Jonathan Lalou's Blog

Archive for the ‘en-US’ Category

Case

How to make ChromeOS work in VirtualBox without Wifi, ie on an ethernet/wired local network, or even offline?

Quick Fix

Shutdown the VM > Select it > Settings > Network > Advanced > Adapter Type > select “Paravirtualized Network (virtio-net)”

Case

On booting ChromeOS Vanilla within Virtual Box, I got the following error:
[java]This kernel requires the following features not present on the CPU: pae
Unable to boot – please use a kernel appropriate for your CPU.[/java]

(Actually, the problem occured with ChromeOS but may have appened with another system)

Quick Fix

In Virtual Box, select the VM > Settings > Processor > check “Enable PAE/NX”.

A short reminder: in a try/catch/finally section, the block in the finally is always executed. “Always” means “even if a return statement is reached in the try or catch“.

A short piece of code shows more than a long speech. The following JUnit test ends with no error:
[java]package com.stepinfo.poc.cartography;

import org.junit.Test;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotSame;

/**
* Created with IntelliJ IDEA 12 "Leda" CE
* User: Jonathan LALOU
* Date: 08/Apr/13
* Time: 22:41
*/
public class TestTryCatchFinally {

public static final String TRY = "try";
public static final String CATCH = "catch";
public static final String FINALLY = "finally";

private String tryVersusFinally() {
try {
return TRY;
} catch (Exception e) {
return CATCH;
} finally {
return FINALLY;
}
}

private String catchVersusFinally() {
try {
throw new RuntimeException();
} catch (Exception e) {
return CATCH;
} finally {
return FINALLY;
}
}

@Test
public void testTryFinally() {
assertNotSame(TRY, tryVersusFinally());
assertEquals(FINALLY, tryVersusFinally());
}

@Test
public void testCatchFinally() {
assertNotSame(CATCH, tryVersusFinally());
assertEquals(FINALLY, catchVersusFinally());
}
}
[/java]

Case

Here is a case of stupid error. I started up a new project in IntelliJ IDEA, laying on a Maven archetype. On launching the first unit test, I got the following error:
[java]Cannot instantiate test(s): java.lang.SecurityException: Prohibited package name: java.lalou.jonathan.multiposts[/java]

Quick fix

As you may have noticed, the package name was prefixed with java.… which is prohibited by the JDK. An immediate fix is to restore a package name not starting with java..

The code in the JDK is explicit: the exception with such a message is raised in a unique occasion:
[java] if ((name != null) && name.startsWith("java.")) {
throw new SecurityException
("Prohibited package name: " +
name.substring(0, name.lastIndexOf(‘.’)));
}
[/java]

Case

I have to work on an “old-school” project: without Maven (and even without integration within Eclipse). The JARs depended on by the application are located in a lib/ folder. Besides, I cannot add JARs to company repository.
How to integrate Maven with this lib/ folder?

Solution

First of all, you have to enable the support of Maven within IntelliJ IDEA: select the project > right click > add framework support > select Maven.

Create a pom.xml and complete the main information.
Identify the JARs which are relatively common (eg those available in http://repo1.maven.org/maven2/), and add them as dependencies.

Now, you still have to deal with “uncommon” JARs

Quick and (very) dirty

The quickest way is to add the JARs as dependencies, declared with scope system, eg:
[xml]<dependency>
<groupId>unknownGroupId</groupId>
<artifactId>someArtifactId</artifactId>
<version>someVersion</version>
<scope>system</scope>
<systemPath>${project.basedir}/lib/foo.jar</systemPath>
</dependency>[/xml]

The main drawback of this dirty solution is that when you generate your archive, the JARs depended on with scope system will not be exported… Quiet a limitation, isn’t it?

(A bit) Slower and (far) cleaner

You have to declare a “remote repository”, of which URL is local, such as:
[xml]<repository>
<id>pseudoRemoteRepo</id>
<releases>
<enabled>true</enabled>
<checksumPolicy>ignore</checksumPolicy>
</releases>
<url>file://${project.basedir}/lib</url>
</repository>[/xml]

Then, declare the dependencies like:
[xml]<dependency>
<groupId>UNKNOWN</groupId>
<artifactId>foo</artifactId>
<version>UNKNOWN</version>
</dependency>[/xml]
Move and/or rename the JARs, for instance from lib/foo.jar folder to the actual one, such as lib/UNKNOWN/foo/foo-UNKNOWN.jar.

Now it should be OK ;-).
In my case I prefered to add Maven Assembly plugin with the goal jar-with-dependencies, to be sure to build a unique JAR with complete exploded dependencies.

Target and Constraints

I need a Windows XP running as a virtual machine (VM).  Don’t think of using your former OEM licence, it won’t work: Windows checks and makes a difference between OEM and other licences.

Microsoft provides VHD files: you can consider them as “virtual” HDD. Officially, these VHD files are intented at developpers to test their websites on various Windows (XP to Seven) and Internet versions (6 to 9).

The VHD files provided for Windows XP need a licence key to be activated, and therefore have two main drawbacks:

1. after three days and/or three reboots, the system will allow you to log in anymore. That’s quiet a limitation :-(.
2. But wait, there’s even worse: the VHD file provided by Microsoft will be completely disabled on February 14th, 2013!

At last, I stress on having an absolutely legal solution, since it will be deployed both on personnal (Ubuntu) and professional (Windows 8 ) desktop computers. I do not want to waste my time playing hide and seek with authorities.

Prerequisites

In this post I will assume you are a bit familiar with working on VirtualBox. If you are not, then browse the web, ask Google, RTFM, or, at last, leave a message in the comments, I’ll try to figure out a moment to write a short tutorial.

• Download Windows XP VHD file from this page: Internet Explorer Application Compatibility VPC Image. Even though you get a .exe file, you can uncompress it with a regular 7-zip.
• Download Windows XP SP3 iso file from that page: Windows XP Service Pack 3 – ISO-9660 CD Image File. Keep the xpsp3_5512.080413-2113_usa_x86fre_spcd.iso as is.
• Download PCINTPC5 ethernet drivers from this page: NDIS5 Driver for Microsoft Windows Server 2003, Windows XP, Windows 2000, Windows ME and Windows 98.
  • Unzip and convert this V4.51.zip as an ISO file: as a reminder, the Linux command is:[java]mkisofs -o target.iso -J –rock sourceFolder[/java]
  • Alternatively, you can download that ISO that I prepared: ethernet_drivers_for_WinXP_VirtualBox.iso (don’t forget to thank me for the precomputed work)

Operations

Classic

• Create a VM within VirtualBox
• Name it “Windows XP” for instance
• Set the VHD file as the one downloaded and unzipped above.

Specific

• Run the VM. You must log in as IEUser. The default password is Password1 (on French keyboards: Pqsszord&)
• Do not validate the licence.
• The VM will require CmBatt.sys(and possibly another one):
  • On host system: mount SP3 iso device > CD/DVD Devices> Choose a virtual CD/DVD virtual file > select WinXP SP3 ISO (xpsp3_5512.080413-2113_usa_x86fre_spcd.iso)
  • On guest system: run the CD, eg: Windows+E > D:\ > Autoplay > Install. All the files will be unzipped in a folder such as C:\1a2b3c4d5e... (with hexadecimal value).
  • In the frame asking for CmBatt.sys, select it in C:\1a2b3c4d5e...\i386
• Windows XP will ask for drivers and try to download them. But the ethernet card has not yet been installed!
  • On host system:
  • • Mount the  ethernet_drivers_for_WinXP_VirtualBox.iso (cf. above for details)
    • Devices > Install Guest Additions > accept all
  • On guest system: manually install drivers for ethernet card.
• In order to bypass the limitation of February 14th,
  • if you read this post after February 14th, 2013: set the system time to January 1st 2013 for instance (I didn’t test ; it should work)
  • disable time synchronization between host and guest systems, eg:[java]$VIRTUALBOX_HOME/app32/VBoxManage setextradata "Windows XP" "VBoxInternal/Devices/VMMDev/0/Config/GetHostTimeDisabled" 1[/java]

Now everything should work. I suggest to take a snapshot ;-), and then to revert to it as often as needed.

Conclusions

Officialy, the VHD files provided by Microsoft are intented at developpers who need test their websites on obsolete and out-of-date browsers like Internet Explorer. But you can imagine many other usages. On my side, the interest is to have VM as a module in a complete integrated testing environment and in the frame of a software forge.

My opinion? The solution provided by Microsoft does exist, it’s better than nothing ; anyway, implementing it is a far hard matter. Limitations and complexity of install spoil the user experience. It’s a pity, because the idea of VHD is great, but does not match that of precompiled open source Virtual Boxes: http://www.virtualboxes.org

Case

You have a column of type Date in MySQL. How to get the average value of this series?

(Don’t think to execute select AVG(myColumnDate), it won’t work!)

Fix

Use a query similar to this:

[sql]SELECT FROM_UNIXTIME( ROUND( AVG( UNIX_TIMESTAMP( myDateColumn ) ) ) )

FROM `myTable`

WHERE 1[/sql]

Case

You have a WAR to deploy on Tomcat, let’s say jonathan.war for instance. Usually, the application will be reached through the URL http://machine:port/jonathan.
Let’s say you would like to exclude the WAR name from the address, ie the application to be reached on http://machine:port/. This operation is called “to deploy in root”, since the context will be simple slash: '/'.

Solution

You can implement that with two means:

• rename the war as ROOT.war, then deploy.
• or: edit conf/server.xml, replace [xml]<context>[/xml] with
  [xml]<context path="" docBase="jonathan" debug="0" reloadable="true"> [/xml]

Case

I had the following issue: when I undeployed the WAR from Tomcat using the manager instance, the undeploy failed. As a workaround, I had to restart Tomcat for the undeploy to be taken in account.
This issue occured only in Windows ; when the exact same WAR and the same version of Tomcar on Debian, I was able to deploy and undeploy many times.

Quick Fix

In the %CATALINA_HOME%\conf\context.xml, replace:
[xml]<Context>[/xml]
with:
[xml]<Context antijarlocking="true" antiResourceLocking="true"/>[/xml]

Case

On running a web application hosted on Jetty, I get the following stracktrace:
[java]Nested in org.springframework.beans.factory.BeanCreationException: Error creating bean with name ‘sessionFactory’ defined in ServletContext resource [/WEB-INF/classes/config/spring/beans/HibernateSessionFactory.xml]: Invocation of init method failed; nested exception is org.hibernate.HibernateException: Unable to instantiate default tuplizer [org.hibernate.tuple.entity.PojoEntityTuplizer]:
java.lang.NoSuchMethodError: org.objectweb.asm.ClassWriter.<init>(I)V[/java]
Unlike what I immediatly thought at first glance, the problem is not induced by the Tuplizer ; the actual error is hidden at the bottom: java.lang.NoSuchMethodError: org.objectweb.asm.ClassWriter.

Here are some of the dependencies:
[java]org.hsqldb:hsqldb:jar:2.2.8:compile
org.springframework:spring:jar:2.5.6:compile
org.hibernate:hibernate:jar:3.2.7.ga:compile
javax.transaction:jta:jar:1.0.1B:compile
| +- asm:asm-attrs:jar:1.5.3:compile
| \- asm:asm:jar:1.5.3:compile[/java]

Fix

Main fix

The case is a classic problem of inherited depencencies. To fix it, you have to excluse ASM 1.5.3, and replace it with more recent version. In the pom.xml, you would then have:
[xml]
<properties>
<spring.version>3.1.0.RELEASE</spring.version>
<hibernate.version>3.2.7.ga</hibernate.version>
<asm.version>3.1</asm.version>
</properties>
…
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate</artifactId>
<version>${hibernate.version}</version>
<exclusions>
<exclusion>
<groupId>asm</groupId>
<artifactId>asm</artifactId>
</exclusion>
<exclusion>
<groupId>asm</groupId>
<artifactId>asm-attrs</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>asm</groupId>
<artifactId>asm</artifactId>
<version>${asm.version}</version>
</dependency>
[/xml]

Other improvements

I took the opportunity to upgrade Spring 2.5 to Spring 3.1 (cf the properties above).
Besides, I modified the *.hbm.xml files to use object types, rather than primary types, eg replacing:
[xml]<id name="jonathanId" type="long">[/xml]
with:
[xml]<id name="jonathanId" type="java.lang.Long">[/xml]