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 * 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
 * Unless required by applicable law or agreed to in writing,
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 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.

package org.apache.axiom.util.stax.xop;

import org.apache.axiom.util.UIDGenerator;

 * Content ID generator interface. Implementations of this interface are used by
 * {@link XOPEncodingStreamReader} to generate content IDs for use in <tt>xop:Include</tt>
 * elements.
public interface ContentIDGenerator {
     * Default content ID generator that preserves any existing content ID.
    ContentIDGenerator DEFAULT = new ContentIDGenerator() {
        public String generateContentID(String existingContentID) {
            if (existingContentID == null) {
                return UIDGenerator.generateContentId();
            } else {
                return existingContentID;
     * Generate a content ID.
     * @param existingContentID
     *            An existing content ID for the {@link javax.activation.DataHandler} being
     *            processed, as returned by
     *            {@link org.apache.axiom.ext.stax.datahandler.DataHandlerReader#getContentID()},
     *            or <code>null</code> if no existing content ID is known. The implementation is
     *            free to use this information or not.
     * @return the content ID; may not be <code>null</code>
    String generateContentID(String existingContentID);