Top posts
Latest articles
MSAccess and a really weird behaviour with distinct
(No Ratings Yet)
Loading ...Recently I started working with MS Access databases, I know not the best choice. I ran into a really weird problem with the database, which I didn’t expect.
I have a relativly simple select query which contains a distinct. Something like “select distinct id, content from table”. Nothing fancy so you’d expect the content of the table excluding all duplicates.
But this is also where the weirdness begins with MS Access. I was using this type of query to select data for my search engine. But some data wasn’t included for some reason.
After a lot of debugging my queries and code it turned out that MS Access ODBC was only returning the first 255 characters of a MEMO field. So I thought the driver was to blame, until I ran the same query in MS Access itself. As it turns out Access was the one truncating MEMO fields to VARCHAR(255) fields when using a DISTINCT in a query.
Controlling Tomcat using Ant scripting
As a Java webdeveloper you are faced with a lot of different aspects of development. One is testing and debugging code, to do this you need an application server like Tomcat. One of the issues I recently encountered was the need to control various Tomcat instances with a single Ant build script. Below are some of the solutions I’ve used to manipulate Tomcat.
Note: some parts of this script rely on the ant-contrib library. Download this library and include it in the tomcat.xml with the following code:
<taskdef resource="net/sf/antcontrib/antcontrib.properties"> <classpath> <pathelement location="./ant-contrib-1.0b3.jar"/> </classpath> </taskdef>
Starting tomcat
Though starting tomcat may seem easy. You could just use the development IDE (like Netbeans) to start and stop Tomcat, but what this lacks is the ability to control several instances with easy shortcuts. So I defined the following Ant macrodef in a file called tomcat.xml:
<macrodef name="tomcat-start">
<sequential>
<trycatch>
<try>
<if>
<not><http url="http://localhost"/></not>
<then>
<java classname="org.apache.catalina.startup.Bootstrap"
fork="yes"
dir="${tomcat.dir}"
spawn="true"
jvm="${tomcat.java.home}/bin/java">
<jvmarg value="-Dcatalina.home=${tomcat.dir}"/>
<jvmarg value="-Dcatalina.base=${tomcat.dir}"/>
<jvmarg value="-Djava.io.tmpdir=${tomcat.dir}/temp"/>
<jvmarg value="-Djava.endorsed.dirs=${tomcat.dir}/common/endorsed"/>
<jvmarg value="-Xdebug"/>
<jvmarg value="-Xrunjdwp:transport=dt_socket,address=8000,server=y,suspend=n"/>
<classpath>
<pathelement location="${tomcat.java.home}/lib/tools.jar"/>
<pathelement location="${tomcat.dir}/bin/bootstrap.jar"/>
</classpath>
<arg line="start" />
</java>
<waitfor maxwait="10" maxwaitunit="second" checkevery="5000">
<http url="http://localhost"/>
</waitfor>
<echo message="Tomcat started"/>
</then>
<else>
<echo message="Tomcat already started..." />
</else>
</if>
</try>
<catch>
<echo message="Unable to start tomcat"/>
</catch>
</trycatch>
</sequential>
</macrodef>
This macro is really easy. First it starts of by checking if tomcat is not already running (well actually it just checks to see if there is something running on port 80). If nothing is running then tomcat is started using the java defined by the ant property tomcat.java.home. This macro also depends on some other properties that are set by a different macro, which will be a bit further on in the post. Tomcat is started by using the Bootloader class provided by the server, to make sure it loads correctly the classpath is set.
The last step in the macro is to wait for tomcat to start, this has to be done since we start tomcat in a seperate java instance (the spawn option).
Stopping Tomat
Off course you also want to be able to stop tomcat to load some new data, or an entire web-app. I use the following macro to stop Tomcat:
<macrodef name="tomcat-stop">
<sequential>
<trycatch>
<try>
<java classname="org.apache.catalina.startup.Bootstrap"
fork="yes"
dir="${tomcat.dir}"
spawn="true"
jvm="${java.home}/bin/java">
<jvmarg value="-Dcatalina.home=${tomcat.dir}"/>
<jvmarg value="-Dcatalina.base=${tomcat.dir}"/>
<jvmarg value="-Djava.io.tmpdir=${tomcat.dir}/temp"/>
<classpath>
<pathelement location="${tomcat.java.home}/lib/tools.jar"/>
<pathelement location="${tomcat.dir}/bin/bootstrap.jar"/>
</classpath>
<arg line="stop" />
</java>
<kill-java name="Bootstrap" />
<echo message="Tomcat stopped" />
</try>
<catch>
<echo message="Unable to stop tomcat forcing shutdown....."/>
<kill-java name="Bootstrap" />
</catch>
</trycatch>
</sequential>
</macrodef>
Just like with the starting of Tomcat I use the provided Bootloader class to instruct tomcat to stop. Again I use the java that is set in tomcat.java.home as well as some other properties loaded by another macro. Since Tomcat sometimes fails to stop gracefully (due to poorly designed webapps) you also have to kill the Java process of Tomcat. This is done with the call to kill-java.
Killing any java process
As you saw in the tomcat-stop macro I used a macro called kill-java to make sure that Tomcat is really killed and no longer running in the background. The macro is as follows:
<macrodef name="kill-java"
description="Forcefully stop tomcat....">
<attribute name="name"/>
<sequential>
<!-- Execute the jps and check for any Java process with the provided @{name} attribute -->
<exec executable="${tomcat.java.home}/bin/jps" output="pid.out.file" />
<!-- Load in the name / pid file and strip all information except the PID -->
<loadfile srcfile="pid.out.file" property="pid.out">
<filterchain>
<linecontains>
<contains value="@{name}"/>
</linecontains>
<tokenfilter>
<deletecharacters chars="@{name}"/>
<trim/>
<ignoreblank/>
</tokenfilter>
<striplinebreaks/>
</filterchain>
</loadfile>
<echo message="Killing java process with pid ${pid.out}"/>
<!-- Kill the process, warning this only Works on Windows -->
<exec spawn="true" executable="taskkill">
<arg line="/PID ${pid.out}" />
<arg line="/F" />
</exec>
<delete file="pid.out.file" />
</sequential>
</macrodef>
This macro is really simple and relies on the jps application provided by Java. This application returns a list of all running processes with name and process id (PID). All we need to do is get the line containing the process name provided and strip everything except the PID.
Please note: the task killing the proces is designed for Windows, you could change this with kill in Linux.
Rounding it up
Though you now have all you need to manipulate tomcat there is one last macro that we are tegenkant upon. That is the initializer of the various Tomcat properties. I use the following macro:
<macrodef name="tomcat-init">
<attribute name="from"/>
<sequential>
<property name="tomcat.dir" value="${tomcat.@{from}.dir}"/>
<property name="tomcat.server" value="${tomcat.@{from}.server}"/>
<property name="tomcat.port" value="${tomcat.@{from}.port}" />
<property name="j2ee.server.type" value="${tomcat.server}" />
<taskdef name="webapp-stop"
classname="org.apache.catalina.ant.StopTask"
classpath="${tomcat.dir}/server/lib/catalina-ant.jar"/>
<taskdef name="webapp-start"
classname="org.apache.catalina.ant.StartTask"
classpath="${tomcat.dir}/server/lib/catalina-ant.jar"/>
</sequential>
</macrodef>
This little macro will initialize tomcat for a specific environment (for exemple DEV). Of course none of this works without the loading of some preset properties in a property file tomcat.properties. Which contains the following data:
tomcat.java.home=C:/jdk1.5.0_22_32b tomcat.DEV.dir=d:/jakarta/tomcat5.0 tomcat.DEV.server=tomcat55-DEV tomcat.DEV.port=8000 tomcat.MAIN.dir=d:/jakarta/tomcat5.0-MAIN tomcat.MAIN.server=tomcat55-MAIN tomcat.MAIN.port=8000
To load the property file just include the following instruction in the build script:
<property file="./tomcat.properties" />
No HDCP using the Gigabyte MA69GM-S2H onboard card??
Ok I recently got a very weird problem with my HTPC. Since a couple of days I’ve been unable to play any Blu-Ray disc. Even after updating my PowerDVD to the latest patched version.
Before this update of PowerDVD the weird behaviour was the disapearing of PowerDVD when playing discs. No message no error nothing, just gone! After the update the DVD player informed me that HDCP was not available and it could not play protected Blu-Ray discs.
This sounded weirdt to me since I have played them in the past, and I know the onboard graphics chip (the Ati Radeon X1250) supports it.
As it turns out, after a lot of digging, I had recently installed an updated version of the Catalyst Control Center. Which should not be anything strange, its recommended practice by a lot of software developers. However the graphics chipset on the motherboard appears to have some custom stuff, since after installing the latest version from the Ati site HDCP was no longer supported.
When I reinstalled the version of the Catalyst Control Center that came with the PC all my troubles went away. No more warnings / crashes or unable to play disc reports.
Some unexpected down-time
As you may have been able to notice over the past week or so my websites and those I am hosting for clients had some down-time last week. As such I’ve not been doing much other then trying to figure out what is going on, and haven’t had to much time to write something new.
Unfortunattely for me and my clients the problem seems to be with the provider I have to rent my servers. After some digging I found out even their own servers where unreachable. (Could not even setup a SSH connection to my servers).
It seems to be fixed at the moment, so keep praying that it stays that way 
.
PHP catching all function calls
Recently I came accross something really fancy that was introduced in PHP 5. It is appearantly possible for any class to catch all functions that are called on a class. So one function would catch $obj->callOne() as well as $obj->callTwo().
So why is this a nice feature to have, well because I am a very lazy progammer and this feature allows me to magically generate getters and setters. To do this I have the following setting for each class:
- The constructor method __construct initializes an array containing the names of all variables that we want to store. We also create a second array to save the values in for the variables.
- We implement the __call function to catch all functions being called on the object, which is currently still undocumented by PHP.net
So a basic class would look something similar to this:
class MyObject {
private $my_vars = array();
private $allowed_vars;
function __construct() {
$this->allowed_vars = array('var1', 'var2', 'var3');
}
function __calls($function_name, $arguments) {
$_variablename = substr($function_name, 3);
if (array_search($_variablename, $this->allowed_vars) !== FALSE) {
if (stripos($function_name, 'get') == 0 && stripos($function_name, 'get') !== FALSE) {
return $this->my_vars[$_variablename];
} else if (stripos($function_name, 'set') == 0 && stripos($function_name, 'set') !== FALSE) {
$this->my_vars[$_variablename] = $arguments[0];
}
}
else throw new Exception('Unkown function called on '. __CLASS__);
}
}
Which does exactly that which I described above. Mind you it’s just a very basic example but it shows the power of a catch all function.
