Jacl Applets

Below are a few Jacl Applets. These code for these applets is fairly rough, but shows some of the promise and the limitations in Jacl. The source code for these applets is available in jaclapplet.tar.gz.

Embedding a Tcl Shell in another Java Application

TclShell extends the Java Panel Component and uses Jacl to provide the Tcl backend.

Below is how we embedded TclShell in a preexisting Plotter Java application called Ptplot

1. Copied TclShell.java to the ptplot directory and added

   package pt.plot;
   

   to the top.
2. Added TclShell.java to the makefile.
3. Added jacl.jar to the CLASSPATH in the makefile.
4. In Ptplot, the Pxgraph class contains a method _makeButtons, so we added a button labeled Tcl Prompt which calls the method _tclPrompt() when it is depressed.
5. _tclPrompt() looks like:

       private void _tclPrompt() {
           TclShell tclShell = new TclShell();
           Frame shellFrame = new Frame();
   
           shellFrame.pack();
           shellFrame.resize(200,200);
           shellFrame.add(tclShell);
           tclShell.init();
           shellFrame.show();
       }
   

6. Compiled Pxgraph.java and TclShell.java.
7. pxgraph is a shell script calls java with the appropriate arguments, including the proper classpath, so we added the complete path to jacl.jar to the classpath.
   When we run pxgraph, the following command is what is actually run:

   /usr/java/bin/java -classpath /users/cxh/pt/tycho/java:/users/ptdesign/tcltk/itcl/lib/jacl.jar:/usr/java/lib/classes.zip pt.plot.Pxgraph demo/data.plt 
   

8. After starting up pxgraph and hitting the Tcl Prompt button, the TclShell console appears.
9. We can then create a plot of a sample file with:

   set argv [java::new {String []} 1 "demo/data.plt"]
   set plotter [java::new pt.plot.Pxgraph $arg]
   

10. To print all the properties:

    java::info properties $p
    

11. To print one property

    java::prop $p title
    

12. To set one property

    java::prop $p title "This is my plot"
    

    For other commands, see the java Tcl command man page

Limitations

    # Applet exception: error: java.lang.NoSuchMethodError: java.awt.TextArea: 
   method  (Ljava/lang/String;III)V not 
    found
    java.lang.NoSuchMethodError: java.awt.TextArea: method  (Ljava/lang/S
   tring;III)V not found
    * at TclShell.init(TclShell.java:61)
      at TclShellApplet.init(TclShellApplet.java:112)
      at netscape.applet.DerivedAppletFrame.run(DerivedAppletFrame.java)
      at java.lang.Thread.run(Thread.java)

jacl % java::new Integer
TclException during eval of:
java::new Integer
Error was:
cannot load new class into java or tcl package
cannot load new class into java or tcl package
    while executing
"java::new Integer"
jacl % 

netscape.security.AppletSecurityException: security.checkcreateclassloader

Suggestions to the Jacl Developers

java package commands

Netscape4.04 Problems

Be sure that Jacl will run as an applet in a vanilla Netscape4.04 without the JDK1.1 patch.

Under Netscape4.04 without the JDK1.1 patch, the following messages appeared in the Java console when I attempted to run an applet that used Jacl:

# Security Exception: checkResourceAccess security.checkResourceAccess
#  UniversalPropertyRead privilege not enabled: Reading	information stored in your computer, such as your user name
netscape.security.AppletSecurityException: security.checkResourceAccess
#  UniversalPropertyRead privilege not enabled: Reading	information stored in your computer, such as your user name

I never did track down the cause of these errors, but Another fix is that catching SecurityException in jacl1.0/src/java/tcl/lang helped. Below is a diff:

------- Interp.java -------
*** /tmp/da001mz	Wed Dec 31 16:00:00 1969
--- Interp.java	Fri Feb 13 08:36:21 1998
***************
*** 356,363 ****
       * Create the built-in commands.
       */
  
!     createCommands();
! 
      try {
  	/*
  	 * Set up tcl_platform, tcl_version, tcl_library and other
--- 356,368 ----
       * Create the built-in commands.
       */
  
!     try { 
!         createCommands();
!     } catch (SecurityException e) {
!         e.printStackTrace();
!         System.err.println("java/tcl/lang/Interp Interp(): CreateCommands: "
!                 +e);
!     }
      try {
  	/*
  	 * Set up tcl_platform, tcl_version, tcl_library and other
***************
*** 411,418 ****
  	 * Source the init.tcl script to initialize auto-loading.
  	 */
  	
! 	evalResource("/tcl/lang/library/init.tcl");
! 
      } catch (TclException e) {
  	System.out.println(getResult());
  	e.printStackTrace();
--- 416,428 ----
  	 * Source the init.tcl script to initialize auto-loading.
  	 */
  	
!           try {
!               evalResource("/tcl/lang/library/init.tcl");
!           } catch (SecurityException e) {
!               System.err.println(
!                       "java/tcl/lang/Interp Interp(): after evalResource:" +
!                       e);
!           }
      } catch (TclException e) {
  	System.out.println(getResult());
  	e.printStackTrace();
***************
*** 708,716 ****
  	(new BlendExtension()).init(this);
  	RegexpCmd.init(this);
      } catch (TclException e) {
! 	System.out.println(getResult());
! 	e.printStackTrace();
! 	throw new TclRuntimeError("unexpected TclException: " + e);
      }
  }
  
--- 718,735 ----
  	(new BlendExtension()).init(this);
  	RegexpCmd.init(this);
      } catch (TclException e) {
! 	try {
!             System.err.println(getResult());
!             e.printStackTrace();
!             throw new TclRuntimeError("unexpected TclException: " + e);
!         } catch (SecurityException e2) {
!             System.err.println(
!                     "java/tcl/lang/Interp createCommands(): BlendExt2:" + e2);
!         }
!     } catch (SecurityException e) {
!               e.printStackTrace();
!               System.err.println(
!                       "java/tcl/lang/Interp createCommands(): BlendExt:" + e);
      }
  }
  
***************
*** 1876,1882 ****
   *----------------------------------------------------------------------
   */
  
! void
  evalURL(
      URL context, 		// URL context under which s is interpreted.
      String s)  			// The name of URL.
--- 1895,1901 ----
   *----------------------------------------------------------------------
   */
  
! public void
  evalURL(
      URL context, 		// URL context under which s is interpreted.
      String s)  			// The name of URL.
***************
*** 2074,2079 ****
--- 2093,2101 ----
  	eval(new String(charArray), 0);
      } catch (IOException e) {
  	return;
+     } catch (SecurityException e2) {
+               e2.printStackTrace();
+               System.err.println("java/tcl/lang/Interp evalResource():" + e2);
      } finally {
  	closeInputStream(stream);
      }

evalURL

I tried to use it, but under Netscape4.04 with the JDK1.1 patch, it was failing because the content Object was not an instance of InputStream, instead it seemed to be an instance of netscape.net.URLInputStream.

Last updated: 03/07/98 cxh at eecs