// XmlApplet.java: base class for Æfred applet demos.
// NO WARRANTY! See README, and copyright below.
// $Id$
// Modified 11/8/98 to add package statement.
package com.microstar.xml.demo;
import java.applet.Applet;
import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Event;
import java.awt.FlowLayout;
import java.awt.Panel;
import java.awt.TextArea;
import java.net.MalformedURLException;
import java.net.URL;
import com.microstar.xml.XmlHandler;
import com.microstar.xml.XmlParser;
/**
* Base class for Ælfred demonstration applications.
* <p>This class fills in the basic interface, and provides
* an I/O infrastructure for simple applications and applets.
* @author Copyright (c) 1997, 1998 by Microstar Software Ltd.;
* @author written by David Megginson <dmeggins@microstar.com>
* @version 1.1
* @since Ptolemy II 0.2
* @see com.microstar.xml.XmlParser
* @see com.microstar.xml.XmlHandler
* @see EventDemo
* @see TimerDemo
* @see DtdDemo
* @see StreamDemo
*/
public class XmlApplet extends Applet implements XmlHandler {
/**
* Flag to show whether we're running as an applet or application.
*/
public boolean isApplet = false;
public XmlParser parser;
//////////////////////////////////////////////////////////////////////
// Implementation of XmlParser interface.
//
// The following methods provide a full skeleton implementation of the
// XmlHandler interface, so that subclasses can override only
// the methods they need.
//////////////////////////////////////////////////////////////////////
/**
* Resolve an external entity.
* <p>This method could generate a new URL by looking up the
* public identifier in a hash table, or it could replace the
* URL supplied with a different, local one; for now, however,
* just return the URL supplied.
* @see com.microstar.xml.XmlHandler#resolveEntity
*/
public Object resolveEntity(String publicId, String systemId) {
return null;
}
public void startExternalEntity(String systemId) {
}
public void endExternalEntity(String systemId) {
}
/**
* Handle the start of the document.
* <p>Do nothing for now. Subclasses can override this method
* if they want to take a specific action.
* <p>This method will always be called first.
* @see com.microstar.xml.XmlHandler#startDocument
*/
public void startDocument() {
}
/**
* Handle the end the document.
* <p>Do nothing for now. Subclasses can override this method
* if they want to take a specific action.
* <p>This method will always be called last.
* @see com.microstar.xml.XmlHandler#endDocument
*/
public void endDocument() {
}
/**
* Handle a DOCTYPE declaration.
* <p>Do nothing for now. Subclasses can override this method
* if they want to take a specific action.
* <p>Well-formed XML documents might not have one of these.
* <p>The query methods in XmlParser will return useful
* values only after this callback.
* @see com.microstar.xml.XmlHandler#doctypeDecl
*/
public void doctypeDecl(String name, String pubid, String sysid) {
}
/**
* Handle an attribute value specification.
* <p>Do nothing for now. Subclasses can override this method
* if they want to take a specific action.
* @see com.microstar.xml.XmlHandler#attribute
*/
public void attribute(String name, String value, boolean isSpecified) {
}
/**
* Handle the start of an element.
* <p>Do nothing for now. Subclasses can override this method
* if they want to take a specific action.
* @see com.microstar.xml.XmlHandler#startElement
*/
public void startElement(String name) {
}
/**
* Handle the end of an element.
* <p>Do nothing for now. Subclasses can override this method
* if they want to take a specific action.
* @see com.microstar.xml.XmlHandler#endElement
*/
public void endElement(String name) {
}
/**
* Handle character data.
* <p>Do nothing for now. Subclasses can override this method
* if they want to take a specific action.
* @see com.microstar.xml.XmlHandler#charData
*/
public void charData(char[] ch, int start, int length) {
}
/**
* Handle ignorable whitespace.
* <p>Do nothing for now. Subclasses can override this method
* if they want to take a specific action.
* @see com.microstar.xml.XmlHandler#ignorableWhitespace
*/
public void ignorableWhitespace(char[] ch, int start, int length) {
}
/**
* Handle a processing instruction.
* <p>Do nothing for now. Subclasses can override this method
* if they want to take a specific action.
* @see com.microstar.xml.XmlHandler#processingInstruction
*/
public void processingInstruction(String target, String data) {
}
/**
* Handle a parsing error.
* <p>By default, print a message and throw an Error.
* <p>Subclasses can override this method if they want to do something
* different.
* @see com.microstar.xml.XmlHandler#error
*/
public void error(String message, String url, int line, int column) {
displayText("FATAL ERROR: " + message);
displayText(" at " + url + ": line " + line + " column " + column);
throw new Error(message);
}
//////////////////////////////////////////////////////////////////////
// General utility methods.
//////////////////////////////////////////////////////////////////////
/**
* Start a parse in application mode.
* <p>Output will go to STDOUT.
* @see #displayText
* @see com.microstar.xml.XmlParser#run
*/
void doParse(String url) throws java.lang.Exception {
/* String docURL =*/makeAbsoluteURL(url);
// create the parser
parser = new XmlParser();
parser.setHandler(this);
parser.parse(makeAbsoluteURL(url), null, (String) null);
}
static String makeAbsoluteURL(String url) throws MalformedURLException {
URL baseURL;
String currentDirectory = System.getProperty("user.dir");
String fileSep = System.getProperty("file.separator");
String file = currentDirectory.replace(fileSep.charAt(0), '/') + '/';
if (file.charAt(0) != '/') {
file = "/" + file;
}
baseURL = new URL("file", null, file);
return new URL(baseURL, url).toString();
}
/**
* Display text on STDOUT or in an applet TextArea.
*/
void displayText(String text) {
if (isApplet) {
textArea.append(text + '\n');
} else {
System.out.println(text);
}
}
/**
* Escape a string for printing.
*/
String escape(char[] ch, int length) {
StringBuffer out = new StringBuffer();
for (int i = 0; i < length; i++) {
switch (ch[i]) {
case '\\':
out.append("\\\\");
break;
case '\n':
out.append("\\n");
break;
case '\t':
out.append("\\t");
break;
case '\r':
out.append("\\r");
break;
case '\f':
out.append("\\f");
break;
default:
out.append(ch[i]);
break;
}
}
return out.toString();
}
//////////////////////////////////////////////////////////////////////
// Applet support.
//
// These methods and variables are used only if we are running as an
// applet.
//////////////////////////////////////////////////////////////////////
TextArea textArea;
Panel buttonPanel;
Button startButton;
/**
* Initialise the applet the first time it runs.
*/
public void init() {
startButton = new Button("Parse " + getParameter("url"));
isApplet = true;
textArea = new TextArea();
buttonPanel = new Panel();
buttonPanel.setLayout(new FlowLayout());
setLayout(new BorderLayout());
buttonPanel.add("Center", startButton);
add("Center", textArea);
add("South", buttonPanel);
}
/**
* React to a button press.
* <p>This uses the old event model, so that it will work with
* existing browsers. It will cause a 'deprecated' warning
* when you compile.
*/
public boolean action(Event ev, Object target) {
if (target == startButton.getLabel()) {
try {
startParse();
} catch (Exception e) {
System.err.println(e.getMessage());
}
return true;
} else {
return false;
}
}
/**
* Start a parse (in response to a button press).
* <p>Erase the text area, then start the parser running, using
* the value of the "url" parameter.
*/
public void startParse() throws java.lang.Exception {
textArea.setText("");
try {
XmlParser parser = new XmlParser();
parser.setHandler(this);
;
parser.parse(new URL(getDocumentBase(), getParameter("url"))
.toString(), null, (String) null);
} catch (Exception e) {
displayText("Caught exception (" + e.getClass().toString() + "): "
+ e.getMessage());
}
}
}
// end of XmlApplet.java