org.codehaus.stax2.ri.Stax2EventReaderImpl Maven / Gradle / Ivy
/* Woodstox XML processor
*
* Copyright (c) 2004- Tatu Saloranta, [email protected]
*
* Licensed under the License specified in the file LICENSE which is
* included with the source code.
* You may not use this file except in compliance with the License.
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.codehaus.stax2.ri;
import java.util.NoSuchElementException;
import javax.xml.stream.*;
import javax.xml.stream.events.*;
import javax.xml.stream.util.XMLEventAllocator;
import org.codehaus.stax2.XMLEventReader2;
import org.codehaus.stax2.XMLStreamReader2;
/**
* Almost complete implementation of {@link XMLEventReader2}, built on top of
* a generic {@link XMLStreamReader} implementation (using aggregation).
* Designed to be used by concrete Stax2 implementations to provide
* full Event API implementation with minimal effort.
*
* Since there is not much to optimize at this
* level (API and underlying stream reader pretty much define functionality
* and optimizations that can be done), implementation is fairly straight
* forward, with not many surprises.
*
* Implementation notes: the trickiest things to implement are:
*
* - Peek() functionality! Geez, why did that have to be part of StAX
* specs???!
*
* - Adding START_DOCUMENT event that cursor API does not return
* explicitly.
*
*
*/
public abstract class Stax2EventReaderImpl
implements XMLEventReader2,
XMLStreamConstants
{
// // // Enumerated state ids
protected final static int STATE_INITIAL = 1;
protected final static int STATE_END_OF_INPUT = 2;
protected final static int STATE_CONTENT = 3;
// // // Enumerated error case ids
/**
* Current state when getElementText() called not START_ELEMENT
*/
protected final static int ERR_GETELEMTEXT_NOT_START_ELEM = 1;
/**
* Encountered non-textual event (other than closing END_ELEMENT)
* when collecting text for getElementText()
*/
protected final static int ERR_GETELEMTEXT_NON_TEXT_EVENT = 2;
/**
* Encountered CHARACTERS or CDATA that contains non-white space
* char(s), when trying to locate tag with nextTag()
*/
protected final static int ERR_NEXTTAG_NON_WS_TEXT = 3;
/**
* Encountered non-skippable non-text/element event with
* nextTag()
*/
protected final static int ERR_NEXTTAG_WRONG_TYPE = 4;
/*
///////////////////////////////////////////
// Configuration
///////////////////////////////////////////
*/
protected final XMLEventAllocator mAllocator;
protected final XMLStreamReader2 mReader;
/*
///////////////////////////////////////////
// State
///////////////////////////////////////////
*/
/**
* Event that has been peeked, ie. loaded without call to
* {@link #nextEvent}; will be returned and cleared by
* call to {@link #nextEvent} (or, returned again if peeked
* again)
*/
private XMLEvent mPeekedEvent = null;
/**
* High-level state indicator, with currently three values:
* whether we are initializing (need to synthetize START_DOCUMENT),
* at END_OF_INPUT (end-of-doc), or otherwise, normal operation.
* Useful in simplifying some methods, as well as to make sure
* that independent of how stream reader handles things, event reader
* can reliably detect End-Of-Document.
*/
protected int mState = STATE_INITIAL;
/**
* This variable keeps track of the type of the 'previous' event
* when peeking for the next Event. It is needed for some functionality,
* to remember state even when underlying parser has to move to peek
* the next event.
*/
protected int mPrePeekEvent = START_DOCUMENT;
/*
///////////////////////////////////////////
// Construction
///////////////////////////////////////////
*/
protected Stax2EventReaderImpl(XMLEventAllocator a, XMLStreamReader2 r)
{
mAllocator = a;
mReader = r;
}
/*
//////////////////////////////////////////////////////
// Abstract methods sub-classes have to implement
//////////////////////////////////////////////////////
*/
public abstract boolean isPropertySupported(String name);
public abstract boolean setProperty(String name, Object value);
/**
* Method called upon encountering a problem that should result
* in an exception being thrown. If non-null String is returned.
* that will be used as the message of exception thrown; if null,
* a standard message will be used instead.
*
* @param errorType Type of the problem, one of ERR_
* constants
* @param eventType Type of the event that triggered the problem,
* if any; -1 if not available.
*/
protected abstract String getErrorDesc(int errorType, int eventType);
/*
//////////////////////////////////////////////////////
// XMLEventReader API
//////////////////////////////////////////////////////
*/
public void close()
throws XMLStreamException
{
mReader.close();
}
public String getElementText()
throws XMLStreamException
{
/* Simple, if no peeking occured: can just forward this to the
* underlying parser
*/
if (mPeekedEvent == null) {
return mReader.getElementText();
}
XMLEvent evt = mPeekedEvent;
mPeekedEvent = null;
/* Otherwise need to verify that we are currently over START_ELEMENT.
* Problem is we have already went past it...
*/
if (mPrePeekEvent != START_ELEMENT) {
reportProblem(findErrorDesc(ERR_GETELEMTEXT_NOT_START_ELEM, mPrePeekEvent));
}
// ??? do we need to update mPrePeekEvent now
String str = null;
StringBuffer sb = null;
/* Ok, fine, then just need to loop through and get all the
* text...
*/
for (; true; evt = nextEvent()) {
if (evt.isEndElement()) {
break;
}
int type = evt.getEventType();
if (type == COMMENT || type == PROCESSING_INSTRUCTION) {
// can/should just ignore them
continue;
}
if (!evt.isCharacters()) {
reportProblem(findErrorDesc(ERR_GETELEMTEXT_NON_TEXT_EVENT, type));
}
String curr = evt.asCharacters().getData();
if (str == null) {
str = curr;
} else {
if (sb == null) {
sb = new StringBuffer(str.length() + curr.length());
sb.append(str);
}
sb.append(curr);
}
}
if (sb != null) {
return sb.toString();
}
return (str == null) ? "" : str;
}
public Object getProperty(String name) {
return mReader.getProperty(name);
}
public boolean hasNext() {
return (mState != STATE_END_OF_INPUT);
}
public XMLEvent nextEvent()
throws XMLStreamException
{
if (mState == STATE_END_OF_INPUT) {
throwEndOfInput();
} else if (mState == STATE_INITIAL) {
mState = STATE_CONTENT;
return createStartDocumentEvent();
}
if (mPeekedEvent != null) {
XMLEvent evt = mPeekedEvent;
mPeekedEvent = null;
if (evt.isEndDocument()) {
mState = STATE_END_OF_INPUT;
}
return evt;
}
return createNextEvent(true, mReader.next());
}
public Object next() {
try {
return nextEvent();
} catch (XMLStreamException sex) {
throwUnchecked(sex);
return null;
}
}
public XMLEvent nextTag()
throws XMLStreamException
{
// If we have peeked something, need to process it
if (mPeekedEvent != null) {
XMLEvent evt = mPeekedEvent;
mPeekedEvent = null;
int type = evt.getEventType();
switch (type) {
case END_DOCUMENT:
return null;
case START_DOCUMENT:
// Need to skip START_DOCUMENT to get the root elem
break;
case SPACE:
// Ignorable WS is just fine
break;
/* !!! 07-Dec-2004, TSa: Specs are mum about Comments and PIs.
* But why would they not be skipped just like what
* the stream reader does?
*/
case COMMENT:
case PROCESSING_INSTRUCTION:
break;
case CDATA:
case CHARACTERS:
if (((Characters) evt).isWhiteSpace()) {
break;
}
reportProblem(findErrorDesc(ERR_NEXTTAG_NON_WS_TEXT, type));
break; // never gets here, but some compilers whine without...
case START_ELEMENT:
case END_ELEMENT:
return evt;
default:
reportProblem(findErrorDesc(ERR_NEXTTAG_WRONG_TYPE, type));
}
} else {
/* 13-Sep-2005, TSa: As pointed out by Patrick, we may need to
* initialize the state here, too; otherwise peek() won't work
* correctly. The problem is that following loop's get method
* does not use event reader's method but underlying reader's.
* As such, it won't update state: most importantly, initial
* state may not be changed to non-initial.
*/
if (mState == STATE_INITIAL) {
mState = STATE_CONTENT;
}
}
while (true) {
int next = mReader.next();
switch (next) {
case END_DOCUMENT:
return null;
case SPACE:
/* !!! 07-Dec-2004, TSa: Specs are mum about Comments and PIs.
* But why would they not be skipped just like what
* the stream reader does?
*/
case COMMENT:
case PROCESSING_INSTRUCTION:
continue;
case CDATA:
case CHARACTERS:
if (mReader.isWhiteSpace()) {
continue;
}
reportProblem(findErrorDesc(ERR_NEXTTAG_NON_WS_TEXT, next));
break; // just to keep Jikes happy...
case START_ELEMENT:
case END_ELEMENT:
return createNextEvent(false, next);
default:
reportProblem(findErrorDesc(ERR_NEXTTAG_WRONG_TYPE, next));
}
}
}
public XMLEvent peek()
throws XMLStreamException
{
if (mPeekedEvent == null) {
if (mState == STATE_END_OF_INPUT) {
// 06-Mar-2006, TSa: Fixed as per Arjen's suggestion:
//throwEndOfInput();
return null;
}
if (mState == STATE_INITIAL) {
// Not sure what it should be... but this should do:
mPrePeekEvent = START_DOCUMENT;
mPeekedEvent = createStartDocumentEvent();
mState = STATE_CONTENT;
} else {
mPrePeekEvent = mReader.getEventType();
mPeekedEvent = createNextEvent(false, mReader.next());
}
}
return mPeekedEvent;
}
/**
* Note: only here because we implement Iterator interface. Will not
* work, don't bother calling it.
*/
public void remove() {
throw new UnsupportedOperationException("Can not remove events from XMLEventReader.");
}
/*
//////////////////////////////////////////////////////
// XMLEventReader2 API
//////////////////////////////////////////////////////
*/
/**
*
* Note: although the interface allows implementations to
* throw an {@link XMLStreamException}, the reference implementation
* doesn't currently need to.
* It's still declared, in case in future there is need to throw
* such an exception.
*/
public boolean hasNextEvent()
throws XMLStreamException
{
return (mState != STATE_END_OF_INPUT);
}
/*
///////////////////////////////////////////////
// Overridable factory methods
///////////////////////////////////////////////
*/
protected XMLEvent createNextEvent(boolean checkEOD, int type)
throws XMLStreamException
{
try {
XMLEvent evt = mAllocator.allocate(mReader);
if (checkEOD && type == END_DOCUMENT) {
mState = STATE_END_OF_INPUT;
}
return evt;
} catch (RuntimeException rex) {
/* 29-Mar-2008, TSa: Due to some problems with Stax API
* (lack of 'throws XMLStreamException' in signature of
* XMLStreamReader.getText(), for one) it is possible
* we will get a wrapped XMLStreamException. If so,
* we should be able to unwrap it.
*/
Throwable t = rex.getCause();
while (t != null) {
if (t instanceof XMLStreamException) {
throw (XMLStreamException) t;
}
t = t.getCause();
}
// Nope, need to re-throw as is
throw rex;
}
}
/**
* Method called to create the very first event (START_DOCUMENT).
*/
protected XMLEvent createStartDocumentEvent()
throws XMLStreamException
{
XMLEvent start = mAllocator.allocate(mReader);
return start;
}
/*
///////////////////////////////////////////////
// Overridable error reporting methods
///////////////////////////////////////////////
*/
private void throwEndOfInput()
{
throw new NoSuchElementException();
}
protected void throwUnchecked(XMLStreamException sex)
{
/* Wrapped root cause? Let's only unwrap one layer; one that
* must have been used to expose the problem (if any)
*/
Throwable t = (sex.getNestedException() == null) ? sex : sex.getNestedException();
// Unchecked? Can re-throw as is
if (t instanceof RuntimeException) {
throw (RuntimeException) t;
}
if (t instanceof Error) {
throw (Error) t;
}
// Otherwise, let's just wrap it
throw new RuntimeException("[was "+t.getClass()+"] "+t.getMessage(), t);
}
protected void reportProblem(String msg)
throws XMLStreamException
{
reportProblem(msg, mReader.getLocation());
}
protected void reportProblem(String msg, Location loc)
throws XMLStreamException
{
if (loc == null) {
throw new XMLStreamException(msg);
}
throw new XMLStreamException(msg, loc);
}
/*
///////////////////////////////////////////////
// Package methods for sub-classes
///////////////////////////////////////////////
*/
protected XMLStreamReader getStreamReader()
{
return mReader;
}
/*
///////////////////////////////////////////////
// Other internal methods
///////////////////////////////////////////////
*/
/**
* Method used to locate error message description to use.
* Calls sub-classes getErrorDesc() first, and only
* if no message found, uses default messages defined here.
*/
private final String findErrorDesc(int errorType, int currEvent)
{
String msg = getErrorDesc(errorType, currEvent);
if (msg != null) {
return msg;
}
switch (errorType) {
case ERR_GETELEMTEXT_NOT_START_ELEM:
return "Current state not START_ELEMENT when calling getElementText()";
case ERR_GETELEMTEXT_NON_TEXT_EVENT:
return "Expected a text token";
case ERR_NEXTTAG_NON_WS_TEXT:
return "Only all-whitespace CHARACTERS/CDATA (or SPACE) allowed for nextTag()";
case ERR_NEXTTAG_WRONG_TYPE:
return "Should only encounter START_ELEMENT/END_ELEMENT, SPACE, or all-white-space CHARACTERS";
}
// should never happen, but it'd be bad to throw another exception...
return "Internal error (unrecognized error type: "+errorType+")";
}
}