Java example source code file (XMLEventReaderImpl.java)
The XMLEventReaderImpl.java Java example source code/*
* Copyright (c) 2005, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
package com.sun.xml.internal.stream;
import com.sun.xml.internal.stream.events.XMLEventAllocatorImpl;
import java.util.NoSuchElementException;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import javax.xml.stream.events.EntityReference;
import javax.xml.stream.events.XMLEvent;
import javax.xml.stream.util.XMLEventAllocator;
/**
* @author @author Neeraj Bajaj Sun Microsystems
*
*/
public class XMLEventReaderImpl implements javax.xml.stream.XMLEventReader{
protected XMLStreamReader fXMLReader ;
protected XMLEventAllocator fXMLEventAllocator;
//only constructor will do because we delegate everything to underlying XMLStreamReader
public XMLEventReaderImpl(XMLStreamReader reader) throws XMLStreamException {
fXMLReader = reader ;
fXMLEventAllocator = (XMLEventAllocator)reader.getProperty(XMLInputFactory.ALLOCATOR);
if(fXMLEventAllocator == null){
fXMLEventAllocator = new XMLEventAllocatorImpl();
}
fPeekedEvent = fXMLEventAllocator.allocate(fXMLReader);
}
public boolean hasNext() {
//if we have the peeked event return 'true'
if(fPeekedEvent != null)return true;
//this is strange XMLStreamReader throws XMLStreamException
//XMLEventReader doesn't throw XMLStreamException
boolean next = false ;
try{
next = fXMLReader.hasNext();
}catch(XMLStreamException ex){
return false;
}
return next ;
}
public XMLEvent nextEvent() throws XMLStreamException {
//if application peeked return the peeked event
if(fPeekedEvent != null){
fLastEvent = fPeekedEvent ;
fPeekedEvent = null;
return fLastEvent ;
}
else if(fXMLReader.hasNext()){
//advance the reader to next state.
fXMLReader.next();
return fLastEvent = fXMLEventAllocator.allocate(fXMLReader);
}
else{
fLastEvent = null;
throw new NoSuchElementException();
}
}
public void remove(){
//remove of the event is not supported.
throw new java.lang.UnsupportedOperationException();
}
public void close() throws XMLStreamException {
fXMLReader.close();
}
/** Reads the content of a text-only element. Precondition:
* the current event is START_ELEMENT. Postcondition:
* The current event is the corresponding END_ELEMENT.
* @throws XMLStreamException if the current event is not a START_ELEMENT
* or if a non text element is encountered
*/
public String getElementText() throws XMLStreamException {
//we have to keep reference to the 'last event' of the stream to be able
//to make this check - is there another way ? - nb.
if(fLastEvent.getEventType() != XMLEvent.START_ELEMENT){
throw new XMLStreamException(
"parser must be on START_ELEMENT to read next text", fLastEvent.getLocation());
}
// STag content ETag
//[43] content ::= CharData? ((element | Reference | CDSect | PI | Comment) CharData?)*
//<foo>....some long text say in KB and underlying parser reports multiple character
// but getElementText() events....</foo>
String data = null;
//having a peeked event makes things really worse -- we have to test the first event
if(fPeekedEvent != null){
XMLEvent event = fPeekedEvent ;
fPeekedEvent = null;
int type = event.getEventType();
if( type == XMLEvent.CHARACTERS || type == XMLEvent.SPACE ||
type == XMLEvent.CDATA){
data = event.asCharacters().getData();
}
else if(type == XMLEvent.ENTITY_REFERENCE){
data = ((EntityReference)event).getDeclaration().getReplacementText();
}
else if(type == XMLEvent.COMMENT || type == XMLEvent.PROCESSING_INSTRUCTION){
//ignore
} else if(type == XMLEvent.START_ELEMENT) {
throw new XMLStreamException(
"elementGetText() function expects text only elment but START_ELEMENT was encountered.", event.getLocation());
}else if(type == XMLEvent.END_ELEMENT){
return "";
}
//create the string buffer and add initial data
StringBuffer buffer = new StringBuffer();
if(data != null && data.length() > 0 ) {
buffer.append(data);
}
//get the next event -- we should stop at END_ELEMENT but it can be any thing
//things are worse when implementing this function in XMLEventReader because
//there isn't any function called getText() which can get values for
//space, cdata, characters and entity reference
//nextEvent() would also set the last event.
event = nextEvent();
while(event.getEventType() != XMLEvent.END_ELEMENT){
if( type == XMLEvent.CHARACTERS || type == XMLEvent.SPACE ||
type == XMLEvent.CDATA){
data = event.asCharacters().getData();
}
else if(type == XMLEvent.ENTITY_REFERENCE){
data = ((EntityReference)event).getDeclaration().getReplacementText();
}
else if(type == XMLEvent.COMMENT || type == XMLEvent.PROCESSING_INSTRUCTION){
//ignore
} else if(type == XMLEvent.END_DOCUMENT) {
throw new XMLStreamException("unexpected end of document when reading element text content");
} else if(type == XMLEvent.START_ELEMENT) {
throw new XMLStreamException(
"elementGetText() function expects text only elment but START_ELEMENT was encountered.", event.getLocation());
} else {
throw new XMLStreamException(
"Unexpected event type "+ type, event.getLocation());
}
//add the data to the buffer
if(data != null && data.length() > 0 ) {
buffer.append(data);
}
event = nextEvent();
}
return buffer.toString();
}//if (fPeekedEvent != null)
//if there was no peeked, delegate everything to fXMLReader
//update the last event before returning the text
data = fXMLReader.getElementText();
fLastEvent = fXMLEventAllocator.allocate(fXMLReader);
return data;
}
/** Get the value of a feature/property from the underlying implementation
* @param name The name of the property
* @return The value of the property
* @throws IllegalArgumentException if the property is not supported
*/
public Object getProperty(java.lang.String name) throws java.lang.IllegalArgumentException {
return fXMLReader.getProperty(name) ;
}
/** Skips any insignificant space events until a START_ELEMENT or
* END_ELEMENT is reached. If anything other than space characters are
* encountered, an exception is thrown. This method should
* be used when processing element-only content because
* the parser is not able to recognize ignorable whitespace if
* the DTD is missing or not interpreted.
* @throws XMLStreamException if anything other than space characters are encountered
*/
public XMLEvent nextTag() throws XMLStreamException {
//its really a pain if there is peeked event before calling nextTag()
if(fPeekedEvent != null){
//check the peeked event first.
XMLEvent event = fPeekedEvent;
fPeekedEvent = null ;
int eventType = event.getEventType();
//if peeked event is whitespace move to the next event
//if peeked event is PI or COMMENT move to the next event
if( (event.isCharacters() && event.asCharacters().isWhiteSpace())
|| eventType == XMLStreamConstants.PROCESSING_INSTRUCTION
|| eventType == XMLStreamConstants.COMMENT
|| eventType == XMLStreamConstants.START_DOCUMENT){
event = nextEvent();
eventType = event.getEventType();
}
//we have to have the while loop because there can be many PI or comment event in sucession
while((event.isCharacters() && event.asCharacters().isWhiteSpace())
|| eventType == XMLStreamConstants.PROCESSING_INSTRUCTION
|| eventType == XMLStreamConstants.COMMENT){
event = nextEvent();
eventType = event.getEventType();
}
if (eventType != XMLStreamConstants.START_ELEMENT && eventType != XMLStreamConstants.END_ELEMENT) {
throw new XMLStreamException("expected start or end tag", event.getLocation());
}
return event;
}
//if there is no peeked event -- delegate the work of getting next event to fXMLReader
fXMLReader.nextTag();
return (fLastEvent = fXMLEventAllocator.allocate(fXMLReader));
}
public Object next() {
Object object = null;
try{
object = nextEvent();
}catch(XMLStreamException streamException){
fLastEvent = null ;
//don't swallow the cause
NoSuchElementException e = new NoSuchElementException(streamException.getMessage());
e.initCause(streamException.getCause());
throw e;
}
return object;
}
public XMLEvent peek() throws XMLStreamException{
//if someone call peek() two times we should just return the peeked event
//this is reset if we call next() or nextEvent()
if(fPeekedEvent != null) return fPeekedEvent;
if(hasNext()){
//revisit: we can implement peek() by calling underlying reader to advance
// the stream and returning the event without the knowledge of the user
// that the stream was advanced but the point is we are advancing the stream
//here. -- nb.
// Is there any application that relies on this behavior ?
//Can it be an application knows that there is particularly very large 'comment' section
//or character data which it doesn't want to read or to be returned as event
//But as of now we are creating every event but it can be optimized not to create
// the event.
fXMLReader.next();
fPeekedEvent = fXMLEventAllocator.allocate(fXMLReader);
return fPeekedEvent;
}else{
return null;
}
}//peek()
private XMLEvent fPeekedEvent;
private XMLEvent fLastEvent;
}//XMLEventReaderImpl
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