Synergy of Loxal: Patterns & Paradigms

Maven Error: Return code is: 401 - TransferFailedException

2010-09-08T17:25:00.023+02:00

Problem:

Uploading: http://loxal.artifactoryonline.com/loxal/libs-snapshots-local/loxal/example/demo/1.0.1-SNAPSHOT/demo-1.0.1-20100908.151817-6.jar

[INFO] ------------------------------------------------------------------------

[ERROR] BUILD ERROR

[INFO] ------------------------------------------------------------------------

[INFO] Error deploying artifact: Failed to transfer file: http://loxal.artifactoryonline.com/loxal/libs-snapshots-local/loxal/example/demo/1.0.1-SNAPSHOT/demo-1.0.1-20100908.151817-6.jar. Return code is: 401

[INFO] ------------------------------------------------------------------------

[INFO] Trace

org.apache.maven.lifecycle.LifecycleExecutionException: Error deploying artifact: Failed to transfer file: http://loxal.artifactoryonline.com/loxal/libs-snapshots-local/loxal/example/demo/1.0.1-SNAPSHOT/demo-1.0.1-20100908.151817-6.jar. Return code is: 401

Caused by: org.apache.maven.plugin.MojoExecutionException: Error deploying artifact: Failed to transfer file: http://loxal.artifactoryonline.com/loxal/libs-snapshots-local/loxal/example/demo/1.0.1-SNAPSHOT/demo-1.0.1-20100908.151817-6.jar. Return code is: 401

Caused by: org.apache.maven.artifact.deployer.ArtifactDeploymentException: Error deploying artifact: Failed to transfer file: http://loxal.artifactoryonline.com/loxal/libs-snapshots-local/loxal/example/demo/1.0.1-SNAPSHOT/demo-1.0.1-20100908.151817-6.jar. Return code is: 401

Caused by: org.apache.maven.wagon.TransferFailedException: Failed to transfer file: http://loxal.artifactoryonline.com/loxal/libs-snapshots-local/loxal/example/demo/1.0.1-SNAPSHOT/demo-1.0.1-20100908.151817-6.jar. Return code is: 401

Solution:
Add

   <server>
   <id>loxal</id>
   <username>deployer</username>
   <password>password</password>
   </server>

to the section of your settings.xml in

The Maven install: $M2_HOME/conf/settings.xml (this worked for me)
A user's install: ${user.home}/.m2/settings.xml

whereby loxal should be replaced by the repo id where you want to upload your artifacts.

Factory Class Pattern with Interface

2010-09-07T10:44:00.002+02:00

A sample implementation of the factory OO pattern incl. interface which is used in many languages. This example is implemented in Java but the concept is the same in all languages: Creating a factory class that creates settings/environment/parameter-dependent classes. This pattern example can be easily translated into .NET/C#. To get the complete demo code quickly, just pull its source code from this Mercurial repo.

class Cat extends Mammal {

String doWalking() {

return "Cat has been Informed to perform Walk Operation";

}

class Dog extends Mammal {

String doWalking() {

return "Dog has been Informed to perform Walk Operation";

}

class Main {

private static MammalFactory forDogs = new MammalFactory() {

@Override

public Mammal createMammal() {

System.out.println("Dog created...");

return new Dog();

}

};

private static MammalFactory forCats = new MammalFactory() {

@Override

public Mammal createMammal() {

System.out.println("Cat created...");

return new Cat();

}

};

public static void main(String[] args) {

new MammalClient(forDogs).createAndLetWalk();

new MammalClient(forCats).createAndLetWalk();

}

abstract class Mammal {

abstract String doWalking();

}

class MammalClient {

private final MammalFactory factory;

MammalClient(MammalFactory factory) {

this.factory = factory;

}

void createAndLetWalk() {

factory.createMammal().doWalking();

System.out.println("\t...let walk.");

}

interface MammalFactory {

Mammal createMammal();

}

How OSS helps companies to save money

2009-11-24T08:31:00.003+01:00

Yet another money saving aspect of Open Source Software for companies results from the fact that by open-sourcing their software, many developers (hobbyists but also professionals) work with its code and get familiar with it. So the numer of people that know the specific software code rises. Now, if any company that uses OSS needs to customize or evolve this software it don't depend on just a few and therefore very expensive experts but can choose from a lage pool of OSS enthusiasts. And these people are already acquainted with this software and don't need any time (=money) to get familiar with the code base. However this decreases software development costs and therefore facilitates the software development as such.

Google Chrome OS' local file system

2009-11-19T21:50:00.004+01:00

I was curious about the file system of the upcoming Google Chrome OS. As I haven't found this info anywhere on the chromium.org site (ok, Chrome OS was released only just 30min ago :). So I've pulled the source and scrolled through... In the source tree I've found ext2* and ext3* files that indicate that it uses either ext3 only because the ext3 file system is basically the journaled version of ext2 or it uses both ext3 (for local storage) and ext2 (for the static parts). However there were no ext4 files. For those of you not familiar with Linux — all these are Linux file systems.

How to increase the VM memory for IntelliJ IDEA

2009-07-26T22:27:00.004+02:00

To increase the maximum "total heap size" the default value of 256 MiB, you have to modify the /Applications/dev/IntelliJ IDEA 9.0M1.app/Contents/Info.plist file under your Mac OS X. You have to change the VMOptions key:

VMOptions
-Xms64m -Xmx512m -XX:MaxPermSize=256m -Xbootclasspath/a:../lib/boot.jar -ea

...these settings should beware you from hangups during long working sessions.

GWT, Spring@Grails (Java/Groovy), GAE - play together in harmony

2009-05-17T15:31:00.009+02:00

There is the Wentity project which shows as a proof-of-concept how to incorporate these technologies and let them play together in harmony: It uses Google´s App Engine infrastructure for a Spring based version of Grails which also uses Google´s Web Toolkit for RIA content. The project is in a structure-finding draft phase. Nevertheless it can be built and deployed on GAE. Use it as a template for your own project to save time! Along with Groovy you can also use your Java code in this project. Also it has the capability to i18n enhance your web apps to offer internalized/translated versions of them. The Wentity demo site gives you an impression for the functionality which is already been implemented and working.

Google Gears Linux x86_64-bit Plugin Download for Firefox Browser

2009-04-25T03:45:00.002+02:00

There is an issue describing this problem (no x64 version available) on the Google Gears development site. Also you can find continuously updated x86_64-bit versions of the Google Gears Firefox add-on/plugin there.

Importing/Adding GPG keys to Apt-Get/Aptitude

2009-04-13T19:57:00.002+02:00

If you get messages like this...

W: GPG error: http://dl.google.com stable Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A040830F7FAC5991

...when you are updating your package list via apt-get or aptitude, you have to import the missing GPG key, in order to avoid these warning messages in the future:

gpg --recv A040830F7FAC5991
gpg --export --armor A040830F7FAC5991 | sudo apt-key add -

In this way you can add a new GPG signature key for the distributed packages to apt-get.

Audio/Volume control keyboard shortcuts in Xfce configuration

2009-04-13T14:26:00.003+02:00

To control the volume settings in Xfce with keyboard shortcuts, you have to assign the following commands in the "Application Shortcuts" section of the "Keyboard" configuration menu to corresponding shortcuts:

amixer set Master 5+ : increase volume
amixer set Master 5- : decrease volume
amixer set Master toggle : mute/unmute volume switch

Eclipse: 32-bit GWT (GTK) configuration on x86_64 arch to avoid "Failed to load module"/"wrong ELF class"

2009-04-12T21:14:00.003+02:00

If you get "Gtk-Message: Failed to load module "canberra-gtk-module": /usr/lib/gtk-2.0/modules/libcanberra-gtk-module.so: wrong ELF class: ELFCLASS64" messages on the console when you launch a Run/Debug Configuration of your GWT Web Application, you should set the value of the environemtal variable GTK_PATH to /usr/lib32/gtk-2.0:

...whereby ${GTK_32_PATH} should have the value /usr/lib32/gtk-2.0. Eventuall you have to install the ia32-libs-gtk package to make /usr/lib32/gtk-2.0 available.

You haven't to use the x32 JDK/JRE as your default Java VM for the whole x64 system but install ia32-sun-java6-bin package and set this VM as your default JRE only in Eclipse (for the projects) but not for Eclipse itself:

Apt Repository to install: Skype, Acrobat Reader, Real Player, Google Earth, restricted video codecs or the Acrobat Firefox plugin for Linux?

2009-04-11T02:14:00.006+02:00

...if you're looking for anything above, you should add the Medibuntu Ubuntu package repository to your apt-get/aptitude list! This allows you to install pre-configured and actually working Skype, Acrobat Reader, Real Player, Google Earth packages as well as many video codecs to play DVDs and odd video files under Linux. Furthermore you can install the Acrobat Reader plugin for Firefox that allows you to view PDFs within Firefox without opening any additional PDF viewer software. Some speech codecs are included as well and restricted video codecs (ppc-codecs, w32codecs, w64codecs) make it possible to play encrypted DVDs.

Windows Vista x86 vs. x64 (32-/64-bit) - which is better?

2009-04-08T08:28:00.002+02:00

Questions about RAM support (4 GB RAM barrier), performance, and security are clarified in a brief overview on this site. Not only the question whether Win Vista supports 4GB of RAM is clarified, but also security related questions regarding the both architecture editions of Windows Vista will be answered: PatchGuard, DEP, Driver Signing.

Password-less sudo (auto-sudo): Sudo without entering a password

2009-04-05T20:42:00.007+02:00

Sometimes "getting the work done" has a greater priority for people than security: And this how-to addresses those people. However a password-less sudo command execution might decrease the security level of your machine, as executing the sudo command without entering a password, allows all local users (which are also able to execute the sudo command itself) to execute commands as root user. So an auto-sudo may allow local users to gain root privileges.

sudo visudo

...should let you modify the sudoers file and enable auto-sudo:

# [...]
# User privilege specification
root ALL=(ALL) ALL

# Uncomment to allow members of group sudo to not need a password
# (Note that later entries override this, so you might need to move
# it further down)
%sudo ALL=NOPASSWD: ALL

# Members of the admin group may gain root privileges
#%admin ALL=(ALL) ALL

Note that these entries have to be in the "User privilege specification" part of the sudoers file. Entries like %admin ALL=(ALL) ALL would override the pasword-less sudo behavior and should be commented out. The %sudo in %sudo ALL=NOPASSWD: ALL represents the "sudo" group. To make auto-sudo work, you should either add the auto-sudo user to the "sudo" group or replace the "sudo" group by a group which contains the auto-sudo user. There is usually a system group which has the same name as the respective user. So you could use this group name instead of "sudo".

Password-less SSH login (auto-authentication/login) on a remote machine

2009-04-05T08:10:00.018+02:00

ssh-keygen -t rsa

...will generate an id_rsa and an id_rsa.pub file in your ~/.ssh/ directory. Afterwards you have to copy your id_rsa.pub file which is basically your public key, to the ~/.ssh/authorized_keys file on the remote machine. So if you copy the id_rsa file to the /root/.ssh/authorized_keys file of a remote (or local...) machine, you should be able to log-in on this machine as root without providing any password:

scp ~/.ssh/id_rsa.pub root@example.com:/root/.ssh/authorized_keys

scp ~/.ssh/id_rsa.pub anyUser@example.com:/home/anyUser/.ssh/authorized_keys

Also you should pay attention NOT to copy the ~/.ssh/id_rsa file, as this is your private key which should be kept secret. However an auto-login resp. auto-authentication which allows you to login on a remote machine without entering a password might decrease the security level of the remote machine: So if anybody get your private id_rsa key, he is able to auto-login on this machine as well.

How to convert VDI to VMDK; Converting a VirtualBox image to a VMware disk image and vice versa

2009-04-04T11:54:00.007+02:00

You need the QEMU emulator software package

aptitude install qemu

in order to execute this command

qemu-img convert VirtualBox-HardDisk-image.vdi -O vmdk VMware-virtual-machine-image.vmdk

You should keep in mind that you might get an IDE VMware disk image in this way but a SCSI hard disk image is recommended by VMware for more I/O performance.

Just type

qemu-img

to get all supported formats which you can supply as the -O parameter. It is also possible to convert a VMDK to a VDI hard disk image. To convert a VMware image to a VirtulBox image, you have to use the qemu-img-vdi command which you can get by patching QEMU.
Afterwards you may execute this command:

qemu-img-vdi convert VMware-hard-disk-image.vmdk -O VDI VirtualBox-image.vdi

Tuning ext4 for performance with emphasis on SSD usage

2009-04-02T04:24:00.027+02:00

The obligatory disclaimer: The more performance you gain, the more data integrity you loose! But if you want to tune something like a file system, I strongly assume that you know what you are doing :) These tips apply to all major Linux distributions like Fedora/Red Hat, OpenSUSE, and Ubuntu that are already using ext4 or are going to make ext4 their default file system.

As write operations on Solid State Disks (SSD) are expensive the tips below are focused on SSD usage but also apply to HDD usage as well.

My Ubuntu 9.04 Jaunty /etc/fstab after a fresh installation:

[...]
UUID=d818ddf9-ff01-e21a-a67d-3ceab43a9e2b / ext4 relatime,errors=remount-ro 0 1
UUID=0d339122-74e0-e0ea-805a-7879b1fa3172 /home ext4 relatime 0 2
[...]

My tuned Ubuntu 9.04 Jaunty /etc/fstab:

[...]
UUID=d818ddf9-ff01-e21a-a67d-3ceab43a9e2b / ext4 noatime,barrier=0,nobh,commit=100,nouser_xattr 0 1
UUID=0d339122-74e0-e0ea-805a-7879b1fa3172 /home ext4 noatime,barrier=0,data=writeback,nobh,commit=100,nouser_xattr 0 2
[...]

data=writeback: The default data mode is ordered. This mode provides only meta-data journaling which is similar to the default data mode in ReiserFS, XFS, and JFS. Enabling this option on the root partition, caused an error during boot time. So enable this option only on non-root partitions!
nobh: Implies data=writeback; Avoids buffer heads to data pages association.
barrier: The default value is barrier=1 (activated). Deactivating write barriers in the jbd code will improve the performance. If you don't have a battery-backed storage environment, you should not deactivate this mount option.
noatime: Deactivates the file access time modification which is basically a write operation that should be avoid on SSDs.
relatime: This is a faster alternative to the atime (default) option. You can set it, if you need the file access times to be set. However it is still responsible for write operations which should be avoid -- especially on SSDs.
commit: Increases the commit/write interval (default: 5s). Actually it is a sync operation between data and meta-data which is an important data-safety feature.
nouser_xattr: Disable Extended User Attributes if you don't need them. If you are using a desktop setup at home (or in a small office network), you may not need this feature.
errors=remount-ro: Many distribution add also this boot option. In fact this boot option can be omitted without any hesitation as this boot option is set by default.

If throughput is a major issue and latency not a big problem, you may also increase the min_batch_time option value which defaults to 0 microseconds.

The main source for these tips was the kernel reference documentation paper of the ext4 file system.

Note:
You also may be interested in how to tune ext3 for performance or how to use a swap file instead of a swap partition.

Update:
With these pretty aggressive performance settings my data has already survived a couple of crashes (incl. sudden power outages). So I will keep these settings :)

Update 2 (thanks to an anonymous comment!):
To enable the data=writeback on the root (mounted on /) partition boot your machine in recovery mode and execute:

tune2fs -o journal_data_writeback /dev/sdXY

Afterwards you can add the data=writeback option to your root partition in your fstab file.

How to deactivate/disable the webcam module auto-spawn in Ubuntu 9.04 (Jaunty)

2009-04-02T02:01:00.005+02:00

If you don't like the default web cam auto-spawn behavior in Ubuntu 9.04 (Jaunty), you should modify your /etc/modprobe.d/blacklist.conf:

echo -e '# my modifications\nblacklist gspca_m5602\nblacklist gspca_main' >> /etc/modprobe.d/blacklist.conf

...was the solution for my Lenovo 3000 V200. You should replace gspca_main resp. gspca_m5602 by webcam modules in your notebook. You can get a clue for the name of your web cam module reviewing this overview site.

How to speed up the GWT compiler (reduce compilation time)

2009-03-28T15:55:00.001+01:00

If you want to boost you GWT compilation performance by reducing the GWT compilation time significantly, you have to modify your Module.gwt.xml. You can speed up the compilation by reducing the number of supported browsers or/and by reducing the number of supported locales (if you are using I18N at all).

<module>

    <inherits name='com.google.gwt.user.User' />



    <set-property name='user.agent' value='gecko1_8' />


    <inherits name='com.google.gwt.i18n.I18N' />



    <extend-property name='locale' values='ru_RU'/>


    
    
    <inherits name="com.google.gwt.user.theme.standard.Standard"/>
    
    <entry-point class='myModule.client.Module'/>
</module>

You should remember that these settings apply only for deployment compilation. You will not experience any performance advantages during your work within the GWT development browser. However the final deployment compilation should consume not more than 33% of the time!

Disable/deactivate system beep in OpenSolaris (in console and other apps)

2009-03-04T22:38:00.001+01:00

Setting the values of KBD_BEEPER_FREQ and CONSOLE_BEEPER_FREQ to 0 in /etc/default/kbd and a subsequent reboot did not solved the problem for me. But executing

xset b off

as normal user worked well. To deactivate the audible bell permanently, you have to

# pkg install SUNWgnome-config-editor
$ gconf-editor

...and go to /apps/metacity/general/, where you have to uncheck the audible_bell property.

Change grub timeout under OpenSolaris (menu.lst location)

2009-03-04T21:35:00.001+01:00

If you are looking for menu.lst under Solaris where you can set the boot timeout for grub, you should be able to find it under /rpool/boot/grub/menu.lst -- unlike under Linux, where it is located under /boot/grub/menu.lst. Changing the timeout from the 30 s default to a smaller value, results in a shorter boot time during an automatic system restart.

Change/Switch keyboard layout on OpenSolaris

2009-03-04T17:57:00.001+01:00

Changing the system keyboard layout on Solaris is much faster than switching the keyboard layout on Linux: Simply replace the LAYOUT value in /etc/default/kbd by the desired value from the list, you get by executing

kbd -s

...and a subsequent re-login in GNOME solved the problem for me :)

Eclipse sucks, so use NetBeans!

2009-02-28T17:49:00.001+01:00

Eclipse is the most ugliest tool I have ever used: It has more bugs than Windows 95 pre-alpha Edition ever had. The shortcuts used in Eclipse are used nowhere else. So is the search method implemented inconsequently because there are a bunch of search UIs and almost all of them you will never use but you see them all the time.

If you google for "eclipse sucks" you will find about 1.2 million hits. It seems that many people have suffered from this IBM product. In fact it cost me approx. ten years of my life time working six months with Eclipse and many swear words. There are also many former Eclipse users that have switched over to NetBeans and have not regret this decision. And there are many articles in the blogosphere which were written by frustrated Eclipse users to work off the aggression they gathered using this IDE.

And is there any good Eclipse alternative? Yes: NetBeans - for everybody who is fed up with Eclipse!

If you want to tell the world how much Eclipse sucks, write similar articles and link to other "Eclipse sucks" articles. In this way maybe we can cause a paradigm shift in the minds of many people. And if more people use NetBeans Eclipse will not be the de facto standard IDE for Java developers, which forces many people to use Eclipse at work - even if they do not like it.

Call/Execute Python scripts with parameters/arguments/args

2009-02-16T12:47:00.001+01:00

Extern python scripts, executables and other programs can be called/executed as described in this example:

import subprocess
args = (
                ' --flag ',
                ' --flag1 ',
                ' --flag2 ',

                )
subprocess.call(['/opt/googleappengine/dev_appserver.py', args], shell = True)

SVN (Solution): Server sent unexpected return value (403 Forbidden) in response to MKACTIVITY

2009-02-09T15:10:00.001+01:00

This problem was solved after clearing the outdated cached authentication data and re-entering the current valid username and password.

How to get the DDL of an Oracle table

2009-01-31T17:00:00.001+01:00

This is just one of many ways you can get a the DDL of a table in Oracle:

select dbms_metadata.get_ddl('TABLE', 'YOUR_TABLE'.'YOUR_SCHEMA') from dual;