Class XMLStreamReader

• TopLevel.Object
  • dw.io.XMLStreamReader

The XMLStreamReader allows forward, read-only access to XML. It is designed to be the lowest level and most efficient way to read XML data.

The XMLStreamReader is designed to iterate over XML using next() and hasNext(). The data can be accessed using methods such as getEventType(), getNamespaceURI(), getLocalName() and getText();

The next() method causes the reader to read the next parse event. The next() method returns an integer which identifies the type of event just read.

The event type can be determined using getEventType().

Parsing events are defined as the XML Declaration, a DTD, start tag, character data, white space, end tag, comment, or processing instruction. An attribute or namespace event may be encountered at the root level of a document as the result of a query operation.

The following table describes which methods are valid in what state. If a method is called in an invalid state the method will throw a java.lang.IllegalStateException.

The following is a code sample to read an XML file containing multiple “myobject” sub-elements. Only one myObject instance is kept in memory at any given time to keep memory consumption low:

1var fileReader : FileReader = new FileReader(file, "UTF-8");
2var xmlStreamReader : XMLStreamReader = new XMLStreamReader(fileReader);
3
4while (xmlStreamReader.hasNext())
5{
6  if (xmlStreamReader.next() == XMLStreamConstants.START_ELEMENT)
7  {
8    var localElementName : String = xmlStreamReader.getLocalName();
9    if (localElementName == "myobject")
10    {
11      // read single "myobject" as XML
12      var myObject : XML = xmlStreamReader.getXMLObject();
13
14      // process myObject
15    }
16  }
17}
18
19xmlStreamReader.close();
20fileReader.close();

assign, create, create, defineProperties, defineProperty, entries, freeze, fromEntries, getOwnPropertyDescriptor, getOwnPropertyNames, getOwnPropertySymbols, getPrototypeOf, hasOwnProperty, is, isExtensible, isFrozen, isPrototypeOf, isSealed, keys, preventExtensions, propertyIsEnumerable, seal, setPrototypeOf, toLocaleString, toString, valueOf, values

PIData: String (read-only)

Get the data section of a processing instruction.

PITarget: String (read-only)

Get the target of a processing instruction.

XMLObject: Object (read-only)

Reads a sub-tree of the XML document and parses it as XML object.

The stream must be positioned on a START_ELEMENT. Do not call the method when the stream is positioned at document's root element. This would cause the whole document to be parsed into a single XML what may lead to an out-of-memory condition. Instead use #next() to navigate to sub-elements and invoke getXMLObject() there. Do not keep references to more than the currently processed XML to keep memory consumption low. The method reads the stream up to the matching END_ELEMENT. When the method returns the current event is the END_ELEMENT event.

Deprecated:

attributeCount: Number (read-only)

Returns the count of attributes on this START_ELEMENT, this method is only valid on a START_ELEMENT or ATTRIBUTE. This count excludes namespace definitions. Attribute indices are zero-based.

characterEncodingScheme: String (read-only)

Returns the character encoding declared on the XML declaration Returns null if none was declared.

characters: Boolean (read-only)

Identifies if the cursor points to a character data event.

columnNumber: Number (read-only)

Returns the column number where the current event ends or -1 if none is available.

elementText: String (read-only)

Reads the content of a text-only element, an exception is thrown if this is not a text-only element. This method always returns coalesced content.

Precondition: the current event is START_ELEMENT.

Postcondition: the current event is the corresponding END_ELEMENT.

The method does the following (implementations are free to be optimized but must do equivalent processing):

1if ( getEventType() != XMLStreamConstants.START_ELEMENT )
2{
3    throw new XMLStreamException( "parser must be on START_ELEMENT to read next text", getLocation() );
4}
5int eventType = next();
6StringBuffer content = new StringBuffer();
7while ( eventType != XMLStreamConstants.END_ELEMENT )
8{
9    if ( eventType == XMLStreamConstants.CHARACTERS || eventType == XMLStreamConstants.CDATA
10        || eventType == XMLStreamConstants.SPACE || eventType == XMLStreamConstants.ENTITY_REFERENCE )
11    {
12        buf.append( getText() );
13    }
14    else if ( eventType == XMLStreamConstants.PROCESSING_INSTRUCTION || eventType == XMLStreamConstants.COMMENT )
15    {
16        // skipping
17    }
18    else if ( eventType == XMLStreamConstants.END_DOCUMENT )
19    {
20        throw new XMLStreamException( "unexpected end of document when reading element text content", this );
21    }
22    else if ( eventType == XMLStreamConstants.START_ELEMENT )
23    {
24        throw new XMLStreamException( "element text content may not contain START_ELEMENT", getLocation() );
25    }
26    else
27    {
28        throw new XMLStreamException( "Unexpected event type " + eventType, getLocation() );
29    }
30    eventType = next();
31}
32return buf.toString();

Deprecated:

encoding: String (read-only)

Return input encoding if known or null if unknown.

endElement: Boolean (read-only)

Identifies if the cursor points to an end tag.

eventType: Number (read-only)

Returns an integer code that indicates the type of the event the cursor is pointing to.

lineNumber: Number (read-only)

Returns the line number where the current event ends or -1 if none is available.

localName: String (read-only)

Returns the (local) name of the current event. For START_ELEMENT or END_ELEMENT returns the (local) name of the current element. For ENTITY_REFERENCE it returns entity name. The current event must be START_ELEMENT or END_ELEMENT, or ENTITY_REFERENCE.

namespaceCount: Number (read-only)

Returns the count of namespaces declared on this START_ELEMENT or END_ELEMENT, this method is only valid on a START_ELEMENT, END_ELEMENT or NAMESPACE. On an END_ELEMENT the count is of the namespaces that are about to go out of scope. This is the equivalent of the information reported by SAX callback for an end element event.

namespaceURI: String (read-only)

If the current event is a START_ELEMENT or END_ELEMENT this method returns the URI of the prefix or the default namespace. Returns null if the event does not have a prefix.

prefix: String (read-only)

Returns the prefix of the current event or null if the event does not have a prefix

standalone: Boolean (read-only)

Get the standalone declaration from the xml declaration.

startElement: Boolean (read-only)

Identifies if the cursor points to a start tag.

text: String (read-only)

Returns the current value of the parse event as a string, this returns the string value of a CHARACTERS event, returns the value of a COMMENT, the replacement value for an ENTITY_REFERENCE, the string value of a CDATA section, the string value for a SPACE event, or the String value of the internal subset of the DTD. If an ENTITY_REFERENCE has been resolved, any character data will be reported as CHARACTERS events.

textLength: Number (read-only)

Returns the length of the sequence of characters for this Text event within the text character array.

textStart: Number (read-only)

Returns the offset into the text character array where the first character (of this text event) is stored.

version: String (read-only)

Get the xml version declared on the xml declaration. Returns null if none was declared.

whiteSpace: Boolean (read-only)

Identifies if the cursor points to a character data event that consists of all whitespace.

XMLStreamReader(reader: Reader)

Constructs the stream readon on behalf of the reader.

Parameters:

• reader - the reader to use.

close(): void

Frees any resources associated with this Reader. This method does not close the underlying reader.

getAttributeCount(): Number

Returns the count of attributes on this START_ELEMENT, this method is only valid on a START_ELEMENT or ATTRIBUTE. This count excludes namespace definitions. Attribute indices are zero-based.

Returns:

• returns the number of attributes.

getAttributeLocalName(index: Number): String

Returns the localName of the attribute at the provided index.

Parameters:

• index - the position of the attribute.

Returns:

• the local name of the attribute.

getAttributeNamespace(index: Number): String

Returns the namespace of the attribute at the provided index.

Parameters:

• index - the position of the attribute

Returns:

• the namespace URI (can be null)

getAttributePrefix(index: Number): String

Returns the prefix of this attribute at the provided index.

Parameters:

• index - the position of the attribute.

Returns:

• the prefix of the attribute.

getAttributeType(index: Number): String

Returns the XML type of the attribute at the provided index.

Parameters:

• index - the position of the attribute.

Returns:

• the XML type of the attribute.

getAttributeValue(index: Number): String

Returns the value of the attribute at the index.

Parameters:

• index - the position of the attribute.

Returns:

• the attribute value.

getAttributeValue(namespaceURI: String, localName: String): String

Returns the normalized attribute value of the attribute with the namespace and localName If the namespaceURI is null the namespace is not checked for equality

Parameters:

• namespaceURI - the namespace of the attribute
• localName - the local name of the attribute, cannot be null

Returns:

• returns the value of the attribute or null if not found.

getCharacterEncodingScheme(): String

Returns the character encoding declared on the XML declaration Returns null if none was declared.

Returns:

• the encoding declared in the document or null.

getColumnNumber(): Number

Returns the column number where the current event ends or -1 if none is available.

Returns:

• the column number or -1.

getElementText(): String

Reads the content of a text-only element, an exception is thrown if this is not a text-only element. This method always returns coalesced content.

Precondition: the current event is START_ELEMENT.

Postcondition: the current event is the corresponding END_ELEMENT.

The method does the following (implementations are free to be optimized but must do equivalent processing):

1if ( getEventType() != XMLStreamConstants.START_ELEMENT )
2{
3    throw new XMLStreamException( "parser must be on START_ELEMENT to read next text", getLocation() );
4}
5int eventType = next();
6StringBuffer content = new StringBuffer();
7while ( eventType != XMLStreamConstants.END_ELEMENT )
8{
9    if ( eventType == XMLStreamConstants.CHARACTERS || eventType == XMLStreamConstants.CDATA
10        || eventType == XMLStreamConstants.SPACE || eventType == XMLStreamConstants.ENTITY_REFERENCE )
11    {
12        buf.append( getText() );
13    }
14    else if ( eventType == XMLStreamConstants.PROCESSING_INSTRUCTION || eventType == XMLStreamConstants.COMMENT )
15    {
16        // skipping
17    }
18    else if ( eventType == XMLStreamConstants.END_DOCUMENT )
19    {
20        throw new XMLStreamException( "unexpected end of document when reading element text content", this );
21    }
22    else if ( eventType == XMLStreamConstants.START_ELEMENT )
23    {
24        throw new XMLStreamException( "element text content may not contain START_ELEMENT", getLocation() );
25    }
26    else
27    {
28        throw new XMLStreamException( "Unexpected event type " + eventType, getLocation() );
29    }
30    eventType = next();
31}
32return buf.toString();

Deprecated:

getEncoding(): String

Return input encoding if known or null if unknown.

Returns:

• the encoding of this instance or null

getEventType(): Number

Returns an integer code that indicates the type of the event the cursor is pointing to.

Returns:

• an integer code that indicates the type of the event the cursor is pointing to.

getLineNumber(): Number

Returns the line number where the current event ends or -1 if none is available.

Returns:

• the line number or -1.

getLocalName(): String

Returns the (local) name of the current event. For START_ELEMENT or END_ELEMENT returns the (local) name of the current element. For ENTITY_REFERENCE it returns entity name. The current event must be START_ELEMENT or END_ELEMENT, or ENTITY_REFERENCE.

Returns:

• the local name.

getNamespaceCount(): Number

Returns the count of namespaces declared on this START_ELEMENT or END_ELEMENT, this method is only valid on a START_ELEMENT, END_ELEMENT or NAMESPACE. On an END_ELEMENT the count is of the namespaces that are about to go out of scope. This is the equivalent of the information reported by SAX callback for an end element event.

Returns:

• returns the number of namespace declarations on this specific element.

getNamespacePrefix(index: Number): String

Returns the prefix for the namespace declared at the index. Returns null if this is the default namespace declaration.

Parameters:

• index - the position of the namespace declaration.

Returns:

• returns the namespace prefix.

getNamespaceURI(): String

If the current event is a START_ELEMENT or END_ELEMENT this method returns the URI of the prefix or the default namespace. Returns null if the event does not have a prefix.

Returns:

• the URI bound to this elements prefix, the default namespace, or null.

getNamespaceURI(index: Number): String

Returns the uri for the namespace declared at the index.

Parameters:

• index - the position of the namespace declaration.

Returns:

• returns the namespace uri.

getNamespaceURI(prefix: String): String

Return the uri for the given prefix. The uri returned depends on the current state of the processor.

**NOTE:**The 'xml' prefix is bound as defined in Namespaces in XML specification to "http://www.w3.org/XML/1998/namespace".

NOTE: The 'xmlns' prefix must be resolved to following namespace http://www.w3.org/2000/xmlns/

Parameters:

• prefix - The prefix to lookup, may not be null

Returns:

• the uri bound to the given prefix or null if it is not bound

getPIData(): String

Get the data section of a processing instruction.

Returns:

• the data or null.

getPITarget(): String

Get the target of a processing instruction.

Returns:

• the target or null.

getPrefix(): String

Returns the prefix of the current event or null if the event does not have a prefix

Returns:

• the prefix or null.

getText(): String

Returns the current value of the parse event as a string, this returns the string value of a CHARACTERS event, returns the value of a COMMENT, the replacement value for an ENTITY_REFERENCE, the string value of a CDATA section, the string value for a SPACE event, or the String value of the internal subset of the DTD. If an ENTITY_REFERENCE has been resolved, any character data will be reported as CHARACTERS events.

Returns:

• the current text or null.

getTextLength(): Number

Returns the length of the sequence of characters for this Text event within the text character array.

Returns:

• the length of the sequence of characters for this Text event within the text character array.

getTextStart(): Number

Returns the offset into the text character array where the first character (of this text event) is stored.

Returns:

• the offset into the text character array where the first character (of this text event) is stored.

getVersion(): String

Get the xml version declared on the xml declaration. Returns null if none was declared.

Returns:

• the XML version or null.

getXMLObject(): Object

Reads a sub-tree of the XML document and parses it as XML object.

The stream must be positioned on a START_ELEMENT. Do not call the method when the stream is positioned at document's root element. This would cause the whole document to be parsed into a single XML what may lead to an out-of-memory condition. Instead use #next() to navigate to sub-elements and invoke getXMLObject() there. Do not keep references to more than the currently processed XML to keep memory consumption low. The method reads the stream up to the matching END_ELEMENT. When the method returns the current event is the END_ELEMENT event.

Deprecated:

hasName(): Boolean

Identifies if the current event has a name (is a START_ELEMENT or END_ELEMENT)

Returns:

• true if the current event has a name, false otherwise.

hasNext(): Boolean

Returns true if there are more parsing events and false if there are no more events. This method will return false if the current state of the XMLStreamReader is END_DOCUMENT

Returns:

• true if there are more events, false otherwise

hasText(): Boolean

Indicates if the current event has text. The following events have text: CHARACTERS,DTD ,ENTITY_REFERENCE, COMMENT, SPACE.

Returns:

• true if the current event has text, false otherwise.

isAttributeSpecified(index: Number): Boolean

Identifies if this attribute was created by default.

Parameters:

• index - the position of the attribute.

Returns:

• true if this is a default attribute, false otherwise.

isCharacters(): Boolean

Identifies if the cursor points to a character data event.

Returns:

• true if the cursor points to character data, false otherwise.

isEndElement(): Boolean

Identifies if the cursor points to an end tag.

Returns:

• true if the cursor points to an end tag, false otherwise.

isStandalone(): Boolean

Get the standalone declaration from the xml declaration.

Returns:

• true if this is standalone, or false otherwise.

isStartElement(): Boolean

Identifies if the cursor points to a start tag.

Returns:

• true if the cursor points to a start tag, false otherwise.

isWhiteSpace(): Boolean

Identifies if the cursor points to a character data event that consists of all whitespace.

Returns:

• true if the cursor points to all whitespace, false otherwise.

next(): Number

Get next parsing event - a processor may return all contiguous character data in a single chunk, or it may split it into several chunks. If the property javax.xml.stream.isCoalescing is set to true element content must be coalesced and only one CHARACTERS event must be returned for contiguous element content or CDATA Sections.

By default entity references must be expanded and reported transparently to the application. An exception will be thrown if an entity reference cannot be expanded. If element content is empty (i.e. content is "") then no CHARACTERS event will be reported.

Given the following XML:

<foo>content text<![CDATA[<greeting>Hello</greeting>]]>other content</foo>

The behavior of calling next() when being on foo will be:

1- the comment (COMMENT)

2- then the characters section (CHARACTERS)

3- then the CDATA section (another CHARACTERS)

4- then the next characters section (another CHARACTERS)

5- then the END_ELEMENT

NOTE: empty element (such as <tag/>) will be reported with two separate events: START_ELEMENT, END_ELEMENT - This preserves parsing equivalency of empty element to <tag></tag>.

This method will throw an IllegalStateException if it is called after hasNext() returns false.

Returns:

• the integer code corresponding to the current parse event

nextTag(): Number

Skips any white space (isWhiteSpace() returns true), COMMENT, or PROCESSING_INSTRUCTION, until a START_ELEMENT or END_ELEMENT is reached. If other than white space characters, COMMENT, PROCESSING_INSTRUCTION, START_ELEMENT, END_ELEMENT are encountered, an exception is thrown. This method should be used when processing element-only content separated by white space.

Precondition: none

Postcondition: the current event is START_ELEMENT or END_ELEMENT and cursor may have moved over any whitespace event.

Essentially it does the following (implementations are free to optimized but must do equivalent processing):

1int eventType = next();
2while ( (eventType == XMLStreamConstants.CHARACTERS && isWhiteSpace() )
3      || (eventType == XMLStreamConstants.CDATA && isWhiteSpace())
4      || eventType == XMLStreamConstants.SPACE
5      || eventType == XMLStreamConstants.PROCESSING_INSTRUCTION
6      || eventType == XMLStreamConstants.COMMENT )
7{
8    eventType = next();
9}
10if ( eventType != XMLStreamConstants.START_ELEMENT && eventType != XMLStreamConstants.END_ELEMENT )
11{
12    throw new String XMLStreamException( "expected start or end tag", getLocation() );
13}
14return eventType;

Returns:

• the event type of the element read (START_ELEMENT or END_ELEMENT)

readElementText(): String

Reads the content of a text-only element, an exception is thrown if this is not a text-only element. This method always returns coalesced content.

Precondition: the current event is START_ELEMENT.

Postcondition: the current event is the corresponding END_ELEMENT.

The method does the following (implementations are free to be optimized but must do equivalent processing):

1if ( getEventType() != XMLStreamConstants.START_ELEMENT )
2{
3    throw new XMLStreamException( "parser must be on START_ELEMENT to read next text", getLocation() );
4}
5int eventType = next();
6StringBuffer content = new StringBuffer();
7while ( eventType != XMLStreamConstants.END_ELEMENT )
8{
9    if ( eventType == XMLStreamConstants.CHARACTERS || eventType == XMLStreamConstants.CDATA
10        || eventType == XMLStreamConstants.SPACE || eventType == XMLStreamConstants.ENTITY_REFERENCE )
11    {
12        buf.append( getText() );
13    }
14    else if ( eventType == XMLStreamConstants.PROCESSING_INSTRUCTION || eventType == XMLStreamConstants.COMMENT )
15    {
16        // skipping
17    }
18    else if ( eventType == XMLStreamConstants.END_DOCUMENT )
19    {
20        throw new XMLStreamException( "unexpected end of document when reading element text content", this );
21    }
22    else if ( eventType == XMLStreamConstants.START_ELEMENT )
23    {
24        throw new XMLStreamException( "element text content may not contain START_ELEMENT", getLocation() );
25    }
26    else
27    {
28        throw new XMLStreamException( "Unexpected event type " + eventType, getLocation() );
29    }
30    eventType = next();
31}
32return buf.toString();

readXMLObject(): Object

Reads a sub-tree of the XML document and parses it as XML object.

The stream must be positioned on a START_ELEMENT. Do not call the method when the stream is positioned at document's root element. This would cause the whole document to be parsed into a single XML what may lead to an out-of-memory condition. Instead use #next() to navigate to sub-elements and invoke getXMLObject() there. Do not keep references to more than the currently processed XML to keep memory consumption low. The method reads the stream up to the matching END_ELEMENT. When the method returns the current event is the END_ELEMENT event.

require(type: Number, namespaceURI: String, localName: String): void

Test if the current event is of the given type and if the namespace and name match the current namespace and name of the current event. If the namespaceURI is null it is not checked for equality, if the localName is null it is not checked for equality.

Parameters:

• type - the event type
• namespaceURI - the uri of the event, may be null
• localName - the localName of the event, may be null

standaloneSet(): Boolean

Identifies if standalone was set in the document.

Returns:

• true if standalone was set in the document, false otherwise.