Hibernate...

This video is a part of our continuous approach towards learning by sharing knowledge together. We deal with hibernate plugin onto the reverse engineering process we discussed earlier.

[googlevideo=http://video.google.com/videoplay?docid=7169964626981764870]

AJAX

AJAX is simple.... It ought to be as you can even find books titled "Teach yourself AJAX in 10 minutes". I mean even the silliest of technology learning book titles have a minimum time span of 24 hours but by jove 10 minutes?? By the way the simplicity of ajax using jmaki plugin is demostrated in the following screencast(PS:don't feel bad, its a little screechy and 14 mins long but anyway gives an overview of jmaki and dojo). Now to the reality part, what exactly is AJAX? AJAX (asynchronous JavaScript and XML) isn'ta technology. It's really several technologies, each flourishing in its own right, coming together in powerful new ways. AJAX incorporates:

• Standards based presentation using XHTML and CSS


• Dynamic display and interaction using the document object model


• Data interchange and manipulation using XML and XSLT


• Asynchronous data retrieval using  XmlHttpRequest


• and JavaScript binding everything together.

What is important to note is that it is easy to use ajax code from ajax libraries available  such as those from Yahoo, Google and DOJO to name a few, but to write your own code in AJAX its humongus. The only way to be good at AJAX is "Practice, practice and more practice".

Reverse Engineering : An insight into the process of reverse engineering databases

Lets first look into the definition of reverse engineering. Reverse engineering (RE) is the process of discovering the technological principles of a device, object or system through analysis of its structure, function and operation. Reverse Engineering is a very powerful technique for discovering the structures of databases. There are many tools available like Apache Cayenee,Oracle Designer etc. What I want to talk thorough here is the concept of reverse engineering and its relevance into enterprise application development. You must be knowing that in the 3 tier system of Enterprise Applications other than the business code in the middle tier a lot of coding goes into both data access and modification in the innermost layer. So an enterprise app could be seen as a concentric sperical shell of three layers with the ineermost core dedicated to database(say db2),its connections and data access. Once we have this core, i.e. we know exactly what data is to be delt with we could use a tool to map the database directly to code(POJO and DAO combination in case of EJB's) and then build the rest of the application on top of this. This is reverse of the actual front end to back end conceptuation we tend to do and is termed reverse engineering. Its a relatively fast and effective method wherein the focus is exactly on the application data, enabling us to build on both existing databases and our own data logic on any given scenario.

Moving a db2 database

You must have encountered this problem sometime while working on db2. It doesn't have a proper GUI for direct moving of a database from one system to another. Here are the detailed steps.

Step1:
Export using following command sequence

/>db2move databasename export

Commet: this generates files Export.out - ASCI info about export db2move.lst - has table info tabn.ixf - info exchange format, holds data .msg -message files tabna.nnn - large object data

/>db2look -d databasename -e -a -o outputfilename.sql

Comment: generates the sql file holding DDL data

Step2:
move all files to the target system

Step3:
Import using following command sequence

/>db2 create databasename
comment: creates the database
/>db2 -tvf sqlfile.sql
comment: structure the generated database with the sql file from the export
/>db2move databasename load

/*HURRAY DATABASE MOVED */

Design Phase - 3

Continuing further, we see the drawing of sequence diagram. Check the tutorial here. This diagram shows the various actors we have from our use case diagrams interact with the various classes in our class diagram. This UML specified the object to object message passing via various operations.

Eclipse - Problems and solutions

People encounter a lot of nerve wrecking problems, not while installing or using eclipse but while configuring it for particular project requirements. Here are a few common problems are their solutions.

¿   Cannot find Data source explorer view

√  You are using the wrong type/version of eclipse. You need to download the eclipse package for Java EE      developers

¿  Cannot install WAS CE 2.0 in Eclipse ganymade. Gives dependency problems error message.

√ There is no WAS CE plugin available for Eclipse ganymade(3.4). You need to use the older Eclipse Europa(3.3) to solve this dependency issues.

¿ Cannot install WAS CE plugin directly even in Eclipse Europa

√ You need to install the database plugin before installing WAS CE plugins.

¿ the instruction at "0x7c93426d" referenced memory at "0x00000000"

√ Your installation is faulty/ is corrupted. Reinstalling eclipse will solve this problems

Design phase - 2

Continuing further from use cases, we reach the part of designing classes for the users and for different uses they do the system. Again on rational ROSE we've developed the following class diagram. (see this to learn how to draw class diagrams in UML). The next time I write about class diagrams, it would be expanded to its fullest possible extend. Catch a glipse of this to get a sneak peak on UML,

[caption id="attachment_18" align="aligncenter" width="497" caption="Class_diag_ver_1"][/caption]