Friday Feb 20, 2009

A JavaFX compiler debug trick

There is an unsupported (read - can be removed in future without notice!) command line option with JavaFX compiler. If you run javafxc as

    javafxc -XDdumpjava Test.fx

the compiler generates intermediate Java code for your JavaFX program in "./dumpjava" directory (compiler expects you to create ./dumpjava directory before invoking javafxc). This is meant to be a debugging option for JavaFX compiler developers. But, you can look at generated Java code to see what happens behind the scenes - much like C++ programmers used to look at intermediate C code and/or preprocessed code.

JavaFX for Java, JavaScript programmers

I missed attending and speaking at Sun Tech Days at Hyderabad due to a personal reason :-( In fact, I prepared slides for a talk titled "JavaFX for Java, JavaScript programmers". This is much like my earlier language comparison blog entries such as Java, JavaScript and Jython, Java, Groovy and JRuby etc. The idea is to learn a language by language comparison - and not to conclude "better"/"worse" language and so on. So, no politics please :-) Although I could not attend Sun Tech Days, I am posting the slides here : slides in a .pdf file

Tuesday Dec 23, 2008

Installed Ubuntu 8.10 on my PS3

Ubuntu on PS3

I wanted to install Ubuntu on my PlayStation 3.

My Setup

  • PS3 is NTSC 60 GB hard disk version - updated with firmware version 2.42.
  • PS3 is connected to 32 inch 720p Sony LCD TV via HDMI.
  • PS3 is connected to wireless network.

Stuff needed in addition to the above

  1. USB keyboard.
  2. USB mouse.
  3. CD burned with Ubuntu powerpc iso (ubuntu-8.10-alternate-powerpc+ps3.iso).

Preparing PS3

  1. Backup your PS3 hard disk using [Settings] -> [System Settings] -> [Backup Utility] menu. I didn't bother to backup the hard disk.
  2. Go to [Settings] -> [System Settings] > [Format Utility] menu.
  3. Select [Format Hard Disk] and click [Yes].
  4. Choose [Custom] and [Allot 10GB to the Other OS].
  5. Select [Quick Format] and confirm with [Yes].

Installing Ubuntu

  1. Connect USB keyboard and mouse to PS3.
  2. Insert the disk with Ubuntu iso image into PS3.
  3. Go to [Settings] -> [System Settings] > [Install Other OS]. PS3 will detect the install CD and copy files and instruct you to ..
  4. Select [Settings] -> [System Settings] -> [Default System] -> [Other OS]. This will boot PS3 with other OS. From then onwards, follow the Ubuntu installation instructions.

Small hiccup

The installation was smooth except for one small issue - the installation seemed to hang in "Select and install software" step. After 6% the progress bar did not increase at all! Fortunately, this seems to be a known issue with text mode installer. Please refer to Ubuntu 8.10 release notes and bug 290234. I pressed Alt-F4 and Alt-F1 to toggle between logging console and main screen to check the progress. Eventually, the installation completed! While installing I configured network as well -- i.e., giving WEP password etc. -- not sure if this is mandatory, but in my case I have wireless connectivity and so I supplied the configuration values for the same.

Switching between Operating Systems

  • From Ubuntu to Game OS, use the command
        sudo boot-game-os
  • From Game OS to Ubuntu, use the menu
       [Settings] -> [System Settings] -> [Default System] -> [Other OS]

Few Screenshots

Wednesday Dec 17, 2008

Debugging option for javac and javafxc

I work on JavaFX compiler these days. The command line (debugging) option that I often use is -doe ("dump on error"). This option prints stack trace of the compiler when error message is printed. NOTE: This is an internal option and can be removed any time without notice! But, it is useful for debugging. This option works for javac as well as javafxc. When I misspelled "class" as "clas" and run compiler with -doe option, I got the stack trace below:

$ javac -doe class, interface, or enum expected
clas t {}
1 error

Wednesday Dec 10, 2008

Yet another reason for using VirtualBox

I bought a laptop from ELCOT for my sons. It came with SUSE Linux Enterprise Desktop 10 SP2. Kids wanted to see how it is like playing games in the "old" days. Nothing better than seeing and really playing! And so VirtualBox :-)

Also, having access to more than one OS without having to partition does not hurt -- even for a kid's laptop! We can run OLPC, OpenSolaris, Puppy Linux, or anything else!

Thursday Dec 04, 2008

Playing with Alice and PhET

These days, my son is playing with these (apart from usual game sites):
Alice is a 3D programming environment. He likes it as much as he likes Scratch.
Interactive simulation tool for physical phenomena from University of Colorado. He kept trying to soft land "on the moon" :-) I guess Chandrayaan I has impressed him a lot!

What is the common between Alice and PhET apart from being great education tools? It is Java! With the advent of JavaFX, we can expect that such fantastic rich GUI applications will be written in JavaFX.

Friday Aug 08, 2008

Scriptifying BTrace?

One of the issues reported with BTrace is that the trace authors have to write "verbose" code [some people say Java is "verbose"!]. In BTrace, we have to repeat the same set of imports, annotations in every btrace file and all methods have to be "public static void" and so on. Instead of inventing a new scripting language, I've added a simple C preprocessor like step in BTrace compilation. This preprocessor is based on the one in the GlueGen project. Thanks to Ken Russell for this code and for reviewing my changes specific to BTrace project. The preprocessor solution does not rule out a scripting solution in future :-) If you have nice ideas or would like contribute in this area, you are always welcome! But, I think preprocessor solution is simple and will be useful to some.

Simple Example:


To run this sample, the following command can be used:

   btrace -I . <pid-of-the-traced-process>

Without the -I option in command line, BTrace skips the preprocessor step.

Friday Jul 25, 2008

Playing with JSqueak

Squeak is a open source implementation of Smalltalk. What is JSqueak? JSqueak is a Squeak interpreter written in Java. You can download JSqueak source code and play with it. I did the following:
  • Expanded the downloaded under a directory, say c:\\JSqueak.
  • cd c:\\JSqueak
  • javac -d . \*.java
  • copy mini.image.gz JSqueak
  • java JSqueak.Main
Even if you are not going to learn Smalltalk (why?), you can have the fun of reading Smalltalk VM implemented in Java. If you are lazy and don't want to compile, you can run directly by JNLP link from Inside the Squeak environment, I wrote the legendary "Hello World" :-) This is how it looks...

Friday Jul 18, 2008

BTrace and JMX

You can dyanamically attach BTrace to a Java process to inject trace code into it. BTrace client classescollect the trace output via a socket -- these client classes are used by BTrace command line client as well as VisualVM plugin for BTrace. How about attaching a JMX client to collect BTrace's trace data? Yes, it is possible to access a BTrace class's static fields as attributes of a MBean with this RFE.

There are two MBean samples in the BTrace repository. I attached both BTrace samples to a "Java2D demo" process. And then I attached VisualVM to view the Mbean registered by these BTrace samples:

  1. - this sample instruments java.lang.Thread.start() method to update a counter field. This counter field is accessible by JMX clients.

  2. - this sample collects histogram of java.awt.Component objects created by an application and exposes the histogram (map) as MBean attribute.

Friday Jun 27, 2008

Working from an office -- for a change!

I work from home in Chennai, India. There is maintenance power shutdown in my part of the city today [from 9.00 AM to 5.00 PM). I'm writing this blog from a Sun office in Apeejay Business Centre, Chennai. It is nice to be in an office after quite some time - at least as a change! But, I think I'd rather prefer to avoid travel, preparation to go office etc. every day :-)

Thursday Jun 26, 2008

BTrace aggregations - contribution from community

If you have used DTrace, chances are that you have used aggregations. For performance issues, aggregated data is often more useful than individual data points. With BTrace, aggregating data is bit painful (you have to manage using Maps explicitly). It would be nice to have DTrace-style aggregation functions such as sum, max, min and so on. Glencross, Christian M (cited in my previous entry) has contributed code changes, doc and a sample for easy-to-use aggregation facility for BTrace. Please refer to the sample code ( that demonstrates aggregations.

Now something unrelated to aggregations, but related to BTrace : I came to know about another use-case of BTrace. See also

Monday Jun 16, 2008

BTrace in the real world

In the last few weeks, I came to know about two cases of real world use of BTrace.
  1. Glencross, Christian M (his blog?) wrote about attempting to write a script to track SQL statements executed by a Java application (private email). Thanks to him for permitting me to blog about his BTrace script. I've made few formatting changes to fit his code in this blog and added few explanatory comments (staring with "VERBOSE:").
    import static com.sun.btrace.BTraceUtils.\*;
    import java.sql.Statement;
    import java.util.Map;
    import java.util.concurrent.atomic.AtomicLong;
    import com.sun.btrace.\*;
    import com.sun.btrace.annotations.\*;
     \* BTrace script to print timings for all executed JDBC statements on an event.
     \* <p>
     \* @author Chris Glencross
    public class JdbcQueries {
        private static Map preparedStatementDescriptions = newWeakMap();
        private static Map statementDurations = newHashMap();
        // VERBOSE: @TLS makes the field "thread local" -- sort of like using java.lang.ThreadLocal
        private static String preparingStatement;
        private static long timeStampNanos;
        private static String executingStatement;
         \* If "--stack" is passed on command line, print the Java stack trace of the JDBC statement.
         \* VERBOSE: Command line arguments to BTrace are accessed as $(N) where N is the command line arg position.
         \* Otherwise we print the SQL.
        private static boolean useStackTrace = $(2) != null && strcmp("--stack", $(2)) == 0;
        // The first couple of probes capture whenever prepared statement and callable statements are
        // instantiated, in order to let us track what SQL they contain.
         \* Capture SQL used to create prepared statements.
         \* VERBOSE: +foo in clazz means foo and it's subtypes. Note the use of regular expression
         \* for method names. With that BTrace matches all methods starting with "prepare". The
         \* type "AnyType" matches any Java type.
         \* @param args - the list of method parameters. args[1] is the SQL.
        @OnMethod(clazz = "+java.sql.Connection", method = "/prepare.\*/")
        public static void onPrepare(AnyType[] args) {
            preparingStatement = useStackTrace ? jstackStr() : str(args[1]);
         \* Cache SQL associated with a prepared statement.
         \* VERBOSE: By default, @OnMethod matches method entry points. Modifying with @Location 
         \* annotation to match the method return points.
         \* @param arg - the return value from the prepareXxx() method.
        @OnMethod(clazz = "+java.sql.Connection", method = "/prepare.\*/", location = @Location(Kind.RETURN))
        public static void onPrepareReturn(AnyType arg) {
            if (preparingStatement != null) {
                print("P"); // Debug Prepared
                Statement preparedStatement = (Statement) arg;
                put(preparedStatementDescriptions, preparedStatement, preparingStatement);
                preparingStatement = null;
        // The next couple of probes intercept the execution of a statement. If it execute with no-args,
        // then it must be a prepared statement or callable statement. Get the SQL from the probes up above.
        // Otherwise the SQL is in the first argument.
        @OnMethod(clazz = "+java.sql.Statement", method = "/execute.\*/")
        public static void onExecute(AnyType[] args) {
            timeStampNanos = timeNanos();
            if (args.length == 1) {
                // No SQL argument; lookup the SQL from the prepared statement
                Statement currentStatement = (Statement) args[0]; // this
                executingStatement = get(preparedStatementDescriptions, currentStatement);
            } else {
                // Direct SQL in the first argument
                executingStatement = useStackTrace ? jstackStr() : str(args[1]);
        @OnMethod(clazz = "+java.sql.Statement", method = "/execute.\*/", location = @Location(Kind.RETURN))
        public static void onExecuteReturn() {
            if (executingStatement == null) {
            print("X"); // Debug Executed
            long durationMicros = (timeNanos() - timeStampNanos) / 1000;
            AtomicLong ai = get(statementDurations, executingStatement);
            if (ai == null) {
                ai = newAtomicLong(durationMicros);
                put(statementDurations, executingStatement, ai);
            } else {
                addAndGet(ai, durationMicros);
            executingStatement = null;
        // VERBOSE: @OnEvent probe fires whenever BTrace client sends "event" command.
        // The command line BTrace client sends BTrace events when user pressed Ctrl-C 
        // (more precisely, on receiving SIGINT signal)
        public static void onEvent() {
            printNumberMap("JDBC statement executions / microseconds:", statementDurations);

    And he has expressed few wish lists for BTrace based on his experience with DTrace. We plan to investigate those items in near future.

  2. Binod P.G exchanged private e-mails about BTrace usage to track down a memory leak. Subsequently, he has blogged about the same.

Wednesday May 28, 2008

BTrace JavaOne2008 BOF slides..

I received emails asking for BTrace BOF (JavaOne-2008) slides. Better late than never... I've uploaded PDF of the slides. The BOF was mostly around demos -- slides do not contain much. But, slides have few pointers that may be useful.

Friday May 09, 2008

Thursday May 8, JavaOne

Here are the few highlights from the talks that I attended today:

TS-5428 Java Technology Meets the Real World: Intelligence Everywhere.

This talk is about pervasive computing (a.k.a ubiquitous computing) with products from Sentilla. There was an interesting demo about humidity sensor detecting changes and sending a message to a host. The "motes" run CLDC 1.1 VM (+ proprietary profile for motes). These motes have ports for sensors and actuators and some built-in sensor. There were many interesting suggestions for embedded programming for such small devices (don't allocate in inner loops and there by leading to to GC kick-in, avoid too many static fields, avoid threads whenever possible and so on).

TS-7575 Using Java Technology-Based Class Loaders to design and implementing a Java platform, Micro Edition

The basic idea is to run JavaME applications (developed for different configurations/profiles/subsets of optional packages) on top of JavaSE. The extended JavaSE classes and packages not available in specific profile or optional package set [implemented by a specific phone] should not be made available to JavaME apps targeted. i.e., only the classes available to a specific phone model should be available. If the JavaME app tries to access any other class, it should receive ClassNotFoundException. The speakers explained how to achieve such "containers" by class loader based isolation. The problem is that they seem to solve only the class access. What about extended methods and fields? For example, platform core classes on JavaSE have superset of methods [more methods on the same class available on JavaME - eg. java.util.Hashtable has more methods on JavaSE). The application classes have to bytecode analyzed and instrumented to take care of field/method accces. It seems that their current product that does not address this yet.

PAN-5542 Developing Semantic Web Applications on the Java Platform.

The discussion started with some nice demos. There was a demo with AllegroGraph RDF store, Twine, a demo with using GRDDL and getting RDF triples by a proxy server. i.e., a proxy serves does the GRDDL transformations to get RDF triples from sites [which could be stored/analyzed with RDF stores subsequently] and a demo with FOAF files. Interesting take aways from the discussion include:

  • We don't have to wait for SEMANTIC WEB with full fledged reasoners and so on. Instead, add little semantic bits to existing web (say using RDFa, GRDDL etc.) in your current web projects/pages.
  • There are many Java tools. There is need to standard Java APIs for triple store access etc. Right now, we have to write for Jena, Sesame etc. It was also felt that APIs will need to wait for more usage scenarios.
  • There are tools to expose your existing databases as virtual RDF stores -- for example: D2RQ. Probably, most of the RDF triples could come from existing data.
  • Privacy, security of the information is very important. Work needs to be done in this area.
  • Natural language processing and getting triples out of it is very hard. You may want to refer to systems like DBpedia.

Thursday May 08, 2008

Wednesday May 7, JavaOne

Today Bill, Chihiro, Jaya and I talked on Blu-ray. The talk was centered around the open source project @ - a library and a set of tools to build Blu-ray discs. If you haven't checked out code/docs, you may want to checkout and play with the code. All you need is a laptop with blu-ray drive and a BD-RE disc. Optionally, for added fun you may want to have a hardware bluray player such as PS3 -- so that you can see the output on your TV rather than on a laptop. Other than the session, we also had a very informal BOF on blu-ray, OCAP etc. during the evening. It is good to meet experts in respective technologies in one place!

Other than the the blu-ray stuff, I did attend other talks/BOF. Just after Blu-ray session, I attended "TS-6000 Improving Application Performance with Monitoring and Profiling Tools" talk. This talk was about OS specific tools, JDK tools and third-party tools for profiling and monitoring. Gregg Sporar and Jaroslav Bachorik (NetBeans Profiler team) presented very well. There were many interesting questions/discussions as well. If you haven't done so already, you may want to download VisualVM. If you want bit more fun doing monitoring/profiling, you may want to check out the sources from and build it yourself. You can build BTrace VisualVM plugin using the command:

    c:\\visualvm\\plugins>ant build

assuming you have checked out VisualVM sources under "c:\\visualvm". If you have already checked out BTrace sources under some other directory, say "c:\\btrace", you can use

    c:\\visualvm\\plugins>ant -Dbtrace.home=c:\\btrace build

To run VisualVM with all the plugins that you built, you can use the following command:

    c:\\visualvm\\plugins>ant -Dbtrace.home=c:\\btrace run

Please let us know what features you'd like to see with BTrace and/or BTrace VisualVM plugin.

I attended and liked the "Class Loader Rearchitected (BOF-6180)" BOF. If you have ever written class loaders, chances are that you have faced mysterious deadlocks or ClassCastException that said "ClassCastException: Foo cannot be cast to Foo" or having to decide between overriding loadClass and findclass, you probably should have attended this talk and gave your opinions/suggestions/ideas :-) If I understood properly, I think there was a suggestion to add class loader info. to the ClassCastException (something like class-loader-class-name@identity-HashCode style string?) so that one can quickly see it is a class loader issue. Also, there were many questions on loading classes from jar files. Looks like there will be changes to class loader API and class loading in VM for JDK 7.




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