001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.camel;
018
019import java.io.IOException;
020import java.io.OutputStream;
021
022/**
023 * Tagging interface to indicate that a type is capable of caching the underlying data stream.
024 * <p/>
025 * This is a useful feature for avoiding message re-readability issues.
026 * This interface is mainly used by the {@link org.apache.camel.spi.StreamCachingStrategy}
027 * for determining if/how to wrap a stream-based message.
028 * <p/>
029 * The Camel routing engine uses the {@link org.apache.camel.processor.CamelInternalProcessor.StreamCachingAdvice}
030 * to apply the stream cache during routing.
031 *
032 * @version 
033 */
034public interface StreamCache {
035
036    long DEFAULT_SPOOL_THRESHOLD = 128 * 1024;
037
038    /**
039     * Resets the StreamCache for a new stream consumption.
040     */
041    void reset();
042
043    /**
044     * Writes the stream to the given output
045     *
046     * @param os the destination to write to
047     * @throws java.io.IOException is thrown if write fails
048     */
049    void writeTo(OutputStream os) throws IOException;
050
051    /**
052     * Whether this {@link StreamCache} is in memory only or
053     * spooled to persistent storage such as files.
054     */
055    boolean inMemory();
056
057    /**
058     * Gets the length of the cached stream.
059     * <p/>
060     * The implementation may return <tt>0</tt> in cases where the length
061     * cannot be computed, or if the implementation does not support this.
062     *
063     * @return number of bytes in the cache.
064     */
065    long length();
066
067}