J2EE and other web technologies

Uninstalling .apk file from Emulator for refresh issue

2011-12-02T22:12:00.001-08:00

In the SDK's main directory (i.e. "C:/Programming/Android/SDK") there is the folder called "tools" --> Get into that folder. You need to start a console terminal/shell ("Start -> Run... -> type 'cmd'" for Windows PCs). Type-in sth. like the following command:

CODE: SELECT ALL: adb shell rm data/app/{myFile.apk}

For example if you want to uninstall "HelloAndroid.apk" you should type this:

CODE: SELECT ALL: adb shell rm data/app/HelloAndroid.apk

The bright future of software (my personal views)

2009-12-03T06:44:00.001-08:00

Just for a momemt think of what software application you have used for the maximum time in the last few months.
I can bet in 99% of the cases it will be a browser.Sometimes when i or my wife we use the PC at home, i had been
observing that i had been using the OS mainly for login/logout and opening the browser.The OS is becoming less
relevant.This is what is leading to the google microsoft tussle.
The near future for the software lies on the browser.Why i am saying the near future, because may be in 10-15 years
there might be something much better then that, and thats the way the technology runs.If you start observing the
bigger companies you will see that most of them are becoming Service Oriented (in terms of providing services to client and not in terms of SOA) and they have started buying smaller
companies that create products.For the web the near future lies in the

1) Cloud - much hyped but useful, infact for a lot of startups its a boon.

2) SAAS - profitable business model if it picks up, you get a regular cashflow.

3) Web 2.0 - whatever it is one thing i am sure a good look and feel will always be important, whether
buying new pair of shoes from a store or a website, a good look and feel and a good user experience is
needed in both.

4) SOA - bigger companies have to follow this model now or then, the only thing they have to be sure of is
how much money they spend on it.

5) Marketing/Advertising - whether on the web or anywhere else, will always be important.Rarely anything sells
without marketing.Word of mouth creates a viral effect, if you are able to get in that phase your product has picked up.

6) Video - is one of the chief drivers of net, will always remain.

7) Porn - yes, and will always exist on the web, because of ease of use of access everywhere, because of the web.

8) Right Information - not sure how else to term it.There is plethora of info on the web, what is relevant and what is not is important.
Right now to buy a product you read 10-15 reviews on amazon/walmart to make a decision, but are you sure that, that review was written
by some genuine buyer and not by some sales person.I am not sure who has the time to write 1000 words of review for a small toothbrush
that they buy on the net.

Debugging JSPs Using Eclipse

2009-09-25T11:20:00.000-07:00

JSPs are compiled into java classes (servlets) before they are run on the server.For our application we are using Weblogic.
By default weblogic deletes the source files after compiling.
To enable weblogic to keep the source file of the jsps enter these details in the weblogic.xml of the web application
jsp-descriptor
jsp-param
param-name
keepgenerated
param-name
param-value
true
param-value
jsp-param
jsp-descriptor

Also Note that weblogic keeps the compiles jsp classes and source in the same folder.

Now goto Eclipse

Open your web project
Right click and create a Folder inside the project.Name this folder as 'JSP'
In the window that opens click on 'Advanced' and link this folder to that folder where weblogic keeps the compiled jsps/source.
Add this folder to the project build path as Source Folder.
Now run weblogic and include a debug point in the compiled source generated

Note : You might have to manually refresh the folder to see the source.

Learning Ruby on Rails - Part 1

2009-08-04T14:05:00.000-07:00

Steps for creating a new application:
1. Use the rails command to create the application skeleton.
2. Create a database on the database server.
3. Edit database.yml file to tell location of this database
4. Start your webserver.
5. Build your application and test.

Configuring WGET to work with PROXY server

2009-06-04T13:13:00.001-07:00

These are the steps on Windows

1. set http_proxy=http ://:
2. wget --proxy-user= --proxy-password= http://www.yahoo.com

and it would fetch the first page of yahoo.com.....

Hibernate - 1

2009-05-06T14:32:00.000-07:00

Starting with s articles on Hibernate dealing with What/Why and How

1. What is Hibernate ?
Hibernate is an object relational mapping tool for Java Applications. Instead of writing sql code in java, the developer can use Hibernate to persist and retrieve POJOs to the database.

A POJO maps to a database table.On the java side the developer deals with the POJO and populates its instance with data.Its the job of Hibernate to persist the state of this POJO to the database.Basically behind the scene one row of the database is mapped to one instance of the POJO.

2. Why use Hibernate ?

* Its one of the best ORMS available.

* JDBC gets out of hand if the number of screens is very large.

* If the development team is not well aquainted with SQL then using Hibernate will solve that
problem as it optimizes the query before firing them to the database.

* Simple to use only one configuration file

* Supports many databases

* Supports Caching. Can be integrated with many opensource and commercial caches so that
the POJO's can be caches with the data readily available from cache.

* Support Lazy loading i.e to say if we a Person is related to Department.If we need info for
person only we can state that and info for Department is not fetched along with Person.

* Supports outer-join whereby we can fetch multiple object at one shot.

Series on Hibernate

2009-05-06T13:10:00.001-07:00

I am going to post a Series of Articles on Hibernate.

Ajaxifying existing J2EE projects

2009-04-29T07:39:00.000-07:00

Introduction :
This document gives the steps for extending an existing J2EE application using the Spring MVC/ Spring Portlet MVC (JSR 168 compliant) / Hibernate or any other ORM stack.

There are basically 2 types of JavaScript libraries.
1.Client Side Libraries : e.g. Sciptaculous / Dojo / YUI Library, provide ready to use Widgets or client side javascript affects.
2.Server Side JavaScript libraries : Which compile javascript code on the server side. Normally these types of libraries handle ajax call from the client side and connect to the code on the server and fetch back the result in javascript. E.g DWR, JSON.

DWR is a natural choice for Java Web Projects, Simply because it was created with the mindset of having Java on the Server Side.

When multiple jvms are installed

2008-06-17T08:01:00.000-07:00

Sometimes multiple jvms are installed on the box and an executable we downloaded requires a particular jvm only.
To start that exe you can use the following command

start ads.exe %* -console -clean -vm "C:\jdk1.5.0_11\bin\java.exe"

I have used this to start eclipse 3.2 and eclipse europa from the same box.

Running a JSR168 Portlet on Vignette 7.2

2008-03-26T11:07:00.000-07:00

Vignette is a portlet container.It is installed as a web application on the application server.
It manages the life cycle of the portlets.
There are two ways by which portlets can be created on Vignette
1. Using native Vignette code (using PortalBeans, which are classes shipped with the Vignette)
2. Creating a standard jsr168 portlet and deploying it on Vignette.

Creating a JSR 168 portlet and running it on Vignette 7.2 Portlet container.

1) Standard JSR168 portlet is deployed as a war file.
2) Open eclipse create a dynamic web project.
3) Create Portlet e.g SamplePortlet by extending GenericPortlet class.
4) Configure the portlet in portlet.xml file.
5) Bundle the classes,portlet.xml,web.xml and jsps in a war file.
6) Now run the Portlet Packaging tool on the war file.
This file will not become compliant with Vignette
7) Deploy the war file from Weblogic (on the same server that hosts the Vignette)
8) After deploying the portlet gets registered with the Portlet container.
Thereby you can see the Portlet in Vignette Console.You can now control the access permission or
apply portlet to pages etc.

Spring MVC Simple App

2008-03-24T14:37:00.000-07:00

Using Spring MVC (A simple Application)
Using Spring MVC is similar to using Struts except that there are a few changes.

1) Spring has a DispatcherServlet (like Struts ActionController) that transfers the user request to an attached Controller. Basically DispatcherServlet is a FrontController servlet. In Struts for writing an Action class we need to extend the 'Action' class provided by the Struts framework itself, however for Spring we donot extend any classes.For writing the Controller in Spring you need to implement an interface for e.g Controller. Controller class is configured as a bean in Spring.Thereby the power of dependency injection can be used on the Controller class itself. e.g

package com.spring.test;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.Controller;
/** * * Test controller extends the spring controller

* * @author rmehta * */ public class TestController implements Controller { private String greeting; public void setGreeting(String greeting) { this.greeting = greeting; } public ModelAndView handleRequest(HttpServletRequest arg0, HttpServletResponse arg1) throws Exception { System.out.println("Inside the handle request method of Test Controller"); return new ModelAndView("home","greeting",greeting); } }

2) Configure the web.xml file to include the DispatcherServlet

training

org.springframework.web.servlet.DispatcherServlet

training

*.htm

3) Spring needs an xml file (Bean definition file) where all the beans belong to the Spring framework are registered. At runtime this file is picked up and beans are handled accordingly by the Spring Framework. By default Spring mvc tries to pick a file from WEB-INF based on the name of the DispatcherServlet.

4) Also use a ViewResolver for the jsps

Basic EJB

2008-03-24T06:36:00.000-07:00

Creating EJB for Weblogic
1) Create the Java EJB class and interfaces.
2) Write the deployment descriptor
ejb-jar.xml that is compulsory across all the files.
weblogic-ejb-jar.xml is needed for weblogic for specifing ejb name in weblogic jndi server etc.
weblogic-cmp.xml is needed for weblogic.
3) Bundle the files in a Jar file.
4) Deploy the jar in Weblogic in EJB Modules
5) Now the ejb is deployed on the weblogic ejb container and can be used from there.

Creating a WebService on Weblogic 8.1

2008-03-19T13:47:00.001-07:00

Weblogic has an extensive set of documentation and examples for deploying webservices.

There are two ways by which webservices can be created
1) By writing a Java Class.
2) By writing a Stateless EJB

Using Java Class :
1) Write a public java class,public default constructor (no parameters)
2) All the business methods that show result data, must be public
3) Write the Code for this class and the public methods in it.
4) For Building use the ready made build.xml provided with the weblogic examples.
5) Use ServiceGen ant task to create the ear that bundles the server side webservices code.
This command generates the WSDL file,and skeleton classes needed on the Server.It bundles
them in an EAR file.
You can also use the ANT deploy task to deploy this ear on the weblogic server
6) Next use the ANT ClientGen tool to create a jar file.This client jar will contain the stub classes
needed on the client side for accessing the webservices.
7) Put the client jar in classpath and create a Client.java class or client class and access the webservice
deployed on Weblogic.

So basically these steps

Create Java Class -> Build EAR with build.xml -> deploy on weblogic
Server side part is done..Open webconsole and check the webservices.

Create client jar -> put client jar in classpath -> now create a java client, using the stub classes created and
access the business method of the WebService
For the client classes you only require the location of the WSDL file.

DataStructures and Algorithms.

2008-03-11T13:46:00.000-07:00

In Ordered Arrays :
1) Search is fast
2) Insertion is slow
3) Delete is Slow

Arrays are of fixed length,length cannot be changed.

UnOrdered Arrays :
1) Insertion is fast
2) Search is slow
3) Delete is slow

------------------------------------------------------------------

Sorting in Arrays

Bubble Sorting
1) Elements move to the R.H.S
2) Very slow
3) Consider having 5 numbers arranged randomly.
4) Check from the 1st two which ever is greater swap to R.H.S and move the smaller on L.H.S.
5) Now check between position 2 and 3 and again which ever is created move to R.H.S.This way
keep on moving till you reach the end of R.H.S.Finally you will have the largest number on the
R.H.S
6) Next do the same iteration for n-1 numbers now. from 1 to n-1.

Selection Sort :
1) Selection Sort reduces the number of Swaps.
2)

Insertion Sort :
1) Combination of both side of sorts.
2) Divide the number to half.
3) Select a number on index.

-----------------------------------------------------------------

Linked List

Learning Links

2008-02-26T07:29:00.001-08:00

http://en.wikipedia.org/wiki/Concurrency_control

Tutorials

2007-09-27T09:06:00.000-07:00

1. PL/SQL
http://infolab.stanford.edu/~ullman/fcdb/oracle/or-plsql.html

Good SEO article

2007-06-12T05:17:00.000-07:00

http://www.dqindia.com/content/ebiz/2006/106103001.asp

Installing PHP and Apache

2007-02-12T20:53:00.000-08:00

Installing Apache/PHP

1) download apache 2.2 (msi installer)
Install on windows (select all the default options, including installation as a service).
2) Check the installation on port 80 or 8080 (check in httpd.conf)
3) you will also get an apache monitor.

intalling php now
1) download php php-5.2.1-Win32 zip file
2) Unzip in say D:\php
3) Copy php5ts file from d:\php\dev to \bin
4) Put php.ini-dist file in the C:\WINNT or C:\Systemroot and rename it as php.ini
5) Now add these 4 lines in httpd.conf
LoadModule php5_module D:/php/php5apache2_2.dll
AddType application/x-httpd-php .php
# configure the path to php.ini
PHPIniDir "C:/SYSROOT"
6) Restart apache

Now testing the installation
Create test.php

and store in /htdocs
and invoke as http://localhost/test.php

Accessing Tomcat MBeans

2006-11-03T07:11:00.000-08:00

Tomcat5.5+ has support for MBeans.It gives access to its mbeans via the rmi server, that comes with JDK 1.5.
Enable remote monitoring in JDK\lib\managment\management.properties (setup pwd etc if needed, even ssl can be setup)
Now For Tomcat setup JAVA_HOME to this JDK. and JRE_HOME to the JRE for the same.
and start Tomcat.

Note: at the time of starting tomcat, start it with this option -Dcom.sun.management.jmxremote=

Grep for a Process (Excluding the process created by 'Grep' itself )

2006-05-31T01:48:00.002-07:00

ps -aef | grep -v grep | grep "‹PID or String Matching ›"

Executing Scripts with SQL Plus

2006-05-23T08:45:00.000-07:00

http://web.njit.edu/info/limpid/DOC/server.920/a90842/ch6.htm

Web Security

2006-05-10T23:46:00.000-07:00

By sniffing packets on the network,we can get a huge amount of information.By analysing these packets we can make precise conclusions regarding the status of our business or web applications.We can easily find out which machine is putting the maximum load on our web server,or from where the maximum number of requests are coming from,or who is maliciously trying to access our website etc.Getting such kind of information in a normal scenario without sniffing the packets is difficult to obtain.
I recently got interested in this stuff.I am using the tool ethereal for sniffing the packets and reading them.Tried using tcpdump on linux (i guess its bundled along with it),but it doesnot have a good gui.
As the number of pages increase across the web,the need for web security is going higher and higher.There are various ways for securing your web info e.g by using https,going for various levels of authentications, but sniffing will always be a precise way to determine how secure your web info actually is.

Good intro on J2EE

2006-02-10T06:46:00.000-08:00

This is a great link for anybody who wants to start with j2ee.
http://java.sun.com/developer/onlineTraining/J2EE/Intro2/j2ee.html

Using grep for recursive search

2006-01-18T04:48:00.000-08:00

I searched on the web there are a lot of options available for this.Do a grep --help and we can get some info on this.I used this command
grep -i 'pattern to search' *.xml 'pwd' -r
-i : ignore case
*.xml : type of file e.g xml as shown above
'pwd' : searches in the present working directory and under it the sub directories.
-r : for recursive operation.

Using mysql in batch mode

2006-01-08T19:59:00.000-08:00

When you dump your sql queries in a file and want them to execute from the mysql command prompt,the following options can be used

mysql>\. filename
or
mysql> source filename

Using JasperReports

2005-11-06T23:37:00.000-08:00

For JasperReports the bands generated in the report design are quite important.If you want a tabular detailed report,that shows a row (mapped with each table row),then put this report in the 'Detail' band.If you want a chart that should be the summary of all columns or rows of the table then put it in the 'Summary' band so that it is evaluated only once and depicted at the end of the other reports.I would try to post a complete tutorial on JasperReports in my next Post.

JasperReports

2005-11-02T21:17:00.000-08:00

I have not worked on Crystal Reports etc.JasperReports in the only reporting framework i have used.It is excellent and easy to use with IReport.It goes well with java.Check out this good tutorial on the web for JasperReports.

CVS - good book

2005-11-02T20:25:00.000-08:00

I had a hard time searching for some good documentation on CVS.I did get some tutorials but they were not of much help.Currently this book is online and it is a must read for anybody planning to setup and use CVS.I am planning to use CVS even for our small project,coz its extremely useful for keeping different version of the code.The book can be read online here.

Changing font size in the xterm

2005-10-17T23:15:00.000-07:00

use "ctrl" "-" "right mouse button" and select the font type
also you can use xterm -fb arial (to select new font for a new window)...
i am not sure how but i guess even setfont can be used.

Windows Admin Account SID

2005-10-04T20:19:00.000-07:00

For my current project i have to extensively use the Windows Registry for Data.One interesting thing about the registry is,it stores all its users info in the HKEY_USERS key. But the subkeys inside this registry key have some id attached to it.Thats the SID or Security Identifier to uniquely identify user and group accounts in Windows.Know one thing the SID with '500' at the end of it is the default Admin created by windows,when you install the windows on that system and '501' is for the Guest account.
There is a wonderful book on windows security.You can read the book online here ,but the book is really good and my suggestion would be to purchase a hard copy of this one.

Reading Windows Registry using C#

2005-09-28T05:01:00.000-07:00

Using C# you can easily access a Windows registry.There is a predefined Registry Class and RegistryKey class.You can read good doc about this thing here.

Converting WMI raw data to cooked data

2005-09-13T03:15:00.000-07:00

I was working on one of the features of my product which extensively uses the data from the WMI Win32_PerfRawData class.As the name suggests this data is raw and is not useful until it is cooked or formatted.Well in windows 2003 (the os we are using),there is another class PerformattedData which gives us the cooked data that we can directly use,but i had a hard time getting data from that class.
Some of the counters don't show up at all.
i tried wmiadap /f or wmiadap /resyncperf and started stopped the service using
net stop winmgmt /net start mgmt,but nothing worked for me.Thought wmiadap /f is a good command to generate those counters that don't show up directly.
Later i decided to use the RAW data itself and apply some formulas on it.I must tell you guys had i not found this article on the web i wouldn't have been able to do this part of the product.

Integrating Apache 2.0 with application server

2005-09-01T21:33:00.000-07:00

To create a stable j2ee architecture,its a general practise to keep a webserver infront of the Application server.This might help the webserver to serve plain html and .gifs fast to the customer (as static html and gifs reside on it) and can be directly served.While for the dynamic content the request will be forwarded to the Application Server.
I was trying to integrate WebSphere 5.x with Apache 2.0 and believe me even though the docs for websphere are there in the infocenter they are not clear enough.I found a good article on the web that gives extensive description of that,you can access that doc here

Deploying a Simple EJB on Weblogic 8.1 using Eclipse

2005-07-18T20:57:00.000-07:00

I have just installed web tool kit on eclipse,and no specific plugin for weblogic.But you still get the option to deploy on weblogic 8.1 , 7 etc etc.
Before writing and deploying an ejb using eclipse make sure you have
downloaded XDoclet and other necessary files mentioned below......

xdoclet-1.2.1.jar

xdoclet-ejb-module-1.2.1.jar

xdoclet-xdoclet-module-1.2.1.jar

xjavadoc-1.0.3.jar

commons-logging.jar

commons-collections-2.0.jar

Put these jar files in say C:\XDoclet.
Now in the eclipse window choose Windows -> Preferences -> J2EE Annotations -> XDoclet
and specify the path ( for e.g C:\XDoclet) and version 1.2.1 (in my case).

Creating the EJB is simple and the steps are mentioned in this tutorial here

I must say that i could not directly deploy the ejb on weblogic as the jar file created for the ejb module contained another jar file for the ejb client, and weblogic didnot recognize the classes in this client.jar and we get an exception while deploying the ejb on weblogic.
The workaround is to bundle the jar file with the respective client.jar classes manually and then deploy on weblogic.

A better solution would be to download the weblogic plugin(for eclipse) from bea , and use it.I have recently installed this plugin but i have not used it yet,i am not sure how good it is.

How I installed Eclipse on my windows 2000 professional

2005-07-11T22:04:00.000-07:00

Download the eclipse.zip file from here.
For developing web/j2ee projects you need to download these files too.
1) EMF
2) GEF
3) JEM
just unzip all these files in say C:\eclipse and you are done with the installation on windows.
Now click on eclipse.exe and you can start using eclipse.

Also i did a few other changes....
First check if jdk is selected properly....check in Windows - Preferences - Java - Installed Jre....(its better to choose a jdk version 1.4.2 or higher)......
I excluded the debugging option ,i am not sure but it used to hang my machine.For this go to Windows - Preferences - Validation, here choose the type that you would be needing.
I prefered to build and clean manually rather then doing it automatically thereby i disabled the build automatically option from Project - Build Automatically.

A good tutorial on building a web project with eclipse can be found here