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What's new in Tcl/Java?



Version 1.4:

Tcl/Java 1.4 includes a number of exciting new features that make integrating Tcl and Java even easier.

TJC Compiler

The TJC compiler is by far the most significant new development in the Jacl 1.4 release. The TJC compiler is used to convert a Tcl proc to Java bytecode that is then executed directly inside the JVM. In most cases, a TJC compiled proc will execute 10 to 20 times faster than an interpreted proc. Jacl's implementation has also been significantly optimized to support efficient execution of TJC compiled procs. In some cases, TJC compiled procs actually execute more quickly than procs compiled with the built-in compiler included in native Tcl. The TJC compiler can be used either at runtime or in batch mode.

Itcl Extension

Jacl 1.4 now includes support for the Itcl OO extension. A Jacl user would execute the following to load Itcl commands into Jacl:

package require Itcl
This extension was implemented for Jacl by porting the Itcl 3.3 C source code to Java.

Parser Extension

Jacl 1.4 now includes support for the TclPro's Tcl parser extension. A Jacl user would execute the following to load Parser commands into Jacl:

package require parser
The parser extension version 1.4 was implemented for Jacl by porting the C source code to Java.

expr command

Jacl's expr implementation now supports the 'eq' and 'ne' string equality operators.

java::for command

The java package includes a new java::for command. This command provides a mapping to Java's enhanced for loop statement and provides a simplified way to loop over the elements of a Collection or array object. See the documentation for usage examples.

Inner Classes

Inner classes are now fully supported in the Java package. In earlier versions of Tcl/Java, an inner class like java.util.Map.Entry would be indicated by a string like java.util.Map\$Entry. This usage worked in some cases, but it was ugly and did not support imported class names via java::import. The new implementation makes it possible to pass java.util.Map.Entry or import java.util.Map and then pass Map.Entry to any of the java::* commands.

Classloader Implementation

The TclClassLoader used in Jacl and Tcl Blend to load Java classes and resources has been updated to make use of the class loader delagation model introduced in JDK 1.2. Loading of classes and resources is now be delagated to the thread context class loader. This change fixes class and resource loading problems found in Java app server environments like WebSphere, Tomcat, and others. A number of bugs related to loading classes from the env(TCL_CLASSPATH) path have been fixed and support for loading resources from the env(TCL_CLASSPATH) path has been added.

SetInterrupt API for Jacl

A new Interp.setInterrupt() API makes it possible for the user to interrupt a running Jacl interpreter and unwind the stack. For example, this API could be used to implement a service thread that would timeout and cleanup after a certain amount of time. See SetInterrupted for more info.

JPDA debug support

Jacl can now be started in a debug mode that makes it easy to attach a Java debugger. A Java debugger that supports JPDA will automatically load and display the source code that implement Jacl. To start Jacl in debug mode, simply set the JACL_DEBUG env variable to "1" before running jaclsh or jaclsh.bat. Info about how to attach to the shell will be printed to the console.

Version 1.3:

This section covers features introduced in Tcl/Java 1.3.

regexp command

A new implementation of Jacl's regexp and regsub commands has been donated by Colin Stevens of Sun Labs fame. This replaces the Oro regexp implementation. It was binary only and could no longer be supported. Jacl is now 100% Open Source.

binary command

An implementation of Tcl's binary command has been added to Jacl. This new command passes all of the Tcl regression tests for the binary command. Thanks go to Christian Krone for this command.

history command

An implementation of Tcl's history command has been added to Jacl. This new command passes all of the Tcl regression tests for the history command. Thanks go to Christian Krone for this command.

interp command

An implementation of Tcl's interp command has been added to Jacl. This new command passes all of the Tcl regression tests for the interp command. Thanks go to Christian Krone for this command.

fconfigure command

The fconfigure command has been added to Jacl. Thanks go to Bruce Johnson for providing the initial implementation of this command.

encoding command

The encoding command has been added to Jacl. Thanks go to Bruce Johnson for providing the initial implementation of this command.

socket command

The socket command has been added to Jacl. Both client sockets and server sockets are supported. Thanks go to Neil Madden for providing the the initial implementation of this command.

file volumes command

The file volumes subcommand has been added to Jacl. The implementation makes use of the File.listRoots() method introduced in JDK 1.2, so a newer JDK is required to make use of this functionality. Thanks go to Shawn Boyce for providing the initial implementation of this command.

array unset command

The array unset subcommand has been added to the Jacl's array command.

exec command

Jacl can now exec a process in the background by passing the & flag on the exec command line. Exec will also use a second thread to read IO if running under JDK 1.3 or newer. The exec command has been fixed so that will not deadlock under Win XP.

info hostname command

The info hostname command is now implemented in Jacl. Tahnks go to Alexander Pasadyn for providing the implementation of this command.

New IO subsystem for Jacl

The Tcl IO subsystem has been ported to Jacl. Encoding, buffering, and line translations for channels now match Tcl semantics. Non-blocking IO and the fileevent command are not implemented.

Ref Counting in Tcl Blend

A new reference counting system has been implemented for Tcl Blend. A newly created CObject or TclList no longer increments the ref count the native Tcl_Obj. Instead, the ref count for a Tcl_Obj is incremented when TclObject.preserve() is invoked and decremented when TclObject.release() is invoked. If a TclList created inside a Java method is never released, it will be cleaned up when the Java method returns. This new ref counting system does not depend on the Java garbage collector and should not suffer from the memory leaks or shutdown issues that plagued the previous implementation.

Tcl/Java API

The TclObject.takeExclusive() method has a number of problems, and has been deprecated in favor of the new TclObject.duplicate() method. This new duplicate method works identically to Tcl_DuplicateObj. Old code that makes used of the takeExclusive() method will still work, but it should be updated to use duplicate as time permits. See the TclObject manual entry for an example of how to use this new duplicate method.

Tcl Blend Threading

Earlier versions of Tcl Blend made use of a global lock that serialized each Java method call. In the new version, Tcl Blend's JNI code has been rewritten to get rid of this global lock. This change significantly simplifies the code and should increase performance when Java methods are invoked from multiple threads.

Reflected Method/Constructor/Field Access

A new approach to reflected method, constructor, and field access has been implemented. In the previous implementation, package scoped entities were considered when accessing a field, when attempting to resolve a method signature, or when choosing a constructor. In the new implementation, these package scoped entities are only considered when a custom package invoker is defined for the package.

Reflected Object Access

A new approach to reflected object access has been implemented. In the previous implementation, inaccessible objects could be reflected in the interpreter. This type of access would be illegal in Java code, so new Class accessibility checks have been added to each of the java methods. An exception will now be raised on any attempt to interact with an inaccessible class.

Passing TclObjects to Java

It is now possible to pass a TclObject directly to a Java method. In previous versions it was possible to pass a TclObject contained in a ReflectObject, but it was not possible to pass the actual TclObject that contained the ReflectObject. The new implementation makes it possible to directly pass the containing TclObject assuming it is not a ReflectObject that contains a TclObject.

JVM Support

A completely new build system has been added. It now supports the IBM Java-2 1.3 JVM. The new build system also adds support for the Kaffe Open JVM with Tcl Blend. Jacl has worked with Kaffe for some time, but now both Tcl Blend and Jacl can be used with Kaffe. In addition, both Jacl and Tcl Blend can be compiled with JDK 1.5. Earlier versions made use of variables named enum which is now a reserved word in JDK 1.5. Both Jacl and Tcl Blend can be built under Windows using the mingw+msys package, user no longer need to have VC++ installed to build.

JVM Options

The tclblend_init variable has provided a means to pass a single JVM option to a JDK 1.2 or newer JVM. This support has been improved so that multiple JVM options can now be passed.

Version 1.2:

This section covers features introduced in Tcl/Java 1.2.

java::try command

A new java::try command has been added to the java package. This command provides a Tcl binding to Java's try-catch-finally construct. The command is able to manage multiple error conditions unlike Tcl's catch command. The new command can also be used to catch Tcl errors and Java exceptions independently. See the docs on the java::try command for more information.

java::import command

A new java::import command has been added. This command works like the import statement in the Java language, it provides a means to specify Java class names in a shortened format. For example, one could import the class java.util.Hashtable and then use the simple class name Hashtable instead of the fully qualified name java.util.Hashtable.

java::autolock command

The new java::autolock command can be used in interactive sessions to keep java object references from being garbage collected. This can be really handy when you want to quickly test out a java class without the hassle of garbage collection.

clock command

An implementation of Tcl's clock command has been added to Jacl. Jacl's new clock command uses Java's time and date APIs to provide the clock functionality that Tcl users enjoy. This implementation is fully compatible with the clock command from Tcl 8.0.

Namespace Support for Jacl

The namespace features from the Tcl 8.1 core have been ported over to Jacl. This adds the "namespace" command and the "variable" command. Support is still at an early stage and more feedback is needed but this is still an exciting development for Jacl.

Typed Null Reflection

In Tcl/Java 1.1, a single reflect object was used to represent the null Java object. In Java code, the special null object reference can have no type or it can be referenced as any type. We therefore needed to fix Tcl's reflection system so that it acted more like Java. To do this, the implementation was changed to support a type for a reflected null object. A reflected null object's type can be queried at runtime with the java::info command and it can be changed with the java::cast command. To get a reference to an untyped null object in the reflection system one would use the java::null command.

Signature Matching

The signature matching system introduced in Tcl/Java 1.1 did not work correctly when the null Java object was given as an argument to a method or constructor. This has been fixed in 1.2 and the matching system has been updated to take a null objects reflection type into account when disambiguating an overloaded method signature. In addition, the signature matching system will now provide a more descriptive error message in the case of an ambiguous signature.

Unicode Support

Unicode support has been added to the Jacl parser. Users should now be able to pass and unicode string form Java to Jacl and vice versa. Tcl Blend will also support Unicode strings (encoded as UTF-8) when compiled with Tcl 8.1 or better.

New Demo

Tcl/Java 1.2 includes a new pack demo which shows how a Java AWT layout manager and the Tcl/Java reflection system can be used to provide a Tk like pack command for Java widgets. This command can be used just like the pack command in Tk. The demo also includes an example of how the layout manager can be used in stand alone Java code.

JVM/OS Support

Tcl/Java 1.2 adds support for Tcl Blend on Linux and IRIX systems. Tcl/Java on Linux works with both the JDK 1.1 and JDK 1.2 ports. Earlier versions of Tcl Blend did not works on these systems. Support for the Kaffe JVM was also added. Support for Tcl 8.1 and 8.2 has also been added.

Version 1.1:

This section covers features introduced in Tcl/Java 1.1.

java::cast command

A new java::cast command has been added. This command can be used to change the reflected type of Java objects inside an interp. See the documentation for more info and examples on how this new command works.

file nativename command

The nativename subcommand was added to the file command in Jacl. On Windows, "file nativename C:/dir" now returns "C:\dir".

Signature Matching

Java method invocations now use an argument matching system to automatically determine which Java method a user intended to invoke based on the types of the arguments to method. In version 1.0 only the number of arguments to the method were used to disambiguate overloaded method invocations.

Typed Reflection

Tcl/Java now represents all reflected Java objects (A reflected Java object is one that has been added to the interp and has a Tcl command associated with it) as a pairing of instance and Class objects. A single Java object can be referenced as more then one Java Class type. For example, a String object can be referenced as type String or as type Object. Java array objects have also been updated to support typed object reflection.

Execution Time Improvements

Jacl is much faster. The Tcl parser has been completely rewritten, it uses less memory and executes more quickly.

Regexp Package

In Jacl 1.0, the regexp command could only be used in the binary release of Jacl. We have extracted the needed class files and placed the in the source release of Jacl 1.1. The source to the regular expression code is still not provided, just the binary .class files.

exec command

Jacl's exec command for unix and windows has been improved. In Jacl 1.0, the exec command did not treat some strings correctly during an exec which could cause some very strange errors. Commands with a '$' of ' ' char did not work as expected.