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This can’t be closer from the truth :

Pierre

Basically I needed to watch a directory for incoming files and perform a given action based on the owner of the file, in Java.

For the polling part, no problem, but how can I get the owner of a file in Java ? Well after 1 hour searching the internet and concluding that :

• It is not possible in pure Java at least up to 1.5
• It should be done using native code through JNI

I decided to give it a shot since I had another hour in front of me. Here a the steps I followed :

1. Try to find some code that does this in C++ : http://msdn2.microsoft.com/en-us/library/aa446629.aspx

2. Try to compile this code Since I have no Visual Studio or other C++ IDE, let’s go find one .. :

http://www.bloodshed.net/devcpp.html

3. Install Dev++ and compile the code .. and to my great surprise, it works (I must say I have bad college memories about C++, compilers, make files, compiler directives, etc…)

4. Now let’s tackle the JNI part .. since I never used JNI before (but know what it’s about), I type ‘jni tutorial’ in google .. and find :

http://www.codetoad.com/java_simpleJNI.asp

I chose this page because it seemed to have an example of passing a String parameter and getting back a String result – which is exactly what I need since I will pass a file path and get back the file owner.

5. Create a java class

import java.io.*;
public class getowner
{
	private static native String getowner(String arg);
        public static void main(String[] args)
	{
	 	System.load("c:/temp/java/getowner.dll");
		File f = new File(args[0]);
		File[] children = f.listFiles();
		for (int i=0; i < children.length;i++)
		{
			if (children[i].isFile())
				System.out.println(getowner(children[i].getPath()));
	 	}
	}
}

6. Compile the class and generate the header file using javah

javac getowner.java

javah getowner

Which generates the following header file :

/* DO NOT EDIT THIS FILE - it is machine generated */
#include 
/* Header for class getowner */

#ifndef _Included_getowner
#define _Included_getowner
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     getowner
 * Method:    getowner
 * Signature: (Ljava/lang/String;)Ljava/lang/String;
 */
JNIEXPORT jstring JNICALL Java_getowner_getowner
  (JNIEnv *, jclass, jstring);

#ifdef __cplusplus
}
#endif
#endif

7. Write the implementation by modifying the code used in step 2

(see attachment for the complete source code)

8. Compile the whole thing, don’t forget in the project settings to add 2 include directories pointing to the JDK include and include/win32 folder

If you’re lucky you should get a nice getowner.dll file

9. You can now run the java program :

java getowner c:windows

which will output the owner of all the file in you windows directory.

You can download the source code zip getowner.zip that contains :

• the project file
• the cpp source file
• the generated header file
• the java class

Have fun !

P.

The migration to Google Apps for your domain went without problems and everything seems to be functional. We are basically using google calendar and google mail. We are somewhat starting to use Google Talk but the integration with other IM systems seems to me (who is not a big IM fan or user) very complicated. I managed to configure this with my previous standard gmail account but I can’t manage to get things working with our GAFYD accounts.

Anyways, for 50 USD per user / per year we get :

• 10 gig email
• Effective Anti spam
• Splendid Webmail features
• Web based calendar (with sharing and PDA sync on my QTek S110 – see www.goosync.com)

And of course

• A big brother watching you

Btw, I also had to use http://gmailnotifier.net/ to have a working mail notifier for GAFYD

P.

The site drains quite a lot of traffic and I had made very few benchmarks during development phase. When I finally started load testing I realized that the site was performing well in the beginning but after a few minutes it was getting slower and slower ..

I isolated the problem in the Lucene search section. After reading a little more about the IndexSearcher object it finally hit me.

A new IndexSearcher object was created for every search which is definately not the correct way of using it. IndexSearcher is a heavy object and can (and should) be shared by multiple clients (it is threadsafe). The only thing you should of course, is recreate it when the index changes (on index updates and deletes).

After this little incident, I must say I am really amazed at the overall performance of the site, it runs like a charm on Tomcat 5.5 with MySQL behind using a classical JSP 2.0 Struts – IBatis – stack, nothing fancy, no spring, no hibernate, etc ..

P.

I really get a feeling of being back in the year 2000 when the first “internet bubble” exploded, except that the requirements today are :

• Have a really cool design with a nice logo
• Have a cool name (whatever.ici.ous )
• Have AJAX all over the place and demonstrate amazing DHTML and javascript usage ..
• Finally (this one is optional), provide a web based service of some sort and have the words Web 2.0, Social, RSS somewhere on your home page

Personnally I don’t really think all of this is bad, but I am just always amazed on how much money can be put in all these “startups”. Well at least it keeps imagination going.

P.