[jdom-interest] dtd validation question

[Brian Wolf]

Hi,



I'm not sure this is specifically a jdom question, but in the (slightly modified) code from the Java & XML 

below  for dtd validation, I would like  to return a boolean yes/no to valid or not valid. How do I do that, given that 

not valid throws an error exeception?

-manythanks, brian 





/*-- 

Copyright (C) 2001 Brett McLaughlin.

All rights reserved.


Redistribution and use in source and binary forms, with or without

modification, are permitted provided that the following conditions

are met:


1. Redistributions of source code must retain the above copyright

notice, this list of conditions, and the following disclaimer.


2. Redistributions in binary form must reproduce the above copyright

notice, this list of conditions, and the disclaimer that follows 

these conditions in the documentation and/or other materials 

provided with the distribution.

3. The name "Java and XML" must not be used to endorse or promote products

derived from this software without prior written permission. For

written permission, please contact brett at newInstance.com.


In addition, we request (but do not require) that you include in the 

end-user documentation provided with the redistribution and/or in the 

software itself an acknowledgement equivalent to the following:

"This product includes software developed for the

'Java and XML' book, by Brett McLaughlin (O'Reilly & Associates)."

THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED

WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

DISCLAIMED. IN NO EVENT SHALL THE JDOM AUTHORS OR THE PROJECT

CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF

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ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,

OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT

OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

SUCH DAMAGE.

*/

//package javaxml2;

import java.io.IOException;

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

import org.xml.sax.Attributes;

import org.xml.sax.ContentHandler;

import org.xml.sax.ErrorHandler;

import org.xml.sax.InputSource;

import org.xml.sax.Locator;

import org.xml.sax.SAXException;

import org.xml.sax.SAXParseException;

import org.xml.sax.XMLReader;

import org.xml.sax.helpers.XMLReaderFactory;

// This is an XML book - no need for explicit Swing imports

import java.awt.*;

import javax.swing.*;

import javax.swing.tree.*;

/**

* <b><code>SAXTreeValidator</code></b> uses Swing to graphically

* display an XML document, and performs validation.

*/

public class SAXValidator {

/** Default parser to use */

private String vendorParserClass = 

"org.apache.xerces.parsers.SAXParser";

/** The base tree to render */

private JTree jTree;

/** Tree model to use */

DefaultTreeModel defaultTreeModel;

/**

* <p> This initializes the needed Swing settings. </p>

*/

public SAXValidator() {

// Handle Swing setup

//super("SAX Tree Validator");

//setSize(600, 450);

}

/**

* <p> This will construct the tree using Swing. </p>

*

* @param filename <code>String</code> path to XML document.

*/

public void init(String xmlURI) throws IOException, SAXException {

DefaultMutableTreeNode base = 

new DefaultMutableTreeNode("XML Document: " + 

xmlURI);


// Build the tree model

defaultTreeModel = new DefaultTreeModel(base);

//jTree = new JTree(defaultTreeModel);

// Construct the tree hierarchy

buildTree(defaultTreeModel, base, xmlURI);


}

/**

* <p>This handles building the Swing UI tree.</p>

*

* @param treeModel Swing component to build upon.

* @param base tree node to build on.

* @param xmlURI URI to build XML document from.

* @throws <code>IOException</code> - when reading the XML URI fails.

* @throws <code>SAXException</code> - when errors in parsing occur.

*/

public void buildTree(DefaultTreeModel treeModel, 

DefaultMutableTreeNode base, String xmlURI) 

throws IOException, SAXException {

// Create instances needed for parsing

XMLReader reader = 

XMLReaderFactory.createXMLReader(vendorParserClass);

ContentHandler jTreeContentHandler = 

new JValidatorContentHandler(treeModel, base);

ErrorHandler jTreeErrorHandler = new JValidatorErrorHandler();

// Register content handler

reader.setContentHandler(jTreeContentHandler);

// Register error handler

reader.setErrorHandler(jTreeErrorHandler);

// Turn on validation

reader.setFeature("http://xml.org/sax/features/validation", true);


// reader.setFeature("http://apache.org/xml/features/validation/schema-full-checking", true);

// Parse

InputSource inputSource = 

new InputSource(xmlURI);

reader.parse(inputSource);

}

/**

* <p> Static entry point for running the viewer. </p>

*/

public static void main(String[] args) {

try {

if (args.length != 1) {

System.out.println(

"Usage: java javaxml2.SAXTreeViewer " +

"[XML Document URI]");

System.exit(0);

}

SAXValidator viewer = new SAXValidator();


viewer.init(args[0]);

System.out.println(args[0] + " Validated");

// viewer.setVisible(true);

} catch (Exception e) {

e.printStackTrace();

}

}

}

/**

* <b><code>JValidatorContentHandler</code></b> implements the SAX

* <code>ContentHandler</code> interface and defines callback

* behavior for the SAX callbacks associated with an XML

* document's content, bulding up JTree nodes.

*/

class JValidatorContentHandler implements ContentHandler {

/** Hold onto the locator for location information */

private Locator locator;

/** Store URI to prefix mappings */

private Map namespaceMappings;

/** Tree Model to add nodes to */

private DefaultTreeModel treeModel;

/** Current node to add sub-nodes to */

private DefaultMutableTreeNode current;

/**

* <p> Set up for working with the JTree. </p>

*

* @param treeModel tree to add nodes to.

* @param base node to start adding sub-nodes to.

*/

public JValidatorContentHandler(DefaultTreeModel treeModel, 

DefaultMutableTreeNode base) {

this.treeModel = treeModel;

this.current = base;

this.namespaceMappings = new HashMap();

}

/**

* <p>

* Provide reference to <code>Locator</code> which provides

* information about where in a document callbacks occur.

* </p>

*

* @param locator <code>Locator</code> object tied to callback

* process

*/

public void setDocumentLocator(Locator locator) {

// Save this for later use

this.locator = locator;

}

/**

* <p>

* This indicates the start of a Document parse-this precedes

* all callbacks in all SAX Handlers with the sole exception

* of <code>{@link #setDocumentLocator}</code>.

* </p>

*

* @throws <code>SAXException</code> when things go wrong

*/

public void startDocument() throws SAXException {

// No visual events occur here

}

/**

* <p>

* This indicates the end of a Document parse-this occurs after

* all callbacks in all SAX Handlers.</code>.

* </p>

*

* @throws <code>SAXException</code> when things go wrong

*/

public void endDocument() throws SAXException {

// No visual events occur here

}

/**

* <p>

* This indicates that a processing instruction (other than

* the XML declaration) has been encountered.

* </p>

*

* @param target <code>String</code> target of PI

* @param data <code>String</code containing all data sent to the PI.

* This typically looks like one or more attribute value

* pairs.

* @throws <code>SAXException</code> when things go wrong

*/

public void processingInstruction(String target, String data)

throws SAXException {

DefaultMutableTreeNode pi = 

new DefaultMutableTreeNode("PI (target = '" + target +

"', data = '" + data + "')");

current.add(pi);

}

/**

* <p>

* This indicates the beginning of an XML Namespace prefix

* mapping. Although this typically occurs within the root element

* of an XML document, it can occur at any point within the

* document. Note that a prefix mapping on an element triggers

* this callback <i>before</i> the callback for the actual element

* itself (<code>{@link #startElement}</code>) occurs.

* </p>

*

* @param prefix <code>String</code> prefix used for the namespace

* being reported

* @param uri <code>String</code> URI for the namespace

* being reported

* @throws <code>SAXException</code> when things go wrong

*/

public void startPrefixMapping(String prefix, String uri) {

// No visual events occur here.

namespaceMappings.put(uri, prefix);

}

/**

* <p>

* This indicates the end of a prefix mapping, when the namespace

* reported in a <code>{@link #startPrefixMapping}</code> callback

* is no longer available.

* </p>

*

* @param prefix <code>String</code> of namespace being reported

* @throws <code>SAXException</code> when things go wrong

*/

public void endPrefixMapping(String prefix) {

// No visual events occur here.

for (Iterator i = namespaceMappings.keySet().iterator(); 

i.hasNext(); ) {

String uri = (String)i.next();

String thisPrefix = (String)namespaceMappings.get(uri);

if (prefix.equals(thisPrefix)) {

namespaceMappings.remove(uri);

break;

}

}

}

/**

* <p>

* This reports the occurrence of an actual element. It includes

* the element's attributes, with the exception of XML vocabulary

* specific attributes, such as

* <code>xmlns:[namespace prefix]</code> and

* <code>xsi:schemaLocation</code>.

* </p>

*

* @param namespaceURI <code>String</code> namespace URI this element

* is associated with, or an empty <code>String</code>

* @param localName <code>String</code> name of element (with no

* namespace prefix, if one is present)

* @param qName <code>String</code> XML 1.0 version of element name:

* [namespace prefix]:[localName]

* @param atts <code>Attributes</code> list for this element

* @throws <code>SAXException</code> when things go wrong

*/

public void startElement(String namespaceURI, String localName,

String qName, Attributes atts)

throws SAXException {

DefaultMutableTreeNode element = 

new DefaultMutableTreeNode("Element: " + localName);

current.add(element);

current = element;

// Determine namespace

if (namespaceURI.length() > 0) {

String prefix = 

(String)namespaceMappings.get(namespaceURI);

if (prefix.equals("")) {

prefix = "[None]";

}

DefaultMutableTreeNode namespace =

new DefaultMutableTreeNode("Namespace: prefix = '" +

prefix + "', URI = '" + namespaceURI + "'");

current.add(namespace);

}

// Process attributes

for (int i=0; i<atts.getLength(); i++) {

DefaultMutableTreeNode attribute =

new DefaultMutableTreeNode("Attribute (name = '" +

atts.getLocalName(i) + 

"', value = '" +

atts.getValue(i) + "')");

String attURI = atts.getURI(i);

if (attURI.length() > 0) {

String attPrefix = 

(String)namespaceMappings.get(namespaceURI);

if (attPrefix.equals("")) {

attPrefix = "[None]";

}

DefaultMutableTreeNode attNamespace =

new DefaultMutableTreeNode("Namespace: prefix = '" +

attPrefix + "', URI = '" + attURI + "'");

attribute.add(attNamespace); 

}

current.add(attribute);

}

}

/**

* <p>

* Indicates the end of an element

* (<code>&lt;/[element name]&gt;</code>) is reached. Note that

* the parser does not distinguish between empty

* elements and non-empty elements, so this occurs uniformly.

* </p>

*

* @param namespaceURI <code>String</code> URI of namespace this

* element is associated with

* @param localName <code>String</code> name of element without prefix

* @param qName <code>String</code> name of element in XML 1.0 form

* @throws <code>SAXException</code> when things go wrong

*/

public void endElement(String namespaceURI, String localName,

String qName)

throws SAXException {

// Walk back up the tree

current = (DefaultMutableTreeNode)current.getParent();

}

/**

* <p>

* This reports character data (within an element).

* </p>

*

* @param ch <code>char[]</code> character array with character data

* @param start <code>int</code> index in array where data starts.

* @param length <code>int</code> index in array where data ends.

* @throws <code>SAXException</code> when things go wrong

*/

public void characters(char[] ch, int start, int length)

throws SAXException {

String s = new String(ch, start, length);

DefaultMutableTreeNode data =

new DefaultMutableTreeNode("Character Data: '" + s + "'");

current.add(data);

}

/**

* <p>

* This reports whitespace that can be ignored in the

* originating document. This is typically invoked only when

* validation is ocurring in the parsing process.

* </p>

*

* @param ch <code>char[]</code> character array with character data

* @param start <code>int</code> index in array where data starts.

* @param end <code>int</code> index in array where data ends.

* @throws <code>SAXException</code> when things go wrong

*/

public void ignorableWhitespace(char[] ch, int start, int length)

throws SAXException {


// This is ignorable, so don't display it

}

/**

* <p>

* This reports an entity that is skipped by the parser. This

* should only occur for non-validating parsers, and then is still

* implementation-dependent behavior.

* </p>

*

* @param name <code>String</code> name of entity being skipped

* @throws <code>SAXException</code> when things go wrong

*/

public void skippedEntity(String name) throws SAXException {

DefaultMutableTreeNode skipped =

new DefaultMutableTreeNode("Skipped Entity: '" + name + "'");

current.add(skipped);

}

}

/**

* <b><code>JValidatorErrorHandler</code></b> implements the SAX

* <code>ErrorHandler</code> interface and defines callback

* behavior for the SAX callbacks associated with an XML

* document's warnings and errors.

*/

class JValidatorErrorHandler implements ErrorHandler {

/**

* <p>

* This will report a warning that has occurred; this indicates

* that while no XML rules were "broken", something appears

* to be incorrect or missing.

* </p>

*

* @param exception <code>SAXParseException</code> that occurred.

* @throws <code>SAXException</code> when things go wrong 

*/

public void warning(SAXParseException exception)

throws SAXException {


System.out.println("**Parsing Warning**\n" +

" Line: " + 

exception.getLineNumber() + "\n" +

" URI: " + 

exception.getSystemId() + "\n" +

" Message: " + 

exception.getMessage()); 

throw new SAXException("Warning encountered");

}

/**

* <p>

* This will report an error that has occurred; this indicates

* that a rule was broken, typically in validation, but that

* parsing can reasonably continue.

* </p>

*

* @param exception <code>SAXParseException</code> that occurred.

* @throws <code>SAXException</code> when things go wrong 

*/

public void error(SAXParseException exception)

throws SAXException {


System.out.println("**Parsing Error**\n" +

" Line: " + 

exception.getLineNumber() + "\n" +

" URI: " + 

exception.getSystemId() + "\n" +

" Message: " + 

exception.getMessage());

throw new SAXException("Error encountered");

}

/**

* <p>

* This will report a fatal error that has occurred; this indicates

* that a rule has been broken that makes continued parsing either

* impossible or an almost certain waste of time.

* </p>

*

* @param exception <code>SAXParseException</code> that occurred.

* @throws <code>SAXException</code> when things go wrong 

*/

public void fatalError(SAXParseException exception)

throws SAXException {


System.out.println("**Parsing Fatal Error**\n" +

" Line: " + 

exception.getLineNumber() + "\n" +

" URI: " + 

exception.getSystemId() + "\n" +

" Message: " + 

exception.getMessage()); 

throw new SAXException("Fatal Error encountered");

}

}

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