/*
* 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.
*/
package org.apache.jackrabbit.api;
import javax.jcr.Value;
/**
* Values returned by Jackrabbit may implement this interface. The interface
* defines optional features. An application should check if the returned value
* is of this type before casting as in:
* <pre>
* if (v instanceof JackrabbitValue) {
* JackrabbitValue j = (JackrabbitValue) v;
* ....
* }
* </pre>
*/
public interface JackrabbitValue extends Value {
/**
* Get a unique identifier of the content of this value. Usually this is a
* message digest of the content (a cryptographically secure one-way hash).
* This allows to avoid processing large binary values multiple times.
* <p>
* This method returns null if the identifier is unknown. The identifier may
* not always be available, for example if the value has not yet been saved
* or processed. Once an identifier is available, it will never change
* because values are immutable.
* <p>
* If two values have the same identifier, the content of the value is
* guaranteed to be the same. However it is not guaranteed that two values
* with the same content will return the same identifier.
* <p>
* The identifier is opaque, meaning it can have any format and size, however
* it is at normally about 50 characters and at most 255 characters long.
* The string only contains Unicode code points from 32 to 127 (including).
*
* @return the unique identifier or null
*/
String getContentIdentity();
}