Since I have received bachelor’s degree in software engineering, I have worked as a software developer continuously. I started my career in Los Angeles, California, USA as an intern and have worked mostly in Seoul, South Korea but this time in Berlin, Germany. I was curious about what is it like to use other technologies, except for Visual Basic and .Net that I used in my first job. Since then, my adventure has begun.
I have mainly used .Net stacks; but, also used Java stacks such as Spring MVC, Struts, Java web service and JSP. I cover from desktop application to web and mobile development because I started my career with desktop applications and have moved to web technologies. Furthermore, I have dedicated into Xamarin Android development in recent months.
When it comes to databases, I have often used MS SQL Server, although I also used other databases such as Realm, Oracle and Sybase. Therefore, I do believe that I have deep knowledge of utilizing MS SQL Server A-Z.
If you want to know more of my career, please see my resume/CV (Word/PDF)
If you think it is not enough, then you can see my experiences in more detailed in my portfolio below.
I was in charge of tackling bugs and issues on sales interface systems such as updating item information into POS in stores, posting daily sales data into the main servers and the store intranet. I dealt with multi-threaded architecture that those system have.
In addition, I also was responsible for packing methods generating program that calculates and generates packing information for vendors and posts it to another vendor extranet as this company is a clothes retailer. Therefore, I developed and maintained this program to meet requirements that given from a PMO team.
I developed new version of the store intranet web application using modern technologies such as ASP.Net MVC 5, Bootstrap, jQuery and Ajax. This work also included re-writing the legacy store intranet web application that developed using ASP classic.
I participated in a South Korea civil service examination application management system that was Java Spring web application system and was in charge of mobile web application and authentication and EDI modules of the system.
For the mobile web, I developed as full-stack developer because there was only me to handle mobile web part. I was given web view designs from a web designer in my team and made it dynamic to interact with back-end side.
For the authentication module, I had to use name, mobile and pubic I-PIN identification authentication as this system was for South Korea government and it is required to use them all methods to verify applicants. The guidance documents were provided from the government and I had to install and set up to request and retrieve API calls.
For the EDI module, I also had to set up the environment on servers to commuicate with the government's central public information sharing server with given guidance documents. It was like a mailbox system that senders send compressed formatted files to recipients' mailboxes and vice versa.
Below pictures are the mobile web pages that are opened to the public.
Mobile site
I developed the replenishment function among CPFR process that my clients wanted to build for their supply chain system. It was built from the scratch so our architect in my team set up the web application structure with Spring MVC and MyBatis. For the front-end UI component, the clients wanted to use Kendo UI hence, we were given some time to study it and applied on our architecture.
Based on this architecture, I developed both back-end and front-end sides as a full-stack developer because the team leader in my team assigned each function to each developer. Besides, each developer was in charge of communicating with clients about the function that he or she is in charge of.
I developed Punch Control and Steel Structure Management Systems that developed using ASP.Net. These systems were for in-house uses and I participated in from the scratch.
I was a full-stack developer and on the front-end side, the SmartClient technology was used for the web UI components. The SmartClient technology is like ActiveX but its alternative one that recommended by Microsoft to replace ActiveX. It is to embed winforms into web pages so it also required application knowledge that I had.
When I attended clients meetings that took place once a week as a part of agile approach, I gave technical proposals or suggestions as a developer.
It was a merchant screening system for credit cards. The system was for in-house use and it was already developed so I maintained and developed additional requirements and fixed defects.
There was a main system and other complementary programs. The main system was a web application using JSP, Java, Javascript, jQuery, Ajax, HTML, CSS, Eclipse and SVN. Other programs were desktop applications developed using VB.Net or Visual Basic 6 in order to deal with image file processing that uploads the files into the content management system. All systems and programs used Oracle database and they directly did query or update without any ORM framework.
Below picture shows the process of the system.
Merchant screening system for credit cards process
It was a project risk management system. The system was for in-house use and I participated in from the start. I worked with two more developers those who are in charge of communication with users. I was in charge of both back-end and front-end development.
For front-end side, I tried not to depend on .Net server controls. Instead of that, I used jQuery, Ajax and Json to make web pages simple, light and intuitive.
For back-end side, I created entity classes to store and manipulate data. Besides, I made back-end like json return API in most cases.
Below picture shows the process of the system.
Project risk management system process
I developed in-house Java Webservice for three months and in-house .Net-based Custom Declaration System with Webservice for another three months at the Korean Air company.
For Java development, I re-wrote functions that developed using ProC communicating with socket into Java Webservice using SOAP 1.1. In order to develop Webservice using SOAP, I used WSDL and SoapUI testing tool. I also developed both client and host of webservice. I analyzed original ProC functions and created functional analysis reports. After confirmation by the manager, then I we-wrote it to Java.
For .Net development, I developed back-end side after being given designed web pages. The Custom Declaration System that I developed pulled data from Webservice out of the system as well as inside of the system. Therefore, it required developing both client and host of webservice using SOAP 1.1.
Below sample pictures show the samples of my works.
Webservice test screen on SoapUI testing tool.
WSDL
Webservice test page on RAD (Rational Application Developer)
I developed pre-arrangement of public works web application as a junior developer in a team that consists of three developers and one project manager. Due to the short development period, the project manager decided to copy another system which has similar functions and then customize it. I participated in development environment set-up as well because there was no developer who can do so I handled it. It was a little bit hard to set up WebLogic but I managed to do it. I was responsible for developing main part of the system and also mentoring two entry level developers.
Below picture shows the process of the system.
Pre-arrangement of public works system process
I developed this system with another developer who is included in the late of development for supporting and I was responsible all development life cycle from setting up the architecture to design functions and views. It was a project for an individual trader who wanted to establish his own asset company later on.
I developed three core functions in this portfolio management system.
Firstly, Analysis functions that analyze fundamental data of listed companies that provided by a financial data provider and make fund managers to make use of it for investment.
Secondly, portfolio management functions that enable for fund managers to see and select listed companies into their portfolios with real-time prices that pulled from Securities' trading API. The fund managers are able to compare their portfolios to benchmark indexes such as KOSPI (NASDAQ in USA) and measure their investment results afterwards.
Lastly, the real-time trading function to the designated Securities however, I made it expandable by interface so other securities' API can be added later on.
This uniERP was a ERP solution and it was customized into the client company, therefore I was in charge of maintenance and additional development tasks of its HR and Payroll parts most of my time. This ERP solution had two versions. One was developed using PowerBuilder as a desktop application and another was developed using ASP classic and ActiveX controls. As they were provided as compiled resources, I had to report any errors or bugs to the service center of them. Accordingly, what I did was manipulating data and developing new modules that interact with existing modules.
In addition to this ERP solution, I maintained and developed Sales and Inventory Management System developed by JSP, Tomcat 6 and MS Sql Server and developed Web POS system using JSP, Tomcat 6 and MS Sql Server which was a simple POS web application interacting with the ERP solution.
Forever21 is a fast-fashion company which has its own system from ordering from vendors to distribution to their stores wholely. Its rival companies are H&M, Zara and Uniqlo.
In this company, I was in Merchandising team in I.T department and was in charge of in-house merchandising and warehouse system. I was mainly in charge of purchasing, allocation and distribution parts of that system and other small distribution programs such as Carton Label printing, Price tag printing and shipping programs. Those programs were developed using Visual Basic 6, Farpoint Spread, Crystal Report 8.5 and MS Sql Server. Besides, I developed using C# for a price tag and sticker printing program and wireless PDA scanner run on Windows CE. In addition to the merchandising system, I participated in some tasks of intranet using ASP classic.
Below pictures are related to my work and functions in merchansiding system that I was in charge of.
Merchandising system process
Wireless PDA scanner
I decided to build my own website to look more professional after making a decision to come over to Berlin to find a job. In the course of searching a good one, I found out the Jekyll and I was shocked that I could build up my website without handling databases. Even better, I could have a free web hosting domain if I deploy it on GitHub Pages under my account. So I chose this way and started to build it up.
I forked the Clean Blog theme and customized it. Everything was as simple as like creating a blog. However, once I wanted to have two categories and put my portfolio and blogs all together, things got harder and I had to do some research to find a way to resolve.
I could have my website that you now have visited within two weeks thanks to modern web technologies.