attrimpl.java

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/*
 * Copyright 1999-2004 The Apache Software Foundation.
 * 
 * Licensed 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.
 */

package com.sun.org.apache.xerces.internal.dom;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

import org.w3c.dom.TypeInfo;
import org.w3c.dom.Attr;
import org.w3c.dom.DOMException;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Text;

/**
 * Attribute represents an XML-style attribute of an
 * Element. Typically, the allowable values are controlled by its
 * declaration in the Document Type Definition (DTD) governing this
 * kind of document.
 * <P>
 * If the attribute has not been explicitly assigned a value, but has
 * been declared in the DTD, it will exist and have that default. Only
 * if neither the document nor the DTD specifies a value will the
 * Attribute really be considered absent and have no value; in that
 * case, querying the attribute will return null.
 * <P>
 * Attributes may have multiple children that contain their data. (XML
 * allows attributes to contain entity references, and tokenized
 * attribute types such as NMTOKENS may have a child for each token.)
 * For convenience, the Attribute object's getValue() method returns
 * the string version of the attribute's value.
 * <P>
 * Attributes are not children of the Elements they belong to, in the
 * usual sense, and have no valid Parent reference. However, the spec
 * says they _do_ belong to a specific Element, and an INUSE exception
 * is to be thrown if the user attempts to explicitly share them
 * between elements.
 * <P>
 * Note that Elements do not permit attributes to appear to be shared
 * (see the INUSE exception), so this object's mutability is
 * officially not an issue.
 * <p>
 * Note: The ownerNode attribute is used to store the Element the Attr
 * node is associated with. Attr nodes do not have parent nodes.
 * Besides, the getOwnerElement() method can be used to get the element node
 * this attribute is associated with.
 * <P>
 * AttrImpl does not support Namespaces. AttrNSImpl, which inherits from
 * it, does.
 *
 * <p>AttrImpl used to inherit from ParentNode. It now directly inherits from
 * NodeImpl and provide its own implementation of the ParentNode's behavior.
 * The reason is that we now try and avoid to always create a Text node to
 * hold the value of an attribute. The DOM spec requires it, so we still have
 * to do it in case getFirstChild() is called for instance. The reason
 * attribute values are stored as a list of nodes is so that they can carry
 * more than a simple string. They can also contain EntityReference nodes.
 * However, most of the times people only have a single string that they only
 * set and get through Element.set/getAttribute or Attr.set/getValue. In this
 * new version, the Attr node has a value pointer which can either be the
 * String directly or a pointer to the first ChildNode. A flag tells which one
 * it currently is. Note that while we try to stick with the direct String as
 * much as possible once we've switched to a node there is no going back. This
 * is because we have no way to know whether the application keeps referring to
 * the node we once returned.
 * <p> The gain in memory varies on the density of attributes in the document.
 * But in the tests I've run I've seen up to 12% of memory gain. And the good
 * thing is that it also leads to a slight gain in speed because we allocate
 * fewer objects! I mean, that's until we have to actually create the node...
 * <p>
 * To avoid too much duplicated code, I got rid of ParentNode and renamed
 * ChildAndParentNode, which I never really liked, to ParentNode for
 * simplicity, this doesn't make much of a difference in memory usage because
 * there are only very few objects that are only a Parent. This is only true
 * now because AttrImpl now inherits directly from NodeImpl and has its own
 * implementation of the ParentNode's node behavior. So there is still some
 * duplicated code there.
 * <p>
 * This class doesn't directly support mutation events, however, it notifies
 * the document when mutations are performed so that the document class do so.
 *
 * <p><b>WARNING</b>: Some of the code here is partially duplicated in
 * ParentNode, be careful to keep these two classes in sync!
 *
 * @xerces.internal
 *
 * @see AttrNSImpl 
 *
 * @author Arnaud  Le Hors, IBM
 * @author Joe Kesselman, IBM
 * @author Andy Clark, IBM 
 * @version $Id: AttrImpl.java,v 1.2.6.1 2005/08/30 11:26:26 sunithareddy Exp $
 * @since PR-DOM-Level-1-19980818.
 *
 */
public class AttrImpl
    extends NodeImpl
    implements Attr, TypeInfo{

    //
    // Constants
    //

    /** Serialization version. */
    static final long serialVersionUID = 7277707688218972102L;
    
    /** DTD namespace. **/
    static final String DTD_URI = "http://www.w3.org/TR/REC-xml";

    //
    // Data
    //

    /** This can either be a String or the first child node. */
    protected Object value = null;

    /** Attribute name. */
    protected String name;
    
    /** Type information */
    // REVISIT: we are losing the type information in DOM during serialization
    transient Object type;

    protected static TextImpl textNode = null;

    //
    // Constructors
    //

    /**
     * Attribute has no public constructor. Please use the factory
     * method in the Document class.
     */
    protected AttrImpl(CoreDocumentImpl ownerDocument, String name) {
    	super(ownerDocument);
        this.name = name;
        /** False for default attributes. */
        isSpecified(true);
        hasStringValue(true);
    }

    // for AttrNSImpl
    protected AttrImpl() {}

    // Support for DOM Level 3 renameNode method.
    // Note: This only deals with part of the pb. It is expected to be
    // called after the Attr has been detached for one thing.
    // CoreDocumentImpl does all the work.
    void rename(String name) {
        if (needsSyncData()) {
            synchronizeData();
        }
        this.name = name;
    }

    // create a real text node as child if we don't have one yet
    protected void makeChildNode() {
        if (hasStringValue()) {
            if (value != null) {
                TextImpl text =
                    (TextImpl) ownerDocument().createTextNode((String) value);
                value = text;
                text.isFirstChild(true);
                text.previousSibling = text;
                text.ownerNode = this;
                text.isOwned(true);
            }
            hasStringValue(false);
        }
    }

    /**
     * NON-DOM
     * set the ownerDocument of this node and its children
     */
    void setOwnerDocument(CoreDocumentImpl doc) {
        if (needsSyncChildren()) {
            synchronizeChildren();
        }
        super.setOwnerDocument(doc);
        if (!hasStringValue()) {
            for (ChildNode child = (ChildNode) value;
                 child != null; child = child.nextSibling) {
                child.setOwnerDocument(doc);
            }
        }
    }

    /**
     * NON-DOM: set the type of this attribute to be ID type.
     * 
     * @param id
     */
    public void setIdAttribute(boolean id){
        if (needsSyncData()) {
            synchronizeData();
        }
        isIdAttribute(id);
    }
    /** DOM Level 3: isId*/
    public boolean isId(){
        // REVISIT: should an attribute that is not in the tree return
        // isID true?
        return isIdAttribute();
    }


    //
    // Node methods
    //
    
    public Node cloneNode(boolean deep) {

        if (needsSyncChildren()) {
            synchronizeChildren();
        }
        AttrImpl clone = (AttrImpl) super.cloneNode(deep);

        // take care of case where there are kids
    	if (!clone.hasStringValue()) {

            // Need to break the association w/ original kids
            clone.value = null;

            // Cloning an Attribute always clones its children, 
            // since they represent its value, no matter whether this 
            // is a deep clone or not
            for (Node child = (Node) value; child != null;
                 child = child.getNextSibling()) {
                 clone.appendChild(child.cloneNode(true));
            }
        }
        clone.isSpecified(true);
        return clone;
    }

    /**
     * A short integer indicating what type of node this is. The named
     * constants for this value are defined in the org.w3c.dom.Node interface.
     */
    public short getNodeType() {
        return Node.ATTRIBUTE_NODE;
    }

    /**
     * Returns the attribute name
     */
    public String getNodeName() {
        if (needsSyncData()) {
            synchronizeData();
        }
        return name;
    }

    /**
     * Implicit in the rerouting of getNodeValue to getValue is the
     * need to redefine setNodeValue, for symmetry's sake.  Note that
     * since we're explicitly providing a value, Specified should be set
     * true.... even if that value equals the default.
     */
    public void setNodeValue(String value) throws DOMException {
    	setValue(value);
    }
    
    /**
     * @see org.w3c.dom.TypeInfo#getTypeName()
     */
    public String getTypeName() {
        return (String)type;
    }

    /**
     * @see org.w3c.dom.TypeInfo#getTypeNamespace()
     */
    public String getTypeNamespace() {
        if (type != null) {
            return DTD_URI;
        }
        return null;
    }
    
    /**
     * Method getSchemaTypeInfo.
     * @return TypeInfo
     */
    public TypeInfo getSchemaTypeInfo(){
      return this;
    }

    /**
     * In Attribute objects, NodeValue is considered a synonym for
     * Value.
     *
     * @see #getValue()
     */
    public String getNodeValue() {
    	return getValue();
    }

    //
    // Attr methods
    //

    /**
     * In Attributes, NodeName is considered a synonym for the
     * attribute's Name
     */
    public String getName() {

        if (needsSyncData()) {
            synchronizeData();
        }
    	return name;

    } // getName():String

    /**
     * The DOM doesn't clearly define what setValue(null) means. I've taken it
     * as "remove all children", which from outside should appear
     * similar to setting it to the empty string.
     */
    public void setValue(String newvalue) {

        CoreDocumentImpl ownerDocument = ownerDocument();
        
        if (ownerDocument.errorChecking && isReadOnly()) {
            String msg = DOMMessageFormatter.formatMessage(DOMMessageFormatter.DOM_DOMAIN, "NO_MODIFICATION_ALLOWED_ERR", null);
            throw new DOMException(DOMException.NO_MODIFICATION_ALLOWED_ERR, msg);
        }
        
        Element ownerElement = getOwnerElement();
        String oldvalue = "";
        if (needsSyncData()) {
            synchronizeData();
        }
        if (needsSyncChildren()) {
            synchronizeChildren();
        }
        if (value != null) {
            if (ownerDocument.getMutationEvents()) {
                // Can no longer just discard the kids; they may have
                // event listeners waiting for them to disconnect.
                if (hasStringValue()) {
                    oldvalue = (String) value;
                    // create an actual text node as our child so
                    // that we can use it in the event
                    if (textNode == null) {
                        textNode = (TextImpl)
                            ownerDocument.createTextNode((String) value);
                    }
                    else {
                        textNode.data = (String) value;
                    }
                    value = textNode;
                    textNode.isFirstChild(true);
                    textNode.previousSibling = textNode;
                    textNode.ownerNode = this;
                    textNode.isOwned(true);
                    hasStringValue(false);
                    internalRemoveChild(textNode, true);
                }
                else {
                    oldvalue = getValue();
                    while (value != null) {
                        internalRemoveChild((Node) value, true);
                    }
                }
            }
            else {
                if (hasStringValue()) {
                    oldvalue = (String) value;
                }
                else {
                    // simply discard children if any
                    oldvalue = getValue();
                    // remove ref from first child to last child
                    ChildNode firstChild = (ChildNode) value;
                    firstChild.previousSibling = null;
                    firstChild.isFirstChild(false);
                    firstChild.ownerNode = ownerDocument;
                }
                // then remove ref to current value
                value = null;
                needsSyncChildren(false);
            }
            if (isIdAttribute() && ownerElement != null) {
                ownerDocument.removeIdentifier(oldvalue);
            }
        }

        // Create and add the new one, generating only non-aggregate events
        // (There are no listeners on the new Text, but there may be
        // capture/bubble listeners on the Attr.
        // Note that aggregate events are NOT dispatched here,
        // since we need to combine the remove and insert.
    	isSpecified(true);