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     */
017    package org.apache.camel;
018    
019    import java.io.IOException;
020    import 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     */
034    public 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    }