JWebTerminal - a web-based console

JWebTerminal implements a general-purpose interactive console and terminal emulator: Users can type commands which gets sent to an application, which evaluates the command, and displays the results, typically in some kind of type-script format.

The DomTerm project will supersede JWebTerminal. While DomTerm currently (2015/8) is too unstable and buggy to be very useful, it has a better architecture, and (since the DomTerm core is written in JavaScript) it can be used in more contexts,

There are two basic modes:

• In line-editing mode each input line is an input field you edit locally (in the browser). The finished line is sent to the application when you type Enter.
• In character mode each character is sent directly to the application, which is also responsible for input echoing.

Applications of JWebTerminal include:

• A chat/talk window.
• A read-eval-print-loop for an interactive scripting language.
• A command console.
• A terminal emulator.

JWebTerminal is a rough and incomplete prototype. It is meant to demo my belief that a modern terminal emulator should be based on a web browser engine. It seems reasonable to re-write the "guts" of the terminal emulator code in JavaScript (rather than Java), to make the code useful in non-Java context.

JWebTerminal recognizes a large subset of the standard ANSI/xterm terminal escape sequences for repositioning the cursor, erasing previous text, changing style, etc. Enough of a subset is recognized that you can run programs like the emacs text editor, with styling. This requires you specify the correct terminal type (TERM), which is done automatically by the PtyTerminal application. A matching terminfo entry is provided, but it also should work ok to specify TERM to a standard terminal name, like eterm-color, vte, gnome, konsole, and xterm (all with color), or vt100 or vt220 (both non-color).

The terminfo directory defines the escape sequences supported by the "jfxterm" terminal type, using a terminfo descriptor. The terminal emulation is a subset of the standard xterm/ansi/vt100 ones.

JWebTerminal handles automatic line-wrapping, distinguishing between explicit line-breaks and those caused by line-wrapping. This allows for re-flow on windows re-size (though that is not yet implemented), and "intelligent" cut-and-paste (also not yet implemented).

There is an escape sequence to send HTML to WebTerminal. This allows you to embed images, forms, and other HTML elements in the console output.

The primary class is webterminal.WebTerminal, which is an abstract (overridable) control you embed in your JavaFX scenegraph.

The license of this code is the same as OpenJDK, that is GPL 2 with the "Classpath exception".

Building and running

The prototype requires not only Java, but specifically JavaFX 2.x. The latter is bundled with JDK 8.x. JavaFX is also distributed with newer releases of JDK 7.x; however, you may have to manually set the classpath to include jfxrt.jar.

Build the library and sample applications with the Ant tool:

$ ant

The PtyConsole requires non-portable native code, so it is not built by default. Build it with:

$ ant all

Sample Applications

These sample applications are very simple. There is currently no menues or other "chrome" beside the actual WebTerminal window.

RunInConsole

The utility class webterminal.RunInConsole make it easy to run an old-fashioned console-based Java application in a WebTerminal. It re-binds System.in, System.out, and System.err to the WebTerminal.

For example, the jrunscript tool is a wrapper around the class com.sun.tools.script.shell.Main in tools.jar. So to start up a JavaScript read-eval-print-tool, do:

$ ant run-main -Drunmain.classpath=$JAVA_HOME/lib/tools.jar \
  -Drunmain.class="com.sun.tools.script.shell.Main" \
  -Drunmain.args="-l javascript"

or:

$ java -cp dist/WebTerminal.jar:${JAVA_HOME}/lib/tools.jar \
  webterminal.RunInConsole com.sun.tools.script.shell.Main -l javascript

This uses line-editing mode.

ShellConsole

The application webterminal.ShellConsole uses java.lang.Process to run a process inside a WebTerminal. Currently, it is hard-wired to run /bin/bash. (It does work under Cygwin if you edit the commandWithArgs field.)

You can start this using Ant:

$ ant run

or directly:

$ java -cp dist/WebTerminal.jar:${JAVA_HOME}/lib/tools.jar \
  webterminal.ShellConsole

This also uses line-editing mode.

PtyConsole

An application that implements a terminal emulator using WebTermnal and a PTY to fork off an operating system process.

The TERM and TERMINFO environment variables are set up automatically to use the "jfxterm" terminal type.

PtyConsole does depend on native code that assumes modern Unix-style pseudo-teletypes. At the time of writing it has only been tested on GNU/Linux Fedora 21; it may need some porting effort on older or non-Linux platforms, especially Windows.

You can run this with Ant:

$ ant run-pty

This uses character mode.