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// ContentHandler.java - handle main document content.

// http://www.saxproject.org

// Written by David Megginson

// NO WARRANTY!  This class is in the public domain.

// $Id: ContentHandler.java,v 1.1 2004/12/23 22:38:42 mark Exp $

package org.xml.sax;

/**

 * Receive notification of the logical content of a document.

 *

 * <blockquote>

 * <em>This module, both source code and documentation, is in the

 * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>

 * See <a href='http://www.saxproject.org'>http://www.saxproject.org</a>

 * for further information.

 * </blockquote>

 *

 * <p>This is the main interface that most SAX applications

 * implement: if the application needs to be informed of basic parsing

 * events, it implements this interface and registers an instance with

 * the SAX parser using the {@link org.xml.sax.XMLReader#setContentHandler

 * setContentHandler} method.  The parser uses the instance to report

 * basic document-related events like the start and end of elements

 * and character data.</p>

 *

 * <p>The order of events in this interface is very important, and

 * mirrors the order of information in the document itself.  For

 * example, all of an element's content (character data, processing

 * instructions, and/or subelements) will appear, in order, between

 * the startElement event and the corresponding endElement event.</p>

 *

 * <p>This interface is similar to the now-deprecated SAX 1.0

 * DocumentHandler interface, but it adds support for Namespaces

 * and for reporting skipped entities (in non-validating XML

 * processors).</p>

 *

 * <p>Implementors should note that there is also a

 * <code>ContentHandler</code> class in the <code>java.net</code>

 * package; that means that it's probably a bad idea to do</p>

 *

 * <pre>import java.net.*;

 * import org.xml.sax.*;

 * </pre>

 *

 * <p>In fact, "import ...*" is usually a sign of sloppy programming

 * anyway, so the user should consider this a feature rather than a

 * bug.</p>

 *

 * @since SAX 2.0

 * @author David Megginson

 * @version 2.0.1+ (sax2r3pre1)

 * @see org.xml.sax.XMLReader

 * @see org.xml.sax.DTDHandler

 * @see org.xml.sax.ErrorHandler

 */

public interface ContentHandler

{

    /**

     * Receive an object for locating the origin of SAX document events.

     *

     * <p>SAX parsers are strongly encouraged (though not absolutely

     * required) to supply a locator: if it does so, it must supply

     * the locator to the application by invoking this method before

     * invoking any of the other methods in the ContentHandler

     * interface.</p>

     *

     * <p>The locator allows the application to determine the end

     * position of any document-related event, even if the parser is

     * not reporting an error.  Typically, the application will

     * use this information for reporting its own errors (such as

     * character content that does not match an application's

     * business rules).  The information returned by the locator

     * is probably not sufficient for use with a search engine.</p>

     *

     * <p>Note that the locator will return correct information only

     * during the invocation SAX event callbacks after

     * {@link #startDocument startDocument} returns and before

     * {@link #endDocument endDocument} is called.  The

     * application should not attempt to use it at any other time.</p>

     *

     * @param locator an object that can return the location of

     *                any SAX document event

     * @see org.xml.sax.Locator

     */

    public void setDocumentLocator (Locator locator);

    /**

     * Receive notification of the beginning of a document.

     *

     * <p>The SAX parser will invoke this method only once, before any

     * other event callbacks (except for {@link #setDocumentLocator

     * setDocumentLocator}).</p>

     *

     * @throws org.xml.sax.SAXException any SAX exception, possibly

     *            wrapping another exception

     * @see #endDocument

     */

    public void startDocument ()

        throws SAXException;

    /**

     * Receive notification of the end of a document.

     *

     * <p><strong>There is an apparent contradiction between the

     * documentation for this method and the documentation for {@link

     * org.xml.sax.ErrorHandler#fatalError}.  Until this ambiguity is

     * resolved in a future major release, clients should make no

     * assumptions about whether endDocument() will or will not be

     * invoked when the parser has reported a fatalError() or thrown

     * an exception.</strong></p>

     *

     * <p>The SAX parser will invoke this method only once, and it will

     * be the last method invoked during the parse.  The parser shall

     * not invoke this method until it has either abandoned parsing

     * (because of an unrecoverable error) or reached the end of

     * input.</p>

     *

     * @throws org.xml.sax.SAXException any SAX exception, possibly

     *            wrapping another exception

     * @see #startDocument

     */

    public void endDocument()

        throws SAXException;

    /**

     * Begin the scope of a prefix-URI Namespace mapping.

     *

     * <p>The information from this event is not necessary for

     * normal Namespace processing: the SAX XML reader will

     * automatically replace prefixes for element and attribute

     * names when the <code>http://xml.org/sax/features/namespaces</code>

     * feature is <var>true</var> (the default).</p>

     *

     * <p>There are cases, however, when applications need to

     * use prefixes in character data or in attribute values,

     * where they cannot safely be expanded automatically; the

     * start/endPrefixMapping event supplies the information

     * to the application to expand prefixes in those contexts

     * itself, if necessary.</p>

     *

     * <p>Note that start/endPrefixMapping events are not

     * guaranteed to be properly nested relative to each other:

     * all startPrefixMapping events will occur immediately before the

     * corresponding {@link #startElement startElement} event,

     * and all {@link #endPrefixMapping endPrefixMapping}

     * events will occur immediately after the corresponding

     * {@link #endElement endElement} event,

     * but their order is not otherwise

     * guaranteed.</p>

     *

     * <p>There should never be start/endPrefixMapping events for the

     * "xml" prefix, since it is predeclared and immutable.</p>

     *

     * @param prefix the Namespace prefix being declared.

     *  An empty string is used for the default element namespace,

     *  which has no prefix.

     * @param uri the Namespace URI the prefix is mapped to

     * @throws org.xml.sax.SAXException the client may throw

     *            an exception during processing

     * @see #endPrefixMapping

     * @see #startElement

     */

    public void startPrefixMapping (String prefix, String uri)

        throws SAXException;

    /**

     * End the scope of a prefix-URI mapping.

     *

     * <p>See {@link #startPrefixMapping startPrefixMapping} for

     * details.  These events will always occur immediately after the

     * corresponding {@link #endElement endElement} event, but the order of

     * {@link #endPrefixMapping endPrefixMapping} events is not otherwise

     * guaranteed.</p>

     *

     * @param prefix the prefix that was being mapped.

     *  This is the empty string when a default mapping scope ends.

     * @throws org.xml.sax.SAXException the client may throw

     *            an exception during processing

     * @see #startPrefixMapping

     * @see #endElement

     */

    public void endPrefixMapping (String prefix)

        throws SAXException;

    /**

     * Receive notification of the beginning of an element.

     *

     * <p>The Parser will invoke this method at the beginning of every

     * element in the XML document; there will be a corresponding

     * {@link #endElement endElement} event for every startElement event

     * (even when the element is empty). All of the element's content will be

     * reported, in order, before the corresponding endElement

     * event.</p>

     *

     * <p>This event allows up to three name components for each

     * element:</p>

     *

     * <ol>

     * <li>the Namespace URI;</li>

     * <li>the local name; and</li>

     * <li>the qualified (prefixed) name.</li>

     * </ol>

     *

     * <p>Any or all of these may be provided, depending on the

     * values of the <var>http://xml.org/sax/features/namespaces</var>

     * and the <var>http://xml.org/sax/features/namespace-prefixes</var>

     * properties:</p>

     *

     * <ul>

     * <li>the Namespace URI and local name are required when

     * the namespaces property is <var>true</var> (the default), and are

     * optional when the namespaces property is <var>false</var> (if one is

     * specified, both must be);</li>

     * <li>the qualified name is required when the namespace-prefixes property

     * is <var>true</var>, and is optional when the namespace-prefixes property

     * is <var>false</var> (the default).</li>

     * </ul>

     *

     * <p>Note that the attribute list provided will contain only

     * attributes with explicit values (specified or defaulted):

     * #IMPLIED attributes will be omitted.  The attribute list

     * will contain attributes used for Namespace declarations

     * (xmlns* attributes) only if the

     * <code>http://xml.org/sax/features/namespace-prefixes</code>

     * property is true (it is false by default, and support for a

     * true value is optional).</p>

     *

     * <p>Like {@link #characters characters()}, attribute values may have

     * characters that need more than one <code>char</code> value.  </p>

     *

     * @param uri the Namespace URI, or the empty string if the

     *        element has no Namespace URI or if Namespace

     *        processing is not being performed

     * @param localName the local name (without prefix), or the

     *        empty string if Namespace processing is not being

     *        performed

     * @param qName the qualified name (with prefix), or the

     *        empty string if qualified names are not available

     * @param atts the attributes attached to the element.  If

     *        there are no attributes, it shall be an empty

     *        Attributes object.  The value of this object after

     *        startElement returns is undefined

     * @throws org.xml.sax.SAXException any SAX exception, possibly

     *            wrapping another exception

     * @see #endElement

     * @see org.xml.sax.Attributes

     * @see org.xml.sax.helpers.AttributesImpl

     */

    public void startElement (String uri, String localName,

                              String qName, Attributes atts)

        throws SAXException;

    /**

     * Receive notification of the end of an element.

     *

     * <p>The SAX parser will invoke this method at the end of every

     * element in the XML document; there will be a corresponding

     * {@link #startElement startElement} event for every endElement

     * event (even when the element is empty).</p>

     *

     * <p>For information on the names, see startElement.</p>

     *

     * @param uri the Namespace URI, or the empty string if the

     *        element has no Namespace URI or if Namespace

     *        processing is not being performed

     * @param localName the local name (without prefix), or the

     *        empty string if Namespace processing is not being

     *        performed

     * @param qName the qualified XML name (with prefix), or the

     *        empty string if qualified names are not available

     * @throws org.xml.sax.SAXException any SAX exception, possibly

     *            wrapping another exception

     */

    public void endElement (String uri, String localName,

                            String qName)

        throws SAXException;

    /**

     * Receive notification of character data.

     *

     * <p>The Parser will call this method to report each chunk of

     * character data.  SAX parsers may return all contiguous character

     * data in a single chunk, or they may split it into several

     * chunks; however, all of the characters in any single event

     * must come from the same external entity so that the Locator

     * provides useful information.</p>

     *

     * <p>The application must not attempt to read from the array

     * outside of the specified range.</p>

     *

     * <p>Individual characters may consist of more than one Java

     * <code>char</code> value.  There are two important cases where this

     * happens, because characters can't be represented in just sixteen bits.

     * In one case, characters are represented in a <em>Surrogate Pair</em>,

     * using two special Unicode values. Such characters are in the so-called

     * "Astral Planes", with a code point above U+FFFF.  A second case involves

     * composite characters, such as a base character combining with one or

     * more accent characters. </p>

     *

     * <p> Your code should not assume that algorithms using

     * <code>char</code>-at-a-time idioms will be working in character

     * units; in some cases they will split characters.  This is relevant

     * wherever XML permits arbitrary characters, such as attribute values,

     * processing instruction data, and comments as well as in data reported

     * from this method.  It's also generally relevant whenever Java code

     * manipulates internationalized text; the issue isn't unique to XML.</p>

     *

     * <p>Note that some parsers will report whitespace in element

     * content using the {@link #ignorableWhitespace ignorableWhitespace}

     * method rather than this one (validating parsers <em>must</em>

     * do so).</p>

     *

     * @param ch the characters from the XML document

     * @param start the start position in the array

     * @param length the number of characters to read from the array

     * @throws org.xml.sax.SAXException any SAX exception, possibly

     *            wrapping another exception

     * @see #ignorableWhitespace

     * @see org.xml.sax.Locator

     */

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

        throws SAXException;

    /**

     * Receive notification of ignorable whitespace in element content.

     *

     * <p>Validating Parsers must use this method to report each chunk

     * of whitespace in element content (see the W3C XML 1.0

     * recommendation, section 2.10): non-validating parsers may also

     * use this method if they are capable of parsing and using

     * content models.</p>

     *

     * <p>SAX parsers may return all contiguous whitespace in a single

     * chunk, or they may split it into several chunks; however, all of

     * the characters in any single event must come from the same

     * external entity, so that the Locator provides useful

     * information.</p>

     *

     * <p>The application must not attempt to read from the array

     * outside of the specified range.</p>

     *

     * @param ch the characters from the XML document

     * @param start the start position in the array

     * @param length the number of characters to read from the array

     * @throws org.xml.sax.SAXException any SAX exception, possibly

     *            wrapping another exception

     * @see #characters

     */

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

        throws SAXException;

    /**

     * Receive notification of a processing instruction.

     *

     * <p>The Parser will invoke this method once for each processing

     * instruction found: note that processing instructions may occur

     * before or after the main document element.</p>

     *

     * <p>A SAX parser must never report an XML declaration (XML 1.0,

     * section 2.8) or a text declaration (XML 1.0, section 4.3.1)

     * using this method.</p>

     *

     * <p>Like {@link #characters characters()}, processing instruction

     * data may have characters that need more than one <code>char</code>

     * value. </p>

     *

     * @param target the processing instruction target

     * @param data the processing instruction data, or null if

     *        none was supplied.  The data does not include any

     *        whitespace separating it from the target

     * @throws org.xml.sax.SAXException any SAX exception, possibly

     *            wrapping another exception

     */

    public void processingInstruction (String target, String data)

        throws SAXException;

    /**

     * Receive notification of a skipped entity.

     * This is not called for entity references within markup constructs

     * such as element start tags or markup declarations.  (The XML

     * recommendation requires reporting skipped external entities.

     * SAX also reports internal entity expansion/non-expansion, except

     * within markup constructs.)

     *

     * <p>The Parser will invoke this method each time the entity is

     * skipped.  Non-validating processors may skip entities if they

     * have not seen the declarations (because, for example, the

     * entity was declared in an external DTD subset).  All processors

     * may skip external entities, depending on the values of the

     * <code>http://xml.org/sax/features/external-general-entities</code>

     * and the

     * <code>http://xml.org/sax/features/external-parameter-entities</code>

     * properties.</p>

     *

     * @param name the name of the skipped entity.  If it is a

     *        parameter entity, the name will begin with '%', and if

     *        it is the external DTD subset, it will be the string

     *        "[dtd]"

     * @throws org.xml.sax.SAXException any SAX exception, possibly

     *            wrapping another exception

     */

    public void skippedEntity (String name)

        throws SAXException;

}

// end of ContentHandler.java