Solution for "Sniffers with type [connector] and type [ejb] should not claim the archive at the same time"

In case you are using GlassFish it may happen you run into this error

"java.lang.IllegalArgumentException: Sniffers with type [connector] and type [ejb] should not claim the archive at the same time. Please check the packaging of your archive" 

In my case it happens when I deployed a web archive out of Eclipse directly into a running GlassFish instance on my machine using the GlassFish plugin. 

I tried a Google search for this error and found a blog posting by Adam Bien describing this error and a solution. Well, indeed my packaging was wrong. I accidentally bundled the artifact glassfish-embedded-all into my WAR archive and this was causing the trouble.

The solution is very simple: Either change the scope in your pom.xml to "provided" or - in case you don't need the dependency - remove it from the dependency section of your pom.

In my case it turns out that the dependency was not necessary anymore and I deleted it.

Stopping Tomcat with remote JMX enabled through script

Tomcat comes with handy start and stop scripts in the bin folder. Those scripts are working very well.
With this script it's pretty simple to start/stop Tomcat on linux systems.

But if you decide to add jmxremote properties to your start script using $JAVA_OPTS variable, stopping of Tomcat (and mostly any other AppServer started with these options) will not succeed.

There will be an error message stating that the address is already in use (BindException) and you have to kill the process manually.

The solution is very simple. Make sure the stop command does not contain the jmxremote properties definition. So you might declare a $JAVA_OPTS for the start command as usual:

 JAVA_OPTS="-Xmx256m -XX:MaxPermSize=128m 
-Dcom.sun.management.jmxremote.port=3336 
-Dcom.sun.management.jmxremote.ssl=false 
-Dcom.sun.management.jmxremote.authenticate=false 
-Djava.rmi.server.hostname=192.168.1.5"  

but for the stop command you must omit those jmx definitions and declare it for example like this:

 JAVA_OPTS_STOP="-Xmx256m -XX:MaxPermSize=128m"  

.
The stop command then forks a JVM with the $JAVA_OPTS_STOP definition NOT trying to open another listening socket on an already bound port.

Setting up an Apache cluster under RedHat Enterprise Linux

If it ever happens that you have to set up an Apache Linux cluster, I highly recommend the step-by-step manual from clusterlabs.org.
The docs are really easy to read and are very helpful.
I only have two negative points:

1. Sometimes the commands you have to enter into the console are not clearly separated from the parameters or text you have to pass. Example:
   

   cat <<-END >>/etc/corosync/service.d/pcmkservice {
           # Load the Pacemaker Cluster Resource Manager
           name: pacemaker
           ver:  1
   }
   END

   The file to create is called /etc/corosync/service.d/pcmk (NOT pcmkservice) and the content of the file starts with "service {
   # Load the Pacemaker ..."
   I assume this has something to do with the formatting of the docs.
2. The docs almost never tell you what to do in case things go wrong or you did a typo or your environment differs from the one used in the docs.
   In that case you have to use google and cross your fingers or use other resources like this one.

After all I only had to consult google once during the complete setup.

My failover tests succeeded after a few hours of setup including writing a howto for my specific setup.

Now the cluster works using corosync and pacemaker as services.

Howto dynamically change webservice endpoint URL with Metro

A really cool feature of Metro (and maybe other webservice stacks) is the possibility to change the webservice endpoint URL at runtime.
In general, you typically generate the code via JAX-WS maven plugin (or ant task), specifying the endpoint URL in the generation properties. This is a fast and reliable way to generate webservices. The downside is, that it seems you can't change the endpoint URL at runtime ...
Well, you can. And it is pretty simple.
The example in this posting is taken from the Metro FAQ.

You can use BindingProvider.ENDPOINT_ADDRESS_PROPERTY to set the endpoint address in your client application code.

Sample:

 //Create service and proxy from the generated Service class.   
  HelloService service = new HelloService();   
  HelloPort proxy = service.getHelloPort();   
  ((BindingProvider)proxy).getRequestContext().  
       put(BindingProvider.ENDPOINT_ADDRESS_PROPERTY, "http://new/endpointaddress");   
     
  proxy.sayHello("Hello World!");   

With the property key

BindingProvider.ENDPOINT_ADDRESS_PROPERTY

you can also get the currently used endpoint url at runtime. This may be helpful for debugging purposes.
Sample:

 LOG.info("Using endpoint URL: "  
        + ((BindingProvider)proxy).getRequestContext().get(  
            BindingProvider.ENDPOINT_ADDRESS_PROPERTY));  

Updating GlassFish 3.1 under RHEL 6 on a 64 Bit machine

Don't be surprised when you have problems updating GlassFish 3.1 on a RedHat Enterprise Linux 6 64 Bit machine. This will not work out of the box (officially Oracle only supports GlassFish on RedHat 4 and 5 not on version 6). But there is a way to get it to work.
You will get this error when executing the pkg command:

 [glassfish@MYMACHINE glassfish3]$ pkg list -u  
 Traceback (most recent call last):  
  File "/opt/glassfish/glassfish3/pkg/bin/client.py", line 61, in ?  
   import pkg.actions as actions  
  File "/opt/glassfish/glassfish3/pkg/vendor-packages/pkg/actions/__init__.py", line 59, in ?  
   globals(), locals(), [modname])  
  File "/opt/glassfish/glassfish3/pkg/vendor-packages/pkg/actions/link.py", line 36, in ?  
   import generic  
  File "/opt/glassfish/glassfish3/pkg/vendor-packages/pkg/actions/generic.py", line 45, in ?  
   import pkg.variant as variant  
  File "/opt/glassfish/glassfish3/pkg/vendor-packages/pkg/variant.py", line 28, in ?  
   from pkg.misc import EmptyI  
  File "/opt/glassfish/glassfish3/pkg/vendor-packages/pkg/misc.py", line 49, in ?  
   import zlib  
 ImportError: libz.so.1: cannot open shared object file: No such file or directory  
 ---------------------------------------------------------------  
 There was an error running  
   
 /opt/glassfish/glassfish3/pkg/bin/../python2.4-minimal/bin/python  
   
 You are running on a 64 bit Linux distribution and the 32 bit Linux  
 compatibility libraries do not appear to be installed. In order to use  
 the Update Center tools you must install the 32 bit compatibility libraries.  
   
 On Ubuntu (and possibly other Debian based systems) please install the  
 ia32-libs package. On RedHat 4 (and other RPM based systems), you may  
 need to add multiple 'compat' runtime library packages. Please see the  
 Update Center Release Notes for more information.  
   
   

The solution is to install the following packages using yum

yum install compat-db.i686 zlib.i686 libidn.i686 krb5-libs.i686

The trick is to find out about the correct names of the packages. It's easy on Debian based systems but quiet difficult on RPM based systems.
If you are using CentOS take a closer look at this blog post.

Deep cloning of java objects

I was in need of deep cloning a map with all its keys and values.
All the map implementations in standard Java only do shallow cloning of the map. They don't clone the keys and values. But that was exactly what I want to realize.
I found out about the cloning library which does the job very easy and extremely fast. This library can clone nearly any java object.
A cloning expression is just a two-liner.
Very useful!
On this stackoverflow question you can find more deep cloning libraries.

Don't use commons lang < 2.4 with HtmlUnit

In case you have a project which has a dependency to Apache commons-lang and you plan to use the latest HtmlUnit (as of writing this post this is HtmlUnit 2.9) you should take care of the version of commons-lang.

HtmlUnit is using a method (startsWithIgnoreCase) from commons-lang that was introduced in commons-lang 2.4.
So any commons-lang version below 2.4 will produce runtime exceptions when using HtmlUnit. The stacktrace may be similar to this one:

 java.lang.NoClassDefFoundError: Could not initialize class  
 com.gargoylesoftware.htmlunit.WebClient  
     at net.sourceforge.jwebunit.htmlunit.HtmlUnitTestingEngineImpl.createWebClient(HtmlUnitTestingEngineImpl.java:804)  
     at net.sourceforge.jwebunit.htmlunit.HtmlUnitTestingEngineImpl.initWebClient(HtmlUnitTestingEngineImpl.java:813)  
   
 also :  
   
 java.lang.NoSuchMethodError:  
 org.apache.commons.lang.StringUtils.startsWithIgnoreCase(Ljava/lang/String;Ljava/lang/String;)Z  
     at com.gargoylesoftware.htmlunit.util.URLCreator$URLCreatorStandard.toUrlUnsafeClassic(URLCreator.java:66)  
     at com.gargoylesoftware.htmlunit.util.UrlUtils.toUrlUnsafe(UrlUtils.java:193)  
     at com.gargoylesoftware.htmlunit.util.UrlUtils.toUrlSafe(UrlUtils.java:171)  
     at com.gargoylesoftware.htmlunit.WebClient.<clinit>(WebClient.java:162)  
     at net.sourceforge.jwebunit.htmlunit.HtmlUnitTestingEngineImpl.createWebClient(HtmlUnitTestingEngineImpl.java:804)  
     at net.sourceforge.jwebunit.htmlunit.HtmlUnitTestingEngineImpl.initWebClient(HtmlUnitTestingEngineImpl.java:813)  
   
   
   

In case you use Maven as your build tool you can check the dependencies using the command:

mvn dependency:tree

To avoid this error you can declare version 2.6 of commons-lang in your project.

Iterating over result list from a JPA query

Sometimes when using EJB 3.x, it is necessary to use JPA QL or SQL native queries to fetch objects from the database. It might be used to achieve better performance or to just fetch a particular set of attributes of the object but not the complete object with all its dependencies.

There's one thing you have to keep in mind when doing this: The result list containing the object will be an array of objects!

"The SELECT clause queries more than one column or entity, the results are aggregated in an object array (Object[]) in the java.util.List returned by getResultList( )"

Working example:

 Query query = manager.createQuery("SELECT v1.bitbit, v1.numnum, v1.someTime, t1.username, t1.anotherNum FROM MasatosanTest t1 JOIN MasatoView v1 ON v1.username = t1.username;");  
   
   List results = query.getResultList( ); // Fetches list containing arrays of object  
   
   Iterator it = results.iterator( );  
   
   while (it.hasNext( )) {  
   
     Object[] result = (Object[])it.next(); // Iterating through array object   
   
     Boolean first = (Boolean) result[0]; // Fetching the field from array  
   
     /* Likewise for all the fields, casting accordingly to the sequence in SELECT query*/  
   
   }  
   
   

There's is even the possibility to avoid casting completely by using a constructor expression with the appropriate arguments in the SELECT section:

 SELECT new org.somepackage.XEntity(x.a, x.b) FROM XEntity x  

Remember to declare the appropriate constructor.

The code fragments and the solution in this blog post was taken from this question on stackoverflow.

How to change the DB schema to dbo on SQLServer 2008

Every now and then you are in need to backup and restore databases from one SQL Server to another. Furthermore, sometimes the version of the source SQL Server differs from the version of the target SQL Server.

With SQL Server 2008 Microsoft separated users from schemas.

Imported tables of an imported database may only become accessible with a prefix like "jonathan.MY_TABLE_NAME".

You can change the schema name of those tables using the ALTER SCHEMA command.

It is described in more detail here.

In my case it worked.

How to solve " Target Filesystem doesn't have /sbin/init" on Ubuntu 10.04

I restarted my Ubuntu 10.04 box today and it wouldn't start. It gave me this error:

 mount: mounting /dev/disk/by-uuid/***************************** on /root  
 failed: Invalid argument  
 mount: mounting /sys on /root/sys failed: No such file or directory  
 mount: mounting /dev on /root/dev failed: No such file or directory  
 mount: mounting /sys on /root/sys failed: No such file or directory  
 mount: mounting /proc on /root/proc failed: No such file or directory  
 Target file system doesn't have /sbin/init  
 No init found. Try passing init= bootarg  

So after googling around I found out that this seems to be a common problem ;-)
I have a JMicron RAID controller in my box using a RAID mirror but that doesn't help very much :-( It's a logical error and therefore replicated on the other disk as well.

I found this forum entry which helped me a lot and applied the fix using the following steps:

1. Install GParted on an USB Stick using Tuxboot (my Linux box does not have a DVD drive)
2. Boot GParted and wait until the graphical partition editor comes up
3. Identify the boot partition (mounted on /). My boot partition is named "/dev/mapper/jmicron_GRAID1"
4. Open a terminal and type in the following command
   sudo e2fsck -f -y -v /dev/mapper/jmicron_GRAID1
5. When e2fsck finishes it usually must have been corrected some errors. So it's best to take a look into the summary.
6. Reboot your system

After I applied these steps my system booted up without errors again.
Now I need to identify the source of the problem ...