A. Sundararajan's Weblog

Thursday May 8, JavaOne

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

( May 09 2008, 08:56:14 PM IST ) Permalink Comments [0] | | | | |

Wednesday May 7, JavaOne

Today Bill, Chihiro, Jaya and I talked on Blu-ray. The talk was centered around the open source project @ http://hdcookbook.dev.java.net - 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 http://visualvm.dev.java.net and build it yourself. You can build BTrace VisualVM plugin using the command:

    c:\visualvm\plugins>ant build

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

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

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.

( May 08 2008, 08:28:58 PM IST ) Permalink Comments [0] | | | | |

Tuesday May 6, JavaOne

In today's sessions that I attended I liked the following:

JRuby: Why, What, How... Do It Now

This talk is a good introduction to (J)Ruby the language and important applications of (J)Ruby. And many pointers to related (J)Ruby sessions. Nice summary!

JavaScript programming language: The Language Everybody Loves to Hate

great talk by Roberto Chinnici. Nice summary of functional and prototype-based object orientation aspects of JavaScript. You can easily impress your friends will some neat snippets of JavaScript You may want to continue the fun by reading Doug Crockford's pages, if you have not do already!

At 7.30 PM, we (I and Kannan) talked about BTrace. There were many interesting questions/discussions -- both during and after the BOF! Today (Wed May 7) will be a Blu-ray day -- it starts with TS-5449 Java Technology for Blu-ray and TV: Creating your own Blu-ray Java Discs session. It is about the open source project @ http://hdcookbook.dev.java.net. Meet you all there!

( May 07 2008, 07:52:02 PM IST ) Permalink Comments [0] | | | | |

JVM Languages @ JavaOne 2008

In JavaOne 2008, there are many intesting sessions on "other" JVM languages covering both dynamically typed languages (JavaScript, Groovy, JRuby) and statically typed languages (JavaFX, Scala). As usual, there are many sessions covering application aspects -- like using scripting on Glassfish, Grials (Groovy), Rails (JRuby) and so on. But, my interest is mostly on the programming language aspects and JVM implementation issues. Here is a table of sessions covering those:

( Apr 30 2008, 10:54:42 AM IST ) Permalink Comments [0] | | | | |

BTrace BOF @ JavaOne 2008

We have a BOF on BTrace in this year's JavaOne. But, you will not find the name "BTrace" in session title -- that is because talk was submitted before BTrace was open sourced with that name The details of the BOF is as below. Please visit and let us discuss on dynamic tracing for Java.

( Apr 29 2008, 01:27:31 PM IST ) Permalink Comments [1] | | | | |

Groovy jsr-223 engine updated..

Groovy jsr-223 script engine @ scripting.dev.java.net has been updated to use Groovy version 1.5.6.

( Apr 29 2008, 08:21:13 AM IST ) Permalink Comments [0] | | | | |

Bluray @ JavaOne 2008

If you want to learn more about Blu-ray disc and what Java has to do with it, you may want to attend the following talks/BOFs @ JavaOne 2008!

From our group talk (TS-5449), we will be focusing on the open source project @ https://hdcookbook.dev.java.net. Meet you soon @ JavaOne !!

( Apr 28 2008, 06:35:19 PM IST ) Permalink Comments [0] | | | | |

Latest on scripting for the Java platform...

Updates on the world of Scripting for the Java platform:

• Yoko Harada has updated JRuby jsr-223 engine to use JRuby 1.1RC2.
• I've updated Groovy jsr-223 engine to use Groovy 1.5.4.
• You may know this news already: Jython Gurus have joined Sun
  See also
  • Jython's Future Looking Sunny
  • The Sun is going to shine on Python

( Mar 04 2008, 07:13:30 PM IST ) Permalink Comments [2] | | | | |

VM on a VM on a ...

My recent fun with virtualization continues. In the last JavaOne, I missed the talk titled "Everything Java": JPC, a Fast x86 PC Emulator. But, I downloaded the source and binary of JPC just to check it out. I ran the classic game "Prince". Nostalgia

( Feb 15 2008, 07:01:20 PM IST ) Permalink Comments [3] | | | | |

blu-ray.. blu-ray...

I am thrilled to know this news!! And that is not without a bit of self-interest. I work on some blu-ray related activities @ Sun (more on that in future!).

BTW, if you are interested in learning about blu-ray and related Java programming platform called BD-J, you may consider the following:

• Buy a copy of the nice book Programming HD DVD and Blu-ray Disc.
• Check out the code from the project http://hdcookbook.dev.java.net
• Buy a laptop with blu-ray disc drive. This will come with a blu-ray player software.

( Jan 05 2008, 11:47:15 AM IST ) Permalink | | | | |

Latest on the Scripting project

Updates on the Scripting project.

1. Updated JavaScript script engine with Rhino version 1.6R7. This version supports E4X without requiring XMLBeans.
2. Updated Groovy script engine to use version 1.5.1.
3. Updated Jython script engine to use version 2.2.1.
4. Updated Freemarker script engine to use version 2.3.11.
5. Yoko Harada is planning to update JRuby script engine with version 1.1x.

( Jan 03 2008, 04:57:14 PM IST ) Permalink Comments [3] | | | | |

What's new with Scripting for the Java platform?

Sorry about the looo..ng hibernation! Now, it is time for updates on the Scripting project.

1. Yoko Harada updated JRuby script engine with JRuby 1.0.2 and added few other fixes in engine code.
2. I've pre-built binaries of the project (uploaded the .zip and .tar.gz files)

1. JavaFX Script interpreter had jsr-223 support. Now, the JavaFX Script compiler has jsr-223 support -- you may want to checkout JavaFX Script compiler project. The following code works as expected:

   
   import javax.script.*;
   
   public class Test {
       public static void main(String[] args) throws Exception {
           ScriptEngineManager m = new ScriptEngineManager();
           ScriptEngine e = m.getEngineByName("javafx");
           e.eval("<<java.lang>>.System.out.println(\"hello\");");
       }
   }
   
   

   Please note that you need to build JavaFX Script compiler by checking out sources from the SVN repository and put the jar in the CLASSPATH.
2. Xavier Clerc sent a link to the jsr-223 script engine for the Object Caml language. Thanks!
3. Alexandre Bergel sent a link to the jsr-223 script engine for the Smalltalk language. Thanks!

( Nov 12 2007, 01:17:27 PM IST ) Permalink | | | | |

javac's hidden options...

javac has "hidden" and "even more hidden" options. This blog entry is about how to use one such option without actually modifying javac's source code. [Read More]

( Sep 10 2007, 12:49:48 PM IST ) Permalink | | | | |

ANTLRWorks and fun with grammars

If you are a programming languages enthusiast, you'll probably like this. I downloaded ANTLR Parser Generator. In addition to ANTLR, I downloaded the following:

• ANTLRWorks - a grammar development environment for ANTLRv3.
• Java 1.5 ANTLR Grammar It is fun to navigate/debug/view grammars and parse trees. Parse tree of a simple Java class looks as follows:
  
  
  
  
  
  ( Jul 30 2007, 01:59:02 PM IST ) Permalink Comments [1] | | | | |

  ---

Week-end fun with the java compiler source code

I downloaded java compiler (javac) source code from the JDK 7 site. I did not download entire JDK – I just downloaded compiler-7-ea-src-b15-05_jul_2007.zip I've installed JDK 6 and NetBeans 5.0

I extracted the source zip file into c:\javac directory. From NetBeans IDE, File->Open Project menu, I chose c:\javac\compiler directory. Then, I build the project – I scrolled the build output log to the end and I saw:

Building jar: C:\javac\compiler\dist\lib\javac.jar

build-bin.javac:

Copying 1 file to C:\javac\compiler\dist\bin

build:

BUILD SUCCESSFUL (total time: 8 seconds)

So, I tried to run the newly compiled java compiler. I attempted to compile a simple “Hello World” program. I got the following error:

C:\javac\compiler\dist\lib>java -jar javac.jar Hello.java

Exception in thread "main" java.lang.NoClassDefFoundError: com/sun/tools/javac/Main

What happened? I looked at the build log again. I missed the following lines – because I had seen only at the end!!

Copying 7 files to C:\javac\compiler\build\bootclasses

recompiling compiler with itself

javac: invalid flag: C:\javac\compiler\build\classes

Usage: javac <options> <source files>

use -help for a list of possible options

Java Result: 2

Copying 7 files to C:\javac\compiler\build\classes

Copying 1 file to C:\javac\compiler\build\classes\com\sun\tools\javac\resources

Building jar: C:\javac\compiler\dist\lib\javac.jar

build-bin.javac:

Copying 1 file to C:\javac\compiler\dist\bin

build:

BUILD SUCCESSFUL (total time: 8 seconds)

Looks like there is a build error. The compiler in built in two steps:

1. The sources are built with javac in JDK 6 (on which my NetBeans IDE ran)

2. Then, compiler sources are built again – but this time with the new compiler binary generated by step (1).

Looks we got error in the step (2) [see above: recompiling compiler with itself] . I searched the ant script used to build for “recompiling compiler with itself”. The following is the fragment after that:

<echo message="recompiling compiler with itself"/>

<pathconvert pathsep=" " property="src.javac.files">

<path>

<fileset dir="${src.classes}">

<patternset refid="src.javac"/>

</fileset>

</path>

</pathconvert>

<java fork="true" classpath="${build.bootclasses}" classname="com.sun.tools.javac.Main">

<arg value="-sourcepath"/>

<arg value=""/>

<arg value="-d"/>

<arg file="${build.classes}"/>

<arg value="-g:source,lines"/>

<arg line="${src.javac.files}"/>

</java>

The problem seems to be with “java” command above. Empty string is set as value for -sourcepath option. I changed that to the following:

<arg value="-sourcepath"/>

<arg value="${src.classes}"/>

When I re-built the compiler after the above change, there were no errors – yes, I scrolled the build output to check it And newly compiled javac could compile “Hello World” program.

Now, I wanted to make some to “interesting” but simple change to the compiler source. From a “doc” page, I came to know that there is a hidden javac option called “-printflat”. It appears that with -printflat option javac prints source code after doing transformations for generic types, inner classes, enhanced for-loops, assertions etc. It would be great to visualize the kind of transformations done by javac. So, I wanted to make “hidden” option available. I searched for “printflat” in the project. I got three hits:

1. JavaCompiler.java

2. RecognizedOptions.java

3. java.properties

As usual, I am impatient – wanted to enable printflat option always [regardless of what the command line is]. So, I changed the following line in JavaCompiler.java

printFlat = options.get("-printflat") != null;

to

printFlat = true; // options.get("-printflat") != null;

so that the secret option is enabled always. After rebuilding the compiler, I tried compiling my “Hello World” program. Surprise! I got the following error:

C:\javac\compiler\dist\lib>java -jar javac.jar Hello.java

Exception in thread "main" java.lang.NoClassDefFoundError: com/sun/tools/javac/Main

When I checked “javac.jar” by “jar tvf javac.jar”, I saw only “.java” files instead of “.class” files! Remember I mentioned that javac is recompiled by itself (step (2) above)? Apparently with “-printflat” option, javac just write transformed files but does not generate .class files! Because I had hardcoded printflat to be true always, during the second bootstrap compilation javac did not generate .class files. Looks like my lazy way does not work! I need to find how to really change the code to accept printflat command line option explicitly. I cut the story shot and just summarize the changes I made:

1. added a enum value to com.sun.tools.javac.main.OptionName – PRINTFLAT("-printflat");

2. In com.sun.tools.javac.main.RecognizedOptions class, I added PRINTFLAT to “static Set<OptionName> javacOptions” initialization value.

3. In public static Option[] getAll(final OptionHelper helper) method of RecognizedOptions class, I added “new HiddenOption(PRINTFLAT)” as an element in the returned Option[].

I managed to compile and run the compiler after the above changes! Now when I can pass “printflat” option!! I compiled the following simple Book.java:

class Book {
  private String name;
  public Book(String name) {
     this.name = name;
  }

  class Order {
     private int quantity;
     public Order(int quantity) {
        this.quantity = quantity;
     }
  }
}

c:\javac\compiler\dist\lib\>java -jar javac.jar -printflat c:\Book.java

Now, I can see the generated Book.java and Book$Order.java in the current directory where java compiler was run:

class Book {
    private String name;
    
    public Book(String name) {
        super();
        this.name = name;
    }
    {
    }
}

class Book$Order {
    /*synthetic*/ final Book this$0;
    private int quantity;
    
    public Book$Order(/*synthetic*/ final Book this$0, int quantity) {
        this.this$0 = this$0;
        super();
        this.quantity = quantity;
    }
}

Wow! I can see how java compiler generates a hidden synthetic parameter for the outer class object and so on. Note that the java compiler does not overwrite your original source files. You need to run the compiler in a different directory – compiler generates new files [which is good, you won't accidentally overwrite your original code with generics, inner classes and so on].

Now, you can experiment with constructs like asserts, inner class methods accessing outer's private methods/fields, anonymous/local classes, local class accessing final parameters/locals of enclosing method, generics, enhanced for-loop and so on and see how java compiler transforms those constructs to generate good-old “flat” classes without these features. Have fun!!

( Jul 14 2007, 11:28:29 PM IST ) Permalink Comments [1] | | | | |