Cort Dougan: Good Programmers are Not Lazy

Made me knowingly  smile...

Book: Domain-Driven Design (Eric Evans)

In the last summer ('08) I had the time to read that book. A friend of mine (thanks to Thorben) suggested that the book is really worth a try. The cover says: "Tackling complexity in the Heart of Software". And that is a really summary.

Evans describes with short examples situations in software development projects which can lead to critical problems later. He uses the short stories to analyze the situation, make the problem and cause clear. Based upon that he describes a pattern (a style to develop software; mostly organizational stuff) to get rid of it.

The first one he suggests is a "ubiquitous language". In short he says that all people connected to the project should use the same language, so that everyone can talk to everyone about the domain. That is not about technical stuff or infrastructure. It is mere that all know all what the software should / will be used to.

It's a quite good book with well choosen practical examples and it helped to understand that real development differs from educational stuff in a sense of organization, time and size. It would have been helpful, if I read it earlier.

Lecture: Open Wins – the Future of Software & Technology (Scott McNealy, SUN)

Scott McNealy the chairmen and a co-founder of SUN visited the TU Berlin on 06-11-08. He visited the university to give a short talk about open source software and why it became and will be  a pushing element for technical innovations. Because he is with SUN the content of the talk was mostly about how  SUN was, is and will be involved in the development of open source.
The essance of the talk was:
    Open Source is good (not only code, also products [specifications])
        reducing the dependency between the developer and the user
        programmers improve their code style (someone else can read your stuff)
    Strategy of SUN
        He anwsered the question why SUN is doing open-source

Interesting points:
    Java
        happens transparently (ref: mobile phone and blue-ray players)
        is running on 6^9 devices (hope I got it right)
    Oracle Enterprise Edition costs 400.000 $ per core(!)
    
Cool quotes:
    "Free is the new black!"
    "Return on no-investment."
    "Steal software legally"
    "We don't want you to do .NET! Watch your hands!"

Provided links during the talk:
    Netbeans.tv: the community site of Netbeans.
    Solaris Express Developer Edition (SXDE) A developer edition of solaris with many tools

All in all I can say that Scott is a really good entertainer. It was a really nice talk!

Thanks to Prof. Brandenburg for the information.

JTree on an JScrollPane and resizing

Early on the morning I read my early morning bug reports ;).

It was about an JTree on a JScrollPane. The model of the will be modified during runtime and fires events if something is changes. So far everything looks pretty straight forward and it works.

The problem occured if the tree gots larger than the parent scrollpane, so I believed the scrollpane starts to activate the scrollbars and everything stays cool... But the tree never changed it's size. It simple stayed in the old size and the scrollpane didn't start scrolling. And so some items of the tree were invisible.

TreeModel model = new DefaultTreeModel();
JTree tree = new JTree(model);
tree.setPreferredSize(new Dimension(100, 100));
JScrollPane pane = new JScrollPane(tree);

The model fires an TreeModelEvent (DefaultTreeModel.nodeStructureChanged) and the tree get's an JTree.treeDidChange() so it can recompute it's size.

This doesn't work out. It was necessary to set the preferred size of the tree to null before excecuting treeDidChange...

Why? I honestly don't know...

VOIP for GNOME Desktop: Ekiga

Yesterday I got some time to start playing with SIP. I used Ekiga a SIP client for the gnome-desktop. After installation I got an account on ekiga.net and everything went fine. The provided configuration wizard is really cool stuff. The hole action consumed 10 minutes and afterwards I spent 1 hour to get the sound devices working. And it did, but it was really annoying. The only problem now is that my built-in (Thinkpad X60) microphone produces a feedback if I use the internal speakers. The only solution is to use headphones and don't type or click during a call.

At last: sip:500@ekiga.net is a echo service, so you can test your configuration. Next week I will try to get my bluetooth headset running.

JAX-WS: ORA-31011

Today, I tried to do something useful for my bachelor thesis. I tried to query a Oracle 11G DBMS via a SOAP-based Webservice. Using the instruction from Andrea and Oracle I got the service up and running. The Webservice was reachable under http://localhost:8080/orawsv and presented it's wsdl via http://localhost:8080/orawsv?wsdl.

Now the trouble started:
The URL from the Oracle HTTP-Server is secured via HTTP-Authentification. Ok so I downloaded the WSDL and created the stubs from a local file with the JDK's wsimport. Now I needed to tell the Webservice Client Provider to authenticate if necessary:

ORAWSVPortType port = new ORAWSVService().getORAWSVPort();
Map<String, Object> requestCtx = ((BindingProvider) port).getRequestContext();
requestCtx.put(BindingProvider.USERNAME_PROPERTY, "user");
requestCtx.put(BindingProvider.PASSWORD_PROPERTY, "password");

The first test ended with a desaster:

Exception in thread "main" java.lang.IllegalArgumentException: faultCode argument for createFault was passed NULL
at com.sun.xml.messaging.saaj.soap.ver1_1.SOAPFactory1_1Impl.createFault(SOAPFactory1_1Impl.java:56)
at com.sun.xml.ws.fault.SOAP11Fault.getProtocolException(SOAP11Fault.java:178)
at com.sun.xml.ws.fault.SOAPFaultBuilder.createException(SOAPFaultBuilder.java:108)
at com.sun.xml.ws.client.sei.SyncMethodHandler.invoke(SyncMethodHandler.java:254)
at com.sun.xml.ws.client.sei.SyncMethodHandler.invoke(SyncMethodHandler.java:224)
at com.sun.xml.ws.client.sei.SEIStub.invoke(SEIStub.java:117)
at $Proxy32.xmlFromQuery(Unknown Source)
at productcatalogws.Main.main(Main.java:49)
Java Result: 1

I couldn't make anything useful out of these messages. The only thing I found was a dead end: bug_id=6587659.

So I started debugging:

First view the SOAPMessages:
I used the cool charles proxy.
Configuration for JAVA:

System.getProperties().put("proxySet", "true");
System.getProperties().put("proxyHost", "localhost");
System.getProperties().put("proxyPort", "8888");

After viewing the messages without noticing anything of interesst except:
ORA-31011: XML parsing error, but without any reference to the Webservice.

I found a cool tool to use webservices: soapUI (you can do everything I needed using it!!) and queried the Oracle Webservice by hand. And it worked!

The problem was that the default JAX-WS Provider does send:
Content-Type: text/xml;charset="utf-8"

And the Oracle HTTP Server expects:
Content-Type: text/xml;charset=UTF-8

An example SOAPMessage (including the header):

Authorization: Basic XXXXX
Host: localhost:8080
Content-Length: 314
SOAPAction: "http://localhost:8080/orawsv"
User-Agent: Jakarta Commons-HttpClient/3.0.1
Content-Type: text/xml;charset=UTF-8

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:oraw="http://xmlns.oracle.com/orawsv">
<soapenv:Header/>
<soapenv:Body>
<oraw:query>
<oraw:query_text type="SQL">SELECT * FROM PRODUCT</oraw:query_text>
</oraw:query>
</soapenv:Body>
</soapenv:Envelope>

The questions are:
Does JAX-WS something wrong during the request or is the DB Webservice the bad guy?
And why doesn't JAX-WS handle the SOAPfault correctly?

Used software:

javac --version:

java version "1.6.0_04"
Java(TM) SE Runtime Environment (build 1.6.0_04-b12)
Java HotSpot(TM) Client VM (build 10.0-b19, mixed mode)

Oracle 11G DBMS:

Oracle Database 11g Release 1 for 32-bit Windows.

OpenSSH using Kerberos via GSSAPI

I missed to activate a small and tiny feature during the update to Debian Etch: OpenSSH with GSSAPI support. What does sat mean?

1. g00se.org uses Kerberos for authentification.
   
2. Kerberos offers Single-Sign-On.

I missed to upload my subversion working copies over ssh without typping my password everytime. So I installed ssh-krb5 to add the cool behavior.

Cyrus and Exim4 authentification using Kerberos via GSSAPI

Today I used my spare time to let the SMTP and the IMAP server of g00se.org using the GSSAPI for authentification.
The necessary cyrus-sasl libaries were already installed. So I really don't know which are exactly required. I suppose the cyrus-sasl gssapi libary should meet all requirements. I needed to install the exi4-daemon-heavy instead of the light one. The the heavy one does support authentification using the cyrus-sasl libary.
I created the principals imap/g00se.org and smtp/g00se.org and put them into the default keytab.
And modified the configuration files of both services to let them propose GSSAPI as alternate authentification mechanism:
(cyrus): imapd.conf:
sasl_mech_list: PLAIN GSSAPI
and
(exim4): [/etc/exim4/conf.d/auth/01_exim4-config_gssapi]
gssapi_server:
driver = cyrus_sasl
public_name = GSSAPI
server_mech = gssapi
server_hostname = g00se.org
#server_realm = G00SE.ORG
server_set_id = $auth1
.ifndef AUTH_SERVER_ALLOW_NOTLS_PASSWORDS
server_advertise_condition = ${if eq{$tls_cipher}{}{}{*}}
.endif
Thanks to Sean for a short and easy description.
PS: Exim4 does use the splitted configuration file option of Debian. So you can put the lines anywhere into the authentification section.

Apache with Kerberos authentification

Special thanks to the guys who invented mod_auth_kerb. I removed the PAM authentification modules, which I only used as wrapper to get Kerberos auth through PAM and replaced it with mod_auth_kerb.
Here is the small configuration:

Krb5Keytab /etc/apache2/krb5.keytab
KrbAuthRealms G00SE.ORG
KrbServiceName HTTP
<Directory /x>
AuthType Kerberos
Require valid-user
</Directory>
That's all! Cool.

The Firefox bundled into my OpenSUSE 10.3 does already contain all necessary configurations. I only needed to add g00se.org to network.negotiate-auth.trusted-uris in about:config. So he does accept the offer to do GSSAPI authentification  with these URIS. And that's pretty cool. At least I need to figure a way to get my M$ system use such cool stuff.