javax.xml.xquery
Interface XQSequence

All Superinterfaces:

XQItemAccessor

All Known Subinterfaces:

XQResultSequence

All Known Implementing Classes:

SaxonXQForwardSequence, SaxonXQSequence

public interface XQSequence
extends XQItemAccessor

This interface represents a sequence of items as defined in the XDM. The sequence may be materialized or non-materialized.

The next method is useful to position the XQSequence over the next item in the sequence. If the scrollability is XQConstants.SCROLLTYPE_SCROLLABLE, then the previous method can be called to move backwards. In the case of a forward only sequence, the get methods may be only called once per item. To perform multiple gets on an item, extract the item first from the sequence using the getItem method and then operate on the XQItem object.

 
  XQPreparedExpression expr = conn.prepareExpression("for $i ..");
  XQSequence result = expr.executeQuery();
 
  // create the ItemTypes for string and integer
  XQItemType strType = conn.createAtomicType(XQItemType.XQBASETYPE_STRING);
  XQItemType intType = conn.createAtomicType(XQItemType.XQBASETYPE_INT);

  // positioned before the first item
  while (result.next())
  {
    XQItemType type = result.getItemType();
 
    // If string, then get the string value out
    if (type.equals(strType))
      String str = result.getAtomicValue();
    else if (type.equals(intType))  // if it is an integer..
      int intval = result.getInt();
 
     ...
  }
 
 

In a sequence, the cursor may be positioned on an item, after the last item or before the first item. The getPosition method returns the current position number. A value of 0 indicates that it is positioned before the first item, a value of count() + 1 indicates that it is positioned after the last item, and any other value indicates that it is positioned on the item at that position.

For example, a position value of 1 indicates that it is positioned on the item at position 1.

The isOnItem method may be used to find out if the cursor is positioned on the item. When the cursor is positioned on an item, the next method call will move the cursor to be on the next item.

See also: Section 12 Serialization, XQuery API for Java (XQJ) 1.0, which describes some general information applicable to various XQJ serialization methods.

Method Summary

boolean	absolute(int itempos) Moves the XQSequence's position to the given item number in this object.
void	afterLast() Move to the position after the last item.
void	beforeFirst() Moves to the position before the first item.
void	close() Closes the sequence and frees all resources associated with this sequence.
int	count() Returns a number indicating the number of items in the sequence.
boolean	first() Moves to the first item in the sequence.
XQItem	getItem() Get the current item as an immutable XQItem object.
int	getPosition() Gets the current cursor position.
XMLStreamReader	getSequenceAsStream() Read the entire sequence starting from the current position as an XMLStreamReader object, as described in Section 12.1 Serializing an XDM instance into a StAX event stream (XMLStreamReader), XQuery API for Java (XQJ) 1.0.
String	getSequenceAsString(Properties props) Serializes the sequence starting from the current position to a String according to the XSLT 2.0 and XQuery 1.0 serialization.
boolean	isAfterLast() Checks if the current position is after the last item in the sequence.
boolean	isBeforeFirst() Checks if the current position before the first item in the sequence.
boolean	isClosed() Checks if the sequence is closed.
boolean	isFirst() Checks if the current position at the first item in the sequence.
boolean	isLast() Checks if the current position at the last item in the sequence.
boolean	isOnItem() Check if the sequence is positioned on an item or not.
boolean	isScrollable() Checks if the sequence is scrollable.
boolean	last() Moves to the last item in the sequence.
boolean	next() Moves to the next item in the sequence.
boolean	previous() Moves to the previous item in the sequence.
boolean	relative(int itempos) Moves the cursor a relative number of items, either positive or negative.
void	writeSequence(OutputStream os, Properties props) Serializes the sequence starting from the current position to an OutputStream according to the XSLT 2.0 and XQuery 1.0 serialization.
void	writeSequence(Writer ow, Properties props) Serializes the sequence starting from the current position to a Writer according to the XSLT 2.0 and XQuery 1.0 serialization.
void	writeSequenceToResult(Result result) Writes the entire sequence starting from the current position to a Result.
void	writeSequenceToSAX(ContentHandler saxhdlr) Writes the entire sequence starting from the current position to a SAX handler, as described in Section 12.2 Serializing an XDM instance into a SAX event stream, XQuery API for Java (XQJ) 1.0.

Methods inherited from interface javax.xml.xquery.XQItemAccessor

getAtomicValue, getBoolean, getByte, getDouble, getFloat, getInt, getItemAsStream, getItemAsString, getItemType, getLong, getNode, getNodeUri, getObject, getShort, instanceOf, writeItem, writeItem, writeItemToResult, writeItemToSAX

Method Detail

absolute

boolean absolute(int itempos)
                 throws XQException

Moves the XQSequence's position to the given item number in this object. If the item number is positive, the XQSequence moves to the given item number with respect to the beginning of the XQSequence.

The first item is item 1, the second is item 2, and so on.

If the given item number is negative, the XQSequence positions itself on an absolute item position with respect to the end of the sequence.

For example, calling the method absolute(-1) positions the XQSequence on the last item; calling the method absolute(-2) moves the XQSequence to the next-to-last item, and so on. absolute(0) will position the sequence before the first item.

An attempt to position the sequence beyond the first/last item set leaves the current position to be before the first item or after the last item.

Calling this method on an empty sequence will return false.

Parameters:

itempos - the item position to jump to

Returns:

true if the current position is within the sequence, false otherwise

Throws:

XQException - if (1) the sequence is forward only, or (2) the sequence is in a closed state

afterLast

void afterLast()
               throws XQException

Move to the position after the last item.

Throws:

XQException - if (1) the sequence is forward only, or (2) the sequence is in a closed state

beforeFirst

void beforeFirst()
                 throws XQException

Moves to the position before the first item.

Throws:

XQException - if (1) the sequence is forward only, or (2) the sequence is in a closed state

close

void close()
           throws XQException

Closes the sequence and frees all resources associated with this sequence. Closing an XQSequence object also implicitly closes all XQItem objects obtained from it. All methods other than the isClosed or close method will raise exceptions when invoked after closing the sequence. Calling close on an XQSequence object that is already closed has no effect.

Throws:

XQException - if there are errors during closing of the sequence

isClosed

boolean isClosed()

Checks if the sequence is closed.

Returns:

true if the sequence is in a closed state, false otherwise

count

int count()
          throws XQException

Returns a number indicating the number of items in the sequence.

Returns:

the number of items in this sequence

Throws:

XQException - if (1) the sequence is forward-only, or (2) the sequence is closed

getPosition

int getPosition()
                throws XQException

Gets the current cursor position.

0 indicates that the position is before the first item and count() + 1 indicates position after the last item. A specific position indicates that the cursor is positioned on the item at that position. Use the isOnItem method to verify if the cursor is positioned on the item.

Calling this method on an empty sequence will return 0.

Throws:

XQException - if (1) the sequence is forward-only, or (2) the sequence is closed

isOnItem

boolean isOnItem()
                 throws XQException

Check if the sequence is positioned on an item or not. Calling this method on an empty sequence will return false.

Returns:

true if the sequence is currently positioned on an item, false if sequence is positioned before the first item, or after the last item

Throws:

XQException - if the sequence is in a closed state

isScrollable

boolean isScrollable()
                     throws XQException

Checks if the sequence is scrollable.

Returns:

true if the sequence can be scrolled backward or forward, false otherwise

Throws:

XQException - if the sequence is in a closed state

first

boolean first()
              throws XQException

Moves to the first item in the sequence. The method returns true, if it was able to move to the first item in the sequence false, otherwise. Calling this method on an empty sequence will return false.

Returns:

true if the sequence was positioned on the first item, false otherwise

Throws:

XQException - if (1) the sequence is forward only, or (2) the sequence is in a closed state

getItem

XQItem getItem()
               throws XQException

Get the current item as an immutable XQItem object. In case of an XQResultSequence, the item is an XQResultItem. In the case of forward only sequences, this method or any other get or write method may only be called once on the curent item.

The XQItem object is dependent on the sequence from which it was created and is only valid for the duration of XQSequence lifetime. Thus, the XQSequence is closed, this XQItem object will be implicitly closed and it can no longer be used.

Returns:

an XQItem object

Throws:

XQException - if (1) there are errors retrieving the item, or (2) in the case of a forward only sequence, a get or write method has already been invoked on the current item.

getSequenceAsStream

XMLStreamReader getSequenceAsStream()
                                    throws XQException

Read the entire sequence starting from the current position as an XMLStreamReader object, as described in Section 12.1 Serializing an XDM instance into a StAX event stream (XMLStreamReader), XQuery API for Java (XQJ) 1.0. Note that the serialization process might fail, in which case a XQException is thrown. While the stream is being read, the application MUST NOT do any other concurrent operations on the sequence. The operation on the stream is undefined if the underlying sequence position or state is changed by concurrent operations. After all items are written to the stream, the current position of the cursor is set to point after the last item. Also, in the case of forward only sequences, this method may only be called if the current item has not yet been read through any of the get or write methods.

Returns:

an XML reader object as XMLStreamReader

Throws:

XQException - if (1) there are errors accessing any of the items in the sequence, (2) the sequence is in a closed state, (3) in the case of a forward only sequence, a get or write method has already been invoked on the current item, or (4) in case of an error during serialization of the sequence into a StAX event stream as defined in Section 12.1 Serializing an XDM instance into a StAX event stream (XMLStreamReader), XQuery API for Java (XQJ) 1.0

getSequenceAsString

String getSequenceAsString(Properties props)
                           throws XQException

Serializes the sequence starting from the current position to a String according to the XSLT 2.0 and XQuery 1.0 serialization. Serialization parameters, which influence how serialization is performed, can be specified. Refer to the XSLT 2.0 and XQuery 1.0 serialization and Section 12 Serialization, XQuery API for Java (XQJ) 1.0 for more information. Reading the sequence during the serialization process performs implicit next operations to read the items. After all items are written to the stream, the current position of the cursor is set to point after the last item. Also, in the case of forward only sequences, this method may only be called if the current item has not yet been read through any of the get or write methods.

Parameters:

props - specifies the serialization parameters, null is considered equivalent to an empty Properties object

Returns:

the serialized representation of the sequence

Throws:

XQException - if (1) there are errors accessing the items in the sequence, (2) there are errors during serialization, (3) the sequence is in a closed state, or (4) in the case of a forward only sequence, a get or write method has already been invoked on the current item

isAfterLast

boolean isAfterLast()
                    throws XQException

Checks if the current position is after the last item in the sequence. Calling this method on an empty sequence will return false.

Returns:

true if the current position is after the last item, false otherwise

Throws:

XQException - if (1) the sequence is forward only, or (2) the sequence is in a closed state

isBeforeFirst

boolean isBeforeFirst()
                      throws XQException

Checks if the current position before the first item in the sequence. Calling this method on an empty sequence will return false.

Returns:

true if the current position is before the first item, false otherwise

Throws:

XQException - if (1) the sequence is forward only, or (2) the sequence is in a closed state

isFirst

boolean isFirst()
                throws XQException

Checks if the current position at the first item in the sequence. Calling this method on an empty sequence will return false.

Returns:

true if the current position is at the first item, false otherwise

Throws:

XQException - if (1) the sequence is forward only, or (2) the sequence is in a closed state

isLast

boolean isLast()
               throws XQException

Checks if the current position at the last item in the sequence. Calling this method on an empty sequence will return false.

Returns:

true if the current position is at the last item, false otherwise

Throws:

XQException - if (1) the sequence is forward only, or (2) the sequence is in a closed state

last

boolean last()
             throws XQException

Moves to the last item in the sequence. This method returns true, if it was able to move to the last item in the sequence false, otherwise. Calling this method on an empty sequence will return false.

Returns:

true if the sequence was positioned on the last item, false otherwise

Throws:

XQException - if (1) the sequence is forward only, or (2) the sequence is in a closed state

next

boolean next()
             throws XQException

Moves to the next item in the sequence. Calling this method on an empty sequence will return false.

Returns:

true if the new item is valid, false if there are no more items

Throws:

XQException - if the sequence is in a closed state

previous

boolean previous()
                 throws XQException

Moves to the previous item in the sequence. Calling this method on an empty sequence will return false.

Returns:

true if the new current position is within the sequence, (i.e., not before first); false otherwise.

Throws:

XQException - if (1) the sequence is forward only, or (2) the sequence is in a closed state.

relative

boolean relative(int itempos)
                 throws XQException

Moves the cursor a relative number of items, either positive or negative. Attempting to move beyond the first/last item in the sequence positions the sequence before/after the the first/last item. Calling relative(0) is valid, but does not change the cursor position.

Note: Calling the method relative(1) is identical to calling the method next and calling the method relative(-1) is identical to calling the method previous(). Calling this method on an empty sequence will return false.

Parameters:

itempos - the item position to jump to

Returns:

true if the new current position is within the sequence (i.e., not before first or after last); false otherwise.

Throws:

XQException - if (1) the sequence is forward only, or (2) the sequence is in a closed state.

writeSequence

void writeSequence(OutputStream os,
                   Properties props)
                   throws XQException

Serializes the sequence starting from the current position to an OutputStream according to the XSLT 2.0 and XQuery 1.0 serialization. Serialization parameters, which influence how serialization is performed, can be specified. Refer to the XSLT 2.0 and XQuery 1.0 serialization and Section 12 Serialization, XQuery API for Java (XQJ) 1.0 for more information. Reading the sequence during the serialization process performs implicit next operations to read the items. After all items are written to the stream, the current position of the cursor is set to point after the last item. Also, in the case of forward only sequences, this method may only be called if the current item has not yet been read through any of the get or write methods.

Parameters:

os - the output stream into which the sequence is to be serialized

props - specifies the serialization parameters, null is considered equivalent to an empty Properties object

Throws:

XQException - if (1) there are errors accessing the items in the sequence, (2) there are errors during serialization, (3) the sequence is in a closed state, (4) in the case of a forward only sequence, a get or write method has already been invoked on the current item, or (5) the os parameter is null

writeSequence

void writeSequence(Writer ow,
                   Properties props)
                   throws XQException

Serializes the sequence starting from the current position to a Writer according to the XSLT 2.0 and XQuery 1.0 serialization. Serialization parameters, which influence how serialization is performed, can be specified. Refer to the XSLT 2.0 and XQuery 1.0 serialization and Section 12 Serialization, XQuery API for Java (XQJ) 1.0 for more information.

Warning: When outputting to a Writer, make sure the writer's encoding matches the encoding parameter if specified as a property or the default encoding.

Reading the sequence during the serialization process performs implicit next operations to read the items. After all items are written to the stream, the current position of the cursor is set to point after the last item. Also, in the case of forward only sequences, this method may only be called if the current item has not yet been read through any of the get or write methods.

Parameters:

ow - the writer object into which the sequence is to be serialized

props - specifies the serialization parameters, null is considered equivalent to an empty Properties object

Throws:

XQException - if (1) there are errors accessing the items in the sequence, (2) there are errors during serialization, (3) the sequence is in a closed state, (4) in the case of a forward only sequence, a get or write method has already been invoked on the current item, or (5) the ow parameter is null

writeSequenceToSAX

void writeSequenceToSAX(ContentHandler saxhdlr)
                        throws XQException

Writes the entire sequence starting from the current position to a SAX handler, as described in Section 12.2 Serializing an XDM instance into a SAX event stream, XQuery API for Java (XQJ) 1.0. Note that the serialization process might fail, in which case a XQException is thrown. After all items are written to the stream, the current position of the cursor is set to point after the last item. Also, in the case of forward only sequences, this method may only be called if the current item has not yet been read through any of the get or write methods. The specified org.xml.sax.ContentHandler can optionally implement the org.xml.sax.LexicalHandler interface. An implementation must check if the specified ContentHandler implements LexicalHandler. If the handler is a LexicalHandler comment nodes are reported, otherwise they will be silently ignored.

Parameters:

saxhdlr - the SAX content handler, optionally a lexical handler

Throws:

XQException - if (1) there are errors accessing any of the items in the sequence, (2) the sequence is in a closed state, (3) in the case of a forward only sequence, a get or write method has already been invoked on the current item, (4) in case of an error during serializing the XDM instance into a SAX event stream, or (5) the saxhdlr parameter is null

writeSequenceToResult

void writeSequenceToResult(Result result)
                           throws XQException

Writes the entire sequence starting from the current position to a Result. First the sequence is normalized as described in XSLT 2.0 and XQuery 1.0 serialization. Subsequently it is serialized to the Result object.
Note that the normalization process can fail, in which case an XQException is thrown. An XQJ implementation must at least support the following implementations:

• javax.xml.transform.dom.DOMResult
• javax.xml.transform.sax.SAXResult
• javax.xml.transform.stream.StreamResult

Parameters:

result - the result object into which the sequence is to be serialized

Throws:

XQException - if (1) there are errors accessing any of the items in the sequence, (2) the sequence is in a closed state, (3) in the case of a forward only sequence, a get or write method has already been invoked on the current item, (4) in case of an error while serializing the sequence into the Result object, or (5) the result parameter is null