Package 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 Details

    • 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