/* * Copyright (c) 2000 David Flanagan.  All rights reserved. * This code is from the book Java Examples in a Nutshell, 2nd Edition. * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied. * You may study, use, and modify it for any non-commercial purpose. * You may distribute it non-commercially as long as you retain this notice. * For a commercial use license, or to purchase the book (recommended), * visit http://www.davidflanagan.com/javaexamples2. */package com.davidflanagan.examples.io;import java.io.*;import java.net.*;import java.applet.Applet;import netscape.javascript.JSObject;    // A special class we need/** * An output stream that sends HTML text to a newly created web browser window. * It relies on the netscape.javascript.JSObject class to send JavaScript * commands to the Web browser, and only works for applets running in  * the Netscape Navigator Web browser. **/public class HTMLWriter extends Writer {    JSObject main_window;        // the initial browser window    JSObject window;             // the new window we create    JSObject document;           // the document of that new window    static int window_num = 0;   // used to give each new window a unique name        /**     * When you create a new HTMLWriter, it pops up a new, blank, Web browser     * window to display the output in.  You must specify the applet     * (this specifies the main browser window) and the desired size     * for the new window.     **/    public HTMLWriter(Applet applet, int width, int height) {        // Verify that we can find the JSObject class we need.  Warn if not.        try { Class c = Class.forName("netscape.javascript.JSObject"); }        catch (ClassNotFoundException e) {            throw new NoClassDefFoundError("HTMLWriter requires " +        	   "Netscape Navigator 4.0 or higher " +		   "or a browser that supports LiveConnect technology");        }	        // Get a reference to the main browser window from the applet.        main_window = JSObject.getWindow(applet);	        // Create a new window to display output in.  This command sends a	// string of JavaScript to the web browser        window = (JSObject)            main_window.eval("self.open(''," +			     "'HTMLWriter" + window_num++ + "'," +			     "'menubar,status,resizable,scrollbars," +			     "width=" + width + ",height=" + height + "')");        // Obtain the Document object of this new window, and open it.        document = (JSObject) window.getMember("document");        document.call("open", null);    }        /**     * This is the write() method required for all Writer subclasses.     * Writer defines all its other write() methods in terms of this one.     **/    public void write(char[] buf, int offset, int length) {        // If no window or document, do nothing.   This occurs if the stream        // has been closed, or if the code is not running in Navigator.        if ((window == null) || (document == null)) return;        // If the window has been closed by the user, do nothing        if (((Boolean)window.getMember("closed")).booleanValue()) return;        // Otherwise, create a string from the specified bytes        String s = new String(buf, offset, length);        // And pass it to the JS document.write() method to output the HTML        document.call("write", new String[] { s });    }        /**     * There is no general way to force JavaScript to flush all pending output,     * so this method does nothing.  To flush, output a <P> tag or some other     * HTML tag that forces a line break in the output.     **/    public void flush() {}    /**     * When the stream is closed, close the JavaScript Document object     * (But don't close the window yet.)     **/    public void close() { document.call("close", null); document = null; }        /**     * If the browser window is still open, close it.     * This method is unique to HTMLWriter.       **/    public void closeWindow() {        if (document != null) close();        if (!((Boolean)window.getMember("closed")).booleanValue())            window.call("close", null);        window = null;    }        /** A finalizer method to close the window in case we forget. */    public void finalize() { closeWindow(); }        /**     * This nested class is an applet that demonstrates the use of HTMLWriter.     * It reads the contents of the URL specified in its url parameter and     * writes them out to an HTMLWriter stream.  It will only work in      * Netscape 4.0 or later.  It requires an <APPLET> tag like this:     *   <APPLET CODE="HTMLWriter$Test.class" WIDTH=10 HEIGHT=10 MAYSCRIPT>     *   <PARAM NAME="url" VALUE="HTMLWriter.java">     *   </APPLET>     * Note that MAYSCRIPT attribute.  It is required to enable the applet     * to invoke JavaScript.     **/    public static class Test extends Applet {        HTMLWriter out;        /** When the applet starts, read and display specified URL */        public void init() {              try {                // Get the URL specified in the <PARAM> tag                URL url =		    new URL(this.getDocumentBase(), this.getParameter("url"));                // Get a stream to read its contents                Reader in = new InputStreamReader(url.openStream());                // Create an HTMLWriter stream for out output                out = new HTMLWriter(this, 400, 200);                // Read buffers of characters and output them to the HTMLWriter                char[] buffer = new char[4096];                int numchars;                while((numchars = in.read(buffer)) != -1)                     out.write(buffer, 0, numchars);                // Close the streams                in.close();                out.close();            }            catch (IOException e) {}        }        /** When the applet terminates, close the window we created */        public void destroy() { out.closeWindow(); }    }}