src/org/apache/xml/utils/DTMManager.java

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package org.apache.xml.utils;

/**
 * A DTMManager instance can be used to create DTM and
 * DTMIterator objects, and manage the DTM objects in the system.
 *
 * <p>The system property that determines which Factory implementation
 * to create is named "org.apache.xml.utils.DTMFactory". This
 * property names a concrete subclass of the DTMFactory abstract
 *  class. If the property is not defined, a platform default is be used.</p>
 *  
 * <p>An instance of this class <emph>must</emph> be safe to use across 
 * thread instances.  It is expected that a client will create a single instance 
 * of a DTMManager to use across multiple threads.  This will allow sharing 
 * of DTMs across multiple processes.</p>
 *  
 * <p>Note: this class is incomplete right now.  It will be pretty much 
 * modeled after javax.xml.transform.TransformerFactory in terms of its 
 * factory support.</p>
 * 
 * <p>State: In progress!!</p>
 */
public abstract class DTMManager
{

  /**
   * Default constructor is protected on purpose.
   */
  protected DTMManager(){}

  /**
   * Get an instance of a DTM.  If the unique flag is true, a new instance will
   * always be returned.  Otherwise it is up to the DTMManager to return a
   * new instance or an instance that it already created and may be being used
   * by someone else.
   * (I think more parameters will need to be added for error handling, and entity
   * resolution).
   *
   * @param source the specification of the source object.
   * @param unique true if the returned DTM must be unique, probably because it
   * is going to be mutated.
   *
   * @return a non-null DTM reference.
   */
  public abstract DTM getDTM(javax.xml.transform.Source source,
                             boolean unique);
                             
  /**
   * Get an instance of a DTM that "owns" a node handle.
   *
   * @param nodeHandle the nodeHandle.
   *
   * @return a non-null DTM reference.
   */
  public abstract DTM getDTM(int nodeHandle);


  /**
   * Create a new <code>DTMIterator</code> based on an XPath
   * <a href="http://www.w3.org/TR/xpath#NT-LocationPath>LocationPath</a> or
   * a <a href="http://www.w3.org/TR/xpath#NT-UnionExpr">UnionExpr</a>.
   *
   * @param xpathCompiler ??? Somehow we need to pass in a subpart of the
   * expression.  I hate to do this with strings, since the larger expression
   * has already been parsed.
   *
   * @param pos The position in the expression.
   * @return The newly created <code>DTMIterator</code>.
   */
  public abstract DTMIterator createDTMIterator(Object xpathCompiler,
          int pos);

  /**
   * Create a new <code>DTMIterator</code> based on an XPath
   * <a href="http://www.w3.org/TR/xpath#NT-LocationPath>LocationPath</a> or
   * a <a href="http://www.w3.org/TR/xpath#NT-UnionExpr">UnionExpr</a>.
   *
   * @param xpathString Must be a valid string expressing a
   * <a href="http://www.w3.org/TR/xpath#NT-LocationPath>LocationPath</a> or
   * a <a href="http://www.w3.org/TR/xpath#NT-UnionExpr">UnionExpr</a>.
   *
   * @param presolver An object that can resolve prefixes to namespace URLs.
   *
   * @return The newly created <code>DTMIterator</code>.
   */
  public abstract DTMIterator createDTMIterator(String xpathString,
          PrefixResolver presolver);

  /**
   * Create a new <code>DTMIterator</code> based only on a whatToShow and
   * a DTMFilter.  The traversal semantics are defined as the descendant
   * access.
   *
   * @param whatToShow This flag specifies which node types may appear in
   *   the logical view of the tree presented by the iterator. See the
   *   description of <code>NodeFilter</code> for the set of possible
   *   <code>SHOW_</code> values.These flags can be combined using
   *   <code>OR</code>.
   * @param filter The <code>NodeFilter</code> to be used with this
   *   <code>TreeWalker</code>, or <code>null</code> to indicate no filter.
   * @param entityReferenceExpansion The value of this flag determines
   *   whether entity reference nodes are expanded.
   *
   * @return The newly created <code>NodeIterator</code>.
   */
  public abstract DTMIterator createDTMIterator(int whatToShow,
          DTMFilter filter, boolean entityReferenceExpansion);
}