Tomcat – java.lang.UnsupportedClassVersionError: Bad version number in .class file

Author - Webner

This is because your class files were compiled with a Java compiler not compatible with JVM in use within tomcat. If you compiled on same machine on which you have tomcat running, you must be having 2 JDKs (or a JDK and another JRE) with different versions. Solution to this Read more…

Fatal error: Allowed memory size of 16777216 bytes exhausted

Author - Webner

You need to change the maximum memory allowed to a php script to run.
For this you need to open your php.ini (location of this file will depend on where php is installed on your machine). In my case php.ini is in /etc/php5/apache2/php.ini

Open Read more…

Proxy Pattern and Dynamic Proxies

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Proxy pattern is about using proxy in front of another entity. It is a structural pattern, which means, it is implemented by changing/extending the structure of code.
One example of proxy classes is remote communication. In case of remote communication, proxy of remote object resides on client side. Purpose Read more…

SVN Merge

Author - Webner
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I use subeclipse plugin (in eclipse) to communicate with SVN. This discussion is applicable to SVN Merge in general but I have used subclipse references. Go through it even if you do not use eclipse/subclipse. It should be useful to you.
I found it confusing to use SVN merge Read more…

LAN Driver Not Installed

Author - Webner

I had not done Windows XP installation for long time by myself. After I did it couple of weeks back, I went into “My Network Places” to configure internet access, only to find no “Local Area Connection” element there in right frame. I was confused until I found that I Read more…

Forgot Linux Root Password

Author - Webner
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Recently I forgot root password of Open SuSE 10.2 Linux installed on my laptop. I searched over net to find steps below following which I was able to successfully reset (change) root password:

1. Boot the system and when you get Grub screen (Grub is boot manager which presents Read more…

Accessing webserver over LAN (Linux+windows)

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On one machine having SuSE 10.2 OS, I am running Jboss app server 4.2. By default it runs http server on port 8080. I was able to access it from browser using http://127.0.0.1:8080 URL. But I was not able to access it using Read more…

Database Surrogate PKs – Few points

Author - Webner
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I am sure this is obvious stuff but anybody can overlook it, so I thought of adding it in my blog. Many programmers and database designers are using surrogate keys instead of natural keys as PKs (primary keys) now a days. Numeric surrogate keys, obviously are easier and better performance Read more…

Making JRE work in Firefox – Suse 10.2 – 64 bit

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Like a lot of other people, I faced problems in enabling Java in Firefox on Suse 64 bit OS. But it is working now so I thought of writing the obstacles and how to get rid of them. Basically it comes down to 2 things:

1. You have to make Read more…

OOAD Introduction

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OOAD (Object oriented analysis & design)

Scope:

As most of you already know, OOA (Object-oriented analysis) and OOD (Object-oriented design) are put together and called as OOAD. To keep the discussion short I won’t be writing anything on the history of OOAD. Instead, let’s Read more…

Enabling JDK 1.5 support in JSPs on Jboss

Author - Webner
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Applicable to JBoss 4.0.4 GA:

Suppose you are using jdk 1.5 features in JSPs but they fail with following exception

jboss jsp Syntax error, parameterized types are only available if source level is 5.0

that means you need to enable jdk 1.5 vm support for Read more…

Evince – PDF file print problems on SuSE

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Evince is default document viewer for PDF files on SuSE 10.2. I tried to print pdf files opened in Evince but could not get them to print. Sometimes no error is reported (not even in CUPS error log) but document does not print at all. At other times “Broken Read more…

Eclipse 3.3.1 – Server did not start after 50s

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If you face this error – fix is to change “server timeout delay” under Window > Preferences > Server to higher value.
From ‘normal’ I changed that to ‘long’. Server started up in 55s, but still I received similar error , only time was changed to 100s now.
I set it to Read more…

install CUPS-PDF on SuSE 64-bit

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What is CUPS-PDF

CUPS-PDF acts as a virtual printer but instead of printing hard copies of your files, it prints PDF files as output. It appears as a printer under printer list on your machine, and if you select that you would get a pdf file Read more…

JBoss 5 Profile Creation Problem – Eclipse

Author - Webner
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If you face problem “mail.jar not found” on configuring JBoss 5 profile in Eclipse then the reason is JBoss 5 moved server/default/lib*.jar to server/common/lib folder. Fix for this problem is to change jboss5.serverdef under eclipse (${ECLIPSE_HOME}/plugins/org.eclipse.jst.server.generic.jboss_1 Read more…

SVN Switch

Author - Webner
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I am assuming you are working on code from branch A (it may be trunk as well) and have already made some changes locally. Now you find you can’t commit your changes to SVN because they are not stable yet.
First of all, you should have started working on Read more…

Linux – Get full path of a running process

Author - Webner
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2 ways that I know to get the full path of a process in linux:

1. /proc/ /exe is a symlink to the actual exe. Here’s what I get for a program eclipse running on my machine under pid 4825 with this command:

localhost:/home/Office # ls Read more…

DAO with JPA (and service layer/EJB3-Session Beans) or not

Author - Webner

There is a lot of discussion on internet about whether to have DAOs or not with JPA and service layer or with session beans (which is the service layer).

My personal opinion is more favored towards DAO layer and some reasons for this are following:

1. In most of the Read more…

Approach Java (1)

Author - Webner

Free Online Courses With Personalized Certificate

I started writing this tutorial targeting MCA students in Himachal Pradesh University, Shimla, India (from where I did MCA back in 99). This is an attempt to help students learn Java by practice. I am posting this tutorial(work in progress) on my blog Read more…

SCEA 5 – My 2 cents

Author - Webner
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recently became SUN certified Enterprise Architect after clearing all 3 parts of SCEA. It is hard to get answers to all questions one may have regarding SCEA but SCEA forum on javaranch.com is great!! I have shared my experience here for each part to help SCEA seekers.

Part 1 Read more…

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