STAXEventReader xref

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    1   /*
    2    * Copyright 2001-2005 (C) MetaStuff, Ltd. All Rights Reserved.
    3    *
    4    * This software is open source.
    5    * See the bottom of this file for the licence.
    6    */
    7
    8   package org.dom4j.io;
    9
    10  import java.io.InputStream;
    11  import java.io.Reader;
    12  import java.util.Iterator;
    13
    14  import javax.xml.namespace.QName;
    15  import javax.xml.stream.XMLEventReader;
    16  import javax.xml.stream.XMLInputFactory;
    17  import javax.xml.stream.XMLStreamConstants;
    18  import javax.xml.stream.XMLStreamException;
    19  import javax.xml.stream.events.Attribute;
    20  import javax.xml.stream.events.Characters;
    21  import javax.xml.stream.events.Comment;
    22  import javax.xml.stream.events.EndElement;
    23  import javax.xml.stream.events.EntityReference;
    24  import javax.xml.stream.events.Namespace;
    25  import javax.xml.stream.events.ProcessingInstruction;
    26  import javax.xml.stream.events.StartDocument;
    27  import javax.xml.stream.events.StartElement;
    28  import javax.xml.stream.events.XMLEvent;
    29
    30  import org.dom4j.CharacterData;
    31  import org.dom4j.Document;
    32  import org.dom4j.DocumentFactory;
    33  import org.dom4j.Element;
    34  import org.dom4j.Entity;
    35  import org.dom4j.Node;
    36
    37  /***
    38   * Reads a DOM4J {@link Document}, as well as other {@link Node}s, from a StAX
    39   * {@link XMLEventReader}.
    40   *
    41   * @author Christian Niles
    42   */
    43  public class STAXEventReader {
    44      /*** Reference to the DocumentFactory used to build DOM4J nodes. */
    45      private DocumentFactory factory;
    46
    47      /*** A StAX input factory, used to construct streams from IO streams. */
    48      private XMLInputFactory inputFactory = XMLInputFactory.newInstance();
    49
    50      /***
    51       * Constructs a default <code>STAXEventReader</code> instance with a
    52       * default {@link DocumentFactory}.
    53       */
    54      public STAXEventReader() {
    55          this.factory = DocumentFactory.getInstance();
    56      }
    57
    58      /***
    59       * Constructs a <code>STAXEventReader</code> instance that uses the
    60       * specified {@link DocumentFactory}to construct DOM4J {@link Node}s.
    61       *
    62       * @param factory
    63       *            The DocumentFactory to use when constructing DOM4J nodes, or
    64       *            <code>null</code> if a default should be used.
    65       */
    66      public STAXEventReader(DocumentFactory factory) {
    67          if (factory != null) {
    68              this.factory = factory;
    69          } else {
    70              this.factory = DocumentFactory.getInstance();
    71          }
    72      }
    73
    74      /***
    75       * Sets the DocumentFactory to be used when constructing DOM4J nodes.
    76       *
    77       * @param documentFactory
    78       *            The DocumentFactory to use when constructing DOM4J nodes, or
    79       *            <code>null</code> if a default should be used.
    80       */
    81      public void setDocumentFactory(DocumentFactory documentFactory) {
    82          if (documentFactory != null) {
    83              this.factory = documentFactory;
    84          } else {
    85              this.factory = DocumentFactory.getInstance();
    86          }
    87      }
    88
    89      /***
    90       * Constructs a StAX event stream from the provided I/O stream and reads a
    91       * DOM4J document from it.
    92       *
    93       * @param is
    94       *            The I/O stream from which the Document will be read.
    95       *
    96       * @return The Document that was read from the stream.
    97       *
    98       * @throws XMLStreamException
    99       *             If an error occurs reading content from the stream.
    100      */
    101     public Document readDocument(InputStream is) throws XMLStreamException {
    102         return readDocument(is, null);
    103     }
    104
    105     /***
    106      * Constructs a StAX event stream from the provided I/O character stream and
    107      * reads a DOM4J document from it.
    108      *
    109      * @param reader
    110      *            The character stream from which the Document will be read.
    111      *
    112      * @return The Document that was read from the stream.
    113      *
    114      * @throws XMLStreamException
    115      *             If an error occurs reading content from the stream.
    116      */
    117     public Document readDocument(Reader reader) throws XMLStreamException {
    118         return readDocument(reader, null);
    119     }
    120
    121     /***
    122      * Constructs a StAX event stream from the provided I/O stream and reads a
    123      * DOM4J document from it.
    124      *
    125      * @param is
    126      *            The I/O stream from which the Document will be read.
    127      * @param systemId
    128      *            A system id used to resolve entities.
    129      *
    130      * @return The Document that was read from the stream.
    131      *
    132      * @throws XMLStreamException
    133      *             If an error occurs reading content from the stream.
    134      */
    135     public Document readDocument(InputStream is, String systemId)
    136             throws XMLStreamException {
    137         XMLEventReader eventReader = inputFactory.createXMLEventReader(
    138                 systemId, is);
    139
    140         try {
    141             return readDocument(eventReader);
    142         } finally {
    143             eventReader.close();
    144         }
    145     }
    146
    147     /***
    148      * Constructs a StAX event stream from the provided I/O character stream and
    149      * reads a DOM4J document from it.
    150      *
    151      * @param reader
    152      *            The character stream from which the Document will be read.
    153      * @param systemId
    154      *            A system id used to resolve entities.
    155      *
    156      * @return The Document that was read from the stream.
    157      *
    158      * @throws XMLStreamException
    159      *             If an error occurs reading content from the stream.
    160      */
    161     public Document readDocument(Reader reader, String systemId)
    162             throws XMLStreamException {
    163         XMLEventReader eventReader = inputFactory.createXMLEventReader(
    164                 systemId, reader);
    165
    166         try {
    167             return readDocument(eventReader);
    168         } finally {
    169             eventReader.close();
    170         }
    171     }
    172
    173     /***
    174      * Reads a {@link Node}from the event stream. If the next event is a
    175      * {@link StartElement}, all events until the closing {@link EndElement}
    176      * will be read, and the resulting nodes will be added to the returned
    177      * {@link Element}.
    178      *
    179      * <p>
    180      * <strong>Pre-Conditions </strong>: The stream must be positioned before an
    181      * event other than an <code>EndElement</code>,<code>EndDocument</code>,
    182      * or any DTD-related events, which are not currently supported.
    183      * </p>
    184      *
    185      * @param reader
    186      *            The reader from which events will be read.
    187      *
    188      * @return A DOM4J {@link Node}constructed from the read events.
    189      *
    190      * @throws XMLStreamException
    191      *             If an error occurs reading from the stream, or the stream was
    192      *             positioned before an unsupported event.
    193      */
    194     public Node readNode(XMLEventReader reader) throws XMLStreamException {
    195         XMLEvent event = reader.peek();
    196
    197         if (event.isStartElement()) {
    198             return readElement(reader);
    199         } else if (event.isCharacters()) {
    200             return readCharacters(reader);
    201         } else if (event.isStartDocument()) {
    202             return readDocument(reader);
    203         } else if (event.isProcessingInstruction()) {
    204             return readProcessingInstruction(reader);
    205         } else if (event.isEntityReference()) {
    206             return readEntityReference(reader);
    207         } else if (event.isAttribute()) {
    208             return readAttribute(reader);
    209         } else if (event.isNamespace()) {
    210             return readNamespace(reader);
    211         } else {
    212             throw new XMLStreamException("Unsupported event: " + event);
    213         }
    214     }
    215
    216     /***
    217      * Reads a DOM4J {@link Document}from the provided stream. The stream
    218      * should be positioned at the start of a document, or before a {@link
    219      * StartElement} event.
    220      *
    221      * @param reader
    222      *            The event stream from which to read the {@link Document}.
    223      *
    224      * @return The {@link Document}that was read from the stream.
    225      *
    226      * @throws XMLStreamException
    227      *             If an error occurs reading events from the stream.
    228      */
    229     public Document readDocument(XMLEventReader reader)
    230             throws XMLStreamException {
    231         Document doc = null;
    232
    233         while (reader.hasNext()) {
    234             XMLEvent nextEvent = reader.peek();
    235             int type = nextEvent.getEventType();
    236
    237             switch (type) {
    238                 case XMLStreamConstants.START_DOCUMENT:
    239
    240                     StartDocument event = (StartDocument) reader.nextEvent();
    241
    242                     if (doc == null) {
    243                         // create document
    244                         if (event.encodingSet()) {
    245                             String encodingScheme = event
    246                                     .getCharacterEncodingScheme();
    247                             doc = factory.createDocument(encodingScheme);
    248                         } else {
    249                             doc = factory.createDocument();
    250                         }
    251                     } else {
    252                         // duplicate or misplaced xml declaration
    253                         String msg = "Unexpected StartDocument event";
    254                         throw new XMLStreamException(msg, event.getLocation());
    255                     }
    256
    257                     break;
    258
    259                 case XMLStreamConstants.END_DOCUMENT:
    260                 case XMLStreamConstants.SPACE:
    261                 case XMLStreamConstants.CHARACTERS:
    262
    263                     // skip end document and space outside the root element
    264                     reader.nextEvent();
    265
    266                     break;
    267
    268                 default:
    269
    270                     if (doc == null) {
    271                         // create document
    272                         doc = factory.createDocument();
    273                     }
    274
    275                     Node n = readNode(reader);
    276                     doc.add(n);
    277             }
    278         }
    279
    280         return doc;
    281     }
    282
    283     /***
    284      * Reads a DOM4J Element from the provided event stream. The stream must be
    285      * positioned before an {@link StartElement}event. In addition to the
    286      * initial start event, all events up to and including the closing {@link
    287      * EndElement} will be read, and included with the returned element.
    288      *
    289      * @param eventReader
    290      *            The event stream from which to read the Element.
    291      *
    292      * @return The Element that was read from the stream.
    293      *
    294      * @throws XMLStreamException
    295      *             If an error occured reading events from the stream, or the
    296      *             stream was not positioned before a {@linkStartElement}event.
    297      */
    298     public Element readElement(XMLEventReader eventReader)
    299             throws XMLStreamException {
    300         XMLEvent event = eventReader.peek();
    301
    302         if (event.isStartElement()) {
    303             // advance the reader and get the StartElement event
    304             StartElement startTag = eventReader.nextEvent().asStartElement();
    305             Element elem = createElement(startTag);
    306
    307             // read element content
    308             while (true) {
    309                 if (!eventReader.hasNext()) {
    310                     String msg = "Unexpected end of stream while reading"
    311                             + " element content";
    312                     throw new XMLStreamException(msg);
    313                 }
    314
    315                 XMLEvent nextEvent = eventReader.peek();
    316
    317                 if (nextEvent.isEndElement()) {
    318                     EndElement endElem = eventReader.nextEvent().asEndElement();
    319
    320                     if (!endElem.getName().equals(startTag.getName())) {
    321                         throw new XMLStreamException("Expected "
    322                                 + startTag.getName() + " end-tag, but found"
    323                                 + endElem.getName());
    324                     }
    325
    326                     break;
    327                 }
    328
    329                 Node child = readNode(eventReader);
    330                 elem.add(child);
    331             }
    332
    333             return elem;
    334         } else {
    335             throw new XMLStreamException("Expected Element event, found: "
    336                     + event);
    337         }
    338     }
    339
    340     /***
    341      * Constructs a DOM4J Attribute from the provided event stream. The stream
    342      * must be positioned before an {@link Attribute}event.
    343      *
    344      * @param reader
    345      *            The event stream from which to read the Attribute.
    346      *
    347      * @return The Attribute that was read from the stream.
    348      *
    349      * @throws XMLStreamException
    350      *             If an error occured reading events from the stream, or the
    351      *             stream was not positioned before an {@linkAttribute}event.
    352      */
    353     public org.dom4j.Attribute readAttribute(XMLEventReader reader)
    354             throws XMLStreamException {
    355         XMLEvent event = reader.peek();
    356
    357         if (event.isAttribute()) {
    358             Attribute attr = (Attribute) reader.nextEvent();
    359
    360             return createAttribute(null, attr);
    361         } else {
    362             throw new XMLStreamException("Expected Attribute event, found: "
    363                     + event);
    364         }
    365     }
    366
    367     /***
    368      * Constructs a DOM4J Namespace from the provided event stream. The stream
    369      * must be positioned before a {@link Namespace}event.
    370      *
    371      * @param reader
    372      *            The event stream from which to read the Namespace.
    373      *
    374      * @return The Namespace that was read from the stream.
    375      *
    376      * @throws XMLStreamException
    377      *             If an error occured reading events from the stream, or the
    378      *             stream was not positioned before a {@linkNamespace}event.
    379      */
    380     public org.dom4j.Namespace readNamespace(XMLEventReader reader)
    381             throws XMLStreamException {
    382         XMLEvent event = reader.peek();
    383
    384         if (event.isNamespace()) {
    385             Namespace ns = (Namespace) reader.nextEvent();
    386
    387             return createNamespace(ns);
    388         } else {
    389             throw new XMLStreamException("Expected Namespace event, found: "
    390                     + event);
    391         }
    392     }
    393
    394     /***
    395      * Constructs a DOM4J Text or CDATA section from the provided event stream.
    396      * The stream must be positioned before a {@link Characters}event.
    397      *
    398      * @param reader
    399      *            The event stream from which to read the Text or CDATA.
    400      *
    401      * @return The Text or CDATA that was read from the stream.
    402      *
    403      * @throws XMLStreamException
    404      *             If an error occured reading events from the stream, or the
    405      *             stream was not positioned before a {@linkCharacters}event.
    406      */
    407     public CharacterData readCharacters(XMLEventReader reader)
    408             throws XMLStreamException {
    409         XMLEvent event = reader.peek();
    410
    411         if (event.isCharacters()) {
    412             Characters characters = reader.nextEvent().asCharacters();
    413
    414             return createCharacterData(characters);
    415         } else {
    416             throw new XMLStreamException("Expected Characters event, found: "
    417                     + event);
    418         }
    419     }
    420
    421     /***
    422      * Constructs a DOM4J Comment from the provided event stream. The stream
    423      * must be positioned before a {@link Comment}event.
    424      *
    425      * @param reader
    426      *            The event stream from which to read the Comment.
    427      *
    428      * @return The Comment that was read from the stream.
    429      *
    430      * @throws XMLStreamException
    431      *             If an error occured reading events from the stream, or the
    432      *             stream was not positioned before a {@linkComment}event.
    433      */
    434     public org.dom4j.Comment readComment(XMLEventReader reader)
    435             throws XMLStreamException {
    436         XMLEvent event = reader.peek();
    437
    438         if (event instanceof Comment) {
    439             return createComment((Comment) reader.nextEvent());
    440         } else {
    441             throw new XMLStreamException("Expected Comment event, found: "
    442                     + event);
    443         }
    444     }
    445
    446     /***
    447      * Constructs a DOM4J Entity from the provided event stream. The stream must
    448      * be positioned before an {@link EntityReference}event.
    449      *
    450      * @param reader
    451      *            The event stream from which to read the {@link
    452      *            EntityReference}.
    453      *
    454      * @return The {@link org.dom4j.Entity}that was read from the stream.
    455      *
    456      * @throws XMLStreamException
    457      *             If an error occured reading events from the stream, or the
    458      *             stream was not positioned before an {@linkEntityReference}
    459      *             event.
    460      */
    461     public Entity readEntityReference(XMLEventReader reader)
    462             throws XMLStreamException {
    463         XMLEvent event = reader.peek();
    464
    465         if (event.isEntityReference()) {
    466             EntityReference entityRef = (EntityReference) reader.nextEvent();
    467
    468             return createEntity(entityRef);
    469         } else {
    470             throw new XMLStreamException("Expected EntityRef event, found: "
    471                     + event);
    472         }
    473     }
    474
    475     /***
    476      * Constructs a DOM4J ProcessingInstruction from the provided event stream.
    477      * The stream must be positioned before a {@link ProcessingInstruction}
    478      * event.
    479      *
    480      * @param reader
    481      *            The event stream from which to read the ProcessingInstruction.
    482      *
    483      * @return The ProcessingInstruction that was read from the stream.
    484      *
    485      * @throws XMLStreamException
    486      *             If an error occured reading events from the stream, or the
    487      *             stream was not positioned before a {@link
    488      *             ProcessingInstruction} event.
    489      */
    490     public org.dom4j.ProcessingInstruction readProcessingInstruction(
    491             XMLEventReader reader) throws XMLStreamException {
    492         XMLEvent event = reader.peek();
    493
    494         if (event.isProcessingInstruction()) {
    495             ProcessingInstruction pi = (ProcessingInstruction) reader
    496                     .nextEvent();
    497
    498             return createProcessingInstruction(pi);
    499         } else {
    500             throw new XMLStreamException("Expected PI event, found: " + event);
    501         }
    502     }
    503
    504     /***
    505      * Constructs a new DOM4J Element from the provided StartElement event. All
    506      * attributes and namespaces will be added to the returned element.
    507      *
    508      * @param startEvent
    509      *            The StartElement event from which to construct the new DOM4J
    510      *            Element.
    511      *
    512      * @return The Element constructed from the provided StartElement event.
    513      */
    514     public Element createElement(StartElement startEvent) {
    515         QName qname = startEvent.getName();
    516         org.dom4j.QName elemName = createQName(qname);
    517
    518         Element elem = factory.createElement(elemName);
    519
    520         // create attributes
    521         for (Iterator i = startEvent.getAttributes(); i.hasNext();) {
    522             Attribute attr = (Attribute) i.next();
    523             elem.addAttribute(createQName(attr.getName()), attr.getValue());
    524         }
    525
    526         // create namespaces
    527         for (Iterator i = startEvent.getNamespaces(); i.hasNext();) {
    528             Namespace ns = (Namespace) i.next();
    529             elem.addNamespace(ns.getPrefix(), ns.getNamespaceURI());
    530         }
    531
    532         return elem;
    533     }
    534
    535     /***
    536      * Constructs a new DOM4J Attribute from the provided StAX Attribute event.
    537      *
    538      * @param elem
    539      *            DOCUMENT ME!
    540      * @param attr
    541      *            The Attribute event from which to construct the new DOM4J
    542      *            Attribute.
    543      *
    544      * @return The Attribute constructed from the provided Attribute event.
    545      */
    546     public org.dom4j.Attribute createAttribute(Element elem, Attribute attr) {
    547         return factory.createAttribute(elem, createQName(attr.getName()), attr
    548                 .getValue());
    549     }
    550
    551     /***
    552      * Constructs a new DOM4J Namespace from the provided StAX Namespace event.
    553      *
    554      * @param ns
    555      *            The Namespace event from which to construct the new DOM4J
    556      *            Namespace.
    557      *
    558      * @return The Namespace constructed from the provided Namespace event.
    559      */
    560     public org.dom4j.Namespace createNamespace(Namespace ns) {
    561         return factory.createNamespace(ns.getPrefix(), ns.getNamespaceURI());
    562     }
    563
    564     /***
    565      * Constructs a new DOM4J Text or CDATA object from the provided Characters
    566      * event.
    567      *
    568      * @param characters
    569      *            The Characters event from which to construct the new DOM4J
    570      *            Text or CDATA object.
    571      *
    572      * @return The Text or CDATA object constructed from the provided Characters
    573      *         event.
    574      */
    575     public CharacterData createCharacterData(Characters characters) {
    576         String data = characters.getData();
    577
    578         if (characters.isCData()) {
    579             return factory.createCDATA(data);
    580         } else {
    581             return factory.createText(data);
    582         }
    583     }
    584
    585     /***
    586      * Constructs a new DOM4J Comment from the provided StAX Comment event.
    587      *
    588      * @param comment
    589      *            The Comment event from which to construct the new DOM4J
    590      *            Comment.
    591      *
    592      * @return The Comment constructed from the provided Comment event.
    593      */
    594     public org.dom4j.Comment createComment(Comment comment) {
    595         return factory.createComment(comment.getText());
    596     }
    597
    598     /***
    599      * Constructs a new DOM4J Entity from the provided StAX EntityReference
    600      * event.
    601      *
    602      * @param entityRef
    603      *            The EntityReference event from which to construct the new
    604      *            DOM4J Entity.
    605      *
    606      * @return The Entity constructed from the provided EntityReference event.
    607      */
    608     public org.dom4j.Entity createEntity(EntityReference entityRef) {
    609         return factory.createEntity(entityRef.getName(), entityRef
    610                 .getDeclaration().getReplacementText());
    611     }
    612
    613     /***
    614      * Constructs a new DOM4J ProcessingInstruction from the provided StAX
    615      * ProcessingInstruction event.
    616      *
    617      * @param pi
    618      *            The ProcessingInstruction event from which to construct the
    619      *            new DOM4J ProcessingInstruction.
    620      *
    621      * @return The ProcessingInstruction constructed from the provided
    622      *         ProcessingInstruction event.
    623      */
    624     public org.dom4j.ProcessingInstruction createProcessingInstruction(
    625             ProcessingInstruction pi) {
    626         return factory
    627                 .createProcessingInstruction(pi.getTarget(), pi.getData());
    628     }
    629
    630     /***
    631      * Constructs a new DOM4J QName from the provided JAXP QName.
    632      *
    633      * @param qname
    634      *            The JAXP QName from which to create a DOM4J QName.
    635      *
    636      * @return The newly constructed DOM4J QName.
    637      */
    638     public org.dom4j.QName createQName(QName qname) {
    639         return factory.createQName(qname.getLocalPart(), qname.getPrefix(),
    640                 qname.getNamespaceURI());
    641     }
    642 }
    643
    644 /*
    645  * Redistribution and use of this software and associated documentation
    646  * ("Software"), with or without modification, are permitted provided that the
    647  * following conditions are met:
    648  *
    649  * 1. Redistributions of source code must retain copyright statements and
    650  * notices. Redistributions must also contain a copy of this document.
    651  *
    652  * 2. Redistributions in binary form must reproduce the above copyright notice,
    653  * this list of conditions and the following disclaimer in the documentation
    654  * and/or other materials provided with the distribution.
    655  *
    656  * 3. The name "DOM4J" must not be used to endorse or promote products derived
    657  * from this Software without prior written permission of MetaStuff, Ltd. For
    658  * written permission, please contact dom4j-info@metastuff.com.
    659  *
    660  * 4. Products derived from this Software may not be called "DOM4J" nor may
    661  * "DOM4J" appear in their names without prior written permission of MetaStuff,
    662  * Ltd. DOM4J is a registered trademark of MetaStuff, Ltd.
    663  *
    664  * 5. Due credit should be given to the DOM4J Project - http://www.dom4j.org
    665  *
    666  * THIS SOFTWARE IS PROVIDED BY METASTUFF, LTD. AND CONTRIBUTORS ``AS IS'' AND
    667  * ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    668  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    669  * ARE DISCLAIMED. IN NO EVENT SHALL METASTUFF, LTD. OR ITS CONTRIBUTORS BE
    670  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
    671  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
    672  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
    673  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
    674  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
    675  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
    676  * POSSIBILITY OF SUCH DAMAGE.
    677  *
    678  * Copyright 2001-2005 (C) MetaStuff, Ltd. All Rights Reserved.
    679  */