TDD vs Test-last

TDD

First of all TDD can’t be properly applied if you have no idea what the problem is and you don’t know how to solve it.

So an overview should be done before applying TDD.

• Analyze the problem.
• Go through the related existing code if present.
• Identify where the new functionality should be called from and how.
• Define a list of test cases.

TDD process can be depicted by the below diagram

It's Time to Develop Applications for Cheap ESP8266 μC using Arduino IDE

ESP8266 is relatively new and cheap in price. It comes with an inbuilt firmware which supports serial interface and can be controlled using AT commands. Even though we can use this module to offload WiFi functionality from another micro controller or any other processor, this module is not just a serial to WiFi transceiver!

It is comprised of 

1. 32bit 80MHz processor (Tensilica Xtensa LX3)
2. 512KB SPI Flash (W25Q40BVNIG)
3. RAM (64KB sram; 96KB dram)
4. GPIO Pins
5. WiFi tranceiver

Flashing Firmware on ESP8266

In my previous post on ESP8266 I explained how I connected the cheap WiFi module with my computer using a USB to TTL adapter. I had a old version of firmware on WiFi module when I brought it. I wanted to update it to the latest firmware.

GPIO0 pin should be grounded to put ESP8266 into the flash mode. see below diagram. The SW1 should be on before trying to flash the firmware on it.

Getting started with ESP8266 (Cheap WiFi module)

I brought a ESP8266 module from ebay. The whole purpose was to do some experiments with it and understand how to use it in my micro-controller projects. I was not interested in XBee products since those were much expensive compared to ESP8266.

Initially I started with issuing AT commands from my laptop to the WiFi module. To do this I brought a USB to TTL serial adapter.

Data Access With Spring JDBC (Note 1)

When developing enterprise applications, we have lots of options when it comes to the implementation of the DAO (Data access Object) layer. Either we may use an ORM framework like Hibernate, iBatis or pure JDBC. 

JDBC fulfills almost all the necessary data access requirements. and provides low level access to the data access operations. But we have to handle connections and lots of other things. 

Playnig With HTTP Methods

I am highly interested in RESTful web services these days :) . So I tried to implement my own RESTful API and wrote REST client to communicate with the service. GET, POST, PUT, DELETE are basic HTTP methods used in REST services (details of HTTP methods can be found here) . Lets see how I implemented basic CRUD operations using HTTP methods.

For the sake of simplicity I have simply echoed the request body and selected request headers back as the service implementation.

Using SQLite with JDBC

I had to implement an application which should utilize a portable database. For better portability the application was implemented in java. As my first choice I selected several flat files for storing data in a hierarchical manner .

At the run time of the application , read operations were much higher than the write operations. It took minutes for traversing and search through each file on a search operation.

Considering all above facts I selected "SQLite" for storing and managing data in my application. Though it was bit slow while feeding data to the application , it was pretty fast when reading data from the database.

Monitoring JDBC Performance with JDbMonitor

There may be some situations where we need to monitor our JDBC calls. There are few mechanisms available for monitoring JDBC calls. I have tried JDbMonitor in some of my projects because it is easy to use and remove without any code change.

JDbMonitor works as a proxy between our application the JDBC driver. Essentially there may be some performance issue if we use this in a production environment. JDbMonitor provides a GUI application to monitor our JDBC calls.

XML Serialization With XStream

Download : http://xstream.codehaus.org/download.html

XML Serialization is essential in some situations. Most probably we may use XML serialization when we need higher level of portability. XStream is a great library for xml serialization.

Serializing

Ajax with Dojo

It is very safe to use Dojo like java script frameworks for Ajax operations since they ensure browser compatibility. We don't have to change the code based on different browsers. dojo will handle those stuff for us. Any way , If we are using such java script frameworks for Ajax operations  we must carefully choose a proper framework with wide range of browser support.

In this example I have used a very simple Servlet and a simple HTML page to demonstrate the client server model.