Killing processes in linux

I have a laptop running Ubuntu 9.04. Recently Lotus Notes was installed on it. Notes seems to become unstable some times. The instability is so bad that I can't close the program in the normal way (mouse-click the 'x' button in the upper right corner. I would have to run

ps ax | grep notes

to get the process id and then run

sudo kill -9 *procId*

to kill it.

Tyler, a coworker, pointed out to me that I could add 'Force Quit' to the panel at the top. When you press that you can just click on a misbehaving window to kill it.

Java HashSet can "lose" objects

If the hash of an Object changes, the Object is 'lost' in a HashSet.

I have some code that invoked HashSet.remove(Object) and the object was NOT removed. Turned out that after the object was added to the set, a field that is involved in computing the HashSet was changed. Then, because the hash of the object changed, the remove method didn't remove the object. I tested in Sun Java 1.6.0_13 and in on IBM jdk 1.5. I found this blog post about the subject that contains a good explanation.

I don't think this limitation is sufficiently documented Java's HashSet.

Thanks to Boris Kirzner

http://boriskirzner.wordpress.com/2006/10/01/hashsetcontains-does-your-busket-contain-something/

Internet Explorer Collection (Multiple Versions of Internet Explorer Installed on MS Windows)

I have just come across this package that can install many/all compatible Internet Explorer versions in your windows environment. Take a look.

Derby

Thanks to Bruce Phillips for this post on using the derby server that comes with MyEclipse.

Especially the part about adding an attrib to the connect string to create a new schema. (jdbc:derby://localhost:1527/phillipsDB;create=true)

http://www.brucephillips.name/blog/index.cfm/2009/2/28/Using-the-MyEclipse-Derby-Database-Server

MercurialEclipse

Installing MercurialEclipse plugin I've run into the problem that the plugin would say something like 'error when verifying mercurial install...'

Well. I installed the mercurial 1.2.1 windows binary package from here: , set HG environment variable to the path to the hg executable. the hg install directory was added to the PATH. Now the pluggin seems to work well.

Atheros Wireless in Ubuntu 8.10 Intrepid Ibex

Thanks for this blog entry
http://unsharptech.com/2008/10/31/atheros-wireless-in-ubuntu-810-intrepid-ibex/

With my Toshiba L355D-S7825 laptop I have to install a backports package

The package is linux-backports-modules-intrepid-generic

sudo apt-get install linux-backports-modules-intrepid-generic

Could not install cygwin on MS Windows Vista 32-bit

I just did a fresh install of windows on a fairly new laptop. The factory install was corrupt in some way. Windows explorer would crash all the time. It was annoying. So I wiped the harddrive and restored with Toshiba's handy-dandy windows-recovery-and-bloatware-restoration cd.

Any windows machine I use regularly has cygwin installed. I need my linux/unux-like tools. Cause I'd loose my geek card if I didn't unzip files using command line tools.

Something happened during the installation. It froze and never progressed. I've installed cygwin a bunch of times, so I'm confident this was not a case of impatience. I killed the install. Later I started another install. This would fail with a message to the effect that cygwin install failed to start because cygintl-3.dll couldn't be found. This caused bash.exe to hang. Tried a couple more times. Same result.

I decided that there might be something wrong in the cygwin-packages directory. When you run the installer it asks for a package dir and an install dir. So, I deleted the package dir.

The next run of the installer was completely successful.

I messed up my install of Juice podcatcher

Long explanation (If you want the skinny, just look at the summary below)

Update, 2/1: the fix was not completely successful. See the update at the end.

This isn't really a software engineering topic. But, hey! It's my blog. Someone might really need this information!

So I wanted to try the Juice open source podcast receiver (some people call them podcatchers). As of my writing this article, the current version is 2.2. I installed it, started it, opened up the preferences and saved them with a wrong path to the directory where my podcasts should be saved. I think the problem is that by default the path was wrong for Vista. It was "C:\Users\\My Documents\My Received Podcasts"

But it should have been "C:\Users\\Documents\My Received Podcasts".

After I saved the preferences with the invalid path, Juice would crash every time I tried to start it. The following is from the log and shows the error that was crashing Juice.

Traceback (most recent call last):
File "gui.py", line 4, in ?
File "iPodderGui.pyc", line 3573, in main
File "ipodder\configuration.pyc", line 468, in __init__
File "os.pyc", line 154, in makedirs
OSError: [Errno 17] File exists: 'C:\\Users\\Ari Zelanko\\My Documents\\My Received Podcasts'

I tried to find a solution by googling the error. It didn't yield anything. Several people had posted questions on many sites about similar problems. No solutions were published.

I tried to reinstall the application. I uninstalled and reinstalled. No improvement. Juice still crashed on startup. I opened up the readme file in the Juice install directory. It has a section about updated from an older version of Juice (formerly iPodder). This is a quote from the Juice 2.2 readme file:

In iPodder 1.0 the settings were stored in the iPodder installation directory, probably C:\Program Files\iPodder. Starting with version 1.1 the configuration are placed outside the installation directory, in a user-specific directory, if possible. The default location is the NT-style Application directory, usually C:\Documents and Settings\yourname\Application Data\iPodder. If your settings were lost, try locating these three files in the previous installation directory and copying them to the new configuration directory: favorites.txt, history.txt, schedule.txt.

So, I started to look around my user directory for the settings. I found them. On Vista the path to the configuration was "C:\Users\\AppData\Roaming\iPodder".

"I'll just remove the settings folder and Juice will start up normally, right?" I thought. So I deleted the iPodder directory under my user profile. I started up Juice and voila! There was no change. Juice still crashed with the same message! How infuriating! (I should stop the gratuitous use of exclamation points!)

Just when I was about to give up, I thought, "Maybe if I reinstall right now, the problem will go away." ... And that worked.

Summary

The problem:
Because I set an invalid path-to-save-my-podcasts-to in the Juice preferences, the application wouldn't start. Rather it would crash on startup.

The error log:

Traceback (most recent call last):
File "gui.py", line 4, in ?
File "iPodderGui.pyc", line 3573, in main
File "ipodder\configuration.pyc", line 468, in __init__
File "os.pyc", line 154, in makedirs
OSError: [Errno 17] File exists: 'C:\\Users\\Ari Zelanko\\My Documents\\My Received Podcasts'

The Solution:
I removed the iPodder config directory under my user profile ("C:\Users\\AppData\Roaming\iPodder"). I then ran the Juice 2.2 installer again. I started the app and this time set the right directory for saving podcasts!

Update: The fix wasn't successful (2/1/2009)
After a restart, the problem in this post returned. For now I've carefully reproduced the issue, entered a bug with the project and included logs, config files and such. I've uninstalled Juice for now. I think I will look for another free podcatcher program.

Java Resources

Thanks to theServerSide for this great article by Ted Neward.

It contains a lot of resources for an up-and-coming java dev.

Install Ruby from binaries on Windows

Suppose you want to install ruby on Microsoft Windows and you don't want to use the One-click installer. Maybe it's because the installer is for ruby 1.8.6 and the newest stable binaries are for 1.8.7. You just have to get the most up-to-date binaries, because obviously 1.8.6 is just way too old.

I looked around for instuctions and found the answer posted by Lolindrath at stackoverflow.com.

1. Download the windows binaries for Ruby 1.8.7 here: http://www.ruby-lang.org/en/downloads/ extract that to wherever you would like, I use c:\ruby. Then put c:\ruby\bin in your PATH environment variable.
2. Download the zlib package: http://www.zlib.net/zlib123-dll.zip and extract the zlib1.dll, rename it to zlib.dll and move it into your Windows\System32.
3. Download the iconv package: http://sourceforge.net/project/showfiles.php?group_id=25167&package_id=51458. Find and extract the iconv.dll into your Windows\System32.
4. Download the rubygems package and follow the instructions, basically extracting the package and running ruby setup.rb
5. Verify that everything works properly by trying a gem install rails, once that installs then do: rails test_project

These are the steps just as they were posted. I didn't just download the libraries from the links above. I checked for newer versions, but as of this post, there were none. I have not done step five. But I've installed a few gems and a couple of scripts I've written run fine.

That file isn't open!

I sometimes need to do something like delete a file and I can't because, according to windows, a program has the file open. Sometimes this happens because a process doesn't exit when you think it has.

Do you want to find out what program has a file open?

You can do it with a free program called ProcessExplorer.
In the program's Find menu choose 'Find Handle or DLL...' (Or press ctrl-F)
Enter a part of the file's name. Press enter. Voila! You now have a listing that includes the process id that has that file open. If you kill the process, you should have no trouble deleting that pesky file.

If you are not sure what killing a process is or if you should, then just restart the computer and that should fix the problem.

Updating RubyGems broke the gem command

On a windows box where I have ruby installed at "C:\Program Files\ruby\" rather than "C:\ruby\".

I ran:
gem update --system

The result was that the next time I tried to execute the gem command I got the following:

C:\>gem
The filename, directory name, or volume label syntax is incorrect.

I found that the gem.bat file had been changed and there was an extra double-quote on two lines.

@"ruby.exe"" "c:/Program Files/ruby/bin/gem" %1 %2 %3 %4 %5 %6 %7 %8 %9

And

@"ruby.exe"" "%~dpn0" %*

In both these cases, where there were two juxtaposed double-quotes (two double-quotes in a row), I had to remove one of the double quotes. Yielding:

@"ruby.exe" "c:/Program Files/ruby/bin/gem" %1 %2 %3 %4 %5 %6 %7 %8 %9

And

@"ruby.exe" "%~dpn0" %*

Problem was solved. I found a comment on the RubyGems forum that agreed with my fix.

Using patches to manage bug change-sets

I have just discovered that you can manage sets of changes in Eclipse by using patches.

In the Package Explorer, select Team | Create Patch...

Follow wizard to export the patch file to the clipboard, the filesystem or the workspace.

You can then Override and Update to return the workspace to a state corresponding to the CVS repository.

Later, you can Apply Patch.. from the Team submenu, select the patch file you previously exported. Voila, your changes are back.

Identifying the source of a java Class

My coworker, Mike, shared this with me. You can find out what jar a class is loaded from.
Class.forName("com.foo.MyClass")
.getProtectionDomain().getCodeSource()

Setting up Websphere for a remote debugger

Here are a couple of references for configuring Websphere for use with a remote debugger:

Jacoozi: Remote Debugging with Eclipse
IBM Documentation -- another method, i have not tried.

Basically:

In the websphere administration console, go to a server's configuration and set it up.

Getting DB2 Error Code information

There is a way to get DB2 error information if you have DB2 installed.

Start the DB2 Command Line Processor (CLP).

For SQLCODE -551 you type: "? sql551"

For SQLSTATE 56098: "? 56098"

Bugzilla Comments are mostly plain text, so don't use HTML

Today I tried to get fancy using HTML in a bugzilla.

I wanted to do something like

<pre>
... some code ...
</pre>

for the sake of readability.

Well, I found out that doing so will just result in those tags showing up in the comment.

But bugzilla will try to create some hyperlinks for things in comments. See the Hints and Tips page of the bugzilla manual for more information.

ILog JRules BOM Update is trying to remove classes that I need!

Periodically, I need to update the JRules Execution Object Model and then update entries in the Business Object Model, accordingly.

Yesterday, when I did my normal procedure for this, the Update BOM option on a BOM Entry tried to remove a bunch of classes that I needed in the BOM.

I didn't know why.  So I experimented.  I created a brand new BOM Entry and tried to add the classes that JRules wanted to remove from the real BOM Entry.  It threw an error.  I tried to add some classes that were direct dependencies of the first, and they had the same problem.

I tried to think what had changed that these classes suddenly couldn't be in the BOM.  Then I remembered that we had recently changed the base class to use Log4J.  Log4J isn't part of the XOM.  So maybe the BOM can't use a class if it doesn't have a access to to the classes dependencies.  So, I tried adding a Log4J jar to the XOM project.  After doing that, the classes from the XOM that had become dependent upon Log4J stayed in the BOM.  The next time I tried to update the BOM, those classes remained in the BOM.

Deferred Constraints

In the Oracle DB, you can define a constraint as deferable. You can then make the constraint check fire at commit. It turns out, according to the DB people at my employer, that DB2 by IBM cannot. We have a table where rows can reference each other.

For example:

CREATE TABLE SELF_REFERENCE_EXAMPLE(
pk unsigned long;
...
another_row_pk;
CONSTRAINT FOREIGN KEY examplefk REFERENCES SELF_REFERENCE_EXAMPLE (pk);
);

And suppose we had a table like this.

pk |... |another_row_pk
=============================================
101 ... 208
208 101

Now, if we needed to move these rows to a history table, we can't move either because the other referenced row will not be in the history table.

In oracle we could make the history table fk constraint deferred and insert both rows. The fk constraint will be checked at commit, so there is not fk violation.

DB2 won't let us do the constraint deferral trick. So we have to do something like

insert 101 into the history table without its reference to 208.
insert 208 without its reference to 101.
update both rows with their respective references.
commit.

I really don't like ILog JRules

I'm using JRules 6.5.3. I am not loving it. It is really slow.

There is an eclipse-based IDE called ILog Rule Studio. It works somewhat, but builds are slow and you can't use the most recent jvm.

It is restricted to Java 1.4 and Java 5. If you use anything more current, some features of the ILog plug-ins won't work. Ruleset or RuleApp exports did not work until I installed the latest 1.5 JDK.

To use JRules you go through a process of "verbalization". You associate, hopefully, understandable English phases with java code. But doing a verbalization is painfully slow. When you verbalize, the save operation takes an amazing amount of time. I would say 10-30 seconds.

OpenLDAP wouldn't start. Here's how I fixed it.

Yesterday, a power outage brought my computer at work crashing down. When I tried to get my development environment going again, I couldn't interact with my local OpenLDAP server.

The slapd.exe process would essentially hang. I killed the process, and started it from the command line:

$ slapd -d -1

This showed that the process was hanging after loading a file in the data directory.

So I zipped up (zip file) the data directory. and then deleted the contents. Now, it would start up.

But there are no entries in the directory now. So I import an ldif file and, Voila!, I'm back in business.

Prototype extends arrays so they should not be used as hash sets

We've started using the Prototype js library. We were having some weird behavior with some arrays in existing code when the Prototype lib was included in a page.

Turns out that Prototype adds some methods to Array. They are good, but one should be careful using Array objects as hash(key-value) sets.

Here is the blog entry we found that cleared everything up.

The skinny, Use Object as a hash, nothing else.

Thanks for the insight, Andrew Dupont.

Java reflection: primitive arguments in methods

Suppose that we want to reflexively invoke an instance method for a java object. Further, suppose that one or more of the method arguments is of a primitive type (i.e. int, small, double, ...).

In the Class.getDeclaredMethod(String, Class[]) method, you pass in a string representing the method name and an array of Class objects representing the types of any arguments.

For the following class :

public class Reflector {
public void intMethod(String aString, int anInt) { /* Some Code */}
public void integerMethod(String aString, Integer anInteger) { /* Some Code */}
}

You would get the methods reflectively like so:

. . .
Reflector r = new Reflector();
Method m = r.getClass().getDeclaredMethod("intMethod", Class[] {String.class, Integer.TYPE});
Method m2 = r.getClass().getDeclaredMethod("integerMethod", Class[] {String.class, Integer.class});
. . .

And invoke them thusly:

. . .
m.invoke(r, Object[] {"MyString", Integer.valueOf(100)});
m2.invoke(r, Object[]{"MyString", Integer.valueOf(100)});
. . .

For m.invoke, you wrap the int in the wrapper class since we're passing in an array of Object. Java automatically tries to unwrap it for you.

For an argument that is of primitive types use the following when defining the signature:

byte => Byte.TYPE
short => Short.TYPE
int => Integer.TYPE
long => Long.TYPE
float => Float.TYPE
double => Double.TYPE
boolean => Boolean.TYPE

Velocity

Velocity Template Language (VTL)

Statements begin with '#'
ex. #set( $a = "Velocity" )

References (varables, properties, and methods) begin with '$'
Formal notation ${}
Quiet notation $! or $!{}

Literal string delimited by single-quote
ex. 'I know strings'
Interpolated string delimited by double-quote
ex. "I love $a" => I love Velocity

## This is a single line comment

#* This is
a
multiline
comment *#

#**
This is a documentation comment
@author Me
@version 5
*#

escaping characters
$$ => $
This snipet
#set($foo='dude')
Hi $foo
Hi \$foo
Hi \\$foo
Hi \\\$foo
produces
Hi dude
Hi $foo
Hi \dude
Hi \$foo

If a reference is undefined,
Hi $foo
would produce
Hi $foo
because $foo is undefined
while
Hi $!foo
produces
"Hi "
without the ".

Internet Explorer on Linux

http://www.tatanka.com.br

This site offers an option for easily installing several versions of IE for LINUX.