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Tag Archives: Java

Different day, same shit, today: Java 5 on Oracle Enterprise Linux 5

19-Jan-09

Worlds collide: Oracle and Sun JDK. Perfect start to ruin a not so bad Monday morning.

Background: Need to have a Tomcat Server deployed on a Oracle Enterprise Linux 5 system.

I was happy, when i saw a tomcat5 package in the repositories. Great, i thought. All i need. Well. Not.

Under Windows you’ll get between one and ten JVM versions installed with on Oracle product (slight exaggerated), within the OEL5 there was only one ancient 1.4.2 JDK. *sigh* Did i mention that the application that is supposed to run on that thing uses a buttload of Java 5 features?

“yum search java-”… No Java 5. WtF?

There is no Java 5.

Again, do it yourself:

This is a nice entry that describes howto build rpms for the “official” Sun Java 5 jdk.

I used the following steps to build my rpms:

  • Downloaded this rpm
  • Downloaded jdk-1_5_0_15-linux-i586.bin from the Sun JDK archive page
  • Put the later one into /usr/src/redhat/SOURCES/
  • Built the rpms with rpmbuild –rebuild java-1.5.0-sun-1.5.0.15-1jpp.nosrc.rpm. If rpmbuild is not installed, it’s hidden in the package rpm-build, not rpmbuild.
  • Installed missing libXp
  • Installed the rpms: 
    rpm -Uvh /usr/src/redhat/RPMS/i586/java-1.5.0-sun-1.5.0.15-1jpp.i586.rpm
rpm -Uvh /usr/src/redhat/RPMS/i586/java-1.5.0-sun-devel-1.5.0.15-1jpp.i586.rpm
rpm -Uvh /usr/src/redhat/RPMS/i586/java-1.5.0-sun-src-1.5.0.15-1jpp.i586.rpm
rpm -Uvh /usr/src/redhat/RPMS/i586/java-1.5.0-sun-demo-1.5.0.15-1jpp.i586.rpm
rpm -Uvh /usr/src/redhat/RPMS/i586/java-1.5.0-sun-plugin-1.5.0.15-1jpp.i586.rpm
rpm -Uvh /usr/src/redhat/RPMS/i586/java-1.5.0-sun-fonts-1.5.0.15-1jpp.i586.rpm
rpm -Uvh /usr/src/redhat/RPMS/i586/java-1.5.0-sun-alsa-1.5.0.15-1jpp.i586.rpm
rpm -Uvh /usr/src/redhat/RPMS/i586/java-1.5.0-sun-jdbc-1.5.0.15-1jpp.i586.rpm
  • Last step: Choose the right java version with alternatives –config java

After that, everything could be fine. Well, it wasn’t:

sun.misc.InvalidJarIndexException: Invalid index

Jehova! Finally not a NPE but something new, at least to me. Sometimes i wonder why i always run into bugs like these.

Some script changes and repackages all jar files in some weird ways so that a standard JDK has funny problems.

My solution to it: Reindex everything in /usr/share/java after you’ve chosen your newly installed java with the following command:

find /usr/share/java/ -iname "jakarta*commons*.jar" -exec jar -i {} \;

I opted to reindex only the jakarta commons files, that got Tomcat up and running with Java 5.

One last note: The /usr/bin/dtomcat5 is broken imho, at least when run from /etc/init.d/tomcat5. In ignores /etc/tomcat5/tomcat5.conf and therefore cannot stop Tomcat.

My solution: Replace

if [ -z "$CATALINA_HOME" ]; then
    TOMCAT_CFG="/etc/tomcat5/tomcat5.conf"
fi

(in line 55 on my setup) with

if [ -z "$CATALINA_HOME" ]; then
    TOMCAT_CFG="/etc/tomcat5/tomcat5.conf"
    [ -r "$TOMCAT_CFG" ] && . "${TOMCAT_CFG}"
fi

and remove

if [ -z "$CATALINA_HOME" ]; then
    [ -r "$TOMCAT_CFG" ] && . "${TOMCAT_CFG}"
fi

(in line 105 on my setup).

I wonder why simple things like these always are a pain in the ass. Stupid nuisances that keeps people from getting their work done. *sigh* Not a good start for the week.

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Division by zero

26-May-08

Just a quick reminder for myself:

int a = 0/0; // Throws ArithmeticException
double d1 = 0/0.0; // d1 is NaN
double d2 = 1/0.0; // d2 is Infinity
double d3 = -1/0.0; // d3 is -Infinity

Can cause some headache if things fall apart in the JDBC driver and not before. Grmpf.

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SCJP, finally!

06-May-08

More than a year ago i decided to do the Sun Certified Java Programmer. Shortly after i bought this book, the projects at work and at home were somewhat overwhelming and after all, i realized that a big part of the SCJP is about some weird, crazy and sometimes wrong design decisions of the Java language. Some of them i mentioned under this tag.

Last month i realized i had some spare time, signed up at Prometric and had a 2nd look at the book and on my good Java experience from the last 6 years.

First thing: The “Java 5 Study Guide” isn’t a bad book but the “MasterExam” software on the enclosed cd is a master piece of crap. Not only the gui is as shitty as it gets but some of the answers are just plain wrong.

Second thing: I bought the preparation kit from Whizlabs for 50€. This thing isn’t bad at all and helps you get prepared for the craziness thrown at you.

Third: Being good at something is always great :D It rocks, really. Like single trail riding or music with electric guitars while driving open. It’s like drugs but not that unhealthy.

After about 2 weeks of preparing, I arrived 30 minutes early at “New Horizons” in Cologne, took the test certainly in english as i prepared with english material and finished somewhat 50 minutes later (you have officially around 3 hours to take the test). The nice proctor asked me if i wanted to use the toilet as she saw my report being printed: 90%, pass! Wooot!

I thought about this post at Jans. I really like the guy who wins a million dollars at Who wants to be a Millionaire and has the guts to call his dad but not ask for help and instead tells him he is going to win a million dollars. I can totally relate to that as i always had fun taking test and scoring at the upper limit :D

So today i’m gonna eat an extra portion of Cookies & Cream and leave you with the following piece of Java madness:

More…

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Tired of all the powerpoint presentations…

23-Apr-08

Right now i’m in Wiesbaden, attending the JAX 2008 conference.

The mood is somewhat different compared to the DOAG i used to visit the last years. The people are more open minded, partially much younger and generally try to be much cooler. And for the sake of it, some are even more interesting and after all, there isn’t that ongoing whining about Oracle not engaging in Forms 6i Client Server any more (although, i must admit, i somewhat like Oracle Forms 6i, maybe it’s a love/hate relationship, trust me, i know both worlds, Java and Forms).

The sessions suffer from one big problem: Many of them just seem to play powerpoint karaoke: Throw in a bunch of crappy slides with a handfull code snippets and sing-a-long to that stuff which means basically: Hind behind the slides.

Let me tell you: This is so boring and pointless. In the past i tried to be polite and always stayed to the end of a session but the last 2 or 3 conferences i can’t stand it any more. I can read myself, thanks. If you haven’t got anything additionally to say, just pass me the slide and i’m fine.

The 3 most interesting sessions where the sessions spoken freely with the slides just illustrating the speech. I especially liked Brian Chans presentation of Liferay Portal, Rod Johnsons keynote on the future of J2EE and the most witty one, Ted Newards talk about the renaissance of languages. It was funny, included the audience, was well prepared and freely hold, not to forget the topic: It wasn’t about the nth framework around the corner but about the nearly philosophy topic about the “perfect programming language”.

I really wish that i’d be creative and intelligent enough to design a language that is not predestined to die an early death, but i ain’t. But i can distinguish a sharp tool from a spoon if i see one and i can adopt to it very easily. And in that sense i share Teds opinion that a discussion about abstracting things and about the tool itself is of much more value than implementing some arbitrary pattern (i.e. one be the GOF) in just another framework. For example, many implementations of some patterns in frameworks have been rendered obsolete by more powerful and more expressive languages and i’d like to see this trend go on.

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JDBC: Autogenerated keys revisited.

02-Apr-08

Some months ago i wrote about retrieving auto generated values with JDBC from an Oracle Database: JDBC: Get autogenerated keys on a Oracle DB.

The solution i presented in the previous article doesn’t run in a Oracle Java Stored Procedure.

To accomplish this, use a callable statement like this:

final String sql = "BEGIN INSERT INTO foobar(id, b) VALUES (id.nextval, ?) RETURNING id INTO ?; END;";
CallableStatement cs = connection.prepareCall(sql);
stmt.setString(1, "bar");
stmt.registerOutParameter(2, Types.INTEGER);
stmt.executeUpdate();		
rv = rs.getInt(2);

This way you get the id generated by the sequence id without first selecting and then using it.

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Feeling dizzy…

26-Mar-08

After staring at this

dummy

for about a day in various rotations and flips just to get Oracle GeoRaster work together with a homebrew GIS like application made me feel somewhat dizzy. To be cartesian or not cartesian, that is the question ;)

Otherwise, Oracle GeoRaster works quite well, at least for that bunch of german TK25 maps in GK3 coordinates that used to float around in the filesystem and are now being stored in the database.

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Weird java generics…

07-Feb-08

Generics are not totally bad but one can write really creepy things:

final FutureTask<Collection<LeitungsachseTK25>[]> ft = new FutureTask<Collection<LeitungsachseTK25>[]>(
    new Callable<Collection<LeitungsachseTK25>[]>() {
        public Collection<LeitungsachseTK25>[] call() throws Exception {

Seems like XML and Java finally married… ;)

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Workshops

25-Oct-07

Right now i’m in Frankfurt / Main, attending the iX Workshop Web Programming with Grails (Link in German).

The speaker, Dierk König, encouraged live blogging, so here we are:

Some ActiveRecord bashing and many, many windows machines around. People fiddling around with their Java Paths, IntelliJ IDEA, which should be way better and more impressive than Eclipse or my nifty little TextMate… In the meantime, everything works fine on a real OS (that is everything else than Windows, for that matter…)

I’m already bored and expecting something more to happen. Everything said in the last 3 hours or so has been written down somewhere on the Internet.

As i don’t want to bore anybody else, i’ll guess i have look at my feedreader.

Hey, the beat goes on, configuring some weird IDE has stopped…

Would anybody really read my live blogging? If a tree falls in a forest…

JEHOVA! He said G-String :)

So again, how are strings called in the Groovy JDK? G Strings?

Hm, breaks are wonderful… Too much to eat, too much coffee…

The guy next to me didn’t manage to get the command line version working neither any IDE… Help is not wished.

At least, there’s a recent issue of german magazin in the conference file… With the title story about Ruby on Rails, hrr, hrr ;) .
Sometimes i think the IT world needs more egomaniac, rockstar-like developers like Heinemeier Hansson

Why on earth does one guy write the code from the beamer down on a sheet of paper while he’s checking his emails at the same time?? Sometimes the outer world seems like a strange place to me. Strange and weird.

Funny thing: Received a 1&1 spam mail about some profiseller foobar this morning. There are two guys from 1&1 at the opposite desk… Well, i’m too good educated…

Is it a good idea to but lawyers and webprogrammers into the same hotel? ;)

“Divs are good for updating thingies on the page”

I guess its obvious that english isn’t my native language (can’t get the thought out of my head that tante is mocking me…), but language and spoken words always creates a frame for thoughts and far to often, a cage… And for that being said, one should pay more attention on how to paraphrase things.

I really hate it if the speakers machine is not prepared well. I really do enjoy giving little demonstrations but i’m fastidious to paranoid that everything is taken care of, tested and proved to be working… If their only 8 hours time, not working improvisation sucks.

I have to say, i really do like Groovy, it’s a chance to get some serious scripting into Java at home… err i wanted to say, at work. People tend to focus on just one language and limiting themselves, but with Groovy i can argue: It’s Java with some fancy things on top. And at least for me, it’s a good thing.

“Mit diesen Dingen kann man beliebig fancy werden” — Argh, my head schmerzts…

I should collect some pudding for the gay bar to see if this guy is really as witty as he writes. Would pudding suffer to pay you or do want some Hägen Dasz?

Party is over… Good night & good fight ;)

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A fistfull of readers

23-Oct-07

After presenting a working InputStream on a ByteBuffer, i have to more readers for you out there.

First, the StringBufferReader to efficient read data from a StringBuffer. One can use new java.io.StringReader(sb.toString()) but that would convert the whole StringBuffer (sb) to a string, loosing a whole lotta memory if the string is just big enough. If you can assure that the StringBuffer don’t need to be modified, use the following code:

import java.io.IOException;
import java.io.Reader;
 
public class StringBufferReader extends Reader {
	private int pos;
	private final StringBuffer sb;	
	private boolean closed;
 
	public StringBufferReader(final StringBuffer sb) {
		this.sb = sb;
		this.pos = 0;
		this.closed = false;
	}
 
	@Override
	public void close() throws IOException {
		this.closed = true;
	}
 
	@Override
	public int read(char[] cbuf, int off, int len) throws IOException {
		if(closed)
			throw new IOException("Reader is closed");
		int _len = Math.min(len, sb.length() - pos);		
		sb.getChars(pos, pos + _len, cbuf, off);
		pos += _len;
		return _len == 0 ? -1 : _len;
	}
}

It uses no intermediate buffer.

In the same context i stumbled upon the Byte Order Mark (BOM) in some UTF8 files (especially ones that were created with tools under Microsoft Windows).

The InputReaders and Streams in the JRE don’t skip the BOM, neither does the org.dom4j.io.SAXReader so parsing of such XML files or strings fails with something like “Content not allowed in prolog”. Enter my simple BOMSkippingReader:

import java.io.IOException;
import java.io.Reader;
 
/**
 * This reader skips a possible Byte Order Marker at the 
 * start of UTF8 files which java doesn't.
 * @author michael
 *
 */
public class BOMSkippingReader extends Reader {
	private final Reader decorated;	
	private final boolean rewrite;
	private final int firstchar;
	private int pos = 0;
 
	public BOMSkippingReader(final Reader decorated) throws IOException {
		this.decorated = decorated;
 
		this.firstchar = decorated.read();						
		this.rewrite = firstchar != 65279;			
	}
 
	@Override
	public void close() throws IOException {
		decorated.close();
	}
 
	@Override
	public int read(char[] cbuf, int off, int len) throws IOException {					
		int redone = 0;					
		while(rewrite && pos < 1) {
			cbuf[off + pos++] = (char) firstchar;
			++redone;
		}
		return redone + decorated.read(cbuf, off + redone, len - redone);				
	}
}

If there’s a BOM in the underlying reader, it’s skipped, otherwise written back to the reader. Works well for me and the small while loop doesn’t have much impact on the performance in my app.

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Java: Creating a Stream on a ByteBuffer

18-Oct-07

This example is plain wrong. The InputStream will cause an endless loop as it always returns a value >= 0. Working code as follows:

private static InputStream _newInputStream(final ByteBuffer buf) {
	return new InputStream() {
		public synchronized int read() throws IOException {				
			return buf.hasRemaining() ? buf.get() : -1;
		}
 
		public synchronized int read(byte[] bytes, int off, int len) throws IOException {			
			int rv = Math.min(len, buf.remaining());				
			buf.get(bytes, off, rv);
			return rv == 0 ? -1 : rv;
		}
	};
}

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