// // UrlDemo class // part of the set of documents known as Java no sugar. // Copyright (c) 1996 Sunil Gupta, sunil@magnetic.demon.co.uk // placed into the public domain by the author // import java.awt.*; import java.io.*; import java.net.*; import java.applet.*; public class UrlDemo extends Applet { //******************************************************************* // GLOBALS //******************************************************************* static final String USERDEF="USERDEF"; static final String HOSTPARAM="HOST"; //******************************************************************* // instance variables //******************************************************************* TextArea textarea; TextField textfield; Button btn_doit; boolean user_url = false; String url_string = null; //******************************************************************* // applet methods //******************************************************************* public void init() { GridBagConstraints c; GridBagLayout layout; String param; int gridy=0; //-----FIGURE OUT WHICH URL to use------------------------- param = getParameter(HOSTPARAM); if (param != null) { if (param.equals(USERDEF)) user_url = true; else url_string = param; } //--------BUILD THE USER INTERFACE------------------------- layout = new GridBagLayout(); this.setLayout( layout ); //------------------------add the text area---------------- if (user_url) { textfield = new TextField(30); c = new GridBagConstraints(); c.gridx = 0; c.gridy = 0; c.gridwidth=2; c.gridheight=1; c.fill = GridBagConstraints.BOTH; layout.setConstraints(textfield,c); this.add(textfield); gridy++; } //--------------------------------------------------------- textarea = new TextArea(); c = new GridBagConstraints(); c.gridx = 0; c.gridy = gridy; c.gridwidth=2; c.gridheight=2; c.fill = GridBagConstraints.BOTH; layout.setConstraints(textarea,c); this.add(textarea); //------------------------add button-------------------- btn_doit = new Button("query"); c = new GridBagConstraints(); c.gridx = 2; c.gridy = 0; c.gridwidth=1; c.gridheight=1; c.fill = GridBagConstraints.HORIZONTAL; layout.setConstraints(btn_doit,c); this.add(btn_doit); } public boolean action(Event event, Object arg) { if (event.target == btn_doit) { do_date_url(); return true; } return (false) ; } // // date is a safe choice since most httpd's implement this // private void do_date_url() { URL applet_url, cgi_url; String protocol, data_line; DataInputStream stream; //------------------------------------------------------------------ // clear out any text // textarea.setText(""); //------------------------------------------------------------------ // make sure applet is running from httpd // applet_url = this.getDocumentBase(); protocol = applet_url.getProtocol(); if ( ! protocol.equals("http") ) { textarea.appendText( "This applet must be run from a server\n" + "net.paranoid.geeks have crippled Java applets which\n" + "can only make network connections to the machine\n" + "from whence it came.\n" ); return; } textarea.appendText("Applet is on a server\n"); //------------------------------------------------------------------ // BUILD URL // try { if (user_url) { cgi_url = new URL( textfield.getText()); } else if ( url_string != null) { cgi_url = new URL( url_string); } else { cgi_url = new URL("http", applet_url.getHost(), applet_url.getPort(),"/cgi-bin/date"); } } catch (MalformedURLException e) { textarea.appendText("Error parsing " + e +"\n"); return; } catch (SecurityException e) { textarea.appendText("Security violation detected: " + e +"\n"); return; } textarea.appendText( "Attempting to use URL " + cgi_url.toString()+ "\n"); //------------------------------------------------------------------ // could use getContents, but dont understand how to use it. // textarea.appendText("\nthe output from the cgi-program is\n\n"); try { stream = new DataInputStream(cgi_url.openStream()); while ( (data_line = stream.readLine()) != null) { textarea.appendText(data_line +"\n"); } stream.close(); } catch(IOException e) { textarea.appendText("error reading data from url : "+ e); } } }
file: /Techref/language/java/nosugar/comms/code/UrlDemo.java, 4KB, , updated: 1996/10/10 10:08, local time: 2024/12/24 09:02,
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