - to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA - has announced its Call for Papers is open. Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is...
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...
Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is expected in the amount of information being processed, managed, analyzed, and acted upon by enterprise IT. This amazing is not part of some distant future - it is happening today. One report shows a 650% increase in enterprise data by 2020. Other estimates are even higher....
The cloud market growth today is largely in public clouds. While there is a lot of spend in IT departments in virtualization, these aren’t yet translating into a true “cloud” experience within the enterprise. What is stopping the growth of the “private cloud” market? In his general session at 18th Cloud Expo, Nara Rajagopalan, CEO of Accelerite, explored the challenges in deploying, managing, and getting adoption for a private cloud within an enterprise. What are the key differences between wh...
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 19th International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world and ThingsExpo Silicon Valley Call for Papers is now open.
It is one thing to build single industrial IoT applications, but what will it take to build the Smart Cities and truly society changing applications of the future? The technology won’t be the problem, it will be the number of parties that need to work together and be aligned in their motivation to succeed. In his Day 2 Keynote at @ThingsExpo, Henrik Kenani Dahlgren, Portfolio Marketing Manager at Ericsson, discussed how to plan to cooperate, partner, and form lasting all-star teams to change t...
Connected devices and the industrial internet are growing exponentially every year with Cisco expecting 50 billion devices to be in operation by 2020. In this period of growth, location-based insights are becoming invaluable to many businesses as they adopt new connected technologies. Knowing when and where these devices connect from is critical for a number of scenarios in supply chain management, disaster management, emergency response, M2M, location marketing and more. In his session at @Th...
SYS-CON Events announced today that ReadyTalk, a leading provider of online conferencing and webinar services, has been named Vendor Presentation Sponsor 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. ReadyTalk delivers audio and web conferencing services that inspire collaboration and enable the Future of Work for today’s increasingly digital and mobile workforce. By combining intuitive, innovative tec...
Amazon has gradually rolled out parts of its IoT offerings, but these are just the tip of the iceberg. In addition to optimizing their backend AWS offerings, Amazon is laying the ground work to be a major force in IoT - especially in the connected home and office. In his session at @ThingsExpo, Chris Kocher, founder and managing director of Grey Heron, explained how Amazon is extending its reach to become a major force in IoT by building on its dominant cloud IoT platform, its Dash Button strat...
industrial company for a multi-year contract initially valued at over $4.0 million. In addition to DataV software, Bsquare will also provide comprehensive systems integration, support and maintenance services. DataV leverages advanced data analytics, predictive reasoning, data-driven diagnostics, and automated orchestration of remediation actions in order to improve asset uptime while reducing service and warranty costs.
Vidyo, Inc., has joined the Alliance for Open Media. The Alliance for Open Media is a non-profit organization working to define and develop media technologies that address the need for an open standard for video compression and delivery over the web. As a member of the Alliance, Vidyo will collaborate with industry leaders in pursuit of an open and royalty-free AOMedia Video codec, AV1. Vidyo’s contributions to the organization will bring to bear its long history of expertise in codec technolo...