org.apache.xml.dtm.DTMIterator Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* 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.
*/
/*
* $Id: DTMIterator.java 468653 2006-10-28 07:07:05Z minchau $
*/
package org.apache.xml.dtm;
/**
* DTMIterators are used to step through a (possibly
* filtered) set of nodes. Their API is modeled largely after the DOM
* NodeIterator.
*
* A DTMIterator is a somewhat unusual type of iterator, in that it
* can serve both single node iteration and random access.
*
* The DTMIterator's traversal semantics, i.e. how it walks the tree,
* are specified when it is created, possibly and probably by an XPath
* UnionExpr.
*
* A DTMIterator is meant to be created once as a master static object, and
* then cloned many times for runtime use. Or the master object itself may
* be used for simpler use cases.
*
* At this time, we do not expect DTMIterator to emulate
* NodeIterator's "maintain relative position" semantics under
* document mutation. It's likely to respond more like the
* TreeWalker's "current node" semantics. However, since the base DTM
* is immutable, this issue currently makes no practical
* difference.
*
* State: In progress!!
*/
public interface DTMIterator
{
// Constants returned by acceptNode, borrowed from the DOM Traversal chapter
// %REVIEW% Should we explicitly initialize them from, eg,
// org.w3c.dom.traversal.NodeFilter.FILTER_ACCEPT?
/**
* Accept the node.
*/
public static final short FILTER_ACCEPT = 1;
/**
* Reject the node. Same behavior as FILTER_SKIP. (In the DOM these
* differ when applied to a TreeWalker but have the same result when
* applied to a NodeIterator).
*/
public static final short FILTER_REJECT = 2;
/**
* Skip this single node.
*/
public static final short FILTER_SKIP = 3;
/**
* Get an instance of a DTM that "owns" a node handle. Since a node
* iterator may be passed without a DTMManager, this allows the
* caller to easily get the DTM using just the iterator.
*
* @param nodeHandle the nodeHandle.
*
* @return a non-null DTM reference.
*/
public DTM getDTM(int nodeHandle);
/**
* Get an instance of the DTMManager. Since a node
* iterator may be passed without a DTMManager, this allows the
* caller to easily get the DTMManager using just the iterator.
*
* @return a non-null DTMManager reference.
*/
public DTMManager getDTMManager();
/**
* The root node of the DTMIterator, as specified when it
* was created. Note the root node is not the root node of the
* document tree, but the context node from where the iteration
* begins and ends.
*
* @return nodeHandle int Handle of the context node.
*/
public int getRoot();
/**
* Reset the root node of the DTMIterator, overriding
* the value specified when it was created. Note the root node is
* not the root node of the document tree, but the context node from
* where the iteration begins.
*
* @param nodeHandle int Handle of the context node.
* @param environment The environment object.
* The environment in which this iterator operates, which should provide:
*
* - a node (the context node... same value as "root" defined below)
* - a pair of non-zero positive integers (the context position and the context size)
* - a set of variable bindings
* - a function library
* - the set of namespace declarations in scope for the expression.
*
*
* At this time the exact implementation of this environment is application
* dependent. Probably a proper interface will be created fairly soon.
*
*/
public void setRoot(int nodeHandle, Object environment);
/**
* Reset the iterator to the start. After resetting, the next node returned
* will be the root node -- or, if that's filtered out, the first node
* within the root's subtree which is _not_ skipped by the filters.
*/
public void reset();
/**
* This attribute determines which node types are presented via the
* iterator. The available set of constants is defined above.
* Nodes not accepted by
* whatToShow will be skipped, but their children may still
* be considered.
*
* @return one of the SHOW_XXX constants, or several ORed together.
*/
public int getWhatToShow();
/**
* The value of this flag determines whether the children of entity
* reference nodes are visible to the iterator. If false, they and
* their descendants will be rejected. Note that this rejection takes
* precedence over whatToShow and the filter.
*
* To produce a view of the document that has entity references
* expanded and does not expose the entity reference node itself, use
* the whatToShow flags to hide the entity reference node
* and set expandEntityReferences to true when creating the
* iterator. To produce a view of the document that has entity reference
* nodes but no entity expansion, use the whatToShow flags
* to show the entity reference node and set
* expandEntityReferences to false.
*
* NOTE: In Xalan's use of DTM we will generally have fully expanded
* entity references when the document tree was built, and thus this
* flag will have no effect.
*
* @return true if entity references will be expanded. */
public boolean getExpandEntityReferences();
/**
* Returns the next node in the set and advances the position of the
* iterator in the set. After a DTMIterator has setRoot called,
* the first call to nextNode() returns that root or (if it
* is rejected by the filters) the first node within its subtree which is
* not filtered out.
* @return The next node handle in the set being iterated over, or
* DTM.NULL if there are no more members in that set.
*/
public int nextNode();
/**
* Returns the previous node in the set and moves the position of the
* DTMIterator backwards in the set.
* @return The previous node handle in the set being iterated over,
* or DTM.NULL if there are no more members in that set.
*/
public int previousNode();
/**
* Detaches the DTMIterator from the set which it iterated
* over, releasing any computational resources and placing the iterator
* in the INVALID state. After detach has been invoked,
* calls to nextNode or previousNode will
* raise a runtime exception.
*/
public void detach();
/**
* Specify if it's OK for detach to release the iterator for reuse.
*
* @param allowRelease true if it is OK for detach to release this iterator
* for pooling.
*/
public void allowDetachToRelease(boolean allowRelease);
/**
* Get the current node in the iterator. Note that this differs from
* the DOM's NodeIterator, where the current position lies between two
* nodes (as part of the maintain-relative-position semantic).
*
* @return The current node handle, or -1.
*/
public int getCurrentNode();
/**
* Tells if this NodeSetDTM is "fresh", in other words, if
* the first nextNode() that is called will return the
* first node in the set.
*
* @return true if the iteration of this list has not yet begun.
*/
public boolean isFresh();
//========= Random Access ==========
/**
* If setShouldCacheNodes(true) is called, then nodes will
* be cached, enabling random access, and giving the ability to do
* sorts and the like. They are not cached by default.
*
* %REVIEW% Shouldn't the other random-access methods throw an exception
* if they're called on a DTMIterator with this flag set false?
*
* @param b true if the nodes should be cached.
*/
public void setShouldCacheNodes(boolean b);
/**
* Tells if this iterator can have nodes added to it or set via
* the setItem(int node, int index) method.
*
* @return True if the nodelist can be mutated.
*/
public boolean isMutable();
/** Get the current position within the cached list, which is one
* less than the next nextNode() call will retrieve. i.e. if you
* call getCurrentPos() and the return is 0, the next fetch will
* take place at index 1.
*
* @return The position of the iteration.
*/
public int getCurrentPos();
/**
* If an index is requested, NodeSetDTM will call this method
* to run the iterator to the index. By default this sets
* m_next to the index. If the index argument is -1, this
* signals that the iterator should be run to the end and
* completely fill the cache.
*
* @param index The index to run to, or -1 if the iterator should be run
* to the end.
*/
public void runTo(int index);
/**
* Set the current position in the node set.
*
* @param i Must be a valid index.
*/
public void setCurrentPos(int i);
/**
* Returns the node handle of an item in the collection. If
* index is greater than or equal to the number of nodes in
* the list, this returns null.
*
* @param index of the item.
* @return The node handle at the indexth position in the
* DTMIterator, or -1 if that is not a valid
* index.
*/
public int item(int index);
/**
* Sets the node at the specified index of this vector to be the
* specified node. The previous component at that position is discarded.
*
* The index must be a value greater than or equal to 0 and less
* than the current size of the vector.
* The iterator must be in cached mode.
*
* Meant to be used for sorted iterators.
*
* @param node Node to set
* @param index Index of where to set the node
*/
public void setItem(int node, int index);
/**
* The number of nodes in the list. The range of valid child node indices
* is 0 to length-1 inclusive. Note that this requires running
* the iterator to completion, and presumably filling the cache.
*
* @return The number of nodes in the list.
*/
public int getLength();
//=========== Cloning operations. ============
/**
* Get a cloned Iterator that is reset to the start of the iteration.
*
* @return A clone of this iteration that has been reset.
*
* @throws CloneNotSupportedException
*/
public DTMIterator cloneWithReset() throws CloneNotSupportedException;
/**
* Get a clone of this iterator, but don't reset the iteration in the
* process, so that it may be used from the current position.
*
* @return A clone of this object.
*
* @throws CloneNotSupportedException
*/
public Object clone() throws CloneNotSupportedException;
/**
* Returns true if all the nodes in the iteration well be returned in document
* order.
*
* @return true if all the nodes in the iteration well be returned in document
* order.
*/
public boolean isDocOrdered();
/**
* Returns the axis being iterated, if it is known.
*
* @return Axis.CHILD, etc., or -1 if the axis is not known or is of multiple
* types.
*/
public int getAxis();
}