• Tried to add a new category
• Tried to edit a post
• Tried to comment from the blog post page

When I tried to do the above things I was shown a big fat error message which cried out,

WordPress database error: [Table 'wordpress.wp_post2cat' doesn't exist]
SELECT cat_ID AS ID, MAX(post_modified) AS last_mod FROM wp_posts p LEFT JOIN wp_post2cat pc ON p.ID = pc.post_id LEFT JOIN wp_categories c ON pc.category_id = c.cat_ID WHERE post_status = ‘publish’ GROUP BY cat_ID

I managed to resolve this error in some time but those few moments were somewhat shocking. If you are getting the same error, the solution is quite easy. At first the error looks as something has gone wrong with your database but believe me, your database is fine. The problem maker are the plugins. The main cause of the above error are the following plugins:

• Google Sitemaps Generator
• Posts by Author plugin
• Ultimate Tag Warrior
• Similar Posts

Just disable these plugins and you should see your error disappear. You can later put in the latest versions of the above plugins and activate them. The Ultimate Tag Warrior plugin should not be required in my opinion since Wordpress 2.3 + has the feature of tagging a particular post.

Always remember, before upgrading a Wordpress to a newer version make a double check on the compatibility of the plugins you have already installed. The guys at Wordpress have made out jobs much more easier by putting an alphabetically sorted list of compatible plugins with Wordpress 2.3.

So when you install a plugin for Wordpress in future do the following:

• Download it from the official Wordpress plugin repository
• Check the version of Wordpress till which the plugin is compatible with
• Backup your blog through Wordpress Export feature before trying out a plugin.

Sometimes if you have self coded the theme, the error might not disappear because you might have used some tables like “wp_post2cat” which has been discarded in the newer version. So if your error is still not resolved try using the default theme (Kubrick) and then work your way out.

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 Unsupported major.minor version 49.0

This error is given because the new features introduced in the newer version of Java are not present in the older version. So you have to be careful for using such class files on older environments. For resolving this error you have to follow some simple tips as follows:

1. Check you java version by running the command java – version
2. Check your environment variable JAVA_HOME and the path associated with it
3. Check your server installation if it was installed on an older version
4. Check which path exists in the environment entries

These are the quick tips you would need to do in order to get rid of the error. Sometimes it may happen that the system which you are using might be loaded with 2 to 3 version of Java and you might be required to work on the newer one. In such cases always there is a confusion as to what went wrong and with which version. So if you are left in such crises do the following quick action tips:

1. Edit your JAVA_HOME with the latest java home folder path
2. Edit your path variable which might already have been set with older version
3. For this goto My Computer > Properties > Advanced > Environment Variables > path
4. Remove the earlier version path which might be something like <java_installed_path>/bin and replace it with newer version path
5. If your server was installed on a older version of Java and if it not been used then its better to uninstall it and then install it after making the above changes.

Note: You can check if your server was installed on an older version or not by opening the startup.bat of your Tomcat server or any start up script of other servers and finding the part where the script itself sets the JAVA_HOME variable. If you find that it has been set to a older version then it won’t do any good just by replacing it with a newer version path. You would ultimately have to reinstall the server as per my understanding.

It would be interesting to know if the same can be resolved without having to reinstall the server. Please suggest some alternatives if you have.

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I had NetBeans 5.5 with Sun Application Server prior to downloading Eclipse Europa. NetBeans was very amazing from the very beginning when I started with it. But since the enterprises here, use Eclipse as their de facto Java IDE my mind was made up, to work in their way i.e in Eclipse. Eclipse Europa which released a couple of days ago had the long forgotten feature of Web Application development called WTP built into the IDE along with 20 other sub projects. So this prompted me that, getting started with a new framework and a new IDE would be refreshing.

I had already configured Eclipse Europa to work with the Sun Application server earlier and I had the spring framework api’s with me so it was only a few moments from getting a head start. I created a dynamic web project in Europa making it compatible for running in Sun App Server and made a simple Controller and a view page in JSP, the minimal requirement from a Spring MVC tutorial. The configuration files were made and then I thought of running the project.

As I ran the project the error I got was,

java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory

I started to debug my application to see if any of my code or configuration had this Logger class included. But my code included only a single controller class and its mapping file in which no Logger was used. I thought maybe the Spring.jar wasn’t getting added in the classpath, even though I had added it as a external jar. I decided to manually add the file to WebContent/lib.

But still the error would not budge. I even added the jar file to build directory by making a lib folder in it. This also did not seem to make the error go away. It was insane. I had tried searching for the error on the web but the answer for that was the Logger was missing even though I had not added it anywhere in my code. The solution was to add the appropriate jar but I did not have those like Log4j.

Half of the day was gone in trying to solve an error which shouldn’t have come in the first place. Furious with the error I stopped with my spring campaign and thought of learning JAX-WS. I had the knowledge to use JAX-WS so wanted to give it a try in the new Eclipse IDE which everyone was making a hue and cry about. First of all there was no provision for making a web service project in the IDE. Netbeans 5.5 which I had earlier used way back last year to make web services already had the web service project in built.

I learn’t that for making a web service I had to download STP which meant SOA Tools Platform which had the capabilities to make a web service using JAX-WS in Eclipse. I downloaded STP and wasted about half an hour on it owing to my slow connection. After getting STP I read a tutorial on how to go about making a web service in it. A tutorial on the web stated that before making a web service with STP it should be configured with Apache Celtix Fire (CXF). What the f***?

I already have JDK 1.6 which comes shipped with JAX WS. So what was the need of having another one? Apart from this I also had installed JWSDP 2.0 web services developer pack from SUN. With some hope in mind I thought maybe it could be used instead of CXF. When I tried to configure it, Eclipse it gave out a lame error stating,

You must specify a valid installation location for your selected runtime provider in JAX WS References.

which in other words meant CXF installation.

Growing more and more frustrated at this utter nonsense I decided to download Apache CXF. It was even bigger than I had expected with a size of 21 MB. I kept it for downloading and took a break to start with a fresh mind later in the evening. I hoped to get at least something from that day, But more frustrations were in store for me.

Later in the evening when the download had completed I configured it in Eclipse and made way to the rest of the tutorial. The further steps were to make an interface and implementation and add annotations. I did that and was about to see how the WSDL and proxies would automatically get generated. The tutorial mentioned that when the interface with the annotations is saved the proxies and WSDL immediately get created without required the user to do do anything. But to my bewilderment I already saved the interface quite a lot of times but there was no sign of WSDL nor the proxies. This was even more frustrating than I had imagined.

Searching an answer to this irregular behavior of the IDE I came to know that I wasn’t the only one who faced this. There was another one which I read here. Unfortunately no solution was there. It was in the night that I was still trying to learn something and due to this nonsensical IDE I had gained nothing but frustration. I forgot to mention the regular hang ups which I suffered in between the activities. I was left clueless as to why Eclipse was chosen by enterprises and not NetBeans. One more thing which left me in disappointment was that Eclipse did not allow me to switch between the servers i.e Sun Application Server and Tomcat for running the same application! It said something like this,

Tomcat is not a Java EE 5 complaint server.

Thanks for the info but my project does not have EJB’s for God’s sake!

I gave up on using Eclipse and closed it. It was in the middle of the dark night that I opened NetBeans and heaved a sigh of relief. It looked more lovely than before thanks to the disgusting UI of Eclipse. I thought of making up for lost time by just implementing the things in spring which I wasn’t able to in Eclipse.

I made a new web application and added the spring.jar file, made a controller and view, added the mapping. And lo and behold as I ran the application with Tomcat as the server it flashed me the output in matter of seconds which I had wished way back in the morning. I switched the server to Sun App server and it ran smoothly as on Tomcat. This mere moments that I spent on NetBeans were the best ones in that entire unproductive day. These moments gave me the confidence to learn more the next day, the confidence which I thought I had lost. It was like a breath of fresh air.

I thank God for giving me NetBeans. I don’t know if anyone elsewhere thinks in the same way. But the fact is that it took me just one day to dump Eclipse, and go back to NetBeans. Long live the developers of NetBeans!

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Allowed memory size of 8388608 bytes exhausted (tried to allocate xxxxx bytes)

This means that the server is not allowing to process the size of the data than its maximum alloted size. Remember that there is nothing wrong with the Wordpress installation. Its the matter of the amount of data that the server can process at one time.

Don’t be scared, you can get it resolved in a matter of seconds. There are two ways of resolving this error.

Method #1 : Without Restarting the Server

If the error mentioned appears during the importing, what you need to do is get access to the source code of the Wordpress where you have done the installation.

Once you get the access you will need to modify two files . They are:

1. <installation_directory>/wp-admin/import.php
2. <installation_directory>/wp-admin/import/wordpress.php

Now copy this line of code:

ini_set('memory_limit','16M');

This line increases the server processing capacity by the included size i.e 16M. Paste the above line in the import.php file just after the line of code:

require_once ('admin-header.php');

Now in the second file i.e. wordpress.php paste the code after the line of code:

<?php

Note: If the error mentioned appears during the installation of a plugin then make a note of the path and the .php page which is given out in the error and paste the same line in the mentioned .php page.Remember, the code must be pasted within the php code block i.e in between <?php and php?> in the page since it is to be executed by the server.

Now once again access your Wordpress URL and go to the manage > import menu and try importing. If your problem still remains, just keep increasing the size mentioned in the pasted code in multiples of 4 i.e. in place of “16M”, try “20M”, “24M” etc.

Method #2 : Which Requires a Server Restart

If you want to eliminate this error once and for all then you need to target your server to make the changes. But you should have the permissions to restart the server.

If you have this permission then go to the server installed path and search for the file php.ini file. In this file there will numerous things mentioned. But all you have to do is search for the term “memory_limit“. Change the value of this variable from 8M to either 16M, 24M, etc as required.

Save the file and restart your server. The error will be resolved once and for all. Good luck!

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List list = new ArrayList();
list.add("someString");

The Eclipse IDE flashed a warning beneath the 2nd line of the code.

“Type safety: The method add(Object) belongs to the raw type List. References to generic type List<E> should be parameterized”

I had switched my project preferences to allow compilation of my code with the Java 5 runtime library. It was not before I came to know that it was the Java 5 generics in action. The moment I switched it back to Java 1.4 runtime the warning luckily disappeared.

Java 5 has removed the old technique of having you to cast the collection returned object to predefining the same collection of the type you want to cast. In the above example if I want to indeed include a String object in the List then it is but obvious that I would cast the returned object from the List to String as follows:

String s = (String)list.iterator().next();

To avoid this obvious nature of casting while using a collection Java 5 asks you to parameterize the template you would be using in the collection. So in Java 5 the code I was trying to accomplish would be as follows,

List<String> list = new ArrayList<String>();
list.add("someString");
//and while retrieving
String s = list().iterator().next();

The above code would be much more familiar to C++ programmers who have used templates. In case of Java it would be the same as using templates. Java 5 Generics has much more features and lots of new concepts for a clutter free code while using collections.

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So what is the solution to the defamed 34 minute XP installation hangup problem?
Its as simple as deleting a simple file which caused the installation to freeze.

• Let the XP hang up at 34 minutes remaining for the first time
• remove the CD from the CDROM and reboot
• Dont enter the CD when the installation asks for it, instead open the DOS prompt (Shift + F10)
• goto C:/Windows and type setupapi.log, hit enter
• The setupapi.log file opens in a notepad
• Scroll to the very last few lines in the file and search for the word “inf”
• You will notice that in the last few moments the installation created a file with the extension “.inf” before dying out (in my case it was the faulty modem for which XP created the file mdmcxpt.inf).
• It means that the device mentioned in the last few lines is faulty and you have to make the installation skip through it.
• Close the notepad and go to the folder C:/windows/inf in command prompt
• Browse through the files to find the “.inf” which was related to the faulty device.
• Straightaway delete the inf file (eg: del mdmcxpt.inf)
• now put in the XP installation CD and Continue the installation

It will not put in the drivers related to the faulty device and so it wont freeze this time !!

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